You may not be familiar with the toxic chemical 1,3-butadiene, but it’s everywhere. The U.S. chemical industry makes and uses enormous quantities of it every year—from 1 to 5 billion pounds. It’s used to make materials like synthetic rubber and plastics. EPA’s evaluation of 1,3-butadiene under the Toxics Substances Control Act (TSCA) found that this chemical presents unreasonable risks to people’s health, including cancer, reduced birthweight pregnancies, and other diseases. However, the evaluation was scientifically deficient in several ways that will leave the public at risk.
We highlight some areas of concern below; read our full comments here.
Failing to adequately protect the public from cancer risks
While EPA acknowledges that 1,3-butadiene raises risks of leukemia, it discounts significant evidence that the chemical also contributes to breast and bladder cancers. EPA’s previous evaluation noted the strong evidence of mammary tumors in rodent testing; this indicates a concern for breast cancer in people. With strong rodent evidence and insufficient human evidence, EPA should account for breast cancer risks from 1,3-butadiene.
In its health hazard assessment, EPA found that workers exposed to higher levels of 1,3-butadiene were more likely to die from bladder cancer—but discounts these risks because it states data on smoking (also a risk factor for bladder cancer) were not available. But EPA’s previous evaluation found that workers were not allowed to smoke at facilities because of the explosive nature of 1,3-butadiene—so EPA should assume no smoking and account for bladder cancer risks to workers.
We recommend that EPA apply additional adjustment factors in its assessment to account for risks of breast and bladder cancers from 1,3-butadiene.
Threats to fertility
There are additional health concerns with 1,3-butadiene beyond cancer. EPA’s previous evaluation, as well as an evaluation from the California Office of Environmental Health Hazard Assessment (OEHHA), found that ovarian atrophy was the most sensitive non-cancer health endpoint (observed at lower levels of exposure to 1,3-butadiene than other health harms like reduced fetal weight) based on strong rodent evidence. Ovarian atrophy means that the ovaries shrink and lose their function, including the ability to produce eggs—reducing fertility or causing infertility in the worst case.
EPA dismisses the evidence on ovarian atrophy based on a scientifically unsupported hypothesis by authors who had financial conflicts of interest about the mechanism by which 1,3-butadiene causes this effect in mice, concluding that humans would be less sensitive. But in contrast, OEHHA concluded that humans would likely be more sensitive because of longer lifespans and other factors.
EPA should calculate risks of ovarian atrophy to ensure that people are protected from the risks of 1,3-butadiene exposures damaging the ovaries.
Last minute shoddy analysis downplays cancer risks to communities
EPA’s evaluation of 1,3-butadiene found unreasonable cancer risks for people living near industrial facilities that release the chemical. But then, months after release of the evaluation, EPA published a “supplement” with an unscientific analysis of data from the National Emissions Inventory (NEI) purporting to show lower cancer risks than it found previously to people near facilities. The problem is, instead of performing a comprehensive analysis of the more than 700 facilities with NEI data on 1,3-butadiene, EPA in the supplement arbitrarily evaluates just 9 facilities. The 9 facilities evaluated are not even the ones with the largest emissions of 1,3-butadiene. In addition, the supplement underestimates risk by disregarding 1,3-butadiene emissions from additional closely located facilities, which would combine to result in greater risks to communities than EPA modeled from individual facilities. EPA should draw no additional conclusions about cancer risks to communities based on such a limited and biased analysis.
Overall, EPA must perform a comprehensive evaluation of NEI data and correct the scientific problems PRHE detailed in our comments to protect people from risks of cancers, fertility problems, and other health harms at work and at home, especially for people who live near polluting facilities.
About the author
Veena Singla, PhD, is an assistant adjunct professor at Columbia University and consultant to PRHE. Her work seeks to address health disparities linked to harmful environmental exposures using an interdisciplinary approach incorporating environmental health, exposure science, public health, and policy expertise. She received a BS from the University of California, Berkeley in chemistry and a PhD in cell biology from the University of California, San Francisco.
