Cancer Causing Agents - Carcinogens (cont.)

Of the total worldwide exposure to X-radiation and gamma-radiation, 55 percent is from low-dose medical diagnosis such as bone, chest and dental X-rays, and 43 percent is from natural sources like radon. Other sources, such as industry, scientific research, military weapons testing, nuclear accidents and nuclear power generation, account for about 2 percent.

• Neutrons are also listed in the report as a "known human carcinogen." They cause genetic damage similar to that of X-radiation and gamma radiation, and thus can cause the same cancers. Neutron radiation is used less than other types of radiation in industry, medicine, and research. The general population is exposed to neutrons primarily from cosmic radiation that penetrates the earth's atmosphere.

Eleven substances have been added to the "reasonably anticipated" category:

• Naphthalene is used as an intermediate in the synthesis of many industrial chemicals, and has been used as an ingredient in some moth repellants and toilet bowl deodorants. Naphthalene is listed in the report as "reasonably anticipated to be a human carcinogen," based on inhalation studies in animals which showed it causes rare nasal tumors in rats and benign lung tumors in female mice.

• MeIQ, MeIQx, and PhIP are heterocyclic amine compounds formed when meats and eggs are cooked or grilled at high temperatures. These compounds are also found in cigarette smoke. They are listed in the report as "reasonably anticipated to be human carcinogens" because oral studies in animals showed they caused cancer in multiple organs including the forestomach, colon, liver, oral cavity, mammary gland, skin, and cecum. Several human studies suggest there is an increased risk for breast and colorectal cancers related to consumption of broiled or fried foods that may contain these or other similar compounds.
  • MeIQ is 2-Amino-3, 4-dimethylimidazo [4,5-f]quinoline
  • MeIQx is 2-Amino-3, 8-dimethylimidazo [4,5-f]quinoxaline
  • PhIP is 2-Amino-1-methyl-6-phenylimidazo [4,5-b]pyridine
• Lead is used to make lead-acid storage batteries, ammunition, and cable coverings. Lead compounds are used in paint, glass and ceramics, fuel additives, and in some ethnic and ceremonial cosmetics. The report lists lead and lead compounds as "reasonably anticipated to be human carcinogens" because exposure to lead or lead compounds is associated with a small increased risk for lung or stomach cancer in humans, and cancer of the kidney, brain or lung in studies with laboratory animals.

• Cobalt Sulfate is used in electroplating, as coloring agents for ceramics, and as drying agents in inks and paints. Cobalt sulfate is listed as "reasonably anticipated to be a human carcinogen" based on inhalation studies in laboratory animals that showed it causes adrenal gland and lung tumors.

• Diazoaminobenzene is a chemical used as an intermediate in the production of dyes and to promote adhesion of natural rubber to steel. Diazoaminobenzene is listed as "reasonably anticipated to be a human carcinogen" based on evidence that it is metabolized to benzene, a "known human carcinogen," and because it causes genetic damage in laboratory animals.

• Nitrobenzene is a chemical used mainly in the production of other industrial chemicals. It is listed as "reasonably anticipated to be a human carcinogen" because inhalation studies of this compound produced cancer in experimental animals.

• 1-Amino-2, 4-dibromoanthraquinone is a vat dye that is used in the textile industry. It is listed as "reasonably anticipated to be a human carcinogen" based on evidence that it causes cancer in experimental animals.

• 4,4'-Thiodianiline has been used as an intermediate in the preparation of several kinds of dyes. It is listed as "reasonably anticipated to be a human carcinogen" based on evidence that it causes cancer in experimental animals.

• Nitromethane is used in specialized fuels, explosives, and in the synthesis of pharmaceuticals and agricultural chemicals. It is listed as "reasonably anticipated to be a human carcinogen" based on evidence that it causes cancer in experimental animals.

The Report on Carcinogens, Eleventh Edition, is prepared by the National Toxicology Program, an interagency group coordinated by the U.S. Department of Health and Human Services. The full report is available at the NTP website http://ntp.niehs.nih.gov.

The National Toxicology Program is located at the National Institute of Environmental Health Sciences (NIEHS) in Research Triangle Park, NC. Part of the National Institutes of Health, NIEHS looks at factors in the environment that may be harmful to human health.

Some of the above information has been provided with the kind permission of the National Institutes of Health press release #NIEHS PR #05-01, Jan 31, 2005 (www.nih.gov).

Last Editorial Review: 2/1/2005