OAKLAND, Calif.— Environmental groups filed a formal notice today of their intent to sue the Environmental Protection Agency to force it to update limits on soot, sulfur and nitrogen air pollution.

The standards must be reviewed and updated every five years to account for the latest science on the risks and threats to human health and the environment. But the agency last updated any of the standards for the three pollutants back in 2013.

“The EPA cannot arbitrarily decide to shirk its duty to protect the public and vulnerable wildlife from dangerous air pollution like soot,” said Robert Ukeiley, a senior environmental health attorney at the Center for Biological Diversity. “The Clean Air Act has done a remarkable job of reducing dangerous pollution. But it can only do that work when it’s enforced.”

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. Welfare-based standards address harmful impacts to wildlife, crops, soils, vegetation, climate and visibility.

The agency’s latest update and review of the welfare-based standards for sulfur oxides and nitrogen oxides was in June 2012; new standards were due in June 2017. The EPA last updated the particulate matter welfare-based standards in March 2013, so new updates to those standards were due in March 2018.

“The loss of biodiversity causes stress in people and therefore harms their health and well-being,” said Kaya Allan Sugerman, the Center for Environmental Health’s director of illegal toxic threats. “It is imperative that threatened and endangered species are protected from these threats to help make sure they’re around for generations to come.”

Sulfur oxides are primarily released into the air by burning coal. Sulfur pollution contributes to the acidification of aquatic ecosystems, threatening vulnerable aquatic plants and wildlife. In terrestrial ecosystems, sulfur oxides have been linked to an increase in plant mortality and a decrease in seed regeneration.

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 the levels of life-sustaining oxygen available to aquatic life. 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.