Dioxin Named a Known Carcinogen

By Cat Lazaroff

WASHINGTON, DC, January 24, 2001 (ENS) - Dioxin - already blamed for a host of ills ranging from immune system suppression and infertility to learning disabilities - has now been officially linked to cancer. The National Toxicology Program announced last week that dioxin has been added to a federal list of substances "known to be human carcinogens."


Plastic trash bags and many other common plastic products can contain toxic organochlorines (Photo courtesy Universal Plastic)
In an addendum to the Ninth Report on Carcinogens from the National Toxicology Program (NTP), 2,3,7,8-tetrachlorodibenzo-p-dioxin, also known as TCDD or dioxin, is listed as a known carcinogen.

The report comes eight months after newspapers first carried the leaked news of the new dioxin status. The NTP had to delay announcing their finding after a group of New York restaurant owners and a medical device maker filed suit in federal district court seeking to overturn the finding.

The plaintiffs argued that they would suffer economic harm from the announcement because people would start to avoid dioxin containing products, including most foods. The medical equipment manufacturer objected to NTP statements that polyvinyl chloride containing medical products, including plastic tubing and IV bags, can release dioxin to the environment if they are incinerated.

The publication of the addendum follows a ruling by the U.S. Court of Appeals for the District of Columbia Circuit, said Kenneth Olden, PhD, director of the National Institute of Environmental Health Sciences and the NTP. The court dismissed the plaintiffs request for an injunction against the announcement, though their appeal of an earlier decision upholding the listing is still pending.


Fires, like this one at a PVC plastics plant in Canada, can release enormous amounts of dioxin and other toxins into the air (Photo courtesy Greenpeace)
The plaintiffs in the lawsuit claim that the Department of Health and Human Services and National Toxicology Program had improperly applied the Report on Carcinogens' listing criteria in listing TCDD as a "known human carcinogen."

The change in the listing of dioxin from a "reasonably anticipated" carcinogen to the "known to be a human carcinogen" category had been planned to occur in the Ninth Report, published on May 15, 2000, but the designation was delayed by litigation.

Instead, the Ninth Report listed dioxin as a "reasonably anticipated" human carcinogen, and included a statement warning that an addendum might follow.

"This report shows that dioxin threatens the health of every American," said Lois Marie Gibbs, executive director of the Center for Health, Environment and Justice, when the story was leaked last year. "Dioxin from incinerators, paper mills and polyvinyl chloride (PVC) plastic production is getting into our bodies through the food we eat."

The National Toxicology Program's listing of dioxin in the "known" category is based on evidence from studies in humans that indicate that exposure to dioxin can cause cancer.


Huge amounts of plastic waste are produced each year. Disposing of these wastes without releasing organochlorines into the environment may be nearly impossible (Photo David Humber courtesy National Renewable Energy Lab)
Dioxin is no longer produced commercially, but is still a byproduct of many industrial processes. It has been found as a contaminant in some herbicides and pesticides and is also formed during the incineration of waste.

Dioxin levels in the bloodstreams of Americans have declined in recent years as a result of environmental controls, but the toxin is still widespread in the environment and can be found in very small amounts in the general population.

The Report on Carcinogens is a cancer health hazard identification document that lists substances that may pose a cancer risk to humans. But the report does not assess the conditions under which subtances may pose a risk, so the report is not intended to show which substances might pose a cancer risk to individuals in their daily lives.

Both the U.S. Environmental Protection Agency and the Food and Drug Administration have quantitative assessments of dioxin's cancer risks.


A substantial proportion of the organochlorines which have accumulated in a woman's body during her whole lifetime are passed to her child during development in the womb and through breast feeding (Photo courtesy Greenpeace)
The Report on Carcinogens is a Congressionally mandated listing of known and anticipated human carcinogens. It is prepared by the National Toxicology Program, which is headquartered at the National Institute of Environmental Health Sciences, by the secretary of the Department of Health and Human Services.

The reports include available information on the nature of exposures, the estimated number of persons exposed and the extent to which federal regulations decrease the risk of exposure to these chemicals.

The revised Ninth Report containing all addendum materials is available at: http://www.niehs.nih.gov/oc/news/dioxadd.htm