The U.S. Environmental Protection Agency has proposed to tighten health standards for smog, a move that could lead to more state and local regulations of trucking.

Under the EPA's new smog proposal, the agency wants to set the "primary" standard for ozone, which protects public health, at a level between 0.060 and 0.070 parts per million measured over eight hours. Existing ozone standards are set at 0.075 parts per million, mandated in March 2008.

A separate "secondary" standard is aimed at protecting the environment, particularly plants and trees that can damage from repeated ozone exposure, EPA says.

Where this could affect trucking down the road is if some areas of the country become non-compliance areas, which could lead to governments of those states enacting stricter emissions regulations.

Concerns over clean air and the negative health effects of dirty emissions have already caused states such as California and New York to regulate the trucking industry. Here, authorities want to reduce particulate matter, or "soot," the most visible and obnoxious exhaust ingredient, and nitrogen oxides (NOx), which produce smog and are the source of the annoying odor in exhaust.

One of California's efforts to clean up the air and regulate the trucking industry is the California Air Resources Board's Truck and Bus Rule, which requires most truck owners to install diesel particulate filters on their rigs by Jan. 1, 2011, with nearly all vehicles upgraded by 2014. The regulation is estimated to prevent 9,400 premature deaths over its lifetime. Under federal regulations, California is allowed to set stricter standards than the federal government -- and other states are allowed to adopt California's more stringent rules.

"EPA is stepping up to protect Americans from one of the most persistent and widespread pollutants we face," said Lisa P. Jackson, EPA administrator. "Smog in the air we breathe poses a very serious health threat, especially to children and individuals suffering from asthma and lung disease. It dirties our air, clouds our cities, and drives up our health care costs across the country."

According to the EPA, the new proposal would yield health benefits between $13 billion and $100 billion, and cost the government between $19 and $90 billion.

EPA will take public comment for 60 days after the proposed rule is published in the Federal Register. The agency will hold three public hearings on the proposal: Feb. 2, 2010, in Arlington, Va., and in Houston; and Feb. 4, 2010, in Sacramento, Calif.

For more information, visit www.epa.gov/groundlevelozone.