The now-idled Denka neoprene plant in LaPlace, Louisiana, has reached a settlement with the federal government over allegations it mishandled hazardous waste and disposed of the material in landfills not designed for it.

Under a federal consent agreement, Denka Performance Elastomer has agreed to pay a nearly $1 million penalty to settle the hazardous waste violations. The plant, which suspended production in May 2025, had long been the subject of regulatory action and concern from residents over its emissions of chloroprene, classified as a likely carcinogen.

For at least seven years, Denka workers ferried and dumped byproducts later determined to be hazardous waste in open air, new federal settlement papers allege. That process also emitted toxic and flammable chloroprene fumes at levels tens to hundreds of thousands of times greater than the long-term federal air safety standards, they say.

The chloroprene emissions, which federal regulators say were "excessive and dangerous," were around workers and eventually wafted into neighborhoods near the plant that at one time had the highest cancer risk from air pollution in the nation. Workers were required to wear full-face respirators around some of the work questioned for its open-air emissions, regulators said.

The company also agreed to clean up the site and put in new processes, improved equipment and worker training programs to control emissions if operations restart under its control or another company's. The property has no chloroprene currently in inventory, the EPA says.

"Denka’s mishandling of hazardous chloroprene waste and its many violations of the law exposed workers and the surrounding community to excessive chloroprene and potentially serious health risks,” Jeffrey A. Hall, an EPA assistant administrator, said in a statement.

"Although this facility has suspended operations for business reasons separate from these enforcement actions, this order ensures that if the facility resumes operation, it will be in compliance with the law."

Denka didn't admit to any of the six alleged hazardous waste violations and avoided a penalty that could have reached in the hundreds of millions of dollars at maximum, though a precise total isn't clear.

In a statement, Denka officials said that the modified processes required under an earlier 2022 agreement "improved waste handling at our facility and delivered further emissions reductions, reflecting the company’s additional investment and innovation by our dedicated employees.”

"DPE is pleased to have this matter fully and comprehensively resolved," the company added.

'Didn't slip through the cracks'

Denka operated the only neoprene production plant in the United States. The synthetic rubber is used in many products, from wet suits, engine hoses and fan belts to electrical insulation and mouse pads.

In 2010, however, EPA scientists determined chloroprene — the critical chemical building block of neoprene — would be considered a likely human carcinogen.

The announcement set off years of regulatory efforts, community activism and litigation to have DuPont, which invented neoprene in the early 1930s, and then Denka, which bought the plant from DuPont in late 2015, slash chloroprene emissions.

The latest agreement stems from an unresolved EPA hazardous waste inquiry dating to 2022.

Since 2023, other regulatory actions against the company have been dropped amid the shifting focuses of the Biden and Trump administrations. The Trump EPA is also reconsidering chloroprene air standards finalized by the Biden EPA in 2024.

The latter administration has seen the former's emphasis on environmental justice as an inappropriate racial focus and legal overreach that hurts economic growth.

Some alleged violations, including those related to hazardous waste handling and disposal, continued for seven years until an EPA order in late 2022 directed interim changes. But the violations also faulted the company for not identifying the waste as hazardous for more than a decade.

Under the law, the EPA could have assessed fines of as much as $124,426 for each day of a violation, plus inflation, under each of the six hazardous waste counts. The precise penalty is $996,703.35, representing about eight days of violations at maximum penalty.

A representative for a St. John community group that, for years, has highlighted toxic pollution concerns said they welcomed the settlement.

"We are very happy that this actually didn’t slip through the cracks just to be totally removed, because every other protection that's been given to us has been reversed, so this makes us feel really good," said Tish Taylor, program director for Concerned Citizens of St. John.

Taylor added the penalty seemed sufficient, given Denka is no longer operating, but said she would like it to remain closed.

Previous investigations

For years, Denka attempted to challenge the EPA cancer risk standard for chloroprene and had charged that a now-dropped Clean Air Act suit the EPA filed against the company in 2023 was politically motivated after it had spent $35 million to cut emissions.

EPA says the interim changes to the waste handling had cut chloroprene emissions by 1 ton, a small portion of Denka's overall air emissions.

In 2016, Denka emitted 119 tons of chloroprene into the air. By 2024, the last full year of operations, annual emissions had fallen by 90% to 12 tons, an EPA database says.

Before EPA inspectors uncovered the hazardous waste handling process, Denka and Dupont had faced earlier federal and state investigations. It reached an earlier consent agreement with the state in 2017 to cut emissions.

The open-air, hazardous waste process continued, however, the consent agreement says. State hazardous waste inspections also did not flag that process, as a site inspection in 2021 found no violations.

Known as "Poly Kettle Strainer Waste" and as treated chloroprene and butadiene popcorn waste, the materials are a mix of chloroprene, butadiene, toluene and other chemicals and were the result of Denka's batch production of neoprene.

That process involved reacting chemicals, then washing and straining them and carrying them in open carts to open, outdoor brine pits to solidify the material. An excavator was then used to grab and move the solidified waste into open waste bins for landfill shipment, according to the consent agreement.

EPA testing showed the material was highly reactive and could easily catch fire. It also found high chloroprene emissions from the waste handling.

In one example, EPA inspectors found that when the Poly Kettle Strainer Waste was ferried to the open brine pits, chloroprene levels hit 243,000 micrograms per cubic meter, which is 810,000 times the lifetime exposure standard allowed at the plant's fenceline.

The brine pits were used to reduce the "Poly Kettle" waste's potential risk for fire and explosions before disposal in residential or industrial landfills not designated for hazardous waste. The EPA says this process was never authorized; Denka began using a hazardous waste landfill in early 2023.

EPA found similar unauthorized treatment and disposal with the butadiene and chloroprene popcorn, which are now sent to a hazardous waste incinerator.

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