For three years, U.S. Environmental Protection Agency [EPA] has been reassessing the toxicity of dioxin and other dioxin-like chemicals, including dibenzofurans and some PCBs [polychlorinated biphenyls]. PCBs are industrial chemicals now banned in the U.S. because of widespread environmental damage. Dioxins and furans are unwanted byproducts of many industrial operations including incineration, tire burning, combustion of coal and oil, manufacture of paper and some pesticides, and metal smelting. Dioxins and furans are created when chlorine combines with other chemicals at high temperatures.

In 1990, the paper and chlorine industries campaigned to force EPA to undertake a thorough review of dioxin science (RHWN #275). It is now abundantly clear that the reassessment has not turned out the way those industries hoped it would. We have obtained two drafts of the EPA's summary report of its dioxin reassessment titled, "Chapter 9. Risk Characterization of Dioxin and Related Compounds," dated March 7, and May 2, 1994. Some conclusions of the May 2 draft were reported in the NEW YORK TIMES May 11, 1994. [1] What follows here is based entirely on the EPA's May 2 draft. Page numbers inside square brackets refer to that draft.

EPA has identified 30 dioxin-like chemicals (7 true dioxins, 10 furans, and 13 PCBs) that have dioxin-like characteristics. EPA's draft report describes the toxicity of all these 30 chemicals taken together; in this discussion we refer to them as simply dioxin.

EPA has concluded that:

** For non-cancer effects, such as damage to the reproductive, endocrine, and immune systems, in birds, fish and mammals, including humans, dioxin is much more toxic than previously believed [pg. 35].

The agency says, "Indeed, these compounds are extremely potent in producing a variety of effects in experimental animals based on traditional toxicology studies at levels hundreds or thousands of times lower than most chemicals of environmental interest." [pg. 1] And: "There is adequate evidence from studies in human populations as well as in laboratory animals and from ancillary experimental data to support the inference that humans are likely to respond with a plethora [an abundance] of effects from exposure to dioxin and related compounds." [pg. 49]

Dioxin's most powerful effects are seen in the reproductive system, the endocrine (hormone) system, and the immune system. Most sensitive of all are newborn infants and fetuses exposed while in the womb. "In mammals, postnatal functional alterations involving learning behavior and the developing reproductive system appear to be the developmental events most sensitive to perinatal dioxin exposure. The developing immune system may also be highly sensitive." [pg. 36] In other words, dioxin exposure of mammals (including humans) shortly before or shortly after birth ("perinatal") are most likely to impair intellectual development and the immune system. The immune system protects against bacterial and viral disease, and cancer, so damage to the immune system can invite other serious diseases.

** Some of dioxin's powerful effects are observable in humans at dioxin exposure levels already occurring in the U.S. population. [pgs. 34, 37, and Table 9-3 following pg. 43] EPA says, "Some of the effects of dioxin and related compounds have been observed in laboratory animals and humans at or near levels to which people in the general population are exposed." [pg. 47] And: "In humans, subtle changes in enzyme activity indicating liver changes, in levels of circulating reproductive hormones in males, in reduced glucose tolerance, and in cellular changes related to immune function suggest the potential for adverse impacts on human metabolism, reproductive biology, and immune competence at or within one order of magnitude of average background body burden levels." [pgs. 49-50] In other words, average levels of dioxin already present in the bodies of average Americans --or levels not more than 10 times as high as average levels --seem to be capable of damaging the immune system, reducing sex hormones in the blood stream of men, interfering with glucose metabolism (a condition suggestive of diabetes), and causing other negative changes in health and well being.

Table 9-3 shows that the average amount of dioxin in Americans is 9 nanograms per kilogram (ng/kg) of body weight; a nanogram is a billionth of a gram and there are 28 grams in an ounce. Table 9-3 also shows that sex hormones are diminished in men with 13 ng/kg; altered glucose tolerance has been observed in humans with 14 ng/kg; decreased growth is observable in humans having 47 ng/kg; endometriosis is produced in monkeys having 27 ng/kg.

Within the general public, some people are receiving lower-than-average doses of dioxin and others are receiving higher-than-average doses because of their diets, living near facilities emitting dioxin, exposures at work, and so forth. EPA says, "Some more highly exposed members of the population may be at risk for a number of adverse effects including developmental toxicity, reduced reproductive capacity in males based on decreased sperm counts, higher probability of experiencing endometriosis in women, reduced ability to withstand immunological challenge, and others." [pg. 50]

** Dioxin's cancer effects are worse than previously thought. EPA now says flatly, dioxin is "likely to present a cancer hazard to humans" [pg. 52]. And dioxin "probably increases cancer mortality of several types" in humans, EPA says. [pg. 31]

EPA shows numerically that existing levels of dioxin may be a significant cancer hazard: "Modeling estimates suggest that, if dioxin and related compounds are adding to human cancer burden, current background exposure may result in upper bound population cancer risk estimates in the range of one in ten thousand (10**-4) to one in a thousand (10**-3) attributable to exposure to dioxin and related compounds." [pgs. 43-44] In other words, EPA's best estimate is that existing levels of dioxin in the U.S. population may be sufficient to cause cancer in somewhere between one-in-every-thousand people and one-in-every-ten-thousand people each year. Since there are 250 million Americans, EPA is saying that existing dioxin levels may be causing somewhere between 25,000 and 250,000 new cancers each year. There are about one million new cancers diagnosed each year in the U.S. [see RHWN #385], so EPA's best estimate is that dioxin now present in the American people may be responsible for somewhere between 2.5% and 25% of all cancers.

