Lead is a metal found naturally in the environment as well as in manufactured products. The major sources of lead emissions have historically been from
fuels in motor vehicles (such as cars and trucks) and industrial sources. Emissions from on-road vehicles decreased 99% between 1970 and 1995 due primarily
to the use of unleaded gasoline. Use of leaded gasoline in highway vehicles was prohibited on December 31, 1995. Due to the phase out of leaded gasoline,
ore and metals processing is the major source of lead emissions to the air today.
The highest levels of lead in air are generally found near lead smelters. Other stationary sources are waste incinerators, utilities, and lead-acid battery
manufacturers. Combustion and smelting processes operate at high temperatures and emit submicron particulate matter lead. Material handling and mechanical
operations emit larger particles of lead.