LIGHT POLLUTION: Petteri Teikari. Definition, legislation, measurement, modeling and environmental effects.

Transcription

1 B ARCELONA, CATALUNYA SEPTEMBER 19, 2007 LIGHT POLLUTION: Definition, legislation, measurement, modeling and environmental effects Petteri Teikari

2 TABLE OF CONTENTS Table of Contents Introduction Human visual system and light Human vision Photometric units and laws Luminous intensity (cd) Luminous flux (lm) Illuminance (lux) Luminance (cd/m 2 ) Luminous efficacy (lm/w) Lambert s law Radiometric units Radiant power (W) Radiance (W/ster/m 2 ) Irradiance (W/m 2 ) Radiant intensity (W/ster) Astronomic units Apparent magnitude (m) Absolute magnitude (M) Surface brightness (m/arcsec 2, S10vis) Light sources and lamp types Luminaire definitions Light pollution Astronomical light pollution Ecological light pollution Light pollution laws Australia Canada Chile Czech Republic European Union (EU) Finland Italy New Zealand Spain United Kingdom United States of America Light pollution measurement Digital photography (Hollan et al., 2004) Portable spectrophotometer (Cinzano, 2004) Night sky photometry with Sky Quality Meter (SQM, Unihedron)... 30

3 5 Light pollution modeling Model for artificial night sky illumination (Garstang, 1984) Software for classifying luminaires (Hollan, 2001) ILLUMINA (Aubé et al., 2005) RoadPollution software (Cinzano, 2005) Gauss Seidel (G S) iterative technique (Kerola, 2006) LPTRAN/LPDART Model (Cinzano, 2006) DIALux 4.3 (Upward Light Ratio Calculation) Ecological effects Plant physiology Phytochromes Cryptochromes Phototropins Photoreceptor FKF Conclusions Animal physiology Birds Reptiles Amphibians Fishes Invertebrates Human physiology Conclusions References...56

4 1 INTRODUCTION The use of artificial electric lighting has increased rapidly over the last hundred years both in daytime and nighttime use allowing humans to adapt to 24 hour active society. However, the increase in the use of exterior lighting during nighttime has produced undesirable side effects known as light pollution. The term light pollution has been in use for a number of years, but in most circumstances it has referred to the degradation of human views of the night sky (hiding stars). In addition to this, artificial night lighting can have adverse effects on wildlife as well as to humans. Light signal at wrong biological time can interfere with the normal behavior of both plants and animals. In this work, the basics of the concept of light pollution are reviewed. Chapter 2 focuses on the basic characteristics of human vision, photometric (visible light) and astronomic units, light sources and luminaires. This is followed by the further definition of light pollution in chapter 3 including the legislation trying to regulate the amount of exterior lighting. Chapter 4 and chapter 5 review briefly the measurement and modeling methods used with light pollution. Chapter 6 then reviews the physiological effects of artificial night lighting to plants, animals and humans. The main goal of this work is to give a comprehensive review of the different aspects related to light avoiding too detailed review. Introduction 4

5 2 HUMAN VISUAL SYSTEM AND LIGHT In this chapter human visual system is reviewed briefly for those parts that are relevant to this work. The used quantities used in photometry, illumination engineering and astronomy are reviewed briefly along with the typical light sources and luminaire types. The proper understanding of this work is not possible if the contents of this chapter are not understood at the basic level 2.1 Human vision The human eye can only see light in the visible spectrum and has different sensitivities to light of different wavelengths within the spectrum. Human eye consists of three types of photoreceptors: rods, cones, and intrinsically photosensitive retinal ganglion cells (iprgc) [1]. Rods and cones are responsible for the visual responses of light whereas iprgcs entrain human circadian rhythms to external light/dark cycle [2]. The rod system is specialized for vision at very low light levels, but with the expense of poor spatial resolution. When only rods are activated perception is called scotopic vision. With only rods active it is impossible to neither sense color differences nor make exact visual discriminations. The cone system has a very high spatial resolution, with color sensing abilities in the expense of poor light sensitivity. At about the level of starlight cones begin to contribute to vision and they become more and more dominant as light levels increase. At very high light levels such as in sunlight, only cones are active and rods are totally saturated [3]. This condition is called photopic vision. The area between scotopic and photopic vision is called mesopic vision, which is characterized by contribution of both rods and cones. The estimated upper limit of luminance for mesopic vision is 3 10 cd/m 2 [4]. Figure 2 shows an estimate of different visual function in logarithmic scale of luminance. Figure 1 shows the action spectra for human vision under different lighting conditions [5]. Figure 1. Spectral sensitivity functions of the eye. In photopic vision, when cones are active, the sensitivity follows the function V(λ) with a peak wavelength of 555nm. At very low light levels only rods are active, and spectral sensitivity follows V (λ) function with a peak wavelength of 505nm. The V mes (λ) is one example of the possible mesopic spectral sensitivity as there is not a consensus on it yet. The V 10 (λ) is the photopic spectral sensitivity for centrally fixated large target [5]. Figure 2. The range of luminance values over which the visual system operates. At the lowest levels of illumination, only rods are activated. Cones begin to contribute to perception at about the level of starlight and are the only receptors that function under relatively bright conditions [1]. Human visual system and light 5

6 The discovery of non image forming (NIF) photoreceptor was made by David M. Berson et al. [2] in The novel photoreceptor is abbreviated as iprgc (intrinsically photosensitive retinal ganglion cells), or as mrgc (melanopsin containing retinal ganglion cell, mrgc) due to the photopigment responsible for the noticed non image forming (NIF) effects. Melanopsin was first discovered by Ignacio Provencio and his colleagues [6,7], and is named by the cells in which it first was isolated: the dermal melanophores of frog skin. The two main differences of iprgcs compared to cones and rods, are that light depolarizes iprgc while the opposite happens with rods and cones; and iprgcs are far more sluggish compared to rod and cones, response latencies being as long as a minute. The peak wavelength of circadian responses is shifted towards the blue end of the spectrum compared to the traditional visual spectral sensitivities for photopic (V( ), max =555nm), mesopic ( max between photopic and scotopic peak wavelengths) and scotopic (V ( ), max =508nm) vision. According to current knowledge, the peak wavelength seems to be around 480 nm [8] for iprgcs. There is a model for melatonin suppression by Rea et al. [9] (Figure 3), which is a synthesis of an existing literature on melatonin suppression. The model suggests a peak wavelength of 460 nm for melatonin suppression based on older literature. The conventional view has been after the discovery of iprgcs that all non image forming (NIF) functions have the same action spectra as it for example have been found that short wavelength light (460 nm) is more effective in alertness promoting than light at 550nm [10 12], but a recent study by Revell et al. [13] revealed that light at 420 nm was more effective in alertnesspromoting than light at 470 nm. This would mean that the action spectrum presented for melatonin suppression [9,14,15] would not be accurate for alertness promotion. Relative response 1,250 1,000 0,750 0,500 0,250 0,000 Human visual action spectra V' NIF Wavelength [nm] Figure 3. Estimated action spectra for human non image forming (NIF) visual functions by Rea et al. [9]. The model is derived from the literature on melatonin suppression. It should be noted that the peak wavelength of 460 nm in the model seem to be incorrect as well as lightmediated alertness could have a peak wavelength closer to ultraviolet light (< 400nm). Photopic and scotopic action spectra from Stockman et al. [3]. Human visual system and light 6

7 2.2 Photometric units and laws Photometry is the measurement of the intensity of electromagnetic radiation in photometric units, like lumen/lux/etc, or magnitudes. The measurement is done with an instrument with a limited, and carefully calibrated, spectral response. Lux/lumens/etc uses the standard response curve for the eye, while astronomical photometry uses standard filters, with standard spectral response curves, e.g. UBVRI photometry [16,17] Luminous intensity (cd) In photometry, luminous intensity is a measure of the wavelength weighted power emitted by a light source in a particular direction, based on the photopic spectral sensitivity curve V( ), a standardized model of the sensitivity of the human eye. The SI unit of luminous intensity is the candela (cd), an SI base unit. One candela is defined as the luminous intensity of a monochromatic 540 THz light source that has a radiant intensity of 1/683 watts per steradian, or about mw/sr. The 540 THz frequency corresponds to a wavelength of about 555 nm, which is green light near the peak of the eye's response. Since there are about 12.6 steradians in a sphere, the total radiant intensity would be about mw, if the source emitted uniformly in all directions. A typical candle produces very roughly one candela of luminous intensity [18]. dφ I = (1) d ω Where, I = luminous intensity [cd] = luminous flux [lm] = solid angle of the radiated light [sr] Luminous flux (lm) In photometry, luminous flux or luminous power is the measure of the perceived power of light. It differs from radiant flux, the measure of the total power of light emitted, in that luminous flux is adjusted to represent the sensitivity of the human eye. The SI unit of luminous flux is the lumen (lm). One lumen is defined as the luminous flux of light produced by a light source that emits one candela of luminous intensity over a solid angle of one steradian. In other systems of units, luminous flux may have units of power. Luminous flux is often used as an objective measure of the useful power emitted by a light source, and is typically reported on the packaging for light bulbs [19]. Mathematically luminous flux can be calculated from radiant power in watts by weighing it with the V( ) function: 770nm Φ = K Φ V( λ) dλ (2) m 380nm e, λ Where, = luminous flux [lm] K m =, 683 lm/w e, = radiant power in watts [W] V( ) = spectral sensitivity curve for photopic vision (Figure 1), luminous efficacy function Human visual system and light 7

8 2.2.3 Illuminance (lux) Illuminance is a specification of the quantity of light falling on or illuminating a surface. The basic unit is the lux. A surface has an illuminance of 1 lux when it receives 1 lumen/m2 of surface area. Consider a small area on a piece of film that is 1 mm 2. For light with a wavelength of 540 nm, there are 3.8 x photons per second per lumen. An illuminance to the film of 1 lux would be equivalent to 3.8 x 10 2 photons per sec to a 1 mm 2 area. The total light exposure to a film is found by multiplying the illuminance, in lux, by the exposure time, in seconds, and is expressed in units of lux seconds [20]. Φ Lπ I = = = A ρ d E 2 Where, sr E = illuminance [lx] = luminous flux [lm] A = area of the surface [m 2 ] L = luminance [cd/m 2 ] = reflective factor of a surface [%] I = luminous intensity [cd] d = distance between the light source and the surface [m] (3) Luminance (cd/m 2 ) Luminance is the light quantity generally referred to as brightness. It describes the amount of light being emitted from the surface of the light source. The basic unit of luminance (brightness) in USA is the nit, which is equivalent to 1 candela per m 2 of source area. In Europe cd/m 2 is used as an unit for luminance. Another factor that determines luminance is the concentration of light in a given direction. This can be described in terms of a cone or solid angle that is measured in units of steradians (sr) [20]. Sometimes an unit stilb [sb] is used for luminance and one stilb is equivalent to 10,000 cd/m 2. Figure 4. Illustration of the quantities luminance and illuminance [20]. Iθ ρe L = = (4) Acos θ π Where, L = luminance [cd/m 2 ] I = luminous intensity to a direction from the surface normal [cd] A = area of the surface [m 2 ] = the angle between the surface normal and the specified direction = reflective factor of a surface [%] E = illuminance [lx] Human visual system and light 8

9 2.2.5 Luminous efficacy (lm/w) Luminous efficacy is a property of light sources, which indicates what portion of the emitted electromagnetic radiation is usable for human vision. It is the ratio of emitted luminous flux to radiant flux. Luminous efficacy is related to the overall efficiency of a light source for illumination, but the overall lighting efficiency also depends on how much of the input energy is converted into electromagnetic waves (whether visible or not). In SI, luminous efficacy has units of lumens per watt (lm/w). Photopic luminous efficacy has a maximum possible value of 683 lm/w, for the case of monochromatic light at a wavelength of 555 nm. Scotopic luminous efficacy reaches a maximum of 1700 lm/w for narrowband light of wavelength 507 nm [21] Lambert s law A Lambertian emitter is a light source which follows Lambert's law, which says that the surface brightness is independent of direction. The surface brightness can be expressed in candelas per projected square meter (Figure 5 [22], i.e. per square meter perpendicular to the direction of view). An illuminated perfect diffusor is one example of a Lambertian light source. A sphere which is a perfect diffusor, and which is illuminated only by one point light source at infinite distance, will (other things being equal) have a brightness exactly pi times smaller when "half" compared to when "full". Cloud covered Venus gets fairly close to this ideal. The Moon deviates a lot from it: the half Moon is only about 1/10 as bright at the full Moon [16]. The brightness of a flat Lambertian light source in candelas is: Iθ I max = LA = (5) cos θ Where, I max = maximum luminous intensity [cd] L = luminance [cd/m 2 ] A = area of a Lambertian surface I = luminous intensity to a direction from the surface normal [cd] = the angle between the surface normal and the specified direction 2.3 Radiometric units Figure 5. Distribution of luminous intensity (I) and luminance (L) with a Lambertian surface [22]. Radiometry is the measurement of optical radiation, which is electromagnetic radiation within the frequency range between and Hz. This range corresponds to wavelengths between 0.01 and 1000 micrometers ( m), and includes the regions commonly called the ultraviolet, the visible and the infrared. Two out of many typical units encountered are watts/m 2 and photons/sec steradian. The only real difference between radiometry and photometry is that radiometry includes the entire optical radiation spectrum, while photometry is limited to the visible spectrum as defined by the response of the eye [23]. Human visual system and light 9

