Several new studies have implicated chlorinated chemicals in
human disease, including breast cancer and tooth decay. Chlorine
chemistry is clearly the premier example of humans adopting a
new technology without thinking about the consequences.
BREAST CANCER
A recent study in Denmark reveals a relationship between breast
cancer and the chlorinated pesticide dieldrin.[1] The
prospective study examined blood taken in 1976 from 7712 women
enrolled in the Copenhagen City Heart Study. In the following 17
years, 268 of the women developed breast cancer.
The blood samples drawn in 1976 were analyzed in 1993 for 46
chlorinated chemicals, including 28 individual PCBs
[polychlorinated biphenyls], and 18 other chlorinated compounds
such as DDT, mirex, aldrin, dieldrin and others.[2] Of the
compounds studied, only dieldrin was significantly elevated in
the blood of women who developed breast cancer.
Beta-hexachlorocyclohexane (beta-HCH) was also elevated in women
with breast cancer, compared to those without breast cancer, but
the finding was not statistically significant.
In Denmark, about 14% of all women (one in seven) develop breast
cancer, and the incidence of the disease has more than doubled
in the past 30 years.
Most of the identified "risk factors" for breast cancer indicate
that estrogen (female sex hormone) in a woman's blood plays an
important role in the disease. The major known "risk factors"
for breast cancer are early menarche (early age when the period
begins), late menopause, not having any children, late
conception of the first child, and hormone-replacement treatment
after menopause. All of these factors tend to increase a woman's
lifetime exposure to estrogens circulating in the blood.
The Copenhagen study found that the risk of breast cancer was
twice as high in women with the highest concentrations of
dieldrin in their blood serum, compared to women with the lowest
concentrations. Furthermore, a significant dose-response
relationship was evident -- the more dieldrin in the blood, the
greater the chance that breast cancer would develop.
Some previous studies have implicated certain organochlorines in
breast cancer, while other studies have shown no such
relationship. (See REHW #571, #572, #573, #574, #575.)
The authors of the Copenhagen study say theirs is the first to
properly compare blood levels of organochlorine compounds
because they adjusted completely for varying levels of serum in
the blood of each individual. They conclude that, "These
findings support the hypothesis that exposure to xeno-oestrogens
may increase the risk of breast cancer." Xeno-oestrogens are
industrial chemicals (such as pesticides) that can mimic estrogen
in the human body.
The use of dieldrin in Denmark and in the U.S. was banned about
20 years ago but, in the industrialized world, nearly everyone's
body still contains small amounts of stored dieldrin, along with
several hundred other industrial poisons, many of them
chlorinated.
DIOXIN
For several years, U.S. and European health authorities have
been hinting that the general public is being exposed to levels
of dioxin that are probably causing harm in sensitive people.
(See REHW #390, #391, #636.) Now the federal Agency for Toxic
Substances and Disease Registry (ATSDR) has confirmed the bad
news.
The term "dioxin" encompasses a family of 219 different toxic
chlorinated chemicals, all with similar characteristics but
different potencies.
Because some dioxins are more toxic than others, scientists have
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, expressing toxicity in terms of the most
toxic dioxin, which is TCDD, or 2,3,7,8-tetrachlorodibenzo-p-
dioxin.[3]
Dioxin is a highly toxic, unwanted byproduct of many industrial
processes, including incineration of municipal, medical and
hazardous wastes; metal smelting; the burning of fossil fuels;
the manufacture of many pesticides and other chemicals. (See REHW
#636.) We are all exposed to dioxin through our diets, mainly by
eating fish, meat, and milk products. Vegetarians get much less
than the average, but they do not get zero because dioxin falls
out of the air onto vegetation.
Last December, the federal Agency for Toxic Substances and
Disease Registry (ATSDR) in Atlanta published the long-awaited
final report, TOXICOLOGICAL PROFILE FOR CHLORINATED
DIBENZO-P-DIOXINS.[4] The report had been circulating in draft
form since 1991. In the final report, ATSDR establishes a
Minimum Risk Level (MRL) for chronic (long-term) exposure to
dioxin. An MRL is the amount of total dioxins (expressed as
TEQs) that ATSDR believes people can take in day after day
without suffering adverse health effects.
ATSDR's official MRL for chronic (long-term) exposure to dioxin
is one picogram of dioxin TEQ per kilogram of body weight per
day.[4,pg.264] The new ATSDR report says that the average
exposure of U.S. citizens is currently three to six times as
high as this "safe" level.[4,pg.253] (A picogram is one
trillionth of a gram, and there are 28 grams in one ounce.)
Thus ATSDR gives us reason to wonder whether people are being
harmed at current background levels of dioxin.
Shortly after ATSDR released its final dioxin report, a new
study was published showing that some people have defective
teeth as a result of exposure to current background levels of
dioxin.[5]
The new study was conducted by dentists in Finland who have been
studying dioxin for a decade. In the early 1980s, they noticed
that many children had poorly developed molars -- discolored and
soft. The normal hard enamel coating was partially missing,
making the teeth subject to decay.
