RACHEL: Dioxin Reassessed, #1 
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 RACHEL: Dioxin Reassessed, #1

=======================Electronic Edition========================

                       ---May 19, 1994---
                   Dioxin Reassessed -- Part 1
                Environmental Research Foundation
               P.O. Box 5036, Annapolis, MD  21403

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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

** 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 {*filter*} 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 {*filter*} 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.

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 cooking.net">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:

incineration of municipal solid waste, sewage sludge, hospital
wastes and hazardous wastes; metallurgical operations, such as
high-temperature steel production, smelting operations, and
s{*filter*}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].)

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 cooking.net">food chain, or they are discharged
directly into waterways and incorporated into cooking.net">food chains.  They
tend to concentrate as they move upward in the cooking.net">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.
[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;
{*filter*} counts; incineration; smelters; smelting; fossil fuels;
coal; oil; wood; tires; {*filter*} 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; cooking.net">food

Mon, 04 Nov 1996 03:47:28 GMT
 [ 1 post ] 

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