A diesel exhaust particle is a respirable particle produced during the compression ignition of diesel fuel. Diesel particles are composed of elemental and organic carbon compounds as well as trace amount of other elements with toxic properties including transition metals. Diesel exhaust is a complex mixture of combustion products of diesel fuel. The exact composition depends on the type of engine, the speed and load at which it is run, and the composition of the fuel used. In 2000 the US government classified diesel exhaust particulates as “reasonably anticipated to be a human carcinogen” – an agent that causes cancer. There are findings now available of elevated lung cancer rates in occupational groups exposed to diesel exhaust. These groups include railroad workers, mine workers, bus garage workers, and trucking company workers.