Formaldehyde a Known Human Carcinogen, Styrene, Some Glass Fibers Likely, HHS Says

Formaldehyde has been identified as a known human carcinogen in a report released by the Department of Health and Human Services June 10.

The report also lists styrene as a reasonably anticipated human carcinogen.

The two commonly used industrial chemicals are among eight substances added to the 12th Report on Carcinogens, a congressionally mandated report prepared for HHS by the National Toxicology Program.

Worker studies have shown that formaldehyde, which is widely used in production of building materials such as pressed wood, can cause myeloid leukemia along with cancers in the sinuses and upper throat, the report said.

In addition, aristolochic acids, a family of naturally occurring chemicals in plants grown in the United States and other countries, were classified as known human carcinogens.

The Food and Drug Administration issued a warning in 2001 advising against the consumption of herbal products with aristolochic acids due to concerns including the risk of cancer, but they remain on the market, NTP said in a fact sheet about the botanicals.

Human studies have provided “limited evidence” that styrene caused blood cancers such as leukemia, the report said. That evidence was supported by genetic damage found in exposed workers that could lead to cancer, it said.

Additional evidence came from laboratory studies in several strains of mice, the 12th report said.

Five other substances were classified as reasonably anticipated human carcinogens:

  • cobalt-tungsten carbide, which is used to make cutting and grinding tools, dies, and other products for a broad spectrum of industries, including mining;
  • captafol, a fungicide banned in the United States in 1999;
  • o-nitrotoluene, a chemical used to make azo and other dyes, agricultural chemicals, pharmaceuticals, and other compounds; and
  • certain inhalable glass wool fibers.

Not all glass wool or man-made fibers were found to be carcinogenic, NTP said in announcing the report's release.

“The specific glass wool fibers referred to in this report … include only those fibers that can enter the respiratory tract, are highly durable, and are biopersistent, meaning they remain in the lungs for long periods of time,” NTP said.

Riddelliine, a chemical found in some plants in the western United States, also was classified as a reasonably anticipated human carcinogen. The chemical has no known commercial uses in the United States, the 12th report said.

“However, the riddelliine-containing plant Senecio longilobus has been used in medicinal herb preparations in the United States, and S. jacobaea and S. vulgaris, both of which have been shown to contain riddelliine, are used in medicinal preparations in other parts of the world,” the report said.

The Report on Carcinogens is developed through a multi-step process with multiple opportunities for peer review and public comment. HHS makes the final decisions on classifications.

The 12th report includes 240 listings, some of which are classes of related chemicals or substances; 54 substances are listed as known human carcinogens, and 186 are reasonably anticipated to be human carcinogens.

By Pat Rizzuto

12th Report on Carcinogens and related documents are available at