Denka sues EPA over chloroprene monomer toxicity assessment

TOKYO—Denka Performance Elastomers L.L.C. (DPE) has filed a lawsuit against the Environmental Protection Agency, Japanese parent group Denka Co. Ltd. announced Jan. 13.

Through the lawsuit, filed Jan. 11 in the U.S. District Court for the District of Louisiana, DPE is seeking a review of the agency's toxicity assessment of chloroprene monomer.

In its statement, Denka said that, since its acquisition of the chloroprene rubber manufacturing business from DuPont in 2015, its subsidiary had "consistently operated" in compliance with regulatory emissions standards.

DPE, it insisted, "regularly measures the concentration of substances in the atmosphere" around its plants and provides information on environmental measures to local residents and other stakeholders.

The rubber maker, it added, has invested over $35 million and introduced equipment at its LaPlace, La., plant to reduce chloroprene monomer emissions by 85 percent compared to 2014.

And, while DPE is continuing to further reduce environmental emissions, Denka claimed that the toxicity of chloroprene monomer has been "overestimated" based on the Integrated Risk Information System (IRIS).

The EPA, it stated, had previously accepted the application of an alternative physiologically based pharmacokinetic (PBPK) measurement model.

The model suggests the relative level of health risk from chloroprene to be as much as 130 times lower than the IRIS assessment, according to Denka.

This, it added, "would be consistent with the average to below-average levels of cancer incidence recorded near the DPE facility."

However, in a letter issued Oct. 19, 2022, the EPA rejected adoption of the PBPK model on the grounds that "there was no obligation to incorporate more recent science into the assessment," Denka said.

Meanwhile, Denka also is challenging a related allegation that chloroprene monomer discharged from DPE's rubber manufacturing plant, announced Feb. 14, 2020, "caused physical, financial and mental damage."