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183 <br /> 5. POTENTIAL FOR HUMAN EXPOSURE <br /> C now major contributors to total lead releases. Of the estimated 81 million pounds of lead or lead <br /> mpounds released or transferred from industrial facilities that were reported in the Toxics Release <br /> ;ventory (TRI) in 1988, over 48 million pounds were from primary metals facilities, almost 9 million <br /> unds were from electrical facilities, and over 8 million pounds were from chemical facilities (EPA 19891). <br /> N 1988, 30.8 million pounds of lead and lead compounds were released to the environment and 28.2 <br /> olion pounds were transferred off-site by the 1,467 facilities reporting to the 1988 TRI (see Table 5-1) <br /> 1RI88 1990). A TRI facility is any general manufacturing facility with 10 or more full-time employees <br /> hat produces, imports, or processes 75,000 or more pounds of any TRI chemical or that uses more than <br /> 10,000 pounds of a TRI chemical in a year. The data listed in TRI should be used with caution since only <br /> rtain types of facilities are required to report. This is not an exhaustive list. <br /> 3.2.1 Air <br /> 9f particular importance are emissions of lead to the atmosphere, which is the initial recipient for much <br /> If the lead released to the environment. Estimated atmospheric emissions of lead from anthropogenic <br /> int and nonpoint sources in the United States during 1989 were estimated to be 7.2x103 metric tonsPA 1991b). Mobile and stationary sources of lead, although found throughout the nation, tend to be <br /> ncentrated in areas of high population density and near smelters and nonferrous foundries. Natural <br /> :missions of lead to the atmosphere from volcanoes and windblown dust are believed to be of minor <br /> mportance (EPA 1986a). <br /> 9s indicated in Table 5-2, as of 1989, automotive emissions are no longer the largest source of lead <br /> :mitted to the atmosphere. More than 90% (mass basis) of automotive lead emissions from leaded <br /> gasoline are in the form of inorganic particulate matter (e.g., lead bromochloride [PbBrCI]) and <10%- <br /> mass basis) are in the form of organolead vapors (e.g., lead alkyls). The estimated lead emission from <br /> automobiles in 1984 was based on an average lead content of 0.44 g lead/gallon gasoline (EPA 1986a); <br /> however, as of January 1986, the allowable lead content of leaded gasoline dropped to 0.1 g lead/gallon <br /> ;EPA 1985g). There has been a 64% reduction in national lead emissions since 1985, primarily as a result <br /> of the increased use of unleaded gasoline in catalyst-equipped automobiles. Between January and June of <br /> 1990, the actual average lead concentration in leaded gasoline was 0.085 g lead/gallon, indicating <br /> ronsumption of approximately 230,000 kg lead for the production of 2.74 billion gallons of leaded gasoline. <br /> During the same 6-month period, 49 billion gallons of unleaded gasoline were produced in the United <br /> States (EPA 1990b). While EPA allows up to 0.05 g lead/gallon of unleaded gasoline (EPA 1982b), an <br /> toa]ysis of unleaded gasolines conducted in the winter of 1991-1992 indicated that regular grade unleaded <br /> Psoline contained, on average, less than 0.0003 g lead/gallon (MVMA 1992). <br /> Reduction trends for air emissions of lead have continued from the late 1970s through the 1980s for both <br /> Poitlt sources (from 2.9 ug/M3 in 1979 to 0.4 11g/M3 in 1988) and urban sites (from 0.8 µg/m3 in 1979 to <br /> 41 µ9/m3 in 1988) (EPA 1990a). The large decrease for point sources results from the use of emission <br /> Zntrols for both industrial processes as well as automotive controls, whereas the less dramatic decrease <br /> br urban sites is primarily the result of the decreased use.of leaded'gasoline. In June 1990, unleaded <br /> Psoline comprised 94% of all gasoline produced compared with 91% in July 1989 (EPA 1990b), indicating <br /> �t reductions in urban air lead concentrations should continue as the use of leaded gasoline is phased <br /> Of the 30.8 million pounds of lead and lead compounds released to the environment from TRI <br /> lities in 1988, 2.59 million pounds were air emissions (see Table 5-1) (TRI88 1990). <br /> �data are available on the amount of lead released to the environment from lead-based paints applied <br /> brcfree-standing structures. The amount of lead in paints sold for consumer use may not exceed 0.06%,. <br /> 3t<= <br /> ,x <br />