Although long-term exposure to elemental cadmium, a carcinogen, can have detrimental effect on kidneys and bones, limited data exist on CdTe toxicology. However, CdTe is more stable and less soluble than elemental Cd and therefore is likely to be much less toxic. Although the Occupational Safety & Health Administration (OSHA) does not make this distinction, as a general rule, all facilities working with such compounds are encouraged to control the indoor concentrations of CdTe dust or fumes to below the Permissible Exposure Level-Time Weighted Average (PEL-TWA) Cd concentration of 0.005 mg/m3.
The U.S. CdTe PV industry is vigilant in preventing health risks and has established proactive programs in industrial hygiene and environmental control. Workers' exposure to cadmium compounds in PV manufacturing facilities is controlled by rigorous industrial hygiene practices and is continuously monitored by medical tests, thus minimizing health risks.References
Fthenakis, V.; Morris, S.; Moskowitz, P.; Morgan, D. (1999). "Toxicity of cadmium telluride, copper indium diselenide, and copper gallium diselenide." Progress in Photovoltaics, 7, pp. 489-497.
Bohland, J.; Smigielski, K. (September 2000). First Solar's CdTe module manufacturing experience: environmental, health, and safety results. Proceedings of the 28th IEEE Photovoltaic Specialists Conference, Anchorage, AK.
The flame temperature in typical U.S. residential fires is not high enough to vaporize CdTe. Flame temperatures in roof fires range from 800o-900o C, aand flame temperatures in basement rooms range from 900o-1000o C.1 The melting point of CdTe is 1041oC, and evaporation starts at 1050oC. Sublimation occurs at lower temperatures, but the vapor pressure of CdTe at 800oC is only 2.5 torr (0.003 atm). The melting point of CdS is 1750oC, and its vapor pressure due to sublimation at 800oC is only 0.1 torr. Preliminary studies at Brookhaven National Laboratory2 and at the GSF Institute of Chemical Ecology in Germany3 showed that CdTe releases are unlikely to occur during residential fires or during accidental breakage.4 The thin layers of CdTe and CdS are sandwiched between the glass plates, and at typical flame temperatures (800o-1000oC), these compounds would be encapsulated inside the molten glass, so any Cd vapor emissions are unlikely.
References
1. Drysdale, D. (1985). An Introduction to Fire Dynamics, pp. 329-330, Wiley, NY.
2. Moskowitz, P; Fthenakis, V. (1990). Toxic materials released from photovoltaic modules during fires; health risks, Solar Cells, 29, pp. 63-71.
3. Thumm, W.; Finke, A.; Nuemeier, B.; Beck, B.; Kettrup, A.; Steinberger, H.; Moskowitz, P. (1994). "Environmental and health aspects of CIS-module production, use, and disposal." Presented at the First World Conference on Photovoltaic Energy Conversion, Waikoloa, Hawaii, 5-9 December 1994.
4. Steinberger, H. (1997). HSE for CdTe and CIS thin film module operation, IEA expert workshop "Environmental aspects of PV power systems," May 23, 1997, Report No. 97072, Niewlaar E. and Alsema E. (ed.), Utrecht University, The Netherlands.
5. Patterson, M.; Turner, A.; Sadeghi, M.; Marshall, R. (1994). "HSE aspects of the production and use of CdTe thin film modules." Presented at the 12th European PV Solar Energy Conference, Amsterdam.
References
Bohland, J.; Dapkus, T.; Kamm, K.; Smigielski, K. (1998). "Photovoltaics as hazardous materials: the recycling solution." Proceedings of the 2nd IEEE World Photovoltaic Specialists Conference, pp. 716-719.
Fthenakis V. (2002). "" Aug. 2002, Brookhaven National Laboratory, Upton, NY 11973.
Fthenakis, V.; Eberspacher, C.; Moskowitz, P. (1996). "Recycling strategies to enhance the commercial viability of photovoltaics." Progress in Photovoltaics, 4, pp. 447-456. Fthenakis, V.; Gonsiorawski, R. (1999). Lead-free solder technology from ASE Americas, Workshop Report BNL-67536, Oct. 19, 1999, Brookhaven National Laboratory, Upton, NY 11973.
Steinberger, H. (1997). HSE for CdTe and CIS thin film module operation, IEA expert workshop. "Environmental aspects of PV power systems." May 23, 1997, Report No. 97072, Niewlaar E. and Alsema E. (ed.), Utrecht University, The Netherlands.
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