U.S officials have issued a warning list of chemicals and biological agents that may put people at increased risk for cancer. The congressionally mandated 12th Report on Carcinogens (RoC), prepared for the Department of Health and Human Services and released on June 10, contains new classifications for several substances found in building materials.

The designation of formaldehyde as a known human carcinogen garnered the most attention, with industry representatives voicing their objections. The American Chemistry Council, for example, said the “unscientific decision” would jeopardize thousands of U.S. jobs since the chemical is in such widespread use.

Formaldehyde-based binders are used in composite wood products, fiberglass insulation, and other common building components. The chemical was first listed in the 1981 edition of the RoC as “reasonably anticipated to be a human carcinogen.” But since that time, according to the current report, new studies have been published supporting the change in status. Other health effects attributed to offgasing of formaldehyde into the interior environment include fatigue, skin rash, and eye, nose, and throat irritation.

The new version of the RoC follows legislation passed a year ago by Congress limiting emissions of formaldehyde from hardwood plywood, particleboard, and medium-density fiberboard. The limits are based on state regulation established in 2007 by the California Air Resources Board. Although many materials, including structural plywood, structural composite lumber, and oriented strand board are exempt, some sources predict that the RoC’s release will help regulators broaden the legislation’s scope. “The report could strengthen the hand of the Environmental Protection Agency to extend the regulations to more product types,” says Tom Lent, policy director with the Healthy Building Network, an advocacy group working to reduce the environmental and health impacts of building materials.

Several manufacturers already offer products made with alternative or low-emissions binders. So, in many ways, the reclassification of formaldehyde “is a reinforcement of an assessment already made,” says Lent. He maintains that the report’s new designation for styrene as a reasonably anticipated carcinogen is more significant. “It’s the strongest assessment of styrene’s carcinogenic properties to date,” he says. Styrene is an industrial chemical used to make plastics and rubber. It is the key component of expanded and extruded polystyrene insulation, and is also found in some carpeting, carpet backing, and carpet adhesives. The cancer risk associated with products that incorporate the compound is linked primarily to exposure during the manufacturing process, according to the RoC.

The report’s release could reduce pressure on one set of manufacturers — those that make building insulation from glass wool. Previous versions had labeled “Glass Wool (Respirable Size)” as a substance reasonably anticipated to be a human carcinogen. But the new report narrows the type of fibers considered problematic to “Certain Glass Wool Fibers (Inhalable),” since these have been found to be more biopersistent. Although such “inhalable” fibers are found in some building applications, such as high-efficiency air filters and acoustical insulation, the adjustment, according to Lent, shifts the focus away from the type of general-purpose fibers used widely in batt insulation.