Chemicals that can cause cancer and other adverse health effects such as harm to the human respiratory system are known as toxic substances. When these toxic substances are released in the air in the form of fine particles or gasses, they are called air toxics. Air toxics come from a variety of sources, including industrial and utility sources, smaller manufacturing and commercial sources, mobile sources (such as diesel trucks, cars and buses), construction equipment and residential activities (such as burning fireplaces for home heating or using gas-powered lawn equipment). People exposed to air toxics at higher concentrations and over time may have an increased chance of getting cancer or experiencing other adverse health effects. The District implements District, state and federal air toxics regulations, including the state AB 2588 Air Toxics “Hot Spots” Program.