Styrene added to U.S. carcinogens list, objections follow

The U.S. Department of Health and Human Services added styrene, a byproduct of some composites manufacturing operations, to its 12th Report on Carcinogens. ACMA and SIRC vow to fight the listing, claiming that no evidence links styrene definitively to cancer in humans.

The U.S. Department of Health and Human Services (HHS) on June 10 added eight substances to its Report on Carcinogens (RoC), which identifies chemicals and biological agents that may put people at increased risk for cancer.

The substances added include styrene, formaldehyde, aristolochic acids, captafol, cobalt-tungsten carbide (in powder or hard metal form), certain inhalable glass wool fibers, o-nitrotoluene and riddelliine. Styrene in particular is meaningful to the composites manufacturing industry, as this substance is a byproduct of many spray-up molding processes. With these additions, the 12th Report on Carcinogens now includes 240 listings. It is available at ntp.niehs.nih.gov/go/roc12.

"Reducing exposure to cancer-causing agents is something we all want, and the Report on Carcinogens provides important information on substances that pose a cancer risk," says Linda Birnbaum, Ph.D., director of both the National Institute of Environmental Health Sciences (NIEHS) and the National Toxicology Program (NTP). "The NTP is pleased to be able to compile this report."

John Bucher, Ph.D., associate director of the NTP added, "This report underscores the critical connection between our nation's health and what's in our environment."

The Report on Carcinogens is a congressionally mandated document that is prepared for the HHS Secretary by the NTP. The report identifies agents, substances, mixtures, or exposures in two categories: known to be a human carcinogen and reasonably anticipated to be a human carcinogen. A listing in the Report on Carcinogens does not by itself mean that a substance will cause cancer. Many factors, including the amount and duration of exposure, and an individual's susceptibility to a substance, affect whether a person will develop cancer.

According to the report, styrene is on the list based on human cancer studies, laboratory animal studies, and mechanistic scientific information. The limited evidence of cancer from studies in humans shows lymphohematopoietic cancer and genetic damage in the white blood cells, or lymphocytes, of workers exposed to styrene. Styrene is a synthetic chemical used worldwide in the manufacture of products such as rubber, plastic, insulation, fiberglass, pipes, automobile parts, food containers, and carpet backing. People may be exposed to styrene by breathing indoor air that has styrene vapors from building materials, tobacco smoke, and other products. The greatest exposure to styrene in the general population is through cigarette smoking. Workers in certain occupations may potentially be exposed to much higher levels of styrene than the general population.

Chemical and composites organizations, anticipating the listing, had petitioned HHS to keep styrene off; the reaction of these organizations following the listing was swift.

Says Monty Felix, president of the American Composites Manufacturers Assn. (ACMA), "We are very disappointed that the National Toxicology Program failed to address the styrene industry's and Congress' legitimate concerns in its 12th Report on Carcinogens. It is the position of ACMA, as well as leaders in the scientific community, that styrene does not pose a cancer risk.

"European Union scientists recently completed an exhaustive review of styrene's health effects and concluded that exposure to styrene is not likely to cause cancer in humans — a conclusion validated by a myriad of peer-reviewed studies in the United States. In addition, other federal agencies, including OSHA [Occupational Safety and Health Administration] and EPA [Environmental Protection Agency] are aware of the scientific data on the possible linkage between exposure to styrene and development of cancer and have not concluded that there is sufficient risk to require additional regulatory protections.

The Styrene Information and Research Center (SIRC) executive director Jack Snyder says, "The U.S. styrene industry will contest vigorously the U.S. Department of Health and Human Services' (HHS's) listing of styrene in its 12th Report on Carcinogens because the designation is completely unjustified by the latest science and resulted from a flawed process that focuses on only those data that support a cancer concern, and in the case of styrene ignored the preponderance of data that fail to suggest a cancer concern for this substance.

"HHS included styrene in the 12th RoC despite the fact that European Union regulators have determined that styrene does not represent a human cancer concern. E.U. scientists reviewed the full styrene database, weighing all of the available data in reaching their conclusion.

"On May 11, 63 members of the U.S. House of Representatives — 47 Republicans and 16 Democrats — wrote HHS Secretary Kathleen Sebelius asking her to delay the RoC listing of styrene pending a thorough review that weighs the full body of scientific evidence.

"New science that has emerged since the E.U.ís 2007 Risk Assessment Report points even further away from a cancer concern. The peer-reviewed Journal of Occupational and Environmental Medicine in 2009 published a comprehensive review showing that the 'available evidence does not support a causal relationship between styrene exposure and any type of human cancer.'"