=======================Electronic Edition========================
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RACHEL'S ENVIRONMENT & HEALTH WEEKLY #636 .
---February 4, 1999--- .
HEADLINES: .
DIOXINS--THE VIEW FROM EUROPE .
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DIOXINS--THE VIEW FROM EUROPE

The term "dioxin" encompasses a family of 219 different toxic
chemicals, all with similar characteristics but different
potencies.[1] In recent years, the International Agency for
Research on Cancer (IARC), a division of the World Health
Organization, has labeled the most potent dioxin, called TCDD, a
known human carcinogen.[2] IARC has labeled many of the less
potent dioxins "probable" human carcinogens.

Low-level exposures to dioxins are also known to interfere with
the immune system, the reproductive system, the endocrine
system, and the early growth and development of humans and
animals.[3] In sum, dioxins are a family of powerful all-purpose
poisons.

In the early 1990s, many governments, including the U.S.
government, reported that everyone in the industrialized world
is exposed to substantial quantities of dioxins day in and day
out, thus acknowledging a humiliating failure of the world's
public health apparatus.

In 1991, the U.S. EPA [Environmental Protection Agency] with
considerable fanfare announced it was undertaking a full-blown
scientific re-assessment of dioxin. Nine years later, that
re-assessment has now disappeared from view and may have died, a
victim of politics. (See REHW #390, #391.) The big corporate
dioxin dischargers are also major contributors to federal
election campaigns, and the Clinton/Gore administration at this
point in history seems incapable of even gumming the hand that
feeds it. Furthermore, since 1994, the Republican-dominated
Congress has dropped all pretense of acting independently of its
corporate sponsors.

Meanwhile, a meeting of 40 scientists convened in Switzerland
last May by the World Health Organization concluded that dioxin
is 2 to 10 times as toxic as it had seemed in 1990,[3] and a
group of German scientists concluded last April that dioxin may
be responsible for 12% of human cancers in industrialized
countries.[4] If this estimate were correct, it would mean dioxin
is responsible for 120,000 cancers each year in the U.S. This new
German estimate is at least 10 times as high as previous
estimates by U.S. government scientists (see REHW #390, #391).

The good news is that the levels of dioxin in the environment
have dropped as much as 50% in the last decade as governments in
Europe and local activists in this country have forced industry
to adopt cleaner technologies.[3] Still, many of the effects of
dioxins are delayed by a decade or more, so health effects from
past exposures will continue to manifest themselves for several
decades.

Except as laboratory curiosities, dioxins are never
intentionally produced because they have no commercial
value. However, they are created as unwanted byproducts
by most combustion processes; during the manufacture of
many kinds of chemicals, pesticides and wood preserva-
tives; during incineration of medical, municipal and hazard-
ous wastes; in metal smelting; and in the manufacture of
paper. An important pathway for spreading dioxins into the
environment is using sewage sludge as a soil amendment or
a fertilizer.

Dioxins are also present in cigarette smoke at about
the same concentration found in the stack of a municipal
incinerator, the difference being that no one draws the
smoke from an incinerator into their lungs undiluted, or
exhales incinerator flue gas into an enclosed room for
others to breathe.[5]

Some dioxins are more toxic than others, and the scientific
community has established a way of comparing the toxicities and
the quantities of various mixtures of dioxins. The technique is
called TEQ, or toxic equivalents. The TEQ system takes into
account the variations in toxicity and expresses toxicity in
terms of the most toxic dioxin, which is TCDD.

For example, U.S. EPA estimates that total dioxin emissions in
the U.S. averaged about 3000 grams (3 kilograms, or 6.6 pounds)
per year TEQ in 1995. This means that all of the dioxins
released into the environment in 1995 in the U.S. had a total
toxicity equal to the toxicity of 3000 grams of TCDD.[6] (EPA
acknowledges considerable uncertainty in this estimate; the true
average lies somewhere between 1200 grams and 7900 grams TEQ,
EPA says.[6,pg.2-7])

According to EPA, the major sources of dioxins in 1995 were
municipal garbage incinerators (1100 grams, 36% of the national
total); medical waste incinerators (477 grams, 16%); cement
kilns burning hazardous waste (153 grams, 5%); industrial coal
combustion (73 grams, 2.4%); residential wood combustion (63
grams, 2%); industrial wood combustion (29 grams, 1%); diesel
engines (33 grams, 1%); copper smelting (504 grams, 17%);
aluminum smelting (17 grams, 0.5%); forest fires (208 grams,
7%); incineration of sewage sludge (6 grams, 0.2%); plus 375
grams (12% of the national total) spread directly into the
nation's soils in sewage sludge.[6,pg.2-13] (The total is not
exactly 100% because of rounding.)

