Chemical Industry Strategies - Part III
. DANGERS OF CHEMICAL COMBINATIONS .
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DANGERS OF CHEMICAL COMBINATIONS
The chemical industry received some extraordinarily bad news last
week. SCIENCE magazine published a new study showing that
some COMBINATIONS of hormone-disrupting chemicals are much more
powerful than any of the individual chemicals by themselves.
SCIENCE magazine is the conservative voice of mainstream science
in the U.S. Until last week SCIENCE had largely ignored the
possibility that industrial chemicals may be interfering with
hormones in wildlife and humans.
The new study shows that combinations of two or three common
pesticides, at low levels that might be found in the environment,
are up to 1600 times as powerful as any of the individual
pesticides by themselves. The study showed that one chemical,
chlordane, which has no ability to disrupt hormones by itself,
nevertheless greatly magnifies the ability of other chemicals to
disrupt hormones. If these findings are confirmed by follow-up
studies, it could profoundly affect the way chemicals are viewed,
tested for toxicity, and regulated because combinations of
chemicals will have to be considered. The environmental
protection apparatus of the U.S. and, indeed, the world, is
presently based on studies of individual chemicals acting alone.
Hormones are natural chemicals that act as messengers, traveling
through the blood stream, regulating various bodily processes,
coordinating the body's activities to maintain health. Hormones
are particularly important during growth and development of an
egg, an embryo, a fetus, a baby. About 100 different hormones
have now been identified, and they control growth, development
and behavior in all vertebrates (fish, birds, reptiles,
amphibians, and mammals), including humans. (See REHW #263,
Since 1991, studies have shown that at least 50 synthetic
(human-created) industrial chemicals can interfere with hormones
and disrupt normal growth and development in birds, fish,
mammals, reptiles, amphibians, and humans. The results of
such interference can include changes in sexual preference and
behavior; small penises; diminished sperm count; various cancers;
nervous system disorders; birth defects; and damage to the immune
system, among other effects. Many of the 50 hormone-disrupting
chemicals are commonly found in detergents, plastics, and
pesticides. In response to these studies, the chemical industry
has asserted that low-level environmental exposures are not
powerful enough to affect humans. The new study published
this week in SCIENCE shows that the chemical industry's position
is not likely to hold up under scrutiny.
The editors of SCIENCE evidently considered the new study so
important that they simultaneously published two articles
commenting on the findings.[5,6] (Furthermore, in the same
issue, they published a flattering review of the recent book on
hormone-disrupting chemicals, OUR STOLEN FUTURE.)
Even the editors of the NEW YORK TIMES considered the new study
important enough to report on it in a straightforward manner.
In March and April the TIMES had published a series of biased and
inaccurate articles by Gina Kolata, who said the theory that
industrial chemicals might interfere with hormones had been
"refuted by careful studies," none of which she cited or
described. (See REHW #486 and #492.) When scientists wrote
letters to the editor, seeking to restore balance after Ms.
Kolata's reporting, the TIMES refused to publish any of their
letters. One group of scientists finally grew so frustrated that
they took the highly unusual step of purchasing ad space in the
TIMES to complain about Ms. Kolata's inaccuracies and bias.
The idea that common industrial chemicals may be interfering with
the hormones of wildlife and humans, has far-reaching
implications. If it is true, it means that the chemical industry
as we know it is a threat to all life on earth. How can we learn
whether this is true?
Chemicals with vastly different molecular struc-tures have proven
to be hormone disrupters. This means that a chemical's
ability to disrupt hormones cannot be discovered simply by
examining a diagram of the molecule. In other words, the study
of so-called structure/function relationships is not helpful in
the case of hormone-disrupters. Therefore thousands of chemicals
will need to be tested individually for their ability to disrupt
hormones. A thorough battery of tests has not yet been devised,
and there are now 70,000 chemicals currently in commercial use,
with about 1000 new ones added each year. The prospect of
testing the toxicity of this number of chemicals, even one at a
time, is daunting. No one knows where the resources would come
from to conduct such a large number of tests. The new study in
SCIENCE makes the enormous problem of individually testing 70,000
chemicals seem small by comparison. If scientists have to study
COMBINATIONS of chemicals, their job is vastly increased. For
example, to test just the commonest 1000 toxic chemicals in
unique combinations of 3 would require at least 166 million
different experiments (and this disregards the need to study
varying doses). Even if each experiment took just one hour to
complete and 100 laboratories worked round the clock seven days a
week, testing all possible unique 3-way combinations of 1000
chemicals would still take over 180 years to complete.