10 2.3.1 Radiant power (W) Radiant power (radiant flux) is a SI derived unit. It is the derivative of energy with respect to time, dq/dt, and the unit is the watt (W). The recommended symbol for power is F (the uppercase Greek letter phi). An acceptable alternate is P. Power is used for non integrating detectors and continuous sources. Energy is the integral over time of power, and is used for integrating detectors and pulsed sources. Energy is an SI derived unit, measured in joules (J). The recommended symbol for energy is Q. An acceptable alternate is W [23] Radiance (W/ster/m 2 ) Radiance is a SI derived unit and is measured in W/sr/m 2. Radiance is power per unit projected area per unit solid angle. The symbol is L. Radiance is loosely related to the concept of brightness as associated with luminous bodies (as luminance in photometry). However, the use of brightness as a synonym for the photometric term luminance and for the radiometric term radiance should be avoided. For example, according to US Federal Standard 1037C [24], "brightness" should now be used only for nonquantitative references to physiological sensations and perceptions of light. Radiance is the derivative of power with respect to solid angle and projected area, and the integral of radiance over area and solid angle is power [23]: = df L da θ dω cos (6) Where, L = radiance [W/ster/m 2 ] F = power [W] = solid angle of the radiation [sr] A = area of a surface = the angle between the surface normal and the specified direction Radiance can also be defined in emitted photons from a particular area falling within a given solid angle in a specified direction. First we need to define the relationship between the energy of the photon and the frequency of the radiation (wave): hf hc E f = = = e λe Where, [ ev] E f = energy of a single photon [ev] h = Planck s constant, J s f = frequency of light or radiation e = charge of one electron, C, 1 C = 1 J/eV c = speed of light in a vacuum, m/s = wavelength of the radiation (7) From the equation it can be seen as the frequency of radiation increases, the energy of a photon of that radiation increases. This also means in practice that when comparing monochromatic blue and monochromatic red with the same radiant power, the blue light contains less photons than the red light with the same radiant power. Number of photons of per time unit (normally given per second) can be calculated using the following equation [25]: Human visual system and light 10

11 P N = t E f e Where, N = number of photons per time unit P = power of radiation [W] t = time [s] E f = energy of a single photon [ev] e = charge of one electron, C (8) The situation for photon emission for a Lambertian surface (emitting or reflecting) is illustrated in Figure 6. Figure 2 represents what an observer sees. The observer directly above the area element will be seeing the scene through an aperture of area da 0 and the area element da will subtend a (solid) angle of d 0. It can be assumed without loss of generality that the aperture happens to subtend solid angle d when "viewed" from the emitting area element. This normal observer will then be recording Id da photons per second and so will be measuring a radiance of I 0. The observer at angle to the normal will be seeing the scene through the same aperture of area da 0 and the area element da will subtend a (solid) angle of d 0 cos( ). This observer will be recording Icos( )d da photons per second, and so will be measuring a radiance of [26]: I Icos( θ)dωda = dω cos( θ)da IdΩdA = dω da 0 = Where, 2 [ photons/(s cm sr)] I 0 = radiance measured by the observer [photons/(s cm 2 sr)] I = radiance from the emitting area [photons/(s cm 2 sr)]? = the solid angle subtended by the aperture from the viewpoint of the emitting area element da = the area of the emitting Lambertian surface 0 = the solid angle subtended by the aperture from the viewpoint of the observer da 0 = the area of the observing aperture = the angle of the observer to the normal Irradiance (W/m 2 ) Figure 6. Observed intensity (photons/(s cm 2 sr)) for a normal and off normal observer; da 0 is the area of the observing aperture and d is the solid angle subtended by the aperture from the viewpoint of the emitting area element. Irradiance (flux density) is a SI derived unit and is measured in W/m 2. Irradiance is power per unit area (or photons/time/area) incident from all directions in a hemisphere onto a surface that coincides with the base of that hemisphere. A similar quantity is radiant exitance, which is power per unit area leaving a surface into a hemisphere whose base is that surface. The symbol for irradiance is E and the symbol for radiant exitance is M. Irradiance (or radiant exitance) is the derivative of power with respect to area, df/da. The integral of irradiance or radiant exitance over area is power. Irradiance is equivalent in radiometry to illuminance in photometry [23]. If a point source radiates light uniformly in Human visual system and light 11 (9)

12 all directions and there is no absorption, then the irradiance drops off in proportion to the distance from the object squared, since the total power is constant and it is spread over an area that increases with the square of the distance from the source. The distinction between energy flux (W/m 2 ) and photon flux (photons/time/area) is important in plant and animal physiology as many physiological responses depend on the spectral content of radiation. For example with photosynthesis, as photosynthesis is fundamentally driven by photon flux rather than energy flux, but not all absorbed photons yield equal amounts of photosynthesis [27] Radiant intensity (W/ster) Radiant intensity is another SI derived unit and is measured in W/sr. Intensity is power per unit solid angle. The symbol is I. Intensity is the derivative of power with respect to solid angle, df/dw. The integral of radiant intensity over solid angle is power [23]. It is distinct from intensity defined by irradiance or radiant exitance which measure radiation directed at or emitted from a given surface area. 2.4 Astronomic units The well known astronomic unit is magnitude scale, which has been calibrated using standard stars which (hopefully) do not vary in brightness. But how does the astronomical magnitude scale relate to other photometric units? Here we assume V magnitudes, unless otherwise noted, which are at least approximately convertible to lumens, candelas, and luxes: [16] 1 mv= 0 star outside Earth's atmosphere = lux = phot 1 mv= 0 star per sq degree outside Earth's atmosphere = cd/m 2 = stilb 1 mv= 0 star per sq degree inside clear unit airmass = cd/m 2 = stilb (1 clear unit airmass transmits 82% in the visual, i.e. it dims 0.2 magnitudes) One star, Mv=0 outside Earth's atmosphere = cd Apparent magnitude (m) The apparent magnitude (m) of a star, planet or other celestial body is a measure of its apparent brightness as seen by an observer on Earth. The brighter the object appears, the lower the numerical value of its magnitude. Apparent magnitude is thus an irradiance or illuminance, i.e. incident flux per unit area, from all directions. A star is a point light source, and the incident light is only from one direction [16]. The scale upon which magnitude is now measured has its origin in the Hellenistic ( Greek origin ) practice of dividing those stars visible to the naked eye into six magnitudes. The brightest stars were said to be of first magnitude (m = 1), while the faintest were of sixth magnitude (m = 6), the limit of human visual perception (without the aid of a telescope). Each grade of magnitude was considered to be twice the brightness of the following grade (a logarithmic scale). The modern system is no longer limited to 6 magnitudes or only to visible light. Very bright objects have negative magnitudes. For example, Sirius, the brightest star of the celestial sphere, has an apparent magnitude of The modern scale includes the Moon and the Sun; the full Moon has an apparent magnitude of 12.6 and the Sun has an apparent magnitude of The Hubble Space Telescope has located stars Human visual system and light 12

13 with magnitudes of 30 at visible wavelengths and the Keck telescopes have located similarly faint stars in the infrared [28] Absolute magnitude (M) In astronomy, absolute magnitude is the apparent magnitude, m, an object would have if it were at a standard luminosity distance away from us, in the absence of interstellar extinction. It allows the overall brightness of objects to be compared without regard to distance. Absolute magnitude is thus a total flux, expressed in e.g. candela, or lumens. The absolute magnitude uses the same convention as the visual magnitude, with a ~2.512 difference in brightness between step rates (because ). The Milky Way, for example, has an absolute magnitude of about So a quasar at an absolute magnitude of 25.5 is 100 times brighter than our galaxy. If this particular quasar and our galaxy could be seen side by side at the same distance, the quasar would be 5 magnitudes (or 100 times) brighter than our galaxy [16,29] Surface brightness (m/arcsec 2, S10vis) Apparent magnitude per square degree is a radiance, luminance, intensity, or "specific intensity". This is sometimes also called "surface brightness". Another unit for intensity is: 1 S10vis = the intensity (surface brightness) corresponding to one star of 10th (visual) magnitude per square degree of the sky [16]: 1 S10vis = cd/m 2 = stilb (inside clear unit airmass) Still another unit for intensity is magnitudes per square arcsec, which is the magnitude at which each square arcsec of the extended light source shines. Table 1. Comparison chart for magnitudes per square arcsec, S10vis, Nit and cd/m2 [16]. Magnitudes per square Nit = Candelas/m 2 arcsec S10vis inside unit airmass outside atmosphere Table 2. The table below gives approximate intensities (surface brightnesses) of some natural light sources [16]. Luminance Magnitudes per square Nit = cd/m 2 arcsec arcmin Sun Venus (max elong) Clear daytime sky (at horizon) Full Moon Mars at perihelion Overcast daytime sky (at horizon) Jupiter Human visual system and light 13

14 Saturn Heavy daytime overcast (at horizon) Uranus Neptune Sunset at horizon, overcast Clear sky 15 min after sunset (horizon) Clear sky 30 min after sunset (horizon) Fairly bright moonlight (at horizon) Moonless, clear night sky (at horizon) Moonless, overcast night sky (at horizon) Dark country sky between stars (zenith) Table 3. The table below gives approximate intensities (surface brightnesses) of some artificial light sources [16]. Luminance Magnitudes per square Nit = cd/m 2 arcsec arcmin Arc crater (plain carbon) Tungsten lamp filament High pressure mercury vapor lamp Sodium vapor lamp Acetylene burner Candle Light sources and lamp types There are many types of lamps used in outdoor lighting, a much greater variety than are familiar to most lighting users. Each type has applications where it is appropriate. Lighting designers must evaluate a variety of factors when choosing lamps, including available luminous outputs, output maintenance (how the lamp's output decreases with time), efficiency, capital costs, life cycle costs, color, size, lifetime, turn on characteristics, environmental factors such as hazardous materials and effects on wildlife, and availability of fixtures [30]. The most common lamp types (illustrated in Figure 7) used in outdoor lighting are reviewed shortly here in regard to their basic technical specifications. The special characteristics of different lamp types in regard to light pollution are discussed later. The less common or newer lighting technologies such as light emitting diodes Figure 7. Examples of different lamp types: a) traditional incandescent lamp, b) high pressure mercury vapor lamp, c) metal halide (MH) lamp, d) high pressure sodium (HPS) lamp, e) low pressure sodium (LPS) lamp [31]. (LEDs), induction lamps, and others, are not discussed here, though they may occasionally be seen in large projects such as bridge lighting. Incandescent lamps are the lamps most familiar to homeowners; they are commonly used for the majority of residential lighting, both indoor and outdoor. Light is produced by the Human visual system and light 14

15 passage of an electrical current through a tungsten wire in an evacuated or halogen filled glass or silica envelope. Advantages include low capital cost for lamps and luminaires, wide availability, wide variety of both lamp and fixture types, lack of a warm up period, and lack of hazardous wastes. Disadvantages include short lifetimes (most less than a few thousand hours), low efficiency (about 8 20 lumens/watt) with resultant high per lumen energy use and life cycle cost, attraction of insects, and high heat production. Generally the use of incandescent lamps should be avoided [30]. Fluorescent lamps are also seen in residential lighting, and they predominate in indoor retail and office uses, and are occasionally seen in outdoor area lighting, usually in smaller or older installations. Light is produced predominantly by fluorescent powders coated on the inside of the lamp that are activated by ultra violet radiation produced by an electrical arc through a low pressure (about 2/1000th atmospheric pressure) mixture of gases including mercury vapor. Advantages include low initial costs for lamps and fixtures compared with the lamp types below, low life cycle costs and high efficiency compared to incandescent (40 70 lumens/watt mean output), no warm up period, good color rendition, and long lifetimes (10,000 20,000 hrs). Disadvantages include higher initial costs compared to incandescent lamps, large lamp size, low efficiency (compared to lamp types below) and poor output maintenance, attraction of insects, and potentially hazardous mercury waste [30]. Major disadvantage of fluorescent lamps is their poor performance in cold climates such as in Scandinavian winter which limits their use in outdoor lighting. Mercury vapor lamps (sometimes called high pressure mercury, as distinguished from fluorescent) were the first widely used high intensity discharge (HID) lamps. Light is produced by the passage of an electric arc through a small tube filled with mercury vapor at high pressure (2 4 atmospheres). Though highly efficient and long lived compared to the incandescent lighting technology they displaced after the Second World War, they have many disadvantages compared to other lighting sources available today, including low luminous efficiency, poor color rendition, and high ultra violet output. Mercury vapor lamps have now been almost completely replaced in new applications by the more efficient metal halide and high pressure sodium lamps. One unusual characteristic of these lamps is that they seldom "burn out," instead fading to lower and lower outputs over years or even decades, though still consuming essentially the original amount of electrical power [30]. Metal halide lamps are HID lamps, similar to mercury vapor lamps but with the addition of small amounts of various metallic halides, such as scandium, sodium, dysprosium, holmium and thulium iodide. Light is produced, as in the mercury vapor lamp, by the passage of an electrical arc through a small tube filled with mercury vapor and metal halides at 2 4 times atmospheric pressure. The many different varieties of metal halide lamps give a wide variety of slightly different color characteristics, though generally they are white or blue white sources. The technology is still evolving, and new types are appearing regularly. Besides a relatively steep fall off in intensity with time (compared to high pressure sodium; see below), many metal halide lamps also change their color as they age. Metal halide lamps are very commonly used in commercial outdoor lighting where white light with good color rendition is required or simply desired, such as car dealer display lots, sports lighting, and service station canopies. Advantages include a wide variety of moderate to high luminous output lamps ( ,000 lumens mean output), high efficiency compared to incandescent and mercury vapor (45 90 lumens/watt mean), and good color rendition. Disadvantages include lower efficiency and output maintenance compared to high and low pressure sodium, shorter lamp lifetime compared to high Human visual system and light 15

