by Elizabeth Grossman

On June 10th the U.S. Department of Health and Human Services (HHS) and the National Toxicology Program released the department’s 12th Report on Carcinogens, adding eight new substances to the overall list that now includes 240 compounds (or classes of compounds) known or reasonably anticipated to be human carcinogens. Two of these eight – the industrial chemical formaldehyde and the botanical compounds known as aristolochic acids – are listed as known human carcinogens. Six others – styrene, certain inhalable glass wool fibers, o-nitrotoluene, captafol, cobalt-tungsten carbide (in powder or hard metal form), and riddelliine – are listed as reasonably anticipated to be human carcinogens.

“This is an important public health document and information resource on cancer hazards,” National Toxicology Program associate director John Bucher told reporters on a conference call announcing the new report. But, cautioned Dr. Bucher, while a RoC listing may influence how these substances are used, the report “is not a regulatory document.”

Established by Congress in 1978 in “response to concerns from people within the United States regarding the relationship between their environment and cancer,” the first Report on Carcinogens was published in 1980 and contained 26 listings.

The introduction to the 12th report notes that “Most scientists involved in cancer research believe that the environment in which we live and work may be a major contributor to the development of cancer (Lichtenstein et al. 2000)” and that “Many experts firmly believe that much of the cancer associated with the environment may be avoided (Tomatis et al. 1997).” While the Report on Carcinogens does not set any exposure standards or rank potential risks of substances, it does identify circumstances under which the listed substances may be particularly hazardous.

This last detail seems key in relation to two of the latest listings – formaldehyde and styrene – which are being listed now as particular occupational hazards.

Two widely used chemicals
Formaldehyde, first listed as a substance reasonably anticipated to be a human carcinogen in the 2nd Report on Carcinogens in 1981, is widely used to make resins for numerous consumer products, including wood products, plastics, synthetic fibers, textile finishes, and paper product coatings, and as a preservative in medical settings, scientific laboratories, and mortuaries. Urea-formaldehyde and phenol-formaldehyde resins are used in foam insulation, as adhesives in particle board and plywood, and in treating textiles. Its potential as an indoor air hazard has prompted new restrictions on its use in consumer wood products. Formaldehyde is also used as an antibacterial in some consumer products, including soaps, lotions, shampoos, and other hair care products, including the “Brazilian Blow-out Solution” that was found to contain harmful levels of formaldehyde. According to the 12th RoC, the United States produced 10 billion pounds of formaldehyde in 2006.

Formaldehyde is known to be respiratory hazard and skin irritant. OSHA regulates formaldehyde with specific standards for general industry as well as for construction and maritime industries. But OSHA also notes:

Health care professionals; pathology and histology technicians; and teachers and students who handle preserved specimens are potentially at high risk. Consumers may receive exposures from building materials, cosmetics, home furnishings, and textiles.

After listing formaldehyde as “reasonably anticipated to be a human carcinogen” for 20 years, the NTP now has sufficient evidence, Dr Bucher explained, to show that people with high exposure to formaldehyde are at risk for certain rare cancers, including nasopharyngeal cancer and myeloid leukemia.

High exposure, particularly occupational exposure, is also a factor in the styrene listing. Styrene is used to manufacture of products such as rubber, plastic, insulation, fiberglass, pipes, automobile parts, food containers, and carpet backing. Non-occupational exposures may occur through breathing indoor air that has styrene vapors from building materials, tobacco smoke, and other products. But styrene was placed on the list, explained Dr Bucher, because studies indicate that workers exposed to styrene may develop lymphohematopoietic cancer and genetic damage to white blood cells. Small amounts of styrene may also leach from polystyrene and other consumer products containing styrene, but Dr Bucher stressed that the listing was based on potential occupational exposure levels.

These listings, although not regulatory, have prompted a strong response from the chemical manufacturing industry. Immediately following the release of the report, the Styrene Information and Research Center (SIRC), a trade association representing 95 percent of the North American styrene industry, filed a complaint against HHS in the United States District Court for the District of Columbia challenging the listing of styrene in the Report on Carcinogens. The complaint, supported by the Plastics Foodservice Packaging Group and the Expandable Polystyrene Resin Suppliers Group (part of the Plastics Division of the American Chemistry Council) and American Composite Manufacturers Association, contends that the HHS listing is “arbitrary, capricious, an abuse of discretion and not in accordance with law.” The supporting declarations from industry organization representatives, however, all comment on the economic impacts of the RoC listing rather than the assessment of health effects.

According to the U.S. Department of Justice, there have been legal challenges to earlier Report on Carcinogen listings, including one against a dioxin listing, but all were unsuccessful. It’s also worth noting that the RoC reports involve input from numerous federal agencies as well as extensive public comments – the 12th Report had six public comment periods. “The strength of this report lies in the rigorous scientific review process,” said Ruth Lunn, director of the NTP Office of the Report on Carcinogens. “We could not have completed this report without the significant input we received from the public, industry, academia, and other government agencies.”

Elizabeth Grossman is the author of Chasing Molecules: Poisonous Products, Human Health, and the Promise of Green Chemistry, High Tech Trash: Digital Devices, Hidden Toxics, and Human Health, and other books. Her work has appeared in a variety of publications including Scientific American, Salon, The Washington Post, The Nation, Mother Jones, Grist, and the Huffington Post. Chasing Molecules was chosen by Booklist as one of the Top 10 Science & Technology Books of 2009 and won a 2010 Gold Nautilus Award for investigative journalism.