This is not the first evidence that some combinations of
chemicals are more powerful than any of their individual
chemicals. Earlier this year researchers at the Duke University
Medical Center published a study of three chemicals to which U.S.
soldiers were exposed during the Gulf War. None of the three
chemicals, by itself, caused nerve damage in laboratory animals,
but TOGETHER the three chemicals showed powerful nerve-damaging
effects --effects so strong that the researchers concluded that
they may have found the cause of "Gulf War Syndrome," which
plagues at least 30,000 U.S. veterans of that war.
Even earlier, studies had shown that exposure to radiation
enhances the toxicity of certain chemicals, and that tobacco
smoke and asbestos enhance each other's toxicity. However,
the U.S. never tests chemical combinations to assess chemical
dangers. For example, the National Research Council (NRC)
recently studied the problem of doing "risk assessments" for
combinations of chemicals. The NRC concluded that simply adding
up the individual toxicities was the way to handle combinations.
NRC said this approach would underestimate the toxicity of
combinations of chemicals no more than 10-fold.
The new study published in SCIENCE throws the NRC's conclusion
into a cocked hat. Combinations of two and three pesticides turn
out to be anywhere from 160 to 1600 times as powerful as any of
the individual pesticides. Risk assessments that assume chemical
combinations are only 10 times as powerful as the individual
chemicals may underestimate the dangers 100-fold or more.
Most importantly, one chemical (chlordane) by itself showed no
hormone-disrupting effects, yet it magnified the
hormone-disrupting power of other chemicals when combined with
them. This means that we must identify, and protect ourselves
against, even very weak hormone-disrupting chemicals because they
may not be so weak when combined with other common chemicals. It
is hard to imagine a practical, manageable testing program that
can sort through these problems and produce reliable,
comprehensive results in less than a century. By that time, if
damage is being done now, as many scientists believe is the case,
it will be far too late.
The solution to this huge, complex problem? Theo Colborn and
Pete Myers suggested some beginning steps in their recent book,
OUR STOLEN FUTURE (see REHW #486, #487, #490):
** Greatly reduce the number of chemicals on the market. (pg. 226)
** Reduce the number of chemicals used in a given product; make
products simpler. (pg. 226)
** Make and market only chemicals that can be readily detected at
relevant levels in the real world with current technology. (pg.
** Do not produce a chemical unless its degradation in the
environment is well understood. (pg. 227)
** Curtail the introduction of thousands of new synthetic
chemicals each year. (pg. 247)
** Reduce the use of pesticides as much as possible. (pg. 247)
Pesticides should be used only in genuine emergencies. (pg. 217)
** Shift the burden of proof onto manufacturers... To a
disturbing degree, the current system assumes that chemicals are
innocent until proven guilty. This is wrong. The burden of
proof should work the opposite way, because the current approach,
a presumption of innocence, has time and again made people sick
and damaged ecosystems. (pg. 219)
** The tool of risk assessment is now used to keep questionable
compounds on the market until they are proven guilty. It should
be redefined as a means of keeping untested chemicals off the
market and eliminating the most worrisome in an orderly, timely
fashion. (pg. 219)
** Science alone does not always have the answer.... The time
has come to pause and finally ask the ethical questions that have
been overlooked in the headlong rush of the 20th century. Is it
right to change Earth's atmosphere? Is it right to alter the
chemical environment in the womb for every unborn child? (pg. 247)
** Now that we know better, we must have the courage to be
cautious, for the stakes are very high. (pg. 249)
 Steven F. Arnold and others, "Synergistic Activation of
Estrogen Receptor with Combinations of Environmental Chemicals,"
SCIENCE Vol. 272 (June 7, 1996), pgs. 1489-1492.
