U.S. EPA has proposed to revise the nation’s nitrogen dioxide (NO2) air quality standard. The proposed changes to the NO2 standard reflect the latest science on the health effects of exposure to NO2, which is formed by emissions from cars, trucks, buses, power plants, and industrial facilities and can lead to respiratory disease.
EPA’s proposed revisions apply to the primary NO2 standard and would:
- establish, for the first time, a one-hour NO2 standard at a level between 80 – 100 parts per billion (ppb),
- retain the current annual average NO2 standard of 53 ppb,
- add NO2 monitoring within 50 meters of major roads in cities with at least 350,000 residents, and
- continue monitoring of “area-wide” NO2 concentrations in cities with at least 1 million residents.
According to EPA, the proposed new standards and additional monitoring requirements would protect public health by reducing people’s exposure to high, short-term concentrations of NO2, which generally occur near roadways. The proposal would also ensure that area-wide NO2 concentrations remain below levels that can cause public health problems.
Current scientific evidence links short-term NO2 exposures, ranging from 30 minutes to 24 hours, with increased respiratory effects, especially in people with asthma. These effects can lead to increased visits to emergency departments and hospital admissions for respiratory illnesses, particularly in at-risk populations such as children, the elderly, and asthmatics.
EPA first set standards for NO2 in 1971, establishing both a primary standard to protect health and a secondary standard to protect the public welfare at 53 ppb, averaged annually. Annual average NO2 concentrations have decreased by more than 40 percent since 1980. All areas in the United States are well below the current (1971) NO2 standards with annual averages ranging from approximately 10 – 20 ppb.
EPA will accept public comments for 60 days after the proposal is published in the Federal Register. The agency will hold two public hearings in August 2009: one in Los Angeles and one in the Washington, D.C. area. EPA will provide details on the public hearings in a separate notice issued later this summer.
EPA must issue a final decision on the NO2 standard by Jan. 22, 2010. It is the first change in the NO2 limits in 35 years.
Details about the proposal: http://www.epa.gov/air/nitrogenoxides