[[The following is a rewording of this article from a greenleft publication:

"EPA's best estimate is that existing levels of dioxin in the US population may be sufficient to cause cancer in somewhere between one in 10,000 people and one in 1000 people during a lifetime (70 years). Since there are 250 million Americans, EPA is saying that existing dioxin levels may be causing somewhere between 25,000 and 250,000 cancers in a lifetime (70 years), or 350 to 3500 new cancers each year.

If EPA's estimate of the dioxin cancer hazard is correct, an individual's lifetime probability of getting cancer from dioxin in the US falls in the range of 1 in 1700 to 1 in 3300. This is the same risk you would get from 300 to 600 chest x-rays."]]

Another way to estimate the size of the cancer hazard is to note that EPA says the amount of dioxins sufficient to create a one-in-a-million cancer hazard is daily intake of 0.01 picograms of dioxin per kilogram of body weight [pg. 43]. (A picogram is a trillionth of a gram.) Average daily intake of total dioxins among Americans is 3 to 6 picograms per kilogram of body weight [pg. 50], or 300 to 600 times the one-in-a-million hazard level. This means that, in the U.S. population of 250 million, our average daily dose of dioxin in food and air may be causing somewhere between 75,000 and 150,000 cancers each year. Thus both ways of estimating the cancer hazard force the conclusion that dioxins may already be a major cancer hazard for Americans.

Dioxins are produced in very small quantities, if at all, by nature. EPA says, "...the presence of dioxin-like compounds in the environment occurs primarily as a result of industrial practices." [pg. 6]

EPA identifies 4 major sources of dioxin in the environment:

(1) COMBUSTION AND INCINERATION SOURCES. This category includes incineration of municipal solid waste, sewage sludge, hospital wastes and hazardous wastes; metallurgical operations, such as high-temperature steel production, smelting operations, and scrap metal recovery furnaces; and the burning of coal, wood, petroleum products and used tires for power or energy generation. Cigarette smoke, crematories, volcanoes and forest fires are "minor sources," says EPA. [pg. 7] (Forest fires release dioxins that have been discharged by industrial smoke stacks and have fallen onto the leaves of trees; by similar means, leaf compost can be contaminated by dioxins [pg. 8].)

(2) CHEMICAL MANUFACTURING/PROCESSING SOURCES. Dioxins and dioxin-like compounds are created by the manufacture of chlorine and such chlorinated compounds as chlorinated phenols, PCBs, phenoxy herbi-cides (e.g., 2,4,5-T, 2,4-D and 11 others), chlorinated benzenes, chlorinated aliphatic compounds, chlorinated catalysts, and halogenated diphenyl ethers. [pg. 7] Although manufacture of many chlorinated phenols, and PCBs, ceased in the U.S. around 1980, use and disposal are continuing both inside and outside the U.S. Large quantities of PCBs are in "storage" in leaking landfills; another billion pounds of PCBs (about 1/3 of all PCBs ever manufactured) simply cannot be accounted for (see RHWN #327).

(3) INDUSTRIAL/MUNICIPAL PROCESSES: Dioxin-like compounds are created during chlorination of naturally-occurring phenolic compounds, such as those in wood pulp. Chlorine bleaching in the manufacture of bleached pulp and paper has resulted in dioxins in paper products as well as in liquid and solid wastes from this industry. [pg. 7]

(4) RESERVOIR SOURCES: Dioxin degrades very slowly once it is released into the environment. Therefore past releases of dioxin have accumulated in various "reservoirs," such as soils, sediments, organic matter, and waste disposal sites. (The Hyde Park Landfill on the edge of the Niagara River bordering New York and Canada has been estimated to contain as much as a ton of dioxins. See RHWN #188.) When dioxins move from these reservoirs they can become "new sources" of dioxin for a particular locale. All together, these sources emit some 14,000 grams (30.9 pounds) of total dioxins each year in the U.S. [pg. 8] But the amount of dioxins falling on the surface of the U.S. each year is estimated to be between 20,000 and 50,000 grams (44.1 to 110.2 pounds) [pg. 9]. Obviously some important sources of dioxin have not yet been identified. Dioxins may be arriving from other countries, carried on the wind. EPA simply doesn't know.

Dioxins fall out of the atmosphere onto the land and water and are then incorporated into the food chain, or they are discharged directly into waterways and incorporated into food chains. They tend to concentrate as they move upward in the food chain; over 90% of the dioxins in our bodies enter with our food. The major sources of dioxin to humans are meat, fish and dairy products, though inhalation may be important near some emission sources, such as some incinerators.

[To be continued.]
                                                                         --Peter Montague, Ph.D.
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[1] Keith Schneider, "Fetal Harm, Not Cancer, Is Called The Primary Threat From Dioxin," NEW YORK TIMES May 11, 1994, pgs. A1, A20.

Descriptor terms: dioxin; tcdd; 2,3,7,8-tetrachlorodibenzo-p-dioxin; dibenzofurans; furans; dioxins; pcbs; polychlorinated biphenyls; epa reassessment; studies; risk characterization; risk assessment; reprodctive disorders; endocrine disrupters; endocrine system; immune system; immune disorders; immunotoxicity; toxins; poisons; hormones; sex hormones; endometriosis; cancer; diabetes; glucose intolerance; sperm counts; incineration; smelters; smelting; fossil fuels; coal; oil; wood; tires; rubber tires; forest fires; leaf composting; medical wastes; infectious wastes; hospital wastes; sewage sludge; hazardous waste; municipal solid waste; msw; cigarettes; tobacco; volcanoes; cremation; crematories; chlorine; phenoxy herbicides; pesticides; paper; pulp; bleaching; landfilling; hyde park; niagara river; new york; canada; ny; cn; inhalation; food; meat; fish; dairy products; milk; cheese; food safety;