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Government lists styrene as a carcinogen

Styrene is one of eight new substances listed in the 12th Report on Carcinogens, which the U.S. Department of Health and Human Services released this afternoon.

Styrene, used in the building of fiberglass boats, is listed as “reasonably anticipated to be a human carcinogen based on limited evidence of carcinogenicity from studies in humans, sufficient evidence of carcinogenicity from studies in experimental animals and supporting data on mechanisms of carcinogenesis.”

A coalition of groups, including the National Marine Manufacturers Association, had fought against including styrene in the report, saying additional reviews were needed using a “rigorous unbiased transparent process.”

“We are disappointed that HHS has made this decision based solely on its own limited and misguided studies,” NMMA president Thom Dammrich said. “[The National Toxicology Program’s] deficient scientific process combined with their limited breadth of study in the face of a number of outside studies that were not evaluated demands that the listing be carefully examined.”

European Union regulators, a panel of internationally recognized epidemiologists and a Harvard Center for Risk Analysis study determined that styrene does not represent a human cancer concern, the Styrene Information and Research Center said in a recent letter to the department.

The listing is “based on a selective reading of the available scientific information that ignored a large number of important studies that did not support the [toxicology program’s] staff position. Not only was this information ignored, it was effectively excluded from the information presented to the NTP’s Board of Scientific Counselors [for review],” the letter stated.

Styrene is on the list based on human cancer studies, laboratory animal studies, and mechanistic scientific information, according to a statement from the department.

“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,” according to the release. “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.”

Of the other new substances on the report, the industrial chemical formaldehyde and a botanical known as aristolochic acids are listed as known human carcinogens. Six other substances — captafol, cobalt-tungsten carbide (in powder or hard metal form), certain inhalable glass wool fibers, o-nitrotoluene, riddelliine, and styrene — are added as substances that are reasonably anticipated to be human carcinogens.

With these additions, the 12th Report on Carcinogens now has 240 listings.

Styrene is one of two essential components in the composite resin used to build boats, said John McKnight, the NMMA’s director of environmental and safety compliance.

Styrene acts as a cross-linking agent and a solvent when combined with liquid resin. It is the catalyst in an exothermic reaction that, when combined with the resin, creates a new chemical called unsaturated polyester resin. Unsaturated polyester resin is the solid material that makes up the hull and deck of a boat and is reinforced with fiberglass.

“At this time no other material can provide the same high-performance characteristics, quality and cost-effectiveness of styrene,” Knight told Soundings Trade Only. “Styrene is widely used because it has been substituted over the years for other materials to create stronger and lighter, more efficient products. The widespread application of styrene-based, fiberglass-reinforced plastics is also credited with making boats more affordable.”

He said workers involved in gelcoating and resin application in a plant that builds fiberglass boats are protected from exposure to styrene because the plants are required to meet an Occupational Safety and Health Administration exposure level of 100 parts per million over an eight-hour period.

McKnight said that in 1998 the NMMA, the American Composites Manufacturers Association and the Styrene Information Research Center signed an agreement with OSHA that said NMMA and ACMA members would meet a 50-parts-per-million exposure level to provide an adequate level of safety based on exposure studies.

“The health of workers in all manufacturing facilities using styrene, including boat plants, has been monitored for 45 years,” McKnight said. “Studies looking for long-term health effects related to styrene exposure examined the health records of more than 50,000 workers exposed to styrene. These studies have not shown statistically significant increases in long-term health problems of any kind attributable to styrene exposure.”



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