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The original edition of Rachel's #390, dated May 19, 1994,
misinterpreted EPA's estimate of the cancer risk from dioxin.
EPA's estimate (ranging from a one-in-ten-thousand to a
one-in-a-thousand cancer risk) represents a lifetime, or
70-year, risk estimate, not an annual risk.  Below is a
corrected version of #390.  If you forwarded #390 to anyone,
please send them this corrected edition as well.

==================CORRECTED Electronic Edition==================

           ---May 19, 1994; corrected June 7, 1994---
                    DIOXIN REASSESSED--Part 1
                Environmental Research Foundation
               P.O. Box 5036, Annapolis, MD  21403

          Back issues available via anonymous ftp from
      ftp.std.com/periodicals/rachel and via gopher server
   at gopher.std.com and at envirolink.org and at igc.apc.org.

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 {*filter*} stream of men,
interfering with glucose metabolism (a condition suggestive of
diabetes), and causing other negative changes in health and well

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

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 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
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 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 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.]


[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 and Egan O'Connor, X-RAYS; HEALTH
EFFECTS OF COMMMON EXAMS (San 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.

Mon, 25 Nov 1996 05:22:03 GMT
 [ 1 post ] 

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