16 pressure sodium, color changes, ultra violet output if not adequately filtered, and potentially hazardous mercury waste [30]. High pressure sodium lamps are currently the most widely used HID lamps for roadway and parking lot lighting, though in some areas metal halide is becoming more popular. Light is produced by passing an electric arc through a small tube filled with sodium vapor at about 1/4 atmospheric pressure, and a ballast and warm up of about 10 minutes are required. Advantages include a long lifetime, a wide variety of moderate to high luminous output lamps ( ,000 lumens mean output), high efficiency and good maintenance of luminous output compared to all lamp types except low pressure sodium, moderate color rendition compared to low pressure sodium, and wide availability and moderate cost of lamps and luminaires. Disadvantages include poorer color rendition than metal halide, fluorescent and incandescent, poorer output maintenance and efficiency than low pressure sodium, and potentially hazardous mercury waste [30]. Low pressure sodium lamps are widely used in parts of Europe and elsewhere, and in some American cities, particularly those near active astronomical research facilities and those especially concerned about energy issues and municipal electric bills. Light is produced by the passage of an electrical arc through a tube filled with sodium vapor at about 6 millionths of atmospheric pressure. A ballast is required and 7 15 minutes are needed to reach full output. The light produced by LPS lamps is nearly monochromatic at a wavelength near 589 nanometers. Though the eye is very sensitive to this wavelength (leading to the high efficiency of LPS), the eye cannot distinguish colors when LPS light is the only source available. Low pressure sodium lighting is favored where energy consumption and costs are a major concern and where color discrimination is either not needed or is supplied by other lighting. Advantages include the highest luminous efficiency and lowest energy use, low glare associated with the large lamps, good visibility and low scattering, minimal effects on insects and other wildlife, and lack of hazardous mercury wastes. Disadvantages include the lack of color rendition, shorter lamp lifetime and higher lamp replacement costs compared to HPS, and large lamp size in the higher output lamps [30]. "Neon" or "luminous tube" lighting is a term applied to a variety of small diameter glass tube sources, generally used for decorative purposes and signage. Light is produced by the passage of electrical current through the gas fill, producing light with a color or spectrum characteristic of the fill gas or gases and any phosphor coating within the tubing. Luminous outputs are not typically defined per lamp, but rather per foot or per meter, and depend principally on the fill gases and diameter/current rating, but also to some Incandescent Lamp Spectrum nm Mercury Vapor (MV) Lamp Spectrum nm Metal Halide (MH) Lamp Spectrum nm High Pressure Sodium (HPS) Lamp Spectrum nm Low Pressure Sodium (LPS) Lamp Spectrum mm Figure 8. Examples of the spectra of different light sources [30]. extent on the manufacturer and quality. Since luminous tube lighting is used for applications taking advantage of the color variety and shape flexibility inherent in the technology and not for area lighting, it is not meaningful to compare its advantages and disadvantages to the lighting sources above. But such lighting can account for large total outputs in some cases, particularly when used for architectural outlining, and it should not be overlooked in lighting codes [30]. Human visual system and light 16

17 Comparison of the spectral properties of the most common lamp types can be seen in Figure 8 and Figure 9 [31]. It should be noted that especially the spectra of fluorescent lighting (not shown in figures) and metal halide lamps can differ greatly depending on the mixture of different fluorescent materials. Figure 9. Examples of the spectral power distribution (SPD) of different lamp types: (a) high pressure mercury vapor lamp, (b) metal halide (MH) lamp, (c) high pressure sodium (HPS) lamp, (d) low pressure sodium (LPS) lamp [31]. 2.6 Luminaire definitions In addition to different light sources, there are several different types of luminaires with different technical characteristics [32]. The optics typically used in luminaires are designed to focus light on a specific area rather than radiation uniformly in all directions. Figure 10 [33] illustrates the coordinates used in the technical specifications of luminaires. Figure 10a shows the symbols used for different light angles as normally the light beams is not symmetric. The polar coordinate illustration (Figure 10b) gives the amount of candelas (cd) to a given direction. Figure 10. Illustration of the light distribution of a luminaire: a) the basic coordinate system b) [33]. The IES (Illuminating Engineering Society of North America) cutoff criteria (Figure 11) are often used to describe roughly the light distribution of a given luminaire. For these classifications, two relevant zones are defined with respect to the nadir of a luminaire (the nadir is defined as the angle that points directly downward, or 0, from the luminaire). One zone applies to angles at or above 80 above nadir, and the second zone covers all angles at or above 90 above nadir, or above the horizontal plane of the Figure 11. Illustration of the IES Cut off criteria luminaire. Light emitted in the 80 to 90 [54]. zone is more likely to contribute to glare, and light emitted above the horizontal is more likely to contribute to sky glow. Full cutoff is the recommended type of light distribution in outdoor luminaires. In full cutoff The luminous intensity (in candelas) at or above an angle of 90 above nadir is zero, and the luminous intensity (in candelas) at or above a vertical angle of 80 above nadir does not numerically exceed 10% of the luminous flux (in lumens) of the lamp or lamps in the luminaire. [34]. Human visual system and light 17

18 3 LIGHT POLLUTION Light pollution is an unwanted consequence of outdoor lighting and includes such effects as sky glow, light trespass, and glare. An illustration of both useful light and the components of light pollution are illustrated in Figure 12 [35]. Sky glow is a brightening of the sky caused by both natural and human made factors. The key factor of sky glow that contributes to light pollution is outdoor lighting. Light trespass is light being cast where it is not wanted or needed, such as light from a streetlight or a floodlight that illuminates a neighbor s bedroom at night making it difficult to sleep. Glare can be thought of as objectionable brightness. It can be disabling or discomforting. There are several kinds of glare, the worst of which is disability glare, because it causes a loss of visibility from stray light being scattered within the eye. Discomfort glare is the sensation of annoyance or even pain induced by overly bright sources. Figure 12. Light pollution is often caused by the way light is emitted from lighting equipment. Choosing power equipment and carefully mounting and aiming it can make a significant difference [35]. Light pollution can be roughly divided into astronomical light pollution and ecological light pollution. The latter refers to sky glow where stars and other celestial bodies are washed out by light that is either directed or reflected upward. Ecological light pollution then refers to artificial light that can disrupt interspecific interactions evolved in natural patterns of light and dark, with serious implications for community ecology (plants, animals and humans). In this chapter, the concept of light pollution is reviewed including the brief overview of existing legislation on light pollution. Light pollution is not simply an astronomical or ecological light pollution as with light pollution enormous amounts of energy are wasted. For example, at the end of 1990s the amount of sky glow was equivalent to 15 million kwh of energy over Sapporo, Japan; 29 million kwh over London, UK; and 38 million kwh over Paris, France [36]. Roughly estimated the amount used for public outdoor lighting in Helsinki, Finland is 170 million kwh [37] meaning that whole Helsinki could be illuminated with the waste light in Paris over 5 days. With the light sent upward is estimated to produce economical losses worth of billions of euros every year [38]. The wasted energy also means larger CO 2 emissions, and it has been estimated by Philips that by replacing old fashioned mercury vapor lamps with modern lighting technology could reduce the CO 2 emissions by 3.5 million tons every year. Economically this is equivalent to reduced annual costs of 700 million euros even though part of the savings would be spent on the actual replacement process [39]. Light pollution 18

19 3.1 Astronomical light pollution Astronomical light pollution is characterized mainly by sky glow and the lost ability to observe celestial objects due to bright night sky (illustrated in Figure 14 [40,44]). The natural component of sky glow has five sources: sunlight reflected off the moon and earth, faint air glow in the upper atmosphere (a permanent, low grade aurora), sunlight reflected off interplanetary dust (zodiacal light), starlight scattered in the atmosphere, and background light from faint, unresolved stars and nebulae (celestial objects or diffuse masses of interstellar dust and gas that appear as hazy smudges of light). Electric lighting also increases night sky brightness and is the human made source of sky glow. Light that is either emitted directly upward by luminaires or reflected from the ground is scattered by dust and gas molecules in the atmosphere, producing a luminous background. It has the effect of reducing one s ability to view the stars. Sky glow is highly variable depending on immediate weather conditions, quantity of dust and gas in the atmosphere, amount of light directed skyward, and the direction from which it is viewed. In poor weather conditions, more particles are present in the atmosphere to scatter the upwardbound light, so sky glow becomes a very visible effect of wasted light and wasted energy [35]. Draft graphics explaining where the artificial sky glow comes from can be seen in Figure 13 [41]. The numbers are valid for ``CIE sky No. 5'' type of scattering (indicatrix function, to be accurate), usual for a clear, but not extremely clear sky, and for ``zenith extinction'' of 0.3 mag. Figure 13. The relationship between light scattering and the angle of illumination, and the contribution to total sky glow [41]. Amateur astronomers usually judge their skies by noting the magnitude of the faintest star visible to the naked eye. However, naked eye limiting magnitude is a poor criterion. It depends too much on a person's visual acuity (sharpness of eyesight), as well as on the time and effort expended to see the faintest possible stars. One person's "5.5 magnitude sky" is another's "6.3 magnitude sky." One possible way for amateur astronomers to objectively estimate the brightness of night sky is to use The Bortle Dark Sky Scale [42], which is Light pollution 19

20 nine level scale based on the observation of celestial objects with specific surface brightness. When observing the night sky, professional astronomers often measure the dark portion of the sky with their astronomical equipment to have a background value they can use to compare their star signal against. Professional astronomers use an instrument called a photoelectric photometer to make these measurements. Typically such measurements are made at the zenith (in astronomical usage, zenith is the highest point in the sky, directly above the observation point). Other methods to measure sky brightness are discussed in the CIE technical report, Guidelines for Minimizing Sky Glow (CIE 1997) [43] and in separate chapter later. Figure 14. Distribution of artificial lights visible from space. Produced using cloud free portions of low light imaging data acquired by the US Air Force Defense Meteorological Satellite Program Operational Linescan System. Four types of lights are identified: (1) human settlements cities, towns, and villages (white), (2) fires defined as ephemeral lights on land (red), (3) gas flares (green), and (4) heavily lit fishing boats (blue). Image, data processing, and descriptive text by the National Oceanic and Atmospheric Administration s National Geophysical Data Center [40,44]. 3.2 Ecological light pollution Ecological light pollution refers to a type of light pollution that alters natural light regimes in terrestrial and aquatic ecosystems [44]. For example Verheijen (1985) [45] have proposed the term photopollution to mean artificial light having diverse effects on wildlife, but as this literally means light pollution more describing term like ecological light pollution is needed to describe the impact of light to ecosystems. There are several reviews of the potential ecologic affects of light pollution [46 48] of which the most current is the review of Longcore et al. [44], and the book of same Figure 15. Diagram of ecological and astronomical light pollution [44]. Light pollution 20

21 authors [49]. More detailed ecological problems caused by artificial or unnatural light are reviewed in Chapter 6. In contrast to astronomical light pollution, light does not have to be especially bright or pointed upwards (i.e. light does not have to contribute to sky glow) to disrupt ecosystems as illustrated in Figure 15. Sources of ecological light pollution include sky glow, lighted buildings and towers, streetlights, fishing boats, security lights, lights on vehicles, flares on offshore oil platforms, and even lights on undersea research vessels, all of which can disrupt ecosystems to varying degrees. The phenomenon therefore involves potential effects across a range of spatial and temporal scales. In a nutshell, effected animals can experience increased orientation or disorientation from additional illuminations and are attracted to or repulsed by glare, which affects foraging, reproduction, communication, and other critical behaviors [44]. Ecologists are also facing another problem when trying to measure the ecological effects of the polluting light which is the definition of disrupting light. As seen with the chapter on photometry, the illumination on a given surface is measured in luxes which is then a weighed radiation unit fitted for human vision. Because other organisms perceive light differently (e.g. green plants reflect the most the green part of spectrum to which is the human the most sensitive to) including the wavelengths not visible to humans future research on ecological light pollution should also involve the proper quantification of light exposure to different organisms [44]. Ideally, ecologists should measure illumination in photons per square meter per second with associated measurements of the wavelengths of light present. For example Gal et al. [50] have calculated the response curve of mysid shrimp to light and reported illumination in lux adjusted for the spectral sensitivity of the species. Another good example how the use of lux ignores biologically relevant information, is high pressure sodium (HPS) lamps. HPS lamps will attract moths because of the presence of ultraviolet wavelengths, while low pressure sodium (LPS) lamps of the same intensity, but not producing ultraviolet light, will not [51]. For this reason, the successful investigation of ecological light pollution will require collaboration with ecologists, physical scientists and engineers to improve the measurement methods of light characteristics at ecologically relevant levels. 3.3 Light pollution laws In this chapter some of the existing laws and regulations on light pollution are reviewed [52]. Currently the legislation on light pollutions is quite qualitative and rarely any detailed instructions are given Australia Australian standard AS [53] sets out guidelines for control of the obtrusive effects of outdoor lighting and gives recommended limits for the relevant lighting parameters to contain these effects within tolerable levels. As the obtrusive effects of outdoor lighting are best controlled by appropriate design, the guidance given is primarily applicable to new installations; however, some advice is also provided on remedial measures that may be taken for existing installations. The standard refers to the potential effects of lighting systems on nearby residents, users of adjacent roads and transport signaling systems, and on astronomical observations. The standard does not apply to road lighting; internally illuminated advertising signs; brightly lit surfaces (e.g. floodlit Light pollution 21

