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Everything may not cause cancer -- but 228 things do

A report on carcinogens provides an accessible resource for physicians seeking to respond to patients' concerns.

By Susan J. Landers, AMNews staff. Jan. 27, 2003. Additional information

Washington -- That nickel compounds and beryllium should take a spot on a list of 228 known human carcinogens may not be quite as jarring as the placement of steroidal estrogens on that same list. But it makes sense.

"It has been known for some time that estrogens cause endometrial cancer, and there is strong evidence that they may contribute to breast cancer," said Bill Jameson, PhD, who heads the National Institute of Environmental Health Sciences' panel that produces the federal government's "Report on Carcinogens."

A number of individual steroidal estrogens were already listed as "reasonably anticipated carcinogens" in past editions of the report, but this was the first time all the hormones, which are used in hormone replacement therapy and oral contraceptives, were listed as a group.

Also newly listed in the report as "known" causes of cancer in humans are broad-spectrum ultraviolet radiation, whether generated by the sun or by artificial sources such as sun lamps and tanning beds; wood dust created in cutting and shaping wood; nickel compounds and beryllium and its compounds commonly used in industry.

The report makes a distinction between known human carcinogens and "reasonably anticipated" human carcinogens where there is either limited evidence of carcinogenicity from human studies or evidence of carcinogenicity from experimental animal studies. The report is issued every two years by the Dept. of Health and Human Services and is prepared by the National Toxicology Program at NIEHS.

One objective of the report, which was mandated by Congress in the 1978 Public Health Act, is to ensure that the American public is made aware of potential cancer hazards. The report is intended to list substances that expert panels have determined are carcinogens. It does not address or attempt to balance potential benefits of the substances.

The reports can generate publicity, particularly when a medical substance is included.

"When you get to things like HRT and, in a previous report, tamoxifen, they get a lot of attention because people don't understand that things can be carcinogenic and also have therapeutic value," said Michael Thun, MD, head of epidemiologic research for the American Cancer Society in Atlanta.

"In the case of HRT, there is still a lot of uncertainty among physicians about the level of absolute risk [for cancer] and how you make decisions for an individual patient," said Dr. Thun.

A large study on HRT was halted last summer because, in part, too many women were judged to be at risk for invasive breast cancer if the study ran for its scheduled eight years.

Dangers of exposure

Dr. Jameson views the report on carcinogens as a good way for patients to obtain information needed to weigh the risks vs. the benefits of a medical intervention and to take proper precautions if work or a hobby exposes them to hazards.

"By having this information, individuals can discuss this with their physician from an informed position and get help in coming to a decision for their particular situation," he said.

Taking note of the carcinogenic nature of wood dust, newly added to the list, Dr. Jameson gave his son-in-law, a furniture builder, a respirator for Christmas. "If you know wood dust has been shown to cause cancer in the workplace, you can protect yourself and be OK," he noted.

Although the report is not aimed at clinicians, said Dr. Thun, the listing provides a good resource to answer patients' queries on exposure to various substances. While the classification of carcinogenic substances has its largest impact on how the substances are labeled and handled in the workplace, the list is also useful to physicians, said Dr. Thun. It is accessible on the Internet, and it provides a brief and informative summary of carcinogenic products, he noted.

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 ADDITIONAL INFORMATION: 

Copyright 2003 American Medical Association. All rights reserved.