A federal appeals court ruled Tuesday that the Environmental Protection Agency complied with the law in deciding which areas of the country failed to meet federal limits on smog-forming pollution that can cause asthma and respiratory illness.
The U.S. Court of Appeals for the District of Columbia Circuit rejected challenges from states, industry and environmental groups that claimed the agency was being either too strict or too lenient in determining which areas satisfied federal ozone restrictions.
States including Mississippi, Indiana and Texas had challenged the EPA's finding that certain areas within their borders were violating the standard. A finding of noncompliance means states have to spend money to reduce ozone levels.
Connecticut and Delaware argued that the EPA should have designated more than a dozen eastern states in violation, saying their air quality was being hindered by other states.
But the court said the EPA's decisions had not violated the Constitution or any provisions of the Clean Air Act.
EPA spokeswoman Liz Purchia said the agency is pleased with the decision and would continue to work with states "toward implementing ozone standards to protect public health as required by the Clean Air Act."
The Obama administration recently proposed even stricter emission limits on ozone of 65 to 70 parts per billion, below the existing standard of 75 that President George W. Bush put in place in 2008. The EPA has estimated that cutting ozone emissions to 70 parts per billion would cost industry about $3.9 billion in 2025.
Business groups say the latest proposal is unnecessary and would be the costliest regulation in history.
Ozone, the main ingredient in smog, is a powerful lung irritant that has been linked to a range of health problems. Smog is created when emissions from cars, power plants, refineries and other factories mix in sunlight and heat.