22 buildings and advertising signs); lighting systems installed for the purposes of television broadcasting; and lighting systems that are of a cyclic or flashing nature Canada The corporation of the town of Mississippi Mills has set a By law (no ) to regulate outdoor illumination and control light pollution to ensure responsible lighting, light pollution abatement and the conservation of the night sky environment [54]. The By law is fairly detailed in regard what type of light fixtures are allowed for different applications such as lights for: buildings and structures, including canopies and overhangs; recreational areas; parking lot lighting; landscape lighting; billboards and signs; public and private street lighting; display and service area lighting; public and private walkway lighting; rural barn lights; residential yard lights; and outdoor lighting for all residential, commercial, industrial, institutional and provincial and federal government uses not otherwise specified. The recommended lamp type for outdoor lighting is low pressure sodium (LPS) lamp and high pressure sodium lamp (HPS) is considered acceptable. The use of other high intensity Figure 16. Examples of acceptable and unacceptable light fixtures according to by Law no on lighting in the town of Mississippi Mills [54]. Light pollution 22

23 discharge (HID) lamps (metal halide, mercury vapor) is accepted if they are properly shielded. Incandescent and fluorescent lights are also acceptable if they are properly shielded whereas the use of quartz halogen lamps is not recommended. By Law states that all new municipal outdoor street lighting must be Full Cut Off Fixtures installed in accordance with IESNA standards. Some examples of acceptable lighting fixtures are given in Figure Chile According to the Ministry of Environment, Chile is the only country in the world (from 1998) with regulations in regard to emission limits (D.S. Nº 686/98 [55]) for light pollution. This advanced legislation is greatly due to the great number of astronomical observatories (e.g. Cerro Pachón, Cerro Tololo) in Chile [56]. The standard defines that a lamp with a luminous flux equal or less than lm cannot emit more than 0,8% of its nominal flux above horizontal level when installed to a luminaire. For lamps with a luminous flux more than lm should not emit more than 1,8% of their nominal flux above horizontal level when installed to a luminaire. The lamps meant for outdoor lighting should have their spectrum limited to the area of visible radiation (350 to 760 nm) and the luminous efficacy cannot be less than 80 lm/w (not allowing the use of mercury vapor lamps). Different emission limits are given for projector luminaires. For lamps with a luminous flux under lm cannot emit more than 5% of their nominal flux above horizontal levels, and lamps more powerful than lm are treated as normal lamps. Lamps meant for sports lighting should follow the limits given after 2 am and the lamps used for billboard lighting after 1 am. Laser projectors cannot be used pointing above horizontal level at all after 2 am. Standard also defines the conditions for laboratory measurements of the lamps Czech Republic The Czech law on Protection of the Air (signed Wednesday, February 27 and should be valid since June 1, 2002) includes light pollution prevention [38,57]. For the light pollution, the present draft of the regulations which should be issued by the government follows closely the Lombardy law, the 0cd/klm (i.e., FS, Fully Shielded) rule is a key part of it. Concrete measures in both light pollution and greenhouse emissions prevention are up to future implementing regulations demanded by the law. The law allows a fine from CZK 500 to (~ ) to be set by municipality upon a person, which violates at least one of the obligations set by the law. Obligation is defined as: During activities in places and areas set by the implementing regulation, everybody is obliged to obey the dispositions of the municipality and, in accord with that, take measures to prevent the occurrence of light pollution of the air European Union (EU) In European Union there is a standard EN 12464( 2) [58], that loosely sets guidelines for light pollution. This document, currently in draft format (April 2004), will lay down the lighting requirements for various outdoor workplaces ranging from power stations to railway yards in terms of lighting levels and uniformities. A further chapter on Obtrusive Light will highlight the CIE/ILE recommendations [59] for limiting light pollution with reference to one of four Environmental Zones as described in those documents. Light pollution 23

24 3.3.6 Finland The Finnish environmental protection law ( /86) [60] does not give very detailed regulations on light pollution. The law treats environmental pollution from human activity (chemicals, energy, noise, vibration, radiation, light, heat or smell) which can either individually or combined cause: a) health hazard, b) damage to the environment, c) restriction of the use of natural resources, d) decrease of general habitability or cultural values, e) decrease of environmental suitability for recreational use, f) damage to property or to its use, or g) other similar damage to public or private property Italy Regional laws against light pollution have been already enforced in 13 Italians regions (Lombardia 17/00, Emilia Romagna 113/03, Marche 10/02, Lazio 23/00, Campania 13/02, Veneto 22/97, Toscana 37/00, Piemonte 31/00, Valle d'aosta 17/98, Basilicata 41/00, Abruzzo 12/05, Umbria 20/05, Puglia 15/05) which cover more than two thirds of the Italian population and the main cities (Milano, Roma, Venezia, Firenze, Bologna, Napoli). In addition, three Italian technical standard rules refers directly or indirectly to light pollution (UNI10819, UNI10439, UNI9316) [61]. The laws enforced in Italy by different regions can be seen in Figure 17. Resume of the primary technical measures against light pollution looks the following [61]: Figure 17. Light pollution laws (Italy) [61]. 1) Provisions should be applied in the entire territory without ineffective subdivisions in protected areas or poorly defined zoning because light pollution propagates very far from sources. 2) Provisions need to be clearly applied to any NEW lighting installation, both public and private. 3) Light pollution due to reflection by lighted surfaces should be limited by forbidding over lighting and enforcing the use of flux reducers at the proper time or the shut off whenever possible. When a standard rule for safety exists, the average luminance or illuminance should not surpass the minimum value required for safety (e.g. road, walking and working areas). For other kinds of lighting a maximum luminance of 1 cd/m 2 should be permitted (e.g. building lighting). 4) Limitation of direct upward emission produced by fixtures in any direction above the horizon, should be obtained by using a parameter depending on the direction of the light and not on the integrated light flux. A good parameter is the light intensity per unit of flux emitted by the light installation, in cd/klm. The light emissions at small angles above the horizon (the first 45 degrees) should be limited very carefully because they are the most effective in producing the adverse affects of light pollution. 5) The direct upward light emission of fixtures should be limited to 0 cd per 1000 lumens of flux emitted by the fixture, in any direction above the horizon (gamma Light pollution 24

25 angle equal or greater than 90 degrees) for almost any kind of lighting installation. A tolerance of 0.49 cd/klm is allowed in practice, because the limit is given as an integer number and then the measurements can be approximated to the nearest integer. 6) Building and monuments should be lighted from top to bottom, with the same limits given above for the upward lighting emissions, except in cases of proved impossibility (in this case it should be permitted to light from bottom but the border of the light beams should remain inside the boundaries of the lighted surface). 7) Lighting installations for large areas should complain to the same limits above (point 5). 8) Only lamps with the larger efficiency available for the requested use should be used. They save energy and produce less light pollution outside the photopic band and inside the scotopic band. 9) Upward directed light beams, beacons and similar luminous calls should be prohibited, even because they distract car drivers and endanger the road safety. 10) Penalties for not compliant installations should be proportional to the number of fixtures. 11) The existing installations producing huge quantities of light pollution or belonging to the most polluting categories should be adapted. 12) The lighting design made by a professional lighting engineer should be mandatory for any lighting installation (except low power home installations with less than 5 fixtures). It should be completed with the photometries of fixtures in standard EULUMDAT format and a report demonstrating the numerical compliance with these rules. The following prescriptions could also be added, whose precious effects of rationalization have already been pointed out: 1) the yearly growth rate of the installed light flux for nighttime outdoor lighting, public and private, in any municipal district cannot exceed the 2%; 2) the yearly growth rate of the electric power consumptions for nighttime outdoor lighting, public and private, in any municipal district cannot exceed the 1,5%; 3) the fraction of downward flux emitted by the lighting installation outside the surface to be lit should be accurately minimized as much as possible. The limit on the yearly growth rate of the electric power consumptions for nighttime outdoor lighting has been recently enforced by law in some regions of Italy New Zealand The Golden Bay County Council has passed the following Appendix for Outdoor Lighting Code, as part of the Golden Bay District Scheme (New Zealand, November 1989): "The purpose of this Code is to ensure that outdoor lighting does not unreasonably interfere with the reasonable use and enjoyment of property within the district. It is the intent of this Code to encourage the types, kinds, construction, installation, and use of outdoor electrically powered illuminating devices, lighting practices and systems which will conserve energy, while preserving the natural environment and increasing nighttime safety, utility, security, and productivity." [62]. The general principle is similar to the other regulations on lighting. The lighting types are divided into two classes depending on the need of color rendition. The class where color Light pollution 25

26 rendition is unimportant can be operated anytime as long as they are shielded according to the requirements of the specific lamp type. Laser source light and strobe lights and similar high intensity light sources for advertising or entertainment shall not be projected above the horizontal plane. Searchlights used for advertising or entertainment purposes are not permitted. The permanent exemptions are for navigation, port, and airport lighting required for the safe operation of ships and airplanes; and for emergency lighting by police, fire, and rescue authorities Spain In Spain, there are regional laws for autonomic regions of Spain. In Canary Islands there is a Law 31/1988 of 31 October BOE num. 264 of 3 November [63] regulating light pollution, electromagnetic pollution mainly from radio transmitters, and atmospheric pollution as the law says that no industries, activities or services that may produce potential atmospheric pollutants may not be established above an altitude of 1500 m. on the Islands of Tenerife and La Palma. The law recommends the use of low pressure sodium lamps in outdoor lighting as they emit in a narrow band of the visible spectrum leaving the rest clean. The most harmful lamp in outdoor lighting for astronomy is the metal halide lamp that is considered as an incorrect choice for outdoor lighting. This is because of their high UV content, which is the most strongly dispersed by the atmosphere and are of no value for illumination.. The overview of the recommendations can be seen in Figure 18. In Catalonia, Law 6/2001 of 31 May (pg. 8682) [64,65] on the regulation of ambient lighting for the protection of night environment, regulates the light pollution. The intention of the law is to provide optimal conditions for nocturnal environment (animals, plants and Figure 18. Basic recommendations for lighting in Canary Islands in regard to light distribution, lighting angle and lamp type. HPS = high pressure sodium, LPS = low pressure sodium [63]. ecosystems in general), promote energy efficiency, minimize domestic light pollution, and to preserve the possibility to see the night sky. In regard to the law, a pilot program on the evaluation and reduction of light pollution in Catalonia took place as a collaboration with the Departament de Medi Ambient (Ministry of Environment in Catalonia), the Universitat de Barcelona and the Universitat Politècnica de Catalunya. The first stage of the pilot Program which took place between November 1999 and December 2000, was divided in two parts. The first one was directed to the study of the outdoor light fixtures: their characteristics and use as the source of the contamination. The second part goal was the measurement of sky brightness in reference locations. These measurements, besides establishing a comparison with the natural brightness, can as well be used as a reference respect to which the future variations will be able to be measured. Currently in Valencia, in Albufera Natural Reserve area [66] (5000 ha surface area) a project called Ecolight is taking place [67]. Its objective is to correct the light pollution problems caused by exterior public lighting. Light pollution 26

27 United Kingdom In Somerset County (UK), a local agenda 21 vision for Somerset ( ) [68], was drafted about how they would like the county to develop over the next 15 years. Its target in regard to light pollution was: a reduction from 1999 levels of noise and light pollution. The agenda did not give very detailed instructions how this could be achieved and only included the following phrases on light pollution: The local authorities should identify the worst examples of light pollution from domestic, commercial and highway sources. Those responsible should be contacted with advice, particularly over the potential energy wastage, and invited to take action to remove the cause. A public awareness raising campaign should also be mounted on noise and light pollution from domestic sources United States of America In United States of America various different regulations and laws exist as the regulation is being done on a state level. For those interested the different existing legislation can be found from the web site of Internal Dark Sky Association [69] listed by the state. Light pollution 27