The researchers hypothesized that the children were being
exposed to some toxin early in life and this was interfering
with normal growth and development of their teeth.
Chinese children born to mothers who were accidentally exposed
to high levels of dioxins showed tooth problems similar to those
in Finnish children.[6] Taking this as a clue, the Finnish
dentists began exposing rats to low levels of dioxin. They found
that they could produce the same kind of tooth defects in the
rats that had been seen in the Chinese and Finnish children.[7]
Next they studied 102 Finnish children, ages 6 to 7, whose
mother's breast milk had been tested for dioxins when the
children were four weeks old. Seventeen of the 102 children
(16.6%) had soft, mottled molars, with insufficient enamel to
protect the teeth from decay. If a tooth fails to develop a
proper enamel coating, the tooth is subject to decay for the
rest of the person's life because enamel never develops later.
The Finnish study found that children with the worst teeth were
born to mothers with the highest levels of dioxin in their
breast milk, thus establishing a dose-response relationship.
The researchers examined PCBs separately from the other dioxins
and dioxin-like compounds and they found that the PCBs did not
contribute to the children's tooth problems.
The Finnish researchers' new findings "are very exciting in a
scientific sense--and very concerning in a public-health
sense--because they demonstrate effects from [dioxin] exposures
at background levels," says Linda Birnbaum, a well-known dioxin
researcher with the U.S. Environmental Protection Agency
(EPA).[8]
According to ATSDR, many people in the U.S. and elsewhere have
dioxin exposures that exceed the average. These
include:[4,pgs.485-497]
** People who are exposed at work, or through environmental
contamination, such as people living in Times Beach, Missouri;
** People living near incinerators that are burning municipal,
medical or hazardous wastes, or people living downwind from
coal-burning power plants;
** People living near any of the 110 Superfund sites where
dioxins have been identified. (Superfund sites are
chemically-contaminated places that the federal government has
identified as dangerous to human health.)
** Sport fishers in the Great Lakes regions are very likely to
have high exposure to dioxin, with Lake Huron the highest, Lake
Michigan next highest, and Lake Erie the lowest.
** Currently 66 fish advisories have been issued by 21 states
because of dioxin-contaminated fish. Three states -- New York,
New Jersey, and Maine -- have statewide fish advisories in
effect for all of their marine coastal waters, warning people to
limit the amount of fish they eat because of dioxin
contamination.
** Many indigenous people eat far more fish than the average.
Under these circumstances, even low levels of dioxin
contamination in fish can add up to a hazard.
** Subsistence farmers who consume their own farm-reared meat
and dairy products may be highly exposed if they live downwind
from an incinerator or a metal refinery or other source of
dioxins.
** People eating food grown on soil treated with sewage sludge
may be in danger. ATSDR says, "Exposure to [dioxin] from land
application of municipal sewage sludge or paper mill sludge also
can occur through the dietary pathway if people consume food
grown or animals grazed on sludge-amended lands."[4,pg.497] And:
"Most recently, MacLachlan... reported that the prolonged use of
sewage sludge as a soil amendment on English farms under some
conditions can lead to an increase in the concentrations of
[dioxins] in both the soil and in cow's milk."[4,pg.497]
The question is, can humans do things differently in the future,
or are we doomed to stumble from one uninformed decision to
another? Are there social mechanisms (such as environmental
impact analysis) that could help us avoid massive mistakes like
chlorine chemistry?
[1] Annette Pernille Hoyer and others, "Organochlorine Exposure
and Risk of Breast Cancer," LANCET Vol. 352 (December 5, 1998),
pgs. 1816-1820.
[3] M. Van den Berg and others, "Toxic equivalency factors
(TEFs) for PCBs, PCDDs, PCDFs for humans and wildlife,"
ENVIRONMENTAL HEALTH PERSPECTIVES Vol. 106, No. 12 (December
1998), pgs. 775-792.
[4] Agency for Toxic Substances and Disease Registry,
TOXICOLOGICAL PROFILE FOR CHLORINATED DIBENZO-P-DIOXINS
(Atlanta, Ga.: U.S. Department of Health and Human Services,
Public Health Service, Agency for Toxic Substances and Disease
Registry, December, 1998). Available from ATSDR; telephone
1-888-42-ATSDR or (404) 639-6357.
[5] Satu Alaluusua and others, "Developing Teeth as a Biomarker
of Dioxin Exposure," LANCET Vol. 353 (January 16, 1999), pg.
206.
[6] B.C. Gladen and others, "Dermatological findings in children
exposed transplacentally to heat-degraded polychlorinated
biphenyls in Taiwan," BRITISH JOURNAL OF DERMATOLOGY Vol. 122,
No. 6 (June 1990), pgs. 799-808.
[7] A. M. Partanen and others, "Epidermal growth factor receptor
as a mediator of developmental toxicity in mouse embryonic
teeth," LABORATORY INVESTIGATION Vol. 78, No. 12 (December
1998), pgs. 1473-1481.
[8] J. Raloff, "Dioxin can harm tooth development," SCIENCE NEWS
February 20, 1999, pg. 119.
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