Ambient Air
Higher
Concentrations of formaldehyde in ambient air may be of concern in several areas in the U.S. (see Considerations for Decision Making). Background levels of formaldehyde exceeded the U.S. EPA Air Concentration at Specified Risk Level of 1 in one million in over 90% of census tracts analyzed from 1996 emissions data. Major sources of formaldehyde in ambient air include emissions from power plants, manufacturing facilities, and incinerators; and mobile sources such as cars, trucks, and construction equipment.