28 4 LIGHT POLLUTION MEASUREMENT The measurement of light pollutions is briefly reviewed here using digital photography, spectrophotometer or a simple consumer priced measured device. The more detailed review of the used technologies is not within the scope of this work. 4.1 Digital photography (Hollan et al., 2004) The measurement of circadian effective luminance can be also done with non scientific cameras that offer raw format. Hollan [70] compared two commercial digital cameras (Fuji S5000 and Canon EOS D60) for the match of the sensitivity of blue pixels to the action spectrum of the non imaging forming (NIF) human visual system. The action spectrum used in the study was a compound graph (Figure 19) modeled from the results by Brainard et al. [71], Thapan et al. [72], and Hankins and Lucas [73]. Left wing of the curve was corrected with the les transmissivity curve taken from Stockman et al. [74]. The modeled formula consists of two parts, for violet (V) and green (G) wing separately. The wings match at the maximum sensitivity (in the energy domain, not a photon domain) at a wavelength of maxs nanometers, maxs = 460. For x = wavelength / 1 nm, Figure 19. Action spectrum of melatonin suppression by light after Brainard et al. [71], Thapan et al. [72], Hankins and Lucas [73], corrected for lens absorption after Stockman et al. [74]. Graph from Hollan [70]. actspv(x) = av ( x maxs) 2 + bv ( x maxs ) 3 (10) actspg(x) = ag ( x maxs) 2 + bg ( x maxs ) 3 (11) the constants are, av = 7.57e 5 bv = 5.59e 6 ag = 1.30e 4 bg = 3.06e 7 The examined cameras were calibrated using a solar spectrum. The images have been taken with the appropriate angular height of the Sun in the sky, so that its light went through 1,5 times the thickness of the atmosphere. A CD based cardboard spectroscope (with a lit from two razors) had been used, after a series of attempts. Solar spectrum has a lower intensity at a handful of wavelengths, so called spectral lines. After processing the images, the solar spectrum graph as recorded by the three types of camera pixels has been obtained. The results can be seen in Figure 20, with the comparison of CCD colors (Fuji S5000, Figure 20A) and CMOS colors (Canon EOS D60, Figure 20B) to the three sensitivity functions (photopic, scotopic, metabolic or circadian). Light pollution measurement 28

29 (A) (B) Figure 20. Comparison of the camera sensors to photopic, scotopic and proposed metabolic (circadian) spectral sensitivity function. (A) Fuji S5000 CCD sensitivity, and (B) Canon EOS D60 CMOS sensitivity [70]. From the two graphs, it can be seen that at least some CCD cameras can measure melatonin affecting light rather well according to the author [70]. All the needed software is available at for calibration of the camera. However, it is pointed out that it is not easy to use, but what is important that the effective amount of radiation affecting melatonin secretion can be documented for further use. It should be also noticed that the spectral sensitivity curve for circadian visual system and the blue CCD sensor differ significantly from the shape of the sensitivity curve proposed by Rea et al. [75]. This could be naturally corrected with specific optical filters placed in front of the lens. As the study by Hollan [70] was a part of scotobiology (the study of biology as affected by darkness [76]) research, the introduced method could be used to quantify the light pollution affecting human and animal physiology as this area is relatively unknown [77,78]. For example 5% of Czech population perceives unwanted artificial light from outdoors as one of the two main causes of their sleep problems [79]. 4.2 Portable spectrophotometer (Cinzano, 2004) Cinzano [80] presents a portable spectrophotometer for the measurement of light pollution. The basic design goals were: 1) spectral coverage of the visual wavelength range from 400 nm to 1000 nm; 2) lightness, compactness and portability; 3) large field of measurement for fast exposition times; 4) good equilibrium between spectral resolution and fast exposition time; 5) absolute calibration onsite; 6) reasonably quick set up on site with limited needs of time expensive adjustments; 7) possibility of automatic mapping of the entire sky with a series of spectra, with automatic registration of position, elevation, date, time, altazimuthal and equatorial celestial coordinates; 8) automatic data reduction; 9) low cost with easy available components and control software. The device provides maps of the night sky brightness in any photometrical band of the visible spectral range and in the light of main lamps. Figure 21. The WASBAM SSH spectrophotometer [80]. Light pollution measurement 29

30 4.3 Night sky photometry with Sky Quality Meter (SQM, Unihedron) Unihedron Sky Quality Meter (SQM) [81] is an affordable (price ~$120) portable meter for measuring sky brightness for astronomers (Figure 22). The meter uses a light to frequency (TAOS TSL237 [82]) converter covered with Hoya CM filter (filtering IR radiation) [83] as a light sensor. The meter has an effective solid angle of steradians [82] so it is not a spot meter as it accepts light from a wide cone (roughly 80 degrees diameter on the sky). It measures the sky brightness in magnitudes per square arc second. The term magnitudes per square arc second means that the brightness in magnitudes is spread out over a square arcsecond of the sky. If the SQM provides a reading of that would be like saying that a light of a 20th magnitude star brightness was spread over one square arcsecond of the sky. This can be further converted into luminance (candelas per square meter) using the following equation: [value in cd/m 2 ] = ( 0.4*[value in mag/arcsec2]) (12) Figure 23 shows the instruction how to measure sky brightness using the Sky Quality Meter. The SQM's readings are based on the assumption of "best transparency" of the sky, and if needed the reading of SQM could be corrected using for example Clear Sky Clock [84] or the data for the visibility from a local weather station. Other disadvantage of the meter is that it does not provide an external port for PC for automated measurements. The meter was tested and characterized by Pierantonio Cinzano [85] from Light Pollution Science and Technology Institute (ISTIL/LPLAB). The SQM was analyzed with synthetic photometry and laboratory measurements to find out the relationship between the SQM photometrical system and the main systems used in light pollution studies. Also the conversion factors to Johnson's B and V bands, CIE photopic and CIE scotopic responses for typical spectra were evaluated, as well as the spectral mismatch correction factors were given when specific filters were added. In conclusion it was found to be fine and interesting of the night sky and useful for quantifying the light pollution easily and accurately. Figure 22. Portable Unihedron Sky Quality Meter (SQM). Size 9.5 x 6.0 x 2.5 cm [81]. Figure 23. Instructions on the Sky Quality Meter. 1) Point the SQM directly above at the Zenith (the SQM sensor is on the same side as the display). 2) The SQM should be held at or above head level so that shadows or reflections from your body do not interfere with the reading. 3) Avoid using in areas that are shaded by trees or buildings. 4) After you press the button to take a reading, the SQM will beep each second while it is accumulating photons.[81]. Light pollution measurement 30

31 5 LIGHT POLLUTION MODELING Several models have been developed to estimate the amount of light pollution. The model proposed by Garstang et al. [86] in 1984 has been the basis of many models, incorporating the parameters regarding city size and particle density, which is why it has been reviewed here with the most detail. More developed models have been proposed recently but they have been reviewed only briefly as the detailed review of those models in not within the scope of this work. 5.1 Model for artificial night sky illumination (Garstang, 1984) Model proposed by Garstang et al. [86] is one of the first proper models taking account into the main physical features in predicting the brightness of the night sky. Prior to the model there had been numerous studies of light pollution over wider geographical areas [87 92] and some attempts to construct a model to explain observations [93 95]. The situation in the model is shown in Figure 24. The city is idealized as a circular area of uniform brightness with center C and radius R, the city lying in a horizontal plane. The observer is situated at O, at a height A above the plane of the city, and at a distance D from the center of the city measured in the plane of the city (BC). The city is assumed to be at a height H above the sea level. Real cities depart from this ideal due to exceptionally bright local areas such as shopping centers and streamers (highways with ribbon development). Population P and radius R are estimated using the data of an Atlas. Figure 24. Scattering of light by a city. Light from a small area at X is scattered at Q and received by the observer O. Q is at a height h above the plane of the city, is the azimuth of Q, and z is the zenith distance of observation. The observer receives light from a cone of semiangle around QO [86]. Authors initially assumed that artificial lighting produces an output of L lumens per head of the population, so that the total light output is LP lumens. Large cities being somewhat brighter than smaller cities (when corrected for population) due to large shopping centers, brightly lit sports facilities, etc., which are often not found in smaller cities. After several trials following equation was formulated: Light pollution modeling 31

32 P LP = L 0P 100, (13) Where, LP = total light output [lumens] L 0 = constant for light output P = population of a city The exponent 0.1 is quite uncertain and it can be excluded in most cases and the factor (P/100,000) 0.1 is a brightness enhancing factor. It is assumed that a fraction F of the light produced by the city is radiated directly into the sky at angles above the horizontal, and that the remainder (1 F) is radiated toward the ground. The fraction F is assumed to be radiated with an intensity proportional to 4, where is the zenith distance of an upbound light ray (XQ in Figure 24), and the constant of proportionality is determined by normalization. It is assumed also that of the fraction 1 F of light reaching the ground from artificial lights a fraction G is scattered upward with a Lambert distribution, the remaining factor 1 G being absorbed. The following equation can be written for I up total upward intensity in the direction in lumens sterad 1 : I up = LP 2 4 [ 2G( 1 F) cos ψ Fψ ] (14) Where, I up = total upward intensity in the direction in lumens sterad 1 LP = total light output [lumens] G = fraction of upward scattered light with a Lambert distribution F = fraction of the light produced by the city radiated directly into the sky = zenith distance of an upbound light ray (XQ in Figure 24) L can be replaced with L 0 (P/100,000) 0.1 if enhanced luminosity is wished to be used. The coefficients 2 and are introduced to give the correct normalization when I up is integrated over the upward hemisphere. According to Ketvirtis [96], reflectivity for worn asphalt ranges from 12% 14%, 16% 18% for dirty asphalt, 10% for new asphalt, and 25% for new concrete. As most light is reflected from streets and parking lots, value of 15% for G is adopted (G should be increased by about a factor of 4 if the ground were snow covered). The amount of particles in the atmosphere is also estimated in the original work by Garstang [86] for scatter prediction but is not reviewed here for the sake of clarity. Authors have chosen axes x and y in Figure 24 so that CB is the x axis. Light from an element of area dxdy at X(x,y) travels to Q, where it is scattered and some reaches the observer O. Double scattering between X and Q increases the number of photons reaching Q. Extinction takes place between X and Q, and between Q and O. The observer measures the luminous flux arising within a cone of semiangle around the direction QO. The lengths u, l, and d and the angles and are defined as shown in Figure 24. The azimuth of OQ measured from BC as zero is denoted by. Then the geometrical relationships are: Light pollution modeling 32

33 2 2 d = (x D) l = d + lcos θ = A 2 y 2 [ (x D)sin z cosβ] + ( ysin zsinβ) ( A cosz) (15) (16) (17) s = u + l 2ulcosθ (18) l = scosψ + u cosθ (19) h = u cos z + A (20) h = scosψ (21) For a given x, y, u, z, and these equations allow the calculation of d, l,, s,, h, and. The expression for the luminous flux, received at O by a telescope of area w from within the cone of semiangle, can be written: λ = N 1 I up (h) σ 2 dxdy s 2 πr R cos π ( EF) ( DS) XQ ( θ+φ) πδ + N 2 2 u 2 du (h) σ f a w 2 u ( θ+φ) + (EF) QO (22) Where, I up s 2 (dxdy/ R 2 ) = flux per unit area falling on the scattering volume 2 u 2 du at Q from the area dxdy of the city. w/u 2 = solid angle of the telescope as seen from Q (EF) XQ, (EF) QO = extinction factors (DS) = double scattering correction N 1 = molecular component of particle density N 2 = aerosol component of particle density f = scattering function Authors denote the sky brightness by b in lamberts. Then the brightness is b/ lumens cm 2 sterad 1. If a radiation surface of area 2 u 2 is imagined at Q, the received flux can be written as: λ = b πδ π u w 2 u = bδ w (23) Where, = luminous flux b = sky brightness = semiangle (Figure 24) Light pollution modeling 33

34 These equations can be combined and insert the expressions for N 1 (h) and N 2 (h) and introduce a parameter K measuring the ratio of aerosol N at ground level to molecular N at ground level. Parameter K and the basic equation of this model for b can be given as: N a σ a = 11.11KN m σ R exp( ch) (24) Where, N a = aerosol particle density at ground level a = cross section integrated over the whole solid angle K = measure of relative importance of aerosols and molecules for scattering light (indicator of the clarity of the atmosphere) N m = the sea level aerosol particle density (2.55 x cm 3 ) R = integrated cross section for Rayleigh scattering estimation (4.6 x cm 2 molecule at an assumed wavelength 5500 Å for visual observations [97]) c = constant X (0.104 km 1 [98]) H = height above the sea level dxdy 2 b = πn mσ R exp( ch) π du I s (EF) (EF) 2 up XQ R 0 cos2( θ + φ) exp( ch) exp( ah)11.11kf 16π Where, h = the height of point Q above the city (Figure 24) QO ( θ + φ) a = the reciprocal scale height for aerosols ( K) (DS) (25) 5.2 Software for classifying luminaires (Hollan, 2001) Hollan [99] has created a simple command line DOS program to classify luminaires using the EULumDat luminaire files provided by manufacturers. Given that current version of DIALux (reviewed in chapter 0) provides more practical information to aid lighting design, only the parameters for the program are reviewed here. Program ies2tab converts IES photometric data to a table to standard output, or to a line with summary data (including the cutoff category). EULumDat format works as well, conversion to IES one is possible. Its parameters are: a#: Albedo of the ground (default 0.10) c : write heading of Columns (just for an l option) dp : compute sky luminance increment in distance instead of the overall one (valid for the l option); di or la30 are synonyma e[{i m}[<name]] : EuLumDat format e as an input; ei makes an almost ies file too (default name *.ies) (almost: just due to letting >132 characters on a line) em as an output (default name *.ldt) f : assume the data giving the Full space angle of outcoming light h : Help i#: Indicatrix type (default 0, P.Cinzano (2000), 4..6 CIE types also possible) ic: Include Comment lines in the output table l : one Line output only la# : limiting angular height for computing the increment of sky luminance in distance, default 30 (degrees); this increment is then given for the l option m : compute candela multiplier (if it is erroneously set to 1) r : output angles in Radians (to ease polar plots by gnuplot) s[#:[<name>]] : write filenames of <= cutoff categories to <name> Light pollution modeling 34

