Officials stressed that the listings do not mean that any exposure to the substances will cause cancer. Instead, it means that the latest scientific evidence indicates that the agents can cause cancer in some people exposed to enough of the compounds under the right circumstances. Most of the evidence for a cancer risk came from people exposed to relatively high levels in industrial settings.
“A listing . . . does not by itself mean that a substance will cause cancer,” John Bucher, associate director of the National Toxicology Program, which issues the list, said during a briefing for reporters. “Many factors, including the amount and duration of exposure and an individual’s susceptibility to a substance, affect whether a person will develop cancer.”
The listings do not trigger any immediate new restrictions on the substances, but other government agencies may use the information in the future as part of their regulatory decisions, Bucher said. In the meantime, individuals can use the list to make personal choices, he said.
“We’re exposed to carcinogens every day all the time, from sunlight to alcoholic beverages,” Bucher said, noting that most people’s routine exposure to the newly listed substances was probably low. “The purpose is to give people information to allow them to make choices. You can avoid using products that might contain these materials if you think there will be a hazard.”
The listings were immediately denounced by industry groups, which has lobbied against the styrene and formaldehyde listings.
“Exposure to styrene does not cause cancer in humans,” a statement from the American Composites Manufacturers Association said. The association charged that the process used to evaluate the substance was flawed and that the report threatened thousands of jobs in industries that use the chemical.
The report is a congressionally mandated list prepared by the National Institute of Environmental Health Sciences, which is part of the National Institutes of Health.
With the additions in the 12th version of the report, 240 substances are now listed as either “known human carcinogen” or “reasonably anticipated to be a human carcinogen.”
Formaldehyde had been listed in the “reasonably anticipated” category since the second report, based on studies showing it caused nasal cancer in rats.
In addition to being used as a preservative in medical laboratories, formaldehyde is widely added to make resins for household items, such as composite wood products, plastics and coatings for paper products. It also is in some consumer products, such as hair-straighteners.