The U.S. Environmental Protection Agency (EPA) is proposing secondary air quality standards for nitrogen oxides (NOx) and sulfur oxides (SOx) as part of its ongoing effort to reduce emissions from these sources.

According to the EPA, it has made significant progress in developing a multi-pollutant standard that would protect vulnerable ecosystems, including streams and lakes. To ensure any updated standard is effective, the EPA is planning to conduct a field pilot program to collect and analyze additional data and information.

Meantime, the EPA is proposing an additional secondary standard for each pollutant. The new standards would be identical to the public health standards that the agency announced last year. These standards are designed to reduce the amount of NOx and SOx in the air and the harmful effects that the pollutants have on lakes and streams. The EPA is also proposing to retain the existing secondary standards for each pollutant.

The EPA is already taking a number of steps to reduce NOx and SOx emissions, including the recently announced Cross-State Air Pollution Rule, which aims to cut millions of tons of these pollutants from power plants each year.

Nitrogen oxides are typically emitted from sources including vehicles, power plants, off-road equipment, and agricultural sources. Sulfur oxides are emitted from fossil fuel combustion by power plants, large industries, and mobile sources, and from some industrial processes.

The EPA will accept comments for 60 days after the proposed rule is published in the Federal Register and will issue a final rule by March 2012.

For more information on the EPA”s NOx and SOx efforts, visit