The Environmental Protection Agency said Dec. 18 that it's starting a human health review of styrene, ethylbenzene and several other plastics feedstocks as it also moves ahead with a detailed, long-debated toxicity assessment of vinyl chloride.
The agency announced it would look at five chemicals — styrene, ethylbenzene, benzene, 4-tert-Octylphenol and naphthalene — to see if they should be designated as high-priority substances for health assessments under the Toxic Substances Control Act.
It's a continuation of the agency's broader review of health concerns around plastics feedstocks.
It follows a similar announcement from late 2023, when EPA launched a review of vinyl chloride monomer, acrylonitrile and other plastics compounds, including benzenamine, acetaldehyde and 4,4'-Methylenebis(2-chloroaniline), or MBOCA.
In its new announcement, EPA also said it was moving ahead with formal risk assessments of vinyl chloride and the other four chemicals named last year, a process that will take several years.
None of the EPA statements are findings of health risks, but rather they are decisions to move forward on complex assessments by agency scientists.
For the five chemicals newly named in 2024, EPA said it was taking the initial step toward risk assessments because scientific evidence suggests health concerns.
It pointed, for example, to cancer risks from styrene, ethylbenzene and benzene exposure, as well as studies showing other organ and health damage.
"Exposure to styrene may result in a range of harmful health effects such as hearing loss, memory loss, miscarriage and damage to the tissue in the lungs and nasal passages," EPA said. "Epidemiological data show that cancers of the lung, kidney, breast, blood and esophagus in humans may be linked to exposure to styrene and, based on evidence of lung tumors in animal studies, styrene is a probable human carcinogen."
As well, EPA said benzene exposure has been linked to leukemia, fetal malformations and immune system issues, and it connected 4-tert-Octylphenol exposure with kidney inflammation, lowered sperm count and other fertility conditions.
At the end of its process, the agency could issue bans and broad restrictions on a chemical's use, or more narrowly tailor regulations for specific applications or workplace exposures.
"These risk evaluations will be used to determine how to protect people from harmful chemical exposures," said Michel Freedhoff, assistant EPA administrator for the Office of Chemical Safety and Pollution Prevention.