35 default limit is 1 (0=FCO, 1=FS, 2=CIE CO, 4=IES CO, 5=CIE SCO...), default name is sc.lis t[y]# : tilt of the luminaire / 1 degree, around y axis (perp. to the road) tx# : its tilt around x axis (may be OK for long sloped roads) u[#:#:#:#] : compute illumination of a rectangle of xmin:xmax:ymin:ymax luminaire heights, zero being below the luminaire x axis going to 0 degrees and y to 90 degrees (default 0.50:1.50: 3.00:3.00 pole heights); z#: extinction of light in Zenith / 1 mag (default 0.30) [(C) Jan Hollan, N.Copernicus Observatory and Planetarium in Brno, 2001; subject to the GNU General Public License, source code available at ILLUMINA (Aubé et al., 2005) Aubé et al. [100] have provided a new method named ILLUMINA linking spectral measurements of artificial night sky glow and the predictions of a light pollution model. The model computes 1 st and 2 nd order molecular and aerosol scattering, as well as aerosol absorption onto a 3D grid. The model accounts for spatial heterogeneity in lighting angular geometry, in lighting spectral dependence, in ground spectral reflectance and in topography (including the computation of shadows). The basic idea is to stimulate the measurement of a given light pollution spectral detector pointed toward the sky in any position and orientation. Figure 25 gives a graphical representation of the used Aerosol Optical Density (AOD) methodology. Light pollution spectral measurement is done with the Spectrometer for Aerosol Night Detection (SAND) [101] which is a non imaging long slit diffraction grating based instrument. The measuring method focuses on the discrimination of some key spectral lines which are representative of specific kinds of lighting devices frequently used for street and commercial lighting applications (high pressure sodium, metal halide, low pressure sodium). With this instrument, it is relatively easy to separate total light pollution into its major contributing sources. Natural contribution to sky brightness (aurora, moonlight, stars, etc) is easily removed from the detected signal. This instrument was used recently for the 2005 Intensive Light Pollution Spectral Monitoring Experiment, in California Arizona Utah [102]. The model was designed to simulate light scattered back to spectrometer, so that the model does not allow the simulation of direct observation of the ground or any direct sight toward a lighting device (Figure 26). Only the contribution of artificial light to the night glow is implemented to the model excluding the contribution of celestial objects. The total spectral flux (W/nm) entering the simulated spectrometer is given by: Ωon Φ m = I noωno (26) Ω n FOV Figure 25. Graphical representation of the night time AOD measurement technique [100]. Light pollution modeling 35

36 Where, I no = light spectral intensity (W/ster/nm) scattered toward the spectrometer by a model cell crossed by the spectrometer line of sight; no = solid angle subtended by the spectrometer entrance as seen from scattering cell n (Figure 26b) on = solid angle subtended by cell n as seen from the spectrometer position o FOV = solid angle of the spectrometer field of view (FOV) The ratio on FOV gives the ratio of light coming from a given cell n which will in fact enter the instrument. In some cases, the spectrometer will see more ( on FOV > 1) than the cell and sometimes less ( on FOV < 1). The model takes the sum over n to integrate the light scattered along the spectrometer line of sight. It is assumed that I no may be mainly explained by the combination of the first order scattering (with and without reflection on the ground) and the second order scattering (again with and without reflection on the ground). Thus, it can be written the following for I no : I I + I + I + I no 1 r1 2 r 2 (27) Where, I 1 = the single scattered intensity I r1 = the first scattered intensity after reflection on the ground I 2 = the second order scattering intensity I r2 = the second order scattering intensity after reflection on the ground According to the authors [100], ILLUMINA modeling tool is a significant innovation compared to previous light pollution models created during the 1980s (mainly the model by Garstang [86]). One of the most important innovations relies on the implementation of the heterogeneous and complex nature of real environments e.g. in contrast to the model by Garstang [86] which assumed that angular light emission functions as long as ground reflectance values are homogenous. Future work of the authors will include the verification of the importance of near horizon light emissions, impact of snow cover to light pollution, the influence of realistic aerosol optical depth temporal variability on net light pollution variability, and an intercomparison with previous models to ensure the superiority of proposed model to previous simpler models. Figure 26. Modeling geometry and most important contribution to the received flux by a spectrometer in position o. An example MSR was ~40 km and an example MRR was 50 m in a sensitive study for a city with 4900 m radius done by the authors [100]. MSR = maximum scattering radius, MRR = maximum reflective radius. Light pollution modeling 36

37 5.4 RoadPollution software (Cinzano, 2005) RoadPollution [103] is software for the analysis of road lighting installations and for the evaluation of their environmental impact in terms of light pollution. The software is mainly intended for two lane roadways but it could be used for more complex roads by properly specifying the grid size and the observer position. It provides a detailed report including a large number of parameters (Figure 27) which allow to quantify the quality of the lighting design, its effectiveness in energy saving, its correspondence to the requirements for minimizing light pollution and its compliance to laws against light pollution. However, RoadPollution is not intended as lighting design software, even if it computes all typical parameters like average maintained luminance, horizontal, vertical and semicylindrical illuminances, uniformity, glare, luminance/illuminance distributions on the road and much more. Lighting designers can profitably use RoadPollution to check the quality of their design and to experiment how to improve energy saving and light pollution control. The report obtained with RoadPollution can be attached to the lighting plan. Figure 28 demonstrates some of the output parameters given by RoadPollution software. Figure 27. Overview of the RoadPollution software. The rightmost window shows the boxes where the input parameters should be written and the button to start the computation. The leftmost window shows the results as soon as the program compute it [103]. Light pollution modeling 37

38 Input installation data: lamp flux (klm) road width (m) 7.0 luminaire spacing (m) 22.0 luminaire overhang (m) 2.5 luminaire height (m) 7.0 luminaire tilt (deg) 0.0 Light Pollution, integrated parameters: reference out of road surfaces calculated for: lambertian reflectance with rho=0.135 in average direct upward flux ratio UFR % (Rn%): 2.20 road reflected upward flux ratio %: 6.39 (road reflected upward flux ratio for aged asphalt%: 6.24) out of road reflected upward flux ratio %: 5.95 increase of upflux ratio due to direct emission % 34 increase of upflux ratio due to out road emiss. % 93 direct unit uplight density DUUD (lm/m^2): 0.66 road unit uplight density RUUD (lm/m^2): 1.92 out of road unit uplight density WUUD (lm/m^2): 1.79 increase of uplight density due to direct emission %: 34 increase of uplight density due to out road emiss. %: 93 Light Pollution, emispheric and low angles scattering parameters direct scattered flux factor % 1.64 road scattered flux factor % 3.26 out of road scattered flux factor % 3.04 increase of scattered flux due to direct emiss. % 50 increase of scattered flux due to out road emiss.% 93 Figure 28. A part of the example output data given by the RoadPollution software in txt format [103]. 5.5 Gauss Seidel (G S) iterative technique (Kerola, 2006) The model by Kerola [104] uses a straightforward Gauss Seidel (G S) iterative technique [105] applied directly to the integrated form of Chandrasekhar's vectorized radiative transfer equation for the calculation of the downwardly and upwardly directed radiances of multiply scattered light from an offending metropolitan source. This model tries to improve the accuracy of previous models especially with hazy atmospheres. According to the authors, initial benchmark night sky brightness tests of the present G S model using fully consistent optical emission and extinction input parameters yield very encouraging results when compared with the double scattering treatment of Garstang, the only full fledged previously available model. 5.6 LPTRAN/LPDART Model (Cinzano, 2006) Cinzano [106] (2006) present up to date Extended Garstang Models (EGM), which provide a more general numerical solution for the radiative transfer problem applied to the propagation of light pollution in atmosphere. Cinzano also presents a LPTRAN software package which is an application of EGM to DMSP OLS radiance measurements and to digital elevation data providing an up to date method to predict the artificial brightness distribution of the night sky at any site in the World at any visible wavelength for a broad range of atmospheric situations and the artificial radiation density in atmosphere across the territory. Light pollution modeling 38

39 5.7 DIALux 4.3 (Upward Light Ratio Calculation) DIALux is a widely used light planning program for calculation and visualization of indoor and outdoor lighting systems. DIALux is complete and free software with the ability to import from and export to all CAD programs and photorealistic visualization with an integrated ray tracer. DIALux is manufacturer neutral and independent. [107]. The ULR (Upward Light Ratio) value is the percentage of luminaire flux of a luminaire or a lighting installation that is emitted above the horizontal, where all luminaires are considered in their real position in the installation. Sky glow limitations depend on the environmental zone of the lighting installation. The standard defines four environmental zone categories from E 1 to E 4. E 1 category is used for intrinsically dark landscapes like national parks or areas of outstanding natural beauty. E 4 category is used for high district brightness areas like city centers. Sky glow limitations reach from 0% to 25%. DIALux considers only luminaire flux that goes directly into the sky. Luminaire flux above the horizontal, that is both used for lighting of vertical structures such as facades, and is restricted to these structures, will not be considered. Figure 29. Luminous flux that is taken into account for the ULR value [107]. To minimize obtrusive light, EN not only gives limitations for ULR values but also for luminous intensity values in obtrusive directions and light trespass into windows. These limitations depend on the environmental zone category as well. Limitations for light trespass into windows are given in lux. Values can easily be calculated with calculation points and calculation surfaces. To calculate luminous intensity values in obtrusive directions DIALux offers Luminous Intensity Calculation Points. Such points can be placed just like any other calculation points. They consider all luminous intensities of all light emitting surfaces of all placed luminaires. So for a luminaire with two brackets two values are calculated. DIALux uses the luminaire s LDC in the installed position, the luminaire flux, the dimming level and the corrections factor, if applicable, for calculation. A Luminous Intensity Calculation Point can be placed for each potential obtrusive direction. Light pollution modeling 39

40 6 ECOLOGICAL EFFECTS Possible adverse ecological effects of artificial night lighting to plants, animals and humans are reviewed here. In general it can be seen that much more research is needed in every area to properly quantify the ecological effects of adverse night lighting but in most areas the groundwork has already been established. 6.1 Plant physiology Plants physiology is affected by biotic and abiotic signals from their environment. Biotic signals include attacks by insects and pathogens and grazing by larger herbivores. Abiotic signals include temperature changes, changes in water availability, nutrient limitation, osmotic stress, and changes in the light environment. The focus of this chapter is plant photoreceptors, which detect the light signals and thus affect the physiological responses of plants to light exposure. Although there is extensive literature on the effects of spectral light quality, quantity and duration on plant growth and development, its focus has been mainly to optimize the used artificial lighting for plant growth for example in greenhouses. Recently the main focus of such research has been the use of LEDs for optimized plant growth in greenhouses [ ] and space exploration [112]. However, no rigorous studies have examined the effects of artificial night lighting to plants except by the two studies by Cathey and Campbell [113,114]. Currently, research is badly needed in this neglected area of plant biology [49]. There are four photoreceptor families found in plant tissues: phytochromes, cryptochromes, phototropins, and the photoreceptor FKF1. These photoreceptors mediate the physiological and developmental responses in plants. Typically the studies on plant photoreceptors are done with the model plant Arabidopsis thaliana of which many mutants exist lacking specific photoreceptors. In this chapter, the different photoreceptors are not discussed at highly detailed level and those interested in more extensive information should consult the review articles for different families: Smith (1995, 2000) [115,116], Huq and Quail (2005) [117], Tu and Lagarias (2005) [118] for phytochromes; Batschauer (2005) [119] and Cashmore (2005) [120] for cryptochromes; Briggs and Christie (2002,2005) [121,122] for phototropins; Briggs and Huala (1999) [123] for both cryptochromes and phototropins; and Imaizumi et al. (2003) [124] for the photoreceptor FKF Phytochromes he phytochromes are signal transducing photoreceptors that convert between inactive and active forms in response to different wavelengths of light. This conversion is used to synchronize plant development to the exigencies of the light environment. The central hypothesis of phytochrome action, proposed almost 50 years ago from pioneering investigations by S. Hendricks, H. Borthwick and colleagues [125,126], is that the photoreceptors exist in two, photoconvertible forms, Pr and Pfr. Pr is biologically inactive and upon absorption of red photons is converted to Pfr, the active form. Pfr is converted back to Pr by far red photons. Biological action stems from Pfr [116]. Ecological effects 40

