What Is Chloroprene, the Cancer-Causing Chemical at the Center of a Federal Lawsuit?
Trump could drop a federal lawsuit against a petrochemical plant that emits chloroprene. Here’s a look at the cancer-causing chemical
Yoga mats can be made out of the synthetic rubber neoprene, natural rubber and other materials.
The Trump administration may soon drop a federal lawsuit against a Louisiana petrochemical plant to reduce its emissions of chloroprene, a cancer-causing chemical that has been at the heart of a roughly decade-long environmental justice battle.
Chloroprene is a volatile liquid made of chlorine and carbon atoms. When its molecules are linked together to form chains in a process called polymerization, they form polychloroprene—better known as neoprene, a common synthetic rubber that is widely used in wetsuits and other protective gear. Neoprene is relatively inert and resists degradation, and it is used in clothing, masks and accessories. But during neoprene’s production, the crucial ingredient chloroprene can enter the air because of its volatility. An early reported occurrence of high occupational exposure to chloroprene occurred in 1973, when airborne concentrations of the chemical reached up to 24,470 micrograms per cubic meter (24,470 µg/m3) within one manufacturing plant that was monitored by scientists.
Chloroprene’s carcinogenic risk was first noted in the 1970s, when exposed workers started turning up with high rates of cancer. A 1978 study on 234 male neoprene plant workers in the U.S. found 12 deaths from cancer over a 15-year period, three deaths more than would be expected compared to the rate among the company’s workers as a whole. The rate of cancer of the urinary organs in particular raised red flags: Five of the exposed men died of such cancers over 15 years, far higher than the expected rate of one death every 30 years for a similar population that was not exposed to chloroprene. Research on exposed workers in shoe manufacturing factories in Russia linked chloroprene exposure to liver cancer, kidney cancer and leukemia.
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Animal studies have also shown that either ingesting or inhaling chloroprene can cause cancer. In 2010 the U.S. Environmental Protection Agency identified the chemical as a likely human carcinogen. According to the studies the EPA reviewed in that analysis, chloroprene is probably a mutagen—an agent that can damage DNA or trigger genetic mutations.
The EPA set a maximum allowed chloroprene exposure level at 0.2 µg/m3 over 70 years in an attempt to keep the additional cancer risk from exposure below 100 cases per every million people. In 2023 the agency filed a lawsuit against the only plant that emits chloroprene in the U.S.: a former DuPont site that is now owned by the Japanese company Denka in Reserve, La. According to the lawsuit, monitoring found that this Denka Performance Elastomer plant consistently released up to 14 times the maximum allowed amount of chloroprene in the surrounding community. Now the New York Times has reported that the Department of Justice is likely to withdraw that lawsuit as part of its move to axe environmental justice programs. Census Tract 708, where the plant is located, is about 91 percent Black.
“I’m upset, and I just cannot sleep at night,” says Robert Taylor, who was born in Reserve in 1940. Taylor is the founder of Concerned Citizens of St. John, an advocacy group he started in 2016 after learning about the health dangers of chloroprene. “I remember the suffering of my mother with the cancer. My wife got the cancer; my sister got the cancer; my brother [did]. I look around me, at my neighbors. It is a nightmare.”
Reserve sits in “Cancer Alley,” a corridor of petrochemical plants where cancer rates are particularly high. While some advocates for industry blame residents’ health behaviors for these high rates, a 2022 study in the journal Environmental Research Letters found that after controlling for occupation, smoking and obesity, cancer incidence was higher in census tracts with more exposure to toxic compounds in air pollution. And these highly exposed populations were more likely to be predominantly Black.
The U.S. national cancer rate is about 440 cases each year per 100,000 people in the same age range as Louisiana’s population, says Kimberly Terrell, the study’s lead author and a research scientist at the Tulane Environmental Law Clinic. Louisiana averages higher than that, Terrell says— around 480 cases per 100,000 people per year. In Cancer Alley, though, the numbers look even worse.
“The most polluted census tracts that we looked at had an average overall rate above 500,” Terrell says.
There is also evidence tying the Denka plant, in particular, to cancer risk. In 2021 a study published in the journal Environmental Justice found higher cancer incidence closer to the plant. The study researchers surveyed households within a 1.5-kilometer radius of the plant and those located between 1.5 and 2.5 km from it. They then compared the reported cancer numbers in these zones with national averages of Americans, matched to age, race and sex. They found an unusually high cancer rate within the entire study area—9.7 percent of residents reported a cancer diagnosis within the past 23 years—and the rate worsened with closer proximity to the plant. “The levels of cancer in Zone 1 [near the plant] are much more unusual, compared to national cancer statistics, than the levels in Zone 2,” says Ruhan Nagra, an associate professor of law at the University of Utah, who led the study.
Denka has argued that the EPA has set its limit for chloroprene exposure too low. A 2020 study partially funded by the company asserted that mice (which were used in the animal studies of the chemical) are more susceptible to cancer from chloroprene than humans and that the exposure limit should be more than 100 times higher than 0.2 µg/m3. (The lead author of that study did not respond to an interview request). In 2022 the EPA declined to change its exposure limit after an independent peer review of Denka’s toxicology claims, with reviewers finding that the company’s methodology did not support it assertions of reduced cancer risk.
A lawyer for Denka declined to comment on the possible withdrawal of the lawsuit. Taylor says he and his fellow advocates have felt overwhelmed by the developments. “This country has abandoned us to the vagaries of the petrochemical industry,” he says.
“Who decided to sacrifice us and to whom?” Taylor adds. “Who are the beneficiaries of my three-year-old great-grandson, who, at 2.5 years old, had already exceeded the 70-year level of exposure to these chemicals? … Me and my board of directors, we’re in emergency mode. We know we have to come together and come up with some plans. We cannot lay down for this.”
Stephanie Pappas is a freelance science journalist based in Denver, Colo.
Source: www.scientificamerican.com