This story was originally published by Yale E360 and is reproduced here as part of the Climate Desk collaboration.

In April 2024, Tish Taylor and her father, Robert, stood behind President Joe Biden’s Environmental Protection Agency chief, Michael Regan, as he signed a regulation designed to dramatically reduce toxic pollution from petrochemical plants like those that cluster near the Taylors’ homes along the lower Mississippi River, in Louisiana.

Taylor struggled not to cry through the signing ceremony, which followed years of demands from communities like hers—in the 85-mile corridor between New Orleans and Baton Rouge that has become known as Cancer Alley—for tighter limits on plants’ emissions. The new regulation, known as the HON rule, was “a wonderful gift to generations ahead of us,” Taylor said. “It’s hard for me to find the words to say how validated we felt.”

For decades, regulations on emissions of hazardous chemicals such as toluene, ethylene oxide, and vinyl chloride have been weaker than restrictions on more common pollutants, such as those emitted by vehicles.

All nine air toxics rules issued by the Biden administration have been rescinded, revised, or reconsidered.

The Biden administration took major steps to strengthen Clean Air Act rules on those hazardous air pollutants, and the HON rule was a centerpiece of that effort. Toughening requirements on six different pollutants at more than 200 petrochemical plants, it was one of a slate of regulations the Biden administration enacted on air toxics, each covering a specific industry, from steelmaking to tire manufacturing.

But shortly after President Donald Trump began his second term, his administration began unraveling those rules, including the one the Taylors had so recently celebrated. Last year, Trump granted two-year exemptions from the HON rule to more than 50 petrochemical facilities. This July, he issued 20 more temporary exemptions, and the EPA said it would propose a rewrite of the regulation this fall. The new version is all but certain to significantly scale back the rule’s protections.

“Everything that the Biden administration did to help protect us was pretty much just thrown in the garbage,” Tish Taylor said in July, and replaced by “a death sentence.” St. John the Baptist Parish, where her family lives, has the country’s highest risk of cancer from air pollution—nearly 50 times the national average. A disproportionate percentage of those exposed to the highest levels of pollution in the region are Black.

A set of amendments to several existing regulations on toxic air pollutants, the HON rule—which stands for Hazardous Organic National Emission Standards for Hazardous Air Pollutants—requires petrochemical plants to upgrade their pollution control equipment to reduce emissions of two hazardous chemicals: ethylene oxide and chloroprene. It also mandates air monitors at plants’ fencelines to measure concentrations of those chemicals and four more—benzene, ethylene dichloride, vinyl chloride, and 1,3-butadiene—and requires........

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