Receptors outside a manufacturing facility could be exposed to the chemicals via inhalation from stack emissions or fugitive air emissions or from an accidental release after a fire or explosion. Because the chemicals would be dispersed in the ambient air, the exposure of nearby residents or exposure of other workers would be less than the plant workers. A conceptual model for a hypothetical photovoltaic installation on a commercial building would show that the primary receptors of concern are either the workers inside the building or nearby residents/workers. The most likely exposure route for both receptor groups is via inhalation, but only if a leak or fire occurs, both of which are unlikely. At a hypothetical photovoltaic installation on a residential dwelling, the most likely route of exposure is also via inhalation if a leak or fire occurs. At a hypothetical landfill containing spent photovoltaic modules, there are more possible pathways. For example, groundwater seepage could reach a drinking water well or river, but in both cases there would be dilution of the waste leachate before the water was used. Any vapor emissions would be diluted by the ambient air before reaching nearby residents. 4-1
Potential Health and Environmental Concerns Although the more likely route of exposure (inhalation) is similar in the different settings, the list of chemicals present is quite different for a manufacturing facility and a final PV module installation. As discussed in Section 3, manufacturing photovoltaic cells requires large quantities of chemicals such as solvents and acids for cleaning the semiconductor parts, gases for depositing the ultra-thin layers of material, and metals depending on the specific type of PV module being made. Many of these chemicals are highly toxic. The completed module, however, is a solid contained in glass or another sealed container. No solvents or acids are present inside the container, and the metals present would have to be leached out of the solid, broken into particles small enough to be respirable, or released into the air during a fire before there would be any likely route of exposure at a site with installed PV modules. Potential for Human Health Effects Relative Toxicity and Carcinogenicity of Photovoltaic Chemicals Human health effects of the chemicals used to manufacture photovoltaic devices can be divided into two categories: carcinogenic effects and noncarcinogenic effects. Noncarcinogenic effects include effects on specific organs, the reproductive system, the nervous system, or the immune system, as well as more subtle effects such as reduced growth or appetite. A chemical is considered noncarcinogenic if it has not been shown to promote cancerous tumor growth in either humans or animals. Carcinogenic chemicals are those chemicals that have been shown to promote cancerous tumor growth in humans, animals or both. Carcinogenic chemicals may also have other effects on human health.
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