Public-health and environmental-advocacy groups say the federal government is failing to enforce air quality standards in parts of Arizona and Utah.

On Thursday, the groups filed paperwork notifying the Environmental Protection Agency of their intent to sue. 

In 2011, the EPA found that a swath of western Pinal County was in violation of the Clean Air Act’s standards for fine particulate matter, specifically PM2.5.

That designation required Arizona to take corrective action and for the EPA to eventually determine if the air improved. But the Center for Biological Diversity alleges that never happened.

“We don’t know today if the air quality has improved to cleaner standards or not," Jonathan Evans, Environmental Health Legal Director at the Center for Biological Diversity, said.  

“If the air hasn’t improved, if it is still in nonattainment, dirty air status, then Arizona has to create a more stringent plan to clean up pollution,” he said.

Evans said that this kind of fine particulate matter is 30-times smaller than a human hair and can pass into the bloodstream through the lungs.

He said it can form from the chemicals sprayed for agriculture.

A spokesperson for Pinal County Air Quality said their department's measurements have shown that the area is, for the most part, in attainment. 

The Arizona Department of Environmental Quality does not comment on pending litigation, but its website indicates that western Pinal County is in nonattainment for a different particulate matter, PM10.