Potential Health and Environmental Concerns Accidental fires on rooftops or combustion of spent modules in a municipal solid waste incinerator could theoretically release fumes or vapors into the atmosphere. The inhalation of these fumes or vapors by nearby populations could affect human health. The nearby populations are of primary concern because the concentrations of chemicals in the air decline rapidly as distance from the source increases (Moskowitz, 1995). The types of chemicals released by a fire vary depending upon the type of photovoltaic module installed. As discussed in Section 3, incineration of spent modules is not a likely disposal method, compared to eventual recycling. A study conducted by Moskowitz and Fthenakis in 1990 focused on materials released during the combustion of CIS, CdTe, and GaAs modules. GaAs modules are produced only for space applications. CdTe is nonflammable and does not melt until temperatures are over 1000°C (Zweibel, et al., 1998). The study concluded that the overall risk to public health from a fire involving photovoltaic modules would be highest for commercial buildings and would be very small for residential buildings. This conclusion was based on the fact that there could be higher concentrations of chemicals released by a fire due to the larger quantity of photovoltaic modules on a commercial building. The study also found that fires involving photovoltaic modules are typically short-term events. Due to the fact that these fires are short-term in nature, the authors concluded that alerting all residents within about 1 – 2 km of a fire to remain in their homes and to close all their windows should protect public health (Moskowitz and Fthenakis, 1990). Potential for Hazards at Landfills with PV Modules Disposal of large quantities of modules in a single landfill could lead to increased potential risks to humans and biota. The leaching of chemicals from these landfilled modules has the potential to contaminate local ground and surface water. As discussed previously, cadmium exceeded EPA TCLP criterion in leaching tests involving early CdTe modules, and mercury exceeded TCLP criterion in leaching tests conducted on both CdTe and CIS modules (Table 4-5). However, newer CdTe cells did not exceed the cadmium criteria, and the source of the mercury is in question as it is not a component used in cell manufacturing. At present CdTe modules represent only about 0.4 percent of the PV modules being used worldwide, and CIS modules are about smaller percentage (0.2 percent) (Goetzberger et al., 2003). The standard leaching tests are intended to be conservative, and overestimate the potential for release of metals from the enclosed solid PV modules. Because of the relatively long life of PV modules and the fact that the photovoltaic industry is comparatively new, no relevant leachate data from landfills were available.