Workplace safety of nanostructured nanomaterials Dr. Markus Pridöhl Coordinator Nanotechnology markus.pridoehl@degussa.com 2 nd VCI stakeholder dialog Apr 19 th 2007 www.degussa.com www.advanced-nano.com
Aggregation during gas phase synthesis Paticle formation Particle Growth Aggregation/agglomeration Precursor Product Energy
Formation of aggregates in the gas phase Aggregation
Formation of aggregates and agglomerates already in the reactor average primary particle size / nm 10 1 10 1 0 20 40 50 60 80 90 100 residence time / ms 100 primary particles number n / #
Nanomaterials Nanoparticles Aggregates Agglomerates Chemically bonded Van der Waals forces Size determines surface area Fused primary particles Adhering aggregates/ primary particles Half life time of isolated 20 nm particles above 1 mg/m³ < 3,8 s* * Preining (1998) The physical nature of very, very small particles and its impact on their behaviour. J. Aerosol Sci. 29, 481-495
Agglomerates Particles strongly interact due to Van-der-Waals forces The smaller the particles the stronger the interaction, the more energy is needed for disintegration
Disintegration needs high energy Agglomerated aggregates Aggregates Strong shear forces Re-Agglomeration No disintegration without strong shear forces Immediate re-agglomeration without stabilizing surfactants
Nanostructured powders as delivered consist of microscale agglomerates
Take home message Nanoparticles strongly tend to form microscale fine particles Well-tried exposure control measures for fine particles are therefore meaningful for nanoparticles as well
Manufactured Nanomaterial Tentative ISO definition delivered to OECD Material Nanomaterial (one or more external dimensions or an internal or surface structure on the nanoscale) Other Materials Nano-object (one or more external dimensions on the nanoscale) Nano-structured material (internal or surface structure on the nanoscale) Nanorod Nanoplate Nanoparticle Nanocomposite Nanocrystalline Agglomerate Aggregate Manufactured nanomaterials: Nanomaterials intentionally produced to have specific properties or specific composition. Nanomaterial: material which is either a nano-object or is nanostructured Nano-object: material confined in one, two or three dimensions at the nanoscale Nanostructured: having an internal or surface structure on the nanoscale Nanoscale: The size range between 1 nm and 100 nm. Note: Products containing nanomaterials (e.g., tires, electronic equipment, coated DVDs) are not nanomaterials.
Workplace Safety Basis for risk management Investigation of hazard Determination of exposure Risk = Hazard x Exposure Risk reduction measures
Workplace measurement program for ultrafine particles launched First experiences made during measurements in different carbon black plants of 3 companies Number Size Distribution, Mass Concentration, and Particle Composition of PM1, PM2.5 and PM10 in Bag Filling Areas of Carbon Black Production, Kuhlbusch, Neumann, Fissan, Journal of Occupational and Environmental Hygiene, Oct. 2004, 660-671. Degussa launched systematic measurement program in 2006 Measurements at different workplaces in 31Degussa sites worldwide Using same equipment and staff Expected duration about 3 years, depending on learning curve
Workplace exposure monitoring Since more than 20 years regular workplace exposure measurements take place at the Rheinfelden AEROSIL -plant : Result: on the long term average* - Inhalable dust < 2 mg/m³ (WEL Germany : 10 mg/m³) - Respirable dust < 0,5 mg/m³ (WEL Germany : 3 mg/m³) Determination of ultrafine particles (< 0,1 µm) at the workplaces of different carbon black plants** and current measurements in the AEROSIL plant Rheinfelden indicate at failure-free operation the number concentration of ultrafine particulates is comparable to the environmental atmosphere There are unexpected non-process related particle sources * During failure-free operation ** Number Size Distribution, Mass Concentration, and Particle Composition of PM1, PM2,5 and PM10 in Bag Filling Areas of Carbon Black Production, Kuhlbusch, Neumann, Fissan, Journal of Occupational and Environmental Hygiene, Oct. 2004, 660-671.
Measures for workplace safety Technical measures Organizational measures
Workplace safety Technical measures I O 2 H 2 S i C l 4 T e m p e r a t u r e 2 5 0 0 C 1 0 0 0 C H 2 O P r o d u c t S i C l 4 V a r io u s M e t a l H a lid e s : T i C l 4 A l C l 3 H C l A E R O S I L 9 0, 2 0 0, 3 0 0, e t c. T i t a n i u m D io x i d e P 2 5, P 9 0 A l u m i n u m O x id e A l u 6 5, A l u C Process Avoid release of dust by use of closed systems Process runs below atmospheric pressure Local suction Room air ventilation
Workplace Safety Technical measures II Minimization of exposed employees Use of automatic bagging equipments Bagging area
Workplace safety Organizational measures I Good workplace hygiene Individual protection equipment Training and instruction Personal hygiene (bathrooms) Skin care
Workplace safety Organizational measures II Cleanliness Minimize dust in workplace
Occupational medical survey at the Rheinfelden AEROSIL -plant Examination: every 3 years Content of examination: case history, medical talk physical examination, Lung Function test, blood examination, urinal test, eye and hearing test, ECG Since 33 years: regular occupational medical examinations at the Rheinfelden AEROSIL -plant Result: these examinations did not show any sign of a increased number of respiratory disease cases
Information and dialog with customers and creating employees essentials IARC (WHO) alters classification of TiO 2 Information of employees by medical doctors and toxicologists Brochure for employees and customers Adapted safety data sheet See www.degussa-nano.com
Summary Nanoparticles strongly tend to form microscale fine particles Well-tried exposure control measures for fine particles are therefore meaningful for nanoparticles as well Systematic workplace measurement program for nanoparticles launched First published workplace measurements in different carbon black plants and current measurements in the Degussa Aerosil plant Rheinfelden indicate that the number concentration of ultrafine particulates is comparable to the environmental background atmosphere
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