Portland's air currently meets all federal air quality health standards. These standards exist for six pollutants known as the criteria pollutants (carbon monoxide, ozone, particulate matter (PM2.5 and PM10), nitrogen oxides, sulfur oxides and lead. The criteria pollutants of most concern in Portland are ozone and fine particulate matter.
In recent years air toxics have taken center stage as pollutants of concern throughout the Portland region. Air toxics are generally defined as air pollutants known or suspected to cause cancer or other serious health problems. Air toxics include diesel soot, benzene, polycyclic aromatic hydrocarbons (tar-like by-products from auto exhaust and other sources), and metals including manganese, nickel, and lead. Air toxics come from a variety of sources including cars and trucks, all types of burning (including fireplaces and woodstoves), businesses, and consumer products such as paints. There are no federal standards for air toxics.