Intensity is not the only Fundamental EMF Measure: the importance of modulation for production of low intensity biological effects, and other variables & conditions Carl F. Blackman, Ph.D. Former President (1990-1991) of The Bioelectromagnetics Society Raleigh, NC 27607 USA presented at the International EMF Conference - 2009 Stavanger, Norway 17 November 2009 Sponsored by Norges Miljovernforbund Opinions are my own and not necessarily those of my employer
EMF Chemical
Log 10 of P 1 mw/cm 2 = 10 W/m 2 Blackman et al., Bioelectromagnetics 10:115,1989 Power Density, mw/cm 2
Intensity - Calcium efflux; 16 Hz from Blackman et al. Rad Res. 92: 510-520, 1982.
EMF Chemical
Frequency @ 0.69 mgrms (69 nt) - calcium efflux Eggs incubated in 60-Hz fields normalized exp - sham from Blackman et al. Bioelectromagnetics 9:215, 1988
Frequency and magnetic-field strength combinations that influence calcium ion efflux from brain tissue in vitro P < 0.05 P > 0.05 fixed intensity Frequency, Hz fixed frequency Magnetic Field Strength, mg (rms)
Two major features of EMF exposure Intensity Frequency Non-linear responses Responsible mechanism - unknown Present Standards IGNORE these responses
EMF Chemical / response
120 100 Off resonance B dc = 20 mg %NO 80 60 40 On resonance B dc = 591 mg 20 100 200 300 400 500 B ac, mgrms 600 700
Relative orientation of AC and Static (DC) Magnetic Fields ~> Competing chemical pathways
EMF Chemical / response
EMF Chemical / response
Dedifferentiation - Chiabrera et al. amphibian RBC Micro-nuclei - Scarfi et al. WBC from Turner s Syndrome patients DNA synthesis - Takahashi et al. Chinese hamster V-79 cells
Influence of Frequency on DNA Synthesis Takahashi et al., Experientia 42: 185-6, 1986
Influence of Pulse Width on DNA synthesis Takahashi et al., Experientia 42: 185-6, 1986
Influence of Intensity on DNA Synthesis Takahashi et al., Experientia 42: 185-6, 1986
EMF Chemical / bioresponse
When temperature of chick brain is held constant during the 20 minutes of exposure Enhanced efflux only seen at 36 & 37 C, not at 35 or 38 C
EMF Chemical / bioresponse
Frequency and magnetic-field strength combinations that influence calcium ion efflux from brain tissue in vitro P < 0.05 P > 0.05 fixed intensity Frequency, Hz fixed frequency Magnetic Field Strength, mg (rms)
Yes, it is possible for avians
In Vitro results do NOT demonstrate health risks, however, results do demonstrate: Cautious when evaluate exposure scenarios ~> exact EMF exposure conditions are critical Physiological state of cells is very important ~> temperature; imprinting; genetics Can use in vitro findings to identify exposure parameters to examine in vivo ------------------------------------------ Do NOT treat EMF as a single chemical
mammals
The End Do NOT treat EMF as a single chemical Do more than just measure intensity
The End!
LGF B + E + - B LGF B E E LGF from Blackman et al. BEMS 11:159, 1990
DC = 20 mg DC = 366 mg from Blackman et al. FASEB J 9:547, 1995
Endpoint measurement analysis
Standard analyses - - Uses averages of exposed & control groups Marino demonstrated a new analysis - Few reports have noted changes in - Has potential to alter analytical approaches Conclusion -> there is much that remains to be explained in EMF biological effects research
Null result Significant from Blackman et al. BEMS 6:327, 1985
< 2 366 160 366 23 o 366 366 45 o 366 < 2
AC / DC Orientation Dependence NGF-stimulated PC-12 cells from Blackman et al., Biochem Biophys Res Commun 220: 807-811, 1996