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187 5. POTENTIAL FOR HUMAN EXPOSURE Releases from lead-based paints are frequently confined to the area in the immediate vicinity of painted surfaces, and deterioration or removal of the paint can result in high localized concentrations of lead in indoor air and on exposed surfaces. Sand-blasting procedures to remove paint may disperse lead in the local environment. The largest volume of organolead vapors released to the atmosphere results from industrial processes such as primary and secondary nonferrous metal smelting, and from the use of leaded gasoline which contains tetraethyl lead as an antiknock additive. These vapors are photoreactive, and their presence in local atmospheres is transitory. Halogenated lead compounds are also formed and ultimately oxides and carbonates (EPA 1985b). Tetraalkyl lead compounds have been found to contribute 5-10% of the total particulate lead present in the atmosphere. Organolead vapors are most likely to occur in occupational settings (e.g., gasoline transport and handling operations, gas stations, and parking garages) and high-traffic areas (Nielsen 1984). 5.2.2 Water Of the known aquatic releases of lead, the largest ones are from the steel and iron industries and lead production and processing operations (EPA 1982a). In 1988, aquatic releases of lead and lead compounds from TRI facilities totaled 240,014 pounds of lead and 209,468 pounds of lead were released or transferred to publicly owned treatment works (see Table 5-1) (TR188 1990). Urban runoff and atmospheric deposition are significant indirect sources of lead found in the aquatic environment. Lead reaching surface waters is sorbed to suspended solids and sediments (EPA 1982a). Although aquatic releases from industrial facilities are expected to be small, lead may be present in significant levels in drinking water. In areas receiving acid rain (e.g, northeastern United States) the acidity of drinking water may increase, thus increasing the corrosivity of the water, which may, in turn, result in the leaching of lead from water systems, particularly from older systems during the first flush of water through the pipes (McDonald 1985). In addition, the grounding of household electrical systems to the plumbing can increase corrosion rates and the subsequent leaching of lead from the lead solder used for copper pipes. Areas where the pH of the water is less than 8.0 may have higher lead drinking water levels as well (Lee et al. 1989). Lead has been detected in 23% of the surface water samples collected at the NPL hazardous waste sites included in the EPA's Contract Laboratory Program and in 48% of the groundwater samples at geometric mean concentrations in the positive samples of approximately 20 ug/L and 21 µg/L, respectively (CLPSD 1990). Note that the information used from the Contract Laboratory Program Statistical Database includes data from NPL sites only. 5.2.3 Soil Lead-containing solid wastes are produced primarily as a result of domestic ore production and ammunition use. Other sources include solder, weights and ballasts, bearing metals, and iron and steel production. These sources are concentrated primarily in landfills. For examples, lead has been detected in soil samples taken at an estimated 57% of the NPL hazardous waste sites included in EPA's Contract Laboratory Program Statistical Database at a geometric mean concentration of approximately 44 ppm for the positive samples (CLPSD 1990). Note that the information used from the Contract Laboratory Program Statistical Database includes data from NPL sites only.