Los Angeles shrouded in smog in 1995.

Los Angeles, California, shrouded in smog in 1995.

Metro library and archive/Flickr

U.S. introduces new rules for curbing smog-producing ozone

The United States on Wednesday proposed tightening its standard for smog-producing ozone from 75 parts per billion to between 65 and 70 parts per billion. The new threshold, the first change since 2008, was announced by the Environmental Protection Agency (EPA).

Nitrogen oxides and other organic chemicals emitted by cars and industry can react in the lower atmosphere and produce elevated levels of ozone. And close to Earth, this ozone is a pollutant, not a sun-shielding protectant: It can cause asthma and aggravate lung disease. EPA says that the new standard could prevent as many as 960,000 asthma attacks and 4300 premature deaths. Groups such as the American Lung Association applauded the new threshold, but said that EPA should push further to a standard of 60 parts per billion.

EPA’s science advisory board has endorsed lowering the threshold since the late 2000s. But 3 years ago the Obama administration shelved a draft proposal to impose a lower standard, suggesting that achieving it would be too economically onerous at a time when the United States was recovering from a severe recession. Today’s proposal essentially renews much of that earlier proposal. States will be required to comply by 2020 to 2037, depending on the severity of their ozone problem.

Critics say that achieving the new standard will be expensive and difficult. In some U.S. cities—especially those at higher elevations in the mountainous west—naturally occurring background levels of ozone are starting to represent a significant fraction of the total. And global transport of ozone-producing compounds is starting to become a problem. While ozone levels are on the decline in Europe and the United States, they are booming in East Asia. Earlier this year, Science reported on a case of an air quality district in California for the first time blaming China for its local ozone problems.

EPA will accept public comment on the proposal until the end of February 2015 and says it plans to finalize the new rules by 1 October 2015. Some members of Congress, however, are vowing to block implementation. “[W]e will continue our efforts in the new Congress to rein in EPA’s relentless regulatory assault,” said Representative Ed Whitfield (R–KY), a senior member of the House energy committee, in a statement. “EPA is proposing to adopt new standards that could be nearly impossible to meet, especially for areas of the country still struggling to comply with the current ozone standard.”