U.S. States soon may look to mandating emissions retrofits on heavy trucks as they try to meet new federal ozone standards, Today’s Trucking reports.

The administrator of the U.S. Environmental Protection Agency recently signed the nation's most stringent ozone standard ever, lowering the 1997 standard of 84 parts per billion to 75 parts per billion.

The agency evaluated more than 1,700 new scientific studies concluding that ozone causes adverse health effects at levels below the 1997 standard.

Current data suggests that 345 counties with monitors will not meet the new standard, according to the American Trucking Associations. Only 85 counties remain out of compliance with the 1997 standard.

Non-attainment designations will be made in 2010. States will then have three years to file attainment plans. Some states may have up to 20 years to comply depending upon the severity of their non-attainment.

At the same time, the federal government may be working on a way to help pay for retrofits. The House Energy and Commerce Committee last week approved a bill that would allow the EPA to pay to upgrade older engines using settlement funds from companies that violated the Clean Air Act, according to a report in the Detroit News.

The Senate unanimously passed its version Feb. 29.

According to Today’s Trucking, the EPA estimates there are 11 million older diesel engines in the United States that lack emissions control technology.