Eight substances have been added to the list of carcinogens by the HSS (US Department of Health and Human Services) today. The Report of Carcinogens has added formaldehyde, aristolochic acids, o-nitrotoluene, captafol, cobalt-tungsten carbide (in powder or hard metal form), riddelliine, certain inhalable glass wool fibers, and styrene to the list of carcinogens.

There are now 240 carcinogens in the list.

Linda Birnbaum, Ph.D., director of both the NIEHS (National Institute of Environmental Health Sciences) and the NTP (National Toxicology Program), said:

“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. 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 NTP prepares the Report on Carcinogens for the HHS Secretary. It is a congressionally mandated document. It identifies substances, agents, mixtures or exposures in two categories:

  • Those that are known to be human carcinogens
  • Those reasonably anticipated to be human carcinogens

A substance which is included in the list in the Report on Carcinogens does not in itself mean it causes cancer. There are many factors which cause cancer, including how long the human is exposed and a person’s susceptibility to a particular substance.

As soon as a substance is put forward by the private or public sector and is chosen for consideration, it is extensively evaluated with several opportunities for scientific and public contributions. On each substance, the HHS says there were at least six opportunities for public input.

For each candidate substance under review, the NTP used established criteria to evaluate the scientific evidence. Several federal agencies were involved in the evaluations, including the CDC, NIH, FDA, EPA, the US Consumer Product Safety Commission, and the Occupational Safety and Health Administration.

Ruth Lunn, Dr.P.H., director of the NTP Office of the Report on Carcinogens, said:

“The strength of this report lies in the rigorous scientific review process. We could not have completed this report without the significant input we received from the public, industry, academia, and other government agencies.”

Aristolochic acids – people with kidney disease who consumed botanical products which contained aristolochic acids were found to have a higher risk of developing bladder cancer and cancer in the upper urinary tract. Some plant species naturally have amounts of aristolochic acids in them. Even though the FDA in 2001 recommended that people stop using any botanical products with aristolochic acids in them, they are still for sale online and abroad. Several herbal products contain aristolochic acids, such as those for the treatment of inflammation, gout and arthritis.

Formaldehyde – it was initially listed in the 2nd Report on Carcinogens as a substance that was reasonably anticipated to be a human carcinogen, after it was found to cause nasal cancer in laboratory rats. There is now compelling evidence from human studies to demonstrate that people with higher exposure to formaldehyde have a greater risk of developing nasopharyngeal cancer, sinonasal cancer, and myeloid leukemia.

Formaldehyde’s chemical formula is CH2O. It is a colorless, flammable, pungent chemical that is extensively used to make resins for composite wood products, synthetic fibers, textile finishes, and paper product coatings. It is also used as a preservative in mortuaries, medical laboratories, some hair straightening products, and other consumer goods.

Captafol – a fungicide used to protect fruits, vegetables, ornamental plants and grasses. It is also used as a seed treatment. The USA banned it in 1999, but previous exposures may continue to affect health today. Laboratory experiments showed that dietary exposure caused tumors to develop at several different tissue sites in mice and rats.

Cobalt-tungsten carbide (in powder and hard metal form) – used to make dies, cutting and grinding tools, and wear-resistant products for several industries. Cobalt-tungsten hard metals are often referred to as cemented or sintered carbides in the USA.

Some inhalable glass wool fibers – some fibers were included in the list following results from experimental animal studies. The HHS stresses that only some glass wool and man-made fibers were included in the list of carcinogens, not all of them. In this latest report, the glass wool fibers that have been redefined include only those that had been previously mentioned and can enter the respiratory tract, are highly durable, and are stay in the lungs for a long time (biopersistent).

There are two main categories of glass wool fibers, as far as consumers are concerned:

  • Low-cost, general purpose fibers – mainly glass wool used for home and building insulation. This type is less durable and less biopersistent.
  • Special purpose fibers (premium)

o-Nitrotoluene – laboratory studies on rats and mice showed tumor formation at many different tissue sites. This substance is used as an intermediate when preparing azo dyes and some other dyes, including magenta and several sulfur dyes for paper, leather, silk, wool and cotton. o-Nitrotoluene is used in agricultural chemicals, pesticides, petrochemicals, rubber chemicals, explosives and pharmaceuticals. American workers are susceptible to o-Nitrotoluene exposure by breathing it in or through the skin during production and use. This substance has also been found in water and near munitions facilities, as well as near military training facilities.

Riddelliine – animal laboratory studies linked this botanical to a higher risk of developing liver cancer and leukemia in rats, and lung cancer in mice. Riddelliine must not be confused with the ADHD medication Ritalin. Riddelliine is found in some plants of the genus Senecio, which is a member of the daisy family, and grows in sandy areas in the western USA. Examples of plants include groundsel and ragwort. At least 13 Senecio species have been detected in herbal medications. Human exposure can occur by consuming teas, honey, herbal medications, or foods from animals that have been fed on the plants.

Styrene – a synthetic chemical used globally in the manufacturing of plastics, insulation, fiberglass, pipes, food containers, carpet backing and car parts. Human exposure can occur by inhaling styrene from tobacco smoke, building materials and other products. Limited evidence points to a higher risk of lymphohematopoietic cancer and genetic damage in lymphocytes among workers exposed to styrene.

“12th Report on Carcinogens”
National Toxology Program, Department of Health and Human Services

Written by Christian Nordqvist