EPA Fails to Improve Outdated Limits on Soot, Nitrogen Air Pollution

The EPA proposed steps to tighten limits on sulfur air pollution. But the agency estimated that the new standard would not result in any additional emissions reductions from sources of the pollution, such as coal-burning power plants.

This proposals involve so-called “secondary” standards, which are intended to address air pollutants’ harms to wildlife, crops, soils, vegetation, climate and visibility.

The Clean Air Act requires the EPA to set health- and welfare-based “national ambient air quality standards” for air pollutants like sulfur oxides, nitrogen oxides and particulate matter, commonly known as soot.

Yet the agency has not updated the secondary standards for nitrogen or sulfur air pollution since 1971. And the three portions of the agency’s secondary soot standards have not been updated since 1987, 1997 and 2006, respectively.

The agency published this proposal under an agreement that resulted from a 2022 lawsuit brought by the Center for Biological Diversity and the Center for Environmental Health. That agreement requires the agency to finalize its decision on the air quality standards no later than December 10, 2024.

The agency will hold a virtual public hearing on the proposed rule on May 8.

In developing its proposal, the EPA did not complete the required Endangered Species Act consultation with the U.S. Fish and Wildlife Service and National Marine Fisheries Services on how the levels of air pollution allowed by the proposed standards would affect threatened and endangered plants and animals.

Nitrogen oxides are produced by burning fossil fuels and contribute to ozone formation, acid rain, nutrient pollution and poor visibility. Nutrient pollution increases harmful algae growth in aquatic ecosystems, which decreases life-sustaining levels of oxygen in waterbodies; nutrient pollution in groundwater can also contaminate drinking water.

Sources of soot include the burning of fossil fuels and fracking. Reduced visibility and haze are primarily caused by soot, which damages forests and crops by reducing nutrients in soil.

Sulfur pollution is primarily released into the air by burning coal. It contributes to acid rain, threatening vulnerable aquatic plants and wildlife, and increases plant mortality and reproductive harm on land.

Acidification of aquatic ecosystems harms the endangered whooping crane by depleting its food resources. The whooping crane’s preferred prey, such as aquatic insects, crayfish and frogs, are vulnerable to acidic waters.