The U.S. Environmental Protection Agency (EPA) is proposing to tighten the one-hour standard for measuring emissions of nitrogen dioxide (NO2), but not change the annual standard. The long-term exposure would remain at a maximum of 53 parts per million (0.053 ppm) while an acceptable short-term exposure limit would be between 80 and 100 ppm (0.08 - 0.10 ppm).

The EPA believes NO2 exposure has been linked to respiratory problems. The primary man-made sources for NO2 are motor vehicles, coal-burning power plants and factories. In addition to reducing the one-hour standard, the EPA will require additional measuring devices be installed near city roadways where higher levels may be found.

According to the EPA, ambient concentrations of nitrogen dioxide dropped 41 percent between 1980 and 2006. All areas of the country currently meet the existing primary annual air quality standard, according to EPA. The EPA is not proposing any additional actions at this time, such as further reducing auto emissions of nitrogen oxide.

Questions? Contact Stuart Gosswein.