41 The striking characteristic of the phytochromes is their reversible photochromism the property of changing color on photon absorption and of reverting to the original form on the absorption of another photon. The absorption maximum of the phytochrome Pr form is close to that of the chlorophylls (red light), but the Pfr form absorbs at a longer wavelength (far red light) [116]. In effect, this means the phytochromes can be used as sensitive estimators of the spectral changes that happen within plant communities when daylight interacts with photosynthetic structures [127]. The absorption spectra for Pr and Pfr are presented in Figure 30. The absorption spectra of the phytochromes peak at about 665 nm and 730 nm. The absorption bands overlap, so radiation below about 700 nm activates photoconversion of both Pr and Pfr. Plants use the phytochromes as proximity sensors and modify their growth and development, constituting the shade avoidance syndrome [115]. Upon sensing a low red: far red ratio, a shade avoiding plant will exhibit enhanced elongation growth and, if the stratagem is successful, will project its leaves into regions of unattenuated daylight. Phytochromes also provide plants with temporal signals that entrain the phases of the biological clock, and others that ensure crucial developmental steps are initiated at appropriate points in the life cycle. Endogenous circadian rhythms synchronize development to the changing seasons, as exemplified in the photoperiodic control of flowering and dormancy. In these processes, the phytochromes do not work alone; the cryptochromes are often responsible for initiating germination and they have important roles in deetiolation [116]. Figure 30. The photoconversions involve a number of intermediate forms in both directions, and the establishment of an equilibrium between Pr and Pfr takes several minutes even at daylight irradiance levels. The absorption spectra of the phytochromes peak at about 665 nm and 730 nm. The absorption bands overlap, so radiation below about 700 nm activates photoconversion of both Pr and Pfr. Thus, in daylight for example, a photoequlibrium of about 60% Pfr/P (where P = total phytochrome) is established in canopy shade or crowded communities, the photoequilibrium can be as low as Pfr/P = 0.1. This is the basis of the shade avoidance syndrome [116] Cryptochromes In the past few years great progress has been made in identifying and characterizing plant photoreceptors active in the blue/uv A regions of the spectrum. Recent studies have shown that there is at least four different blue light activated signal transduction pathways in Arabidopsis and therefore presumably at least four different blue light photoreceptors [128]. These photoreceptors include cryptochrome 1 (cry1) and cryptochrome 2 (cry2) [123]. It seems that cryptochromes participate in bluelight induced suppression of stem elongation, Figure 31. Absorption spectrum of CRY1 protein expressed in baculovirus infected Sf9 insect cells [130]. Characteristics of absorption spectra are as in published plant cryptochrome spectra (Malhotra et al., 1995) [131]. Ecological effects 41

42 cry2 being more sensitive to lower intensities of light than cry1 [129]. Thus, the two cryptochromes are partly redundant in the growth suppression response but operate over different light intensities. Present studies [130,131] suggest that the two Arabidopsis cryptochromes (cry1 and cry2) share similar action spectra (Figure 31). However, the possibility remains that they may also respond differently to changes in wavelength [129]. Recently [132,133], a third cryptochrome, crydash (subsequently named cry3), have been found in several organisms including flies and humans in addition to Arabidopsis and cyanobacterium. However, the role of cry3 in plants is not yet known Phototropins As noticed already, blue ( nm) and ultraviolet A (UV A; nm) light elicit a variety of physiological responses in plants. Of these, there are four that maximize photosynthetic potential in weak light and prevent damage to the photosynthetic apparatus in excess light. These are phototropism [134] (growth or turgor driven movement of a plant organ toward or away from a light source), light induced opening of stomata (small pores in the leaf and stem epidermis that regulate gas exchange by opening or closing in response to various environmental stimuli) [135,136], chloroplast (organelles found in plant cells and eukaryotic algae that conduct photosynthesis) migration in response to changes in light intensity [137] and solar tracking by leaves of certain plant species [134]. The action spectra for phototropism [ ], stomatal opening [141,142], and the chloroplast accumulation and avoidance responses [143,144] are all similar (Figure 32). They show a band with one major and two minor absorption peaks in the blue region of the spectrum and a broad absorption band in the UV A. These spectral properties are characteristic of a flavoprotein photoreceptor. Figure 32. Stylized action spectrum typically observed for phototropin mediated responses. Notice the presence of a major peak at 450 nm, a shoulder at 425 nm and a minor peak at 470 nm in the blue region of the spectrum. This fine structure is not observed in the broad absorption band at 365 nm in the ultraviolet region of the spectrum [121]. Phototropins 1 (phot1) and 2 (phot2) [145] are the most recently characterized blue light receptors in plants, have spectral properties that closely match these action spectra (Figure 32). Both phot1 and phot2 mediate not only phototropism, after which they were named, but also blue light induced chloroplast migration [ ] and stomatal opening [149]. In addition, the rapid inhibition of stem growth [ ] by blue light is probably mediated by phot1 [154]. phot1 also plays a role in blue light mediated calcium uptake [155] and might have a minor role in blue light induced membrane depolarization [154]. Although significant progress has been made in understanding the early photochemical and biochemical events that follow phototropin excitation, the details of how this excitation activates such different responses (including the role of other photoreceptors) remain to be elucidated [121]. Ecological effects 42

43 6.1.4 Photoreceptor FKF1 After the publication of the complete DNA sequence of the model plant Arabisopsis thaliana used in photoreceptor studies, it became possible to search this database for proteins related to the known photoreceptors. There are now three proteins, FKF1, ZTL, and LKP2, each of which contains a single LOV (Light, Oxygen, or Voltage) domain, highly similar to the LOV domains in the phototropins and showing the same unique photochemistry. Otherwise, these proteins are entirely different from the phototropins [49]. The results by Imaizumi et al. (2003) [124] suggest that a crucial aspect of CO expression involved in day length discrimination may be generated by the circadian control of FKF1 expression and by the light dependent function of FKF1. In addition, authors had provided biochemical and genetic evidence showing that FKF1 functions as a photoperiodic photoreceptor. Furthermore, their findings suggest that FKF1, ZTL and LKP2 constitute a family of blue light photoreceptors in Arabidopsis, while there is a bigger uncertainty with ZTL and LKP2 than with FKF1. Both the ground state absorption spectra (Figure 33A) and the light induced difference spectra of FKF1 LOV domain (A) (B) matched that of the phot1 LOV2 domain (Figure 33B, red spectra), suggesting that they have similar chromophorebinding and light induced photochemistry [124]. In contrast to phototropin LOV domains, the FKF1 LOV domain showed no appreciable dark recovery (Figure 33B, black spectra). The absorption spectra of FKF1 had a maximum at 450nm with vibronic side bands and a smaller peak in the ultraviolet A region (Figure 33A). After light Figure 33. (A) Absorption spectra of FKF1 LOV, phot1 LOV2 and FKF1 LOV C91A. (B) Light minus dark difference spectra of FKF1 irradiation, there was a loss of LOV, phot1 LOV2 and FKF1 LOV C91A. These spectra show the absorption at about 450 nm and light induced absorbance changes (red spectra) and subsequent an increase in absorption at spectral properties in the dark (black spectra) for FKF1 LOV and phot1 LOV2. After a light flash, the difference spectra were taken around 390 nm, which is shown every 5 min for FKF1 or every 15 s for phot1 LOV2. The difference as a difference spectra in Figure spectra of FKF1 LOV C91A did not show any light induced 33B. absorbance changes. [124] Conclusions In conclusion, the photoreceptors allow the plant to measure and respond to four parameters of their light environment: light spectral quality, light intensity, light direction, and light duration. In many cases, two or more photoreceptors share partial functional redundancy, that is, they regulate the same developmental step or other response. That evolution has provided plants with this manifold redundancy underlines the importance of developmental transition from the dark growth pattern to the light growth pattern. Thus, a Ecological effects 43

44 mutation causing a loss of any one of these photoreceptors is not a fatal consequence because others are adequate to do the job [49]. Sometimes these photoreceptors act independently, sometimes redundantly, sometimes cooperatively, sometimes antagonistically, sometimes at the same stage of development. Some of these responses are incredibly sensitive (light levels that are barely perceived by the human eye), whereas others are activated only by high light intensities. Among the many processes affected by light are seed germination, stem elongation, leaf expansion, conversion from vegetative state to flowering state, flower development, fruit development, cessation of leaf production (bud dormancy), and leaf senescence and abscission. From the effects of light to plant physiology, the most important in regard to artificial night lighting, is the effect of light to photoperiodism. Changes in the far red/red light ratio would be most likely to cause problems since those are the wavelengths plants use for photoperiod perception [49]. There are roughly four different response categories to the duration of light exposure: plants failing to flower on long days but readily flowering on short days; plants flowering on long days but not on short days; intermediate plants that flower only when the day is neither too long nor too short; and day neutral that flower only when they reach a certain size independent of daylength which is typical of the largest number of species [49,156,157]. Additionally it has been demonstrated that a light pulse as short as one minute in the middle of a long night would prevent the cocklebur (Xanthium pensylvanicum) from flowering [158,159]. Opposite to this, Downs (1956) [160] demonstrated that a red light pulse in middle of a long night would induce a long day plant to flower. Thus both of these responses showed the red/far red reversibility diagnostic for phytochrome mediated responses (reviewed more extensively by Sage (1992) [161]). This phenomenon is often taken advantage by florists to extend the period of time over which they have flowering plants for sale. As noted already, the information how artificial lighting might affect photoperiodical and other physiological responses is almost completely lacking. In general, the potential ecological consequences of changes by abiotic factors (temperature, humidity, light) in flowering phenology in urbanized areas are not well understood or explicitly studied (see review by Neil et al. (2006) [162]). Cathey and Campbell (1975) [113,114] investigated the effects of five types of lights (illuminance about 10 lux) used for outdoor lighting (incandescent, high pressure sodium vapor, metal halide, fluorescent, and clear mercury vapor) to wide variety of different plants during a 16 hour night. Flowering was noticed to be delayed in some short day plants, vegetative growth was enhanced in several tree species, flowering was promoted in some long day plants, and some species did not show any measurable responses. The strength of response to the various types of light sources was, in decreasing order, incandescent, high pressure sodium vapor, metal halide, cool white fluorescent, and clear mercury vapor [113]. Their second article provides more extensive information on the species dependent differences in responses [114]. Without doubt artificial lighting affects plants, however the short term and long term consequence of such effects remain to elucidated, and further studies are needed badly in this area. Ecological effects 44

45 6.2 Animal physiology The adverse effects of artificial night lighting to animal physiology are reviewed in this chapter. It should be noted that when dealing with animals, their way to perceive to light (regulating both non visual and visual functions) can differ from significantly from humans way to perceive light. The lux measurement places more emphasis on wavelengths of light that the human eye detects best and less on those that humans perceive poorly. Because other organisms perceive light differently including wavelengths not visible to humans future research on ecological light pollution should identify these responses and measure light accordingly. Typically the research on the adverse effects of nocturnal lighting has focused on mammal physiology the circadian disruption (i.e. problems in maintaining daily rhythms of biological functions), but the research have been mainly done in laboratory conditions, and phase shifts in circadian activity have been defined in a way that can be measured only in laboratory [163].Only two studies [164,165] compared artificial light with daylight in terms of their effects on the circadian clock. Mammal physiology is not discussed in this chapter in very detail as the research is rather extensive in laboratory conditions, and the focus has been on the less known effects of light pollution. Artificial night lighting is about as effective as natural light in setting or disrupting the circadian clock, and it can shift the circadian clock by 1 2 hours [166]. It can also be argued what is the optimal study design in order to apply the results to real life situations [167,168], as well as the statistical methods used (equivalence testing [169,170], insignificance of significance testing [171]) Birds Many species of birds typically migrate at night, and it is well known that fires and artificial lights attract birds during migration, particularly when the sky is cloudy and the ceiling is low [172]. This attraction to lights has been used for example by villagers in Jatinga, India to capture and kill birds for food using searchlights [173]. In Africa, attraction to artificial lights has been used to enhance ecotourism [174]. However, the mechanism how birds are attracted to light at night is poorly understood [45]. It has been suggested that when a bird flies into lights at night it loses its visual cues to the horizon, and uses the artificial lights instead, resulting in spatial disorientation [175]. It has been noted also that immature migratory birds are more susceptible to disruption caused by artificial lights than adults [176]. The visual system of birds differ from the human visual system as birds have five different types of visual pigment and seven different types of photoreceptor: rods, double (uneven twin) cones, and four types of single cones [177] in contrast to the three cone system of humans. The extra cone type of birds is responsive to wavelengths in the ultraviolet range of the spectrum. In addition, bird eyes have oil droplets of different colors that narrow receptor sensitivities [178,179]. The spectral sensitivities of different oil droplets, cones and photopic vision are illustrated in Figure 34. It is likely that birds see the environment differently than humans, and it is difficult to speculate how artificial light affects migrating birds at night. In addition to the possibility that artificial lighting disturb the visual cues used by migratory birds, it has been demonstrated in the last decade that certain wavelengths of light appear to influence the magnetoreception of compass information by migratory birds [ ]. Three passerine bird species have shown normal orientation of migratory restlessness under Ecological effects 45