 Anthony W. Norman and Gerald Litwack, HORMONES (San Diego,
Ca.: Academic Press, 1987). See Appendix A.
 Theo Colborn, Frederick S. vom Saal, and Ana M. Soto,
"Developmental Effects of Endocrine-Disrupting Chemicals in
Wildlife and Humans," ENVIRONMENTAL HEALTH PERSPECTIVES Vol. 101,
No. 5 (October, 1993), pgs. 378-384.
 Stephen H. Safe, "Environmental and Dietary Estrogens and
Human Health: Is There a Problem?" ENVIRONMENTAL HEALTH
PERSPECTIVES Vol. 103, No. 4 (April, 1995), pgs. 346-351.
 Jocelyn Kaiser, "New Yeast Study Finds Strength in Numbers,"
SCIENCE Vol. 272 (June 7, 1996), pg. 1418.
 S. Stoney Simons, Jr., "Environmental Estrogens: Can Two
'Alrights' Make a Wrong?" SCIENCE Vol. 272 (June 7, 1996), pg.
 Anne N. Hirschfield and others, "Problems Beyond Pesticides
[review of OUR STOLEN FUTURE]," SCIENCE Vol. 272 (June 7, 1996),
 Warren E. Leary, "Test Developed to Weigh Impact of
Hormone-Like Pollutants," NEW YORK TIMES June 7, 1996, pg. A15.
 "When It Comes to Chemicals, Is Only Good News Fit to Print?
[advertisement]" NEW YORK TIMES May 29, 1996, pg. A19.
 John A. McLachlan, "Functional Toxicology: A New Approach to
Detect Biologically Active Xenobiotics," ENVIRONMENTAL HEALTH
PERSPECTIVES Vol. 101, No. 5 (October, 1993), pgs. 386-387.
 Leslie Lang, "Strange Brew: Assessing Risk of Chemical
Mixtures," ENVIRONMENTAL HEALTH PERSPECTIVES Vol. 103, No. 2
(February, 1995), pgs. 142-145
 The formula for calculating how many different
subcollections of size k can be formed from a collection of n
different chemicals is (n!)/((k!)*((n-k)!)) where n! means n
factorial and * means "multiplied by". In the case under
discussion, k is 3 and n is 1000. See, for example, Michael
Orkin and Richard Drogin, VITAL STATISTICS (New York:
McGraw-Hill, 1975), pg. 285.
 Mohamed B. Abou-Donia and others, "Neurotoxicity Resulting
>From Coexposure to Pyridostigmine Bromide, DEET and Permethrin:
Implications of Gulf War Chemical Exposures," JOURNAL OF
TOXICOLOGY AND ENVIRONMENTAL HEALTH Vol. 48 (1996), pgs. 35-56.
For popular accounts of this study, see Elizabeth Pennisi,
"Chemicals Behind Gulf War Syndrome?" SCIENCE Vol. 272 (April 26,
1996), pgs. 479-480, and Philip J. Hilts, "Chemical Mix May Be
Cause of Illnesses in Gulf War," NEW YORK TIMES April 17, 1996,
 J.G. Sharp and D.A. Crouse, "Apparent Synergism between
Radiation and the Carcinogen 1,2-Dimethylhydrazine in the
Induction of Colonic Tumors in Rats," RADIATION RESEARCH Vol. 117
(1989), pgs. 304-317. And see Frank E. Lundin, Jr., and others,
RADON DAUGHTER EXPOSURE AND RESPIRATORY CANCER; QUANTITATIVE AND
TEMPORAL ASPECTS (Springfield, Va.: National Technical
Information Service, 1971).
 Agency for Toxic Substances and Disease Registry,
TOXICOLOGICAL PROFILE FOR ASBESTOS (UPDATE) (Atlanta, Ga.: Agency
for Toxic Substances and Disease Registry, Public Health Service,
U.S. Department of Health & Human Services [1600 Clifton Rd.
-Mail Stop E-29, Atlanta, GA 30333; phone (404) 639