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#390 - Dioxin Reassessed -- Part 1, 18-May-1994

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 estimates the size of the dioxin cancer hazard as follows:
"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 (10E-4) to one in a thousand (10E-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-ten-thousand people and one-in-every-thousand 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.

EPA expresses the same risk another way: the agency says the amount of
dioxins sufficient to create a one-in-a-million cancer hazard is a
daily intake of 0.01 picograms of dioxin per kilogram of body weight
[pg. 43]. (A picogram is a trillionth of a gram.) EPA says the average
daily intake of total dioxins among Americans is presently 3 to 6
picograms per kilogram of body weight [pg. 50], or 300 to 600 times the
one-in-a-million hazard level.

If EPA's estimate of the dioxin cancer hazard is correct, an
individual's lifetime probability of getting cancer from dioxin in the
U.S. 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.[2] Another way to look
at this hazard is to compare it to the chance of being dealt 4-of-a-
kind in poker, which is about 1 in 4200, or 240 per million. You're
more likely to get cancer from dioxin than to be dealt 4-of-a-kind.[3]

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:

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].)

compounds are created by the manufacture of chlorine and such
chlorinated compounds as chlorinated phenols, PCBs, phenoxy herbicides
(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.]


[1] Keith Schneider, "Fetal Harm, Not Cancer, Is Called The Primary
Threat From Dioxin," NEW YORK TIMES May 11, 1994, pgs. A1, A20.

[2] Joseph Rodricks, CALCULATED RISKS (N.Y.: Cambridge University
Press, paperback edition, 1994), pg. 219, says the risk of death "from
one chest x-ray in a good hospital" is one-in-a-million. John Gofman
Francisco: Sierra Club Books, 1985), pgs. 84-87 agree with this
estimate but only for a male over 45 years old. For people younger than
45 the risks are much larger; chest x-ray hazards diminish with age.

[3] A risk of 300 per million = 1 in 3333; a risk of 600 per million =
1 in 1667. The chances of being dealt 4-of-a-kind in an opening hand of
poker are 1 in 4164, says Les Krantz, WHAT THE ODDS ARE (New York:
HarperCollins, 1992), pg. 213.

Descriptor terms: dioxin; pcdfs; pcbs; dioxin reassessment; studies;
risk characterization; risk assessment; reproductive disorders;
endocrine disrupters; endocrine system; immune system; immune system
disorders; immunotoxicity; hormones; sex hormones; endometriosis;
cancer; diabetes; glucose intolerance; sperm count; incineration;
smelting; fossil fuels; coal; oil; wood; tire burning; rubber tires;
forest fires; composting; medical waste; sewage sludge; hazardous
waste; msw; cigarettes; tobacco; volcanoes; cremation; chlorine;
phenoxy herbicides; pesticides; pulp and paper industry; bleaching;
landfilling; hyde park, ny; niagara river, ny; canada; ny; inhalation;
food; meat; fish; dairy products; milk; cheese; food safety;

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