The 16 nominations for the Eleventh Report on Carcinogens, due out in 2004, include two strains of hepatitis -- B and C, which have been linked to liver cancer -- and human papillomavirus (HPV), which is a leading source of cervical cancer in women. It's the first time viruses have been proposed for the report, which comes out every two years.
The report, which Congress established in the 1970s, initially covered only well-defined chemicals or chemical mixtures. But a mid-1990s review of the statute creating the report encouraged cancer researchers to open its membership to other substances or exposures, says Bill Jameson, who oversees the document for the National Toxicology Program (NTP), a division of the National Institute of Environmental Health Sciences. The ninth report, for example, included exposure to sunlight as a known cause of skin tumors."The data appears to be very strong that there is an association between [the proposed viruses] and cancer in man," Jameson says. "I'm sure in the future there will be others."
Most of the items on the latest list were put there by government researchers, whose review of the scientific literature turned up at least the potential for concern. They include: cobalt sulfate, a substance used in ceramics and electroplating; naphthalene, found chiefly in mothballs and toilet bowl deodorizers; X-ray radiation and neutrons. Exposure to these atomic particles is typically trivial, but patients undergoing neutron radiotherapy and possibly also aircraft travelers and crew may be at increased risk of cancer.
Also among the nominees this round are occupational exposure to lead and lead compounds, such as those churned out by smelting facilities, battery works, steel welding and even firing ranges. Recent evidence suggests that exposure to high levels of lead may up the risk of brain, lung, kidney and other cancers.
A private group, the United Auto Workers, has proposed that diethanolamine, or DEA, make the list. DEA belongs to a group of molecules called surfactants. These chemicals reduce surface tension of liquids and are used in a wide range of applications, from detergents and cosmetics to neonatal intensive care, where they help babies with under-formed lungs breathe. Work in rodents has shown "clear evidence" that DEA, which the auto industry uses in metalworking applications, can cause cancer in some mice, the NTP says.
Franklin Mirer, the UAW's director of health and safety and a noted toxicologist, says, "The data available are from the rodent [test]; however, there is some indication of increased liver toxicity and liver cancer in humans" from skin exposure to the substance.
"Metalworking fluids are at the top of our list of health hazards associated with work for our membership," says Mirer, adding that "thousands" of union members are probably exposed to DEA on the job. The chemical "is probably one of five carcinogens that are routinely found in metalworking fluids. In this case, it's there as something that can be substituted for, or as an unwanted contaminant."
Jameson says suggestions from non-governmental sources are treated the same as those coming from within the federal envelope. "When we receive a nomination from outside the NTP, we take it very seriously and usually go through the effort of putting together a background document to see all the relevant information," he says. On the other hand, Jameson adds, the substances and exposures ultimately reviewed are far fewer than the catalog of chemicals the public proposes.
The list of nominees will now undergo a period of public comment along with a review by government toxicologists, who will determine the cancer risks, if any, of each. Those with clear evidence of their harm to humans are labeled "known" carcinogens, while those with less-certain risks may be considered "reasonably anticipated" to cause cancer.
The initial conclusions will then become part of a draft report, which gets circulated throughout other federal agencies. A final version is due to Congress in 2004.
What To Do
For a complete list of the nominated substances and exposures, visit the National Institute of Environmental Health Sciences.
To learn more about the toxicology report, check out the National Toxicology Program.
For more on cancer, try the American Cancer Society.