Dioxins do not dissolve readily in water, but they do in fat.
Therefore, fat-containing foods tend to be contaminated with
dioxins. Adults in the U.S. take in between one and 10 picograms
of dioxin TEQ per kilogram of body weight per person per day
(pg/kg/day).[1,3] (A kilogram is 1000 grams, or 2.2 pounds; a
picogram is a trillionth of a gram and there are 28 grams in an
ounce.) Eighty to 90 percent of our daily dioxin intake comes
from eating milk, meat and fish.

Breast-fed infants take in 70 picograms of dioxin TEQ per
kilogram of body weight per day -- seven to 70 times as much as
the average adult.[3] Despite this, breast-fed infants are
healthier than infants fed bottled formula.

The cancer hazard from routine exposure to dioxin has recently
been estimated by a group of German scientists.[4] They report
that, for adults, the lifetime cancer hazard lies somewhere
between one per hundred and one per thousand for each picogram
of dioxin TEQ ingested per kilogram of body weight per day (pg/-
kg/day) Since the daily ingestion in the U.S. ranges from one
to 10 pg/kg/day, we can calculate that the cancer hazard from
environmental exposure to dioxin ranges between one per thousand
and 100 per thousand. The middle of this range would be 50 per
thousand. Because the average person's lifetime chance of
getting cancer is now about 400 per thousand (or four in 10), we
can see that routine exposure to environmental dioxins may be
making a substantial (12%) contribution to the danger of cancer
in this country, if the German estimate holds true. If it holds
true, it qualifies as a public health disaster.

The mechanisms by which dioxin causes cancer remain poorly
understood. In most studies, dioxin seems to be a powerful
promoter of cancer, rather than an initiator. In other words,
once a cell has been made cancer-prone by something else, dioxin
may push it over the edge and turn it into a full-blown cancer.
This would explain why dioxin seems to cause a general increase
in many cancers among exposed populations.[2]

However, a study published during 1998 made it clear that dioxin
can cause breast cancer in rats without either initiating it or
promoting it in the traditional sense. As we reported earlier
(REHW #630), researchers in the U.K. exposed pregnant rats to
small amounts of dioxin on the 15th day of pregnancy.[7]

The female offspring of the dioxin-exposed pregnant rats were
born normal, but by the time they were 7 weeks old, their
mammary glands had developed an unusually high number of
"terminal end buds" -- the places in a breast where breast
cancers develop. Four studies have shown that there is a direct
correlation between the number of terminal end buds in a breast
and its susceptibility to breast cancer.

The British researchers went on to expose these young rats (and
a control group) to a well-known carcinogenic chemical,
dimethylbenz[a]anthracene. The dioxin-exposed young rats
developed many more breast cancers than did the control group.

Thus a chemical (like dioxin) that, under some circumstances,
appears to protect against breast cancer may, in fact, under
other circumstances, cause it.

Based on non-cancer health effects, the World Health
Organization's meeting on dioxin in May, 1998, recommended that
the "tolerable daily intake" of dioxin should be between 1 and 4
picograms per kilogram of body weight per day (pg/kg/day). To
reach this number, they took the lowest observed level that
caused problems in laboratory animals and reduced it by a safety
factor of 10. Normal practice in such circumstances would be to
apply a safety factor of 100, but, according to a knowledgable
source who asked not to be quoted, if the WHO group had applied
a safety factor of 100 they would have been declaring much of
the food supply in industrial countries dangerously
contaminated, which they were reluctant to do for political
reasons.

The middle of the range that they adopted -- one to 4 pg/kg/day
-- would be 2.5 pg/kg/day, 4 times as low as the World Health
Organization's 1990 recommendation, which was 10 pg/kg/day as
the tolerable daily intake. Thus the tolerable daily intake
recommended at the May meeting for an adult weighing 70 kg (154
pounds) would be 2.5 x 70 = 175 picograms per day, or 175 x 365
= 63,875 picograms per year.

Now that we know that a picogram of dioxin has some public
health significance, we are in a better position to appreciate
that 3000 grams of dioxin emitted each year by industrial
sources in the U.S. is a very substantial quantity. If we
multiply 3000 grams by a trillion to turn it into picograms,
then divide by the U.S. population (260 million), we can see
that 3000 grams of dioxin TEQ represents 11 million picograms of
dioxin TEQ for each man, woman and child in the U.S. each year.

Scientists at the May, 1998, World Health Organization meeting
concluded that, based on animal experiments, the following
effects might be expected in humans: decreased sperm counts
might be expected in humans who have a daily dioxin intake of 14
pg/kg/day; learning disabilities and endometriosis might be
expected in humans with a dioxin intake of 21 pg/kg/day;
suppression of the immune system might be expected in offspring
of humans with an intake of 37 pg/kg/day.[3,pg.25] The May, 1998
WHO meeting "recognized that subtle effects may already occur
in the general population in developed countries at current
background levels, 2 to 6 pg/kg body weight. They therefore
recommended that every effort should be made to reduce [dioxin]
exposure to the lowest possible level," according to a statement
released by the World Health Organization.[3]

All together, not very reassuring news from Europe about dioxin,
we conclude.

==========

[1] Jean A. Grassman and others, "Animal Models of Human
Response to Dioxins," ENVIRONMENTAL HEALTH PERSPECTIVES Vol.
106, Supplement 2 (April 1998), pgs. 761-775. There are 75
polychlorinated dibenzodioxins (PCDDs), the most potent of which
is TCDD; plus 135 polychlorinated dibenzofurans (PCDFs), plus 9
PCBs (polychlorinated biphenyls) that are structurally
similar to PCDDs and PCDFs.

[2] Douglas B. McGregor and others, "An IARC Evaluation of
Polychlorinated Dibenzo-P-dioxins and Polychlorinated
Dibenzofurans as Risk Factors in Human Carcinogenesis,"
ENVIRONMENTAL HEALTH PERSPECTIVES Vol. 106, Supplement 2 (April
1998), pgs. 755-760.

[3] "Executive Summary; Assessment of the health risk of dioxins:
re-evaluation of the Tolerable Daily Intake (TDI); WHO
Consultation, May 25-29 1998, Geneva, Switzerland." World Health
Organization, WHO European Centre for Environment and Health,
International Programme on Chemical Safety, Final December, 1998. This
paper is marked as follows: "This report does not constitute a
formal WHO publication. It should not be quoted or cited and is
for personal use only!" However, see http://www.who.org/inf-
pr-1998/en/pr98-45.html, a WHO press release announcing the
results of the May meeting. We can send the WHO paper free as an
Adobe acrobat file to anyone who requests is by E-mail. If you
want the paper by U.S. mail, please send $3.00 to cover postage
and handling to Rachel's, P.O. Box 5036, Annapolis, MD 21403 with
a note saying what you want.

[4] Heiko Becher, Karen Steindorf, and Dieter Flesch-Janys,
"Quantitative Cancer Risk Assessment for Dioxins Using an
Occupational Cohort," ENVIRONMENTAL HEALTH PERSPECTIVES Vol.
106, Supplement 2 (April 1998), pgs. 663-670.

[5] H. Muto and Y. Takizawa, "Dioxins in Cigarette Smoke,"
ARCHIVES OF ENVIRONMENTAL HEALTH Vol. 44, No. 3 (May/June 1989),
pgs. 171-174.

[6] U.S. Environmental Protection Agency, THE INVENTORY OF
SOURCES OF DIOXIN IN THE UNITED STATES [EPA/600/P-98/002Aa
External Review Draft] (Washington, D.C.: U.S. Environmental
Protection Agency, April, 1998).

[7] Nadine M. Brown and others, "Prenatal TCDD and
predisposition to mammary cancer in rats," CARCINOGENESIS Vol.
19, No. 9 (1998), pgs. 1623-1629.

Descriptor terms: dioxin; who; epa; standards; tolerable daily
intake; tdi; pcbs; tobacco; cigarettes; iarc; carcinogens;
cancer; endometriosis; sperm counts; immunotoxins; immune system;