[EPA press release - October 19, 1971]

The Environmental Protection Agency today defined, for five of the most common air contaminants, the levels at which "significant harm" to the health of persons might occur during episodes of high air pollution.

The five pollutants are sulfur dioxide, particulate matter, carbon monoxide, photochemical oxidants, and nitrogen dioxide.

The danger levels were stipulated in an amendment to regulations, issued by the EPA on August 14, 1971, to guide States in planning to clean the Nation's air to healthful levels by mid-1975. These regulations require each State plan to spell out steps to be taken to prevent episodes of dangerously high air pollution. Such steps would become progressively more stringent as air pollution concentrations increased toward the danger points.

The EPA emphasized that State action should assure that air pollution never reaches the levels at which significant harm to health may occur. Under the Clean Air Act, the Administrator of the Environmental Protection Agency is empowered to bring suit on behalf of the United States in a Federal district court when air pollution presents an imminent and substantial endangerment to the health of persons.

NOTE: A table showing the danger levels is attached.