|TOTAL all sources||220.88||159.67||74.16||22.89||14.77||7.68||7.05||5.49||4.98||4.17||3.81||3.92||4.05||3.93||4.08||4.14||4.06||4.20||4.23|
|Waste disposal and recycling||2.20||1.60||1.21||0.87||0.84||0.84||0.82||0.77||0.80||0.81||0.81||0.83||0.83||0.60||0.79||0.80||0.81||0.81||0.81|
a Industrial processes comprise chemical and allied product manufacturing, metals processing, and other industrial processes.
b Miscellaneous comprises other nonroad gasoline, engines and vehicles that could not be accurately allocated to specific source categories.
Total lead emissions decreased sharply from 1970 to 1995 as a result of regulatory actions. The lead content of leaded gasoline was reduced dramatically in 1985. In addition, unleaded gasoline was introduced in 1975 for use in automobiles equipped with catalytic control devices. By 1995, unleaded gasoline sales accounted for 99% of the gasoline market.
The EPA now treats lead as a hazardous air pollutant (HAP) and the HAPs emission inventory report is published every three years.
The methodologies used to estimate emissions constantly evolve and undergo major changes. Improved methods are often used to revise estimates for previous years. Therefore, some estimates in this table may not match estimates produced in previous reports, and some trends may not be consistent across years in which major changes in methodology have occurred.
Numbers may not add to totals due to rounding.
1970, 1975: U.S. Environmental Protection Agency, National Air Quality and Emissions Trends Report: 1999 (EPA-454/R-01-004) (Research Triangle Park, NC: March 2001), table A-2; available at Internet website http://www.epa.gov/oar/aqtrnd99/toc.html as of Sept. 5, 2001.
1980, 1985 and 1989-2000: Ibid, Current Emission Trends Summaries, available at internet website http://www.epa.gov/ttn/chief/trends/trends00/trends2000.pdf as of Oct. 17, 2002.
1986-87: Ibid, National Emission Trends source reports database; available at Internet website www.epa.gov/air/data/nettier.html as of Sept. 5, 2001.
1988: Ibid, National Air Pollutant Emission Trends: 1900-1998 (EPA-454/R-00-002) (Research Triangle Park, NC: March 2000), table A-2; available at Internet website http://www.epa.gov/ttn/chief/trends/trends98/browse.html as of Sept. 5, 2001.