Exhaust from trucks, buses, trains, ships, and other equipment with diesel engines contains a mixture of gases and solid particles. These solid particles are known as diesel particulate matter (diesel PM). Diesel PM contains hundreds of different chemicals. Many of these are harmful to health. The highest levels of diesel PM are near ports, rail yards and freeways. People are exposed to diesel PM from breathing air containing diesel exhaust.
A complete description of the Diesel PM indicator can be found in the CalEnviroScreen 3.0 report.
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