INSIGHT

Summer Tracker | Tracker Back Issues

References & Links

Environmental Protection Agency
www.epa.gov/ncea/dioxin.htm

During June, 2000 the Environmental Protection Agency (EPA) took decisive steps against the insecticide chlorpyrifos and issued a controversial draft reassessment of the industrial waste product, dioxin.

On June 8, 2000 citing unacceptable health risks, particularly to children, Carol M. Browner, Administrator of the EPA announced actions against the insecticide chlorpyrifos that would:

• virtually eliminate home, lawn, and garden uses by the end of the year;

• virtually eliminate all termite-control uses in existing homes by the end of the year;

• eliminate chlorpyrifos used as a termiticide for new home and building construction by the end of 2004;

• eliminate the use of chlorpyrifos for all sensitive areas, such as schools, day care centers, parks, hospitals, nursing homes, and malls by the end of the year;

• eliminate or dramatically lower pesticide residues on several foods by next growing season.

Chlorpyrifos is an organophosphate insecticide, which has been available for more than 30 years and is used in tens of millions of homes annually. It is an ingredient in numerous well-known products including Raid sprays, Hartz flea collars, and Black Flag liquid roach and ant killer. As a broad-spectrum crop protection product, chlorpyrifos assists in minimizing insect damage to corn, cotton, wheat, alfalfa, sugarbeets, peanuts, tree fruits, nut crops, and many vegetables.

This regulation of chlorpyrifos stems from the Food Quality Protection Act. Passed in 1996, the Act is a rare law because it was supported by both food industry and environmental groups. For food producers, the Act repealed the hated Delaney Clause that banned the use of pesticides if they posed even the slightest risk of cancer. For environmentalists, the Act ordered the EPA to guarantee that substances used on food do not expose children—considered more vulnerable than adults to some pesticides—to adverse health effects. Last summer, the EPA took the first actions under the new law against two pesticides that posed the greatest threats to children at that time: methyl parathion and azinphosmethyl.

The Act fundamentally changed the rules governing pesticides. Dow AgroSciences, one of the major producers of chlorpyrifos, noted: "the Food Quality Protection Act has fundamentally changed the way in which pesticides are regulated in the U.S.…In its ongoing implementation of the Food Quality Protection Act, the EPA has demonstrated that it intends to apply standards far more restrictive than those historically established by the scientific community.…More than 3,600 studies and reports have been conducted examining critical aspects of chlorpyrifos products as they relate to health and safety. Taken together, these reports and studies show that currently labeled uses of chlorpyrifos products provide wide margins of safety for both adults and children."

On June 12, 2000 the EPA released draft chapters of its long-awaited reassessment of the health risks from dioxin. Several groups will review these draft chapters as part of a scientific and public review scheduled to be completed by the end of the year.

Dioxin is commonly considered the most toxic man-made substance. Dioxin comes from a variety of natural and industrial sources. It is produced in the incineration of certain plastic waste products and the production of paper pulp. Dioxin accumulates in the fat of mammals and fish. Dioxin has had a notorious past: it was the toxic component in Agent Orange—used to clear forests in the Vietnam war—and also caused the evacuation of Times Beach, Missouri, in 1983, and of the Love Canal site in Niagara Falls, New York, in 1978.

In this report, the EPA concludes that the most potent form of dioxin—2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)—is a human carcinogen based on evidence of animal and human studies. The EPA "estimates that the risks for the general population based on dioxin exposure could be as high as a 1 in 100 to 1 in 1,000 increased chance of experiencing cancer related to dioxin exposure. This range for cancer risk indicates an about 10-fold higher chance than estimated in EPA’s earlier (1994) draft of this reassessment."

The mechanism of dioxin’s carcinogenesis probably results from its affinity for the AH receptor, which exists in cells throughout the body and plays a key role in determining how our body reads its DNA. (This receptor has also been implicated in the mechanism by which cigarette smoking causes cancer.)

The draft report finds that dioxin levels in the environment have declined significantly since the 1970s following EPA regulatory controls and industry actions. The EPA’s best estimates of emissions indicate that dioxin emissions in the United States decreased by about 80% between 1987 and 1995, primarily due to reductions in air emissions from municipal and medical waste incinerators. Dietary intake of dioxin also appears to be declining.

The EPA is inviting comments on the dioxin reassessment, which is available at the EPA’s Dioxin Reassessment web site: www.epa.gov/ncea/dioxin.htm. Following completion of scientific and public review, the EPA will issue the final dioxin reassessment document and at the same time will publish a draft Dioxin Risk Management Strategy for public comment. The strategy will propose the EPA policy and programs for dioxin using the reassessment as its scientific basis.

The reassessment is controversial and faces legal challenges. Already a group of New York restaurant owners and a medical device maker have filed suit in federal district court to block the release, claiming that labeling dioxin as a "human carcinogen" would cause them economic harm. The restaurant owners contend that people would stop eating at their restaurants because dioxin is found in food; the device maker objects to the contention that polyvinyl chloride medical products contribute to environmental dioxin when incinerated.

Occupational health providers should be aware of these developments concerning chlorpyrifos and dioxin. Workers exposed to these chemicals are certain to raise questions about health effects. The EPA’s action on chlorpyrifos is largely directed to protect children. The long-term effects of dioxin raise troubling questions for workers exposed to the compound.