46 dim monochromatic light from the blue green range of the spectrum, whereas they were disoriented under yellow and red light [184]. However, it is not known how quickly red light affects the magnetic compass or whether birds are actually using the magnetic compass once a direction has been selected at the beginning of a migratory flight. Early detailed studies on light attraction of birds were conducted on the effects of lighthouses and lightships on migrating birds in the late 1800s [185]. The studies indicated that fixed white lights were more deadly than revolving or colored lights [186]. For example, when the light beam of the lighthouse at Long Point, Lake Erie, Ontario, Canada was made narrower and dimmer in 1989, a dramatic reduction in avian mortality occurred [187]. Mean annual bird kills dropped from 200 birds in spring and 393 in autumn to 18.5 birds in spring and 9.6 in autumn. However, these early observations were not consistent with studies by other others. For example, Munro [188] reported that flashing and rotating lights caused more mortality than fixed lights, and Lewis [189] reporting that flashing white lights causing the greatest mortality and fixed beacons and red lights attracting fewer birds. In a survey by Tufts [190], approximately half of the 45 lighthouses reporting some mortality had fixed lights and half had flashing lights. The confusing results are more likely due to the differences in lamp characteristics, such as the wavelength and intensity which were not reported in detail. In the early 1900s when gas and kerosene lanterns were replaced with electric lamps, collision mortality decreased [191,192], but with the increase of high illuminated manmade structures the mortality of birds attracted to high buildings have increased. In a report published by World Wildlife Fund Canada and the Fatal Light Awareness Program [193], it was estimated that collision of migrating birds to man made structures and windows is a world wide problem that results in the mortality of millions of birds each year in North America. Similarly gas flares on offshore oil and gas platforms and at oil refineries also pose a threat to migrating birds at night [194,195], and numerous reports of mass mortality have been reported [196,197]. Figure 34. Single cone spectral sensitivities calculated from microspectrophotometric data: (A) Absorptance spectra of single cone oil droplets in the blue tit (Parus caeruleus). T, C, Y and R refer to the transparent, colorless, yellow and red oil droplets that filter light incident upon the UVS, SWS, MWS and LWS cone visual pigments, respectively. (B) Calculated relative photon catches of each of he single cones. Visual pigment absorptance is multiplied by oil droplet transmittance (1 absorptance) and by the transmittance of the ocular media (cornea, aqueous humor, lens and vitreous humor. For display, photon catches have been normalized relative to the SWS cone. (C) Relative photopic spectral sensitivity. LWS, MWS, SWS and UVS/VS refer to the long, medium, short and extreme short wavelength sensitive cone visual pigments, respectively [177]. Ecological effects 46

47 Television and FM radio station towers have increased in height above ground level since they were first constructed in the late 1940s, and in the mid 1960s it was estimated that television towers in the United States killed more than a million birds per year [198]. Taller towers need more stabilizing guylines and warning lights for aircraft, which are held responsible for the deaths of hundreds of thousands of birds during nocturnal migration. However recent studies [199,200] indicate a decline in the number of tower fatalities over the last 20 years despite the increased heights. The specific roles of evolutionary adaptation, behavioral habituation, declining populations of migratory birds, changing weather conditions, and changes in tower lighting systems as possible explanations for such declines however are not yet known in detail [200,201]. Bird kills at tall lighted structures in the United States and at Dutch lighthouses show similar lunar periodicity [ ], most kills occurring around the new moon while almost none of the kills occur around full moon. In conclusion, the behavioral effects of artificial light to birds is poorly understood but it seems that same general principles can be applied to bird friendly lighting as to other outdoor lighting excluding the specific information on spectral dependency. Shielded streetlights should be used, and floodlights on the ground that point upward to illuminate buildings, bridges, and monuments should be avoided. If such lighting designs must be used, then they should be turned off during migration seasons when weather conditions (such as misty nights with a low overcast ceiling) could contribute to attraction and mortality. For example, The Fatal Light Awareness Program [193] has developed a Bird Friendly Building Program, aimed at building managers and owners, which has been effective in reducing bird mortality. Also, the recent evidence points out that by changing red warning lights to white strobes on broadcast towers may reduce the mortality of migrating birds [49,193]. However, this poses an additional problem to the people living next to those towers as people can find white flashing lights very disturbing. Like all fields related to the ecological effects of light pollution, the interconnection between birds and artificial light needs further research. In addition to the ecological consequences of artificial light to migrating birds, marine and grassland birds have been also investigates. In general ocean environments tend to have less artificial lighting than terrestrial environments, and much of the artificial lighting on the ocean occurs at intense source points possibly attracting marine birds from very large catchment areas [205,206]. The main sources of artificial light in marine environments include vessels, lighthouses, light induced fisheries, and oil and gas platforms. Many fisheries also use intense artificial lighting to attract, concentrate and facilitate prey capture [207]. It has been estimated that 63 89% of the world catch of squid is caught using light that can be mapped using satellite imagery [205]. Small vessels fishing squid often use a single light, whereas large vessel may use 150 lamps, with about 300 kw of electric power used for them [205]. Like migration birds, marine birds seem to be the most attracted to light during low cloud cover and overcast skies, especially foggy, drizzly conditions that are pervasive in many ocean regions [208]. Similarly to migration birds, the attraction to artificial light is significantly smaller on bright, clear night with a full moon [202,203,209]. Many nocturnal seabirds have a preponderance of rods in their retinas, more rhodopsin, and often larger eyes than related diurnal species [210], possibly making nocturnal seabirds more susceptible to the effects of artificial light. At least 21 species of procellariiform seabirds (large long winged bird with hooked bill and tubular nostrils that wanders the open seas, e.g. albatross) are known to be attracted to artificial lighting [211]. Vulnerability to Ecological effects 47

48 artificial light seems to be greatest among those birds that feed on bioluminescent prey, including even some of the largest of marine birds such as king penguins [212]. This area requires also further research to understand the mortality and ecological consequences of lighted structures at night to marine birds [213] Reptiles Reptiles are tetrapods (e.g. lizards) and amniotes (subgroup of tetrapod vertebrates), animals whose embryos are surrounded by an amniotic membrane, and members of the class Sauropsida. Artificial night lighting is a well documented cause of mortality among hatchling sea turtles, first described in detail by McFarlane in 1963 [214]. Since then several reviews have described the impact of artificial night lighting to sea turtles [215,216], and in this chapter only the key points of those reviews are discussed. Sea turtles normally nest on remote beaches in darkness. Artificial night lighting disrupts the normal behavior of sea turtle females searching for appropriate nest sites and of hatchlings attempting to orient toward the ocean (orientation behavior known as seafinding [217]). These adverse effects of lights on sea turtles in coastal environments have been traditionally tried to reduce by streetlight filters on existing or new lamps and nontraditional lights embedded in roadways instead of mounted on light poles. Turtles are strongly attracted to the shorter, violet to green wavelengths but are either indifferent or repelled by longer wavelengths depending on the species [217,218]. However, a study by Tuxbury (2001) revealed [218] that filtered lighting also attracted the turtles, and the attraction could be reversed by a stronger natural cue, a high silhouette namely resulting in seaward orientation. Also the response to identical silhouette differed in two different turtle species due to differences in spectral sensitivity of light. Another study by Nelson (2002) [219] showed that filtering a high pressure sodium (HPS) lamp does make its light less attractive to the turtles. They also showed that the attraction depends on the intensity of the light as well. In Boca Raton, Florida, USA, street lighting on poles was replaced by an embedded lighting by LEDs to the street surface along a 1 km section of coastal roadway (Figure 35) [220]. It was noticed in the experiment that the orientation was disrupted when the streetlights were turned on but not when the embedded lights were on or when both the streetlights and embedded lights were switched off. Additionally pedestrians, cyclists, and motorists all responded favorably to the lighting modification. As disruption of hatchling orientation is especially common at coastal roadway sites in Florida, a working group consisting of representatives from industry, state and federal government, and technical experts formulated a Coastal Roadway Lighting Manual to meet this problem [221]. Basically the manual involves three elements: keeping light off the beach by repositioning or shielding the light; reduce luminance by turning lights off, installing fewer lights, or lowering wattage; and minimize the disruptive wavelengths by using light filters or low pressure sodium luminaires. The manual also emphasizes the importance of incorporating new technology as it becomes available. In conclusion, the impacts of artificial night lighting to sea turtles are relatively well known compared to the Ecological effects 48 (A) (B) Figure 35. (A) Illustration of a Smartstud pavement marker. (B) Photo of the roadway after lighting system revisions [220].

49 other fields of ecological light pollution. However, the solution to the problems caused by artificial lighting does not seem to be that easy. For example in Florida, the near coastal approach involving the replacement of lamps will reduce the lighting directly visible from the beach but will not reduce inland sources that produce ever increasing sky glow. In addition to problems experienced by sea turtles, it has been estimated that reptile species (also known as herpetofauna) are disappearing at a rate that is at least comparable to that of amphibians [222], yet little is being paid attention to this. With reptiles, the term night light has been also used in different context which should not be confused with nocturnal light pollution. Night lighting is a common technique used to search at night for taxa that possess a reflective layer called the tapetum lucidum in their retinas, which causes light from searchers to be reflected, allowing target animals such as crocodiles to be located [223]. A light trap is one of the most common tools used by entomologists to sample nocturnal invertebrates, many of which are strongly attracted by artificial light over various wavelengths [224,225]. Many reptile species, primarily geckos, have taken advantage of this and some geckos are locally very common around houses [226]. There is also a single published report of a nocturnal snake, the African brown house snake, foraging under lights and capturing a gecko [227]. A survey done by Henderson et al. (2001) [228] on the responses of West Indian reptiles to human presence revealed that nine species of diurnal lizard (from surveyed 69 species) and one species of diurnal snake (from 18 surveyed species) extended their activity into the night near artificial lights. These results with a recent report on diurnal snake lying in ambush for diurnal lizards at night lights [229], suggest that artificial light may allow whole feeding webs to extend their activity times. Exposure to different artificial lighting regimes under laboratory conditions is commonly used to study behavior and physiology in (primarily diurnal) reptiles [230]. Such studies have shown that a lighting regime can affect, for example, the interaction between temperature and hormone levels [231] and response to externally administered hormones [232], like in humans as later seen. However, practically no research has been done to study the effects of artificial lights to free ranging individuals. The example of geckos show suggest that some species can take advantage of extended photoperiod possibly without negative effects, but the information is not there for the possible negative effects on reptiles [49]. Further research is especially needed to study the effects of diffuse illumination for reptiles in urban and suburban contexts, and to what extent do artificial lights increase the ability of introduced species to establish and become invasive. There has been a recent increased interest in urban ecology (e.g. Pickett et al [233]), and it can be hoped that ecological consequences of artificial night lighting would receive more attention also Amphibians Anuran amphibians (frogs and toads) are experiencing global declines in population size and diversity [234,235]. Although anecdotal reports on the effects of artificial lights are common in literature on frog natural history (e.g. Goin (1958) [236]; Long (1901) [237], Figure 36), there have been few direct experimental studies of the effects of artificial night lighting on anurans. As most foraging in frogs is visually mediated, artificial night lighting can have a significant impact on the behavior of frogs. The studied species of frogs maximize the capture of light necessary to form visual images at low illuminations by having large retinal surfaces with more photoreceptors and through spatial summation, with multiple photoreceptors simulating a single neuron, and/or temporal summation, with photoreceptors collecting multiple photons before stimulating a neuron [238].For example, Ecological effects 49

50 squirrel tree frogs (Hyla squirella) have excellent low illumination visual capabilities, some individuals attempting to capture prey using vision alone at illuminations as low as 10 5 lx [239]. Anurans are thought to have a color vision [240], although it is not known whether color vision functions at low nocturnal illuminations. Most frogs studied have trichromatic color vision [241,242] like in humans, and possibly tetrachromatic color vision with sensitivity in the ultraviolet wavelengths [243]. Frogs typically exhibit strong blue preference and Muntz (1962) [241] suggested that the preference of frogs to move toward blue light (less than 500 nm) is an adaptive response that causes semiaquatic frogs to jump toward the pond rather than toward the shore when they detect a predator. A few species tested by Hailman and Jaeger (1974) exhibited a U shaped spectral response curve (preferring light less than 475 nm and greater than 600 nm) [240], suggesting that frogs are more drawn (positive phototaxis) to violet or red light [244]. It also seems that the light intensity determines the spectral preferences of the frog [245]. Dark adapted frogs at low illuminations are more likely to be attracted to blue light and to light of longer wavelengths (yellow, orange, and red), whereas those same frogs are likely to be attracted to green and or violet wavelengths at slightly higher illuminations. Figure 36. Attraction of frogs to a candle set out on a small raft. Illustration by Charles Copeland of an experiment in northern Maine or Canada described by William J Long (1901) [237]. Twelve or fifteen bullfrogs (Rana catesbeiana) climbed on to the small raft before it flipped over [44]. It has been noticed that frogs tend to aggregate under streetlights, where they presumably capture insects attracted to lights [228,246]. If frogs consistently move toward permanent light sources, and away from natural habitats concentrating in areas around lights, this being a classic example of an evolutionary trap [247]. Also, the slight increases in illumination caused by nearby lights, bright distant lights, or sky glow may be sufficient to allow foraging by frogs at times when visually mediated foraging would not normally be possible. Artificial lighting also can alter the mate choice behavior as female Túngara frogs (Physalaemus pustulosus) were more likely to choose mates and be more discriminating of mates under darker conditions than under brighter conditions [248]. The possible reason for this behavior could have been the greater perceived threat to predation being more visible to visually oriented predators. Little is known about the possible disruptive effects of artificial lighting to frog circadian rhythms. Early study by Higginbotham (1939) [249] studied circadian rhythms in Bufo Americanus and Bufo fowleri and found wide variation in individual responses to illumination, whereas constant illumination was only minimally disruptive to normal activity patterns. Melatonin hormone has been implicated in the control of variety of processes in frogs [250], including color change, gonadal development, and reproduction [ ]. Even one minute of exposure to light during scotophase (the dark segment of a light dark cycle) can disrupt melatonin production, although the light intensity required for this is not quantitatively known [254]. However, this disruption in melatonin production is likely to have a variety of serious physiological consequences [250]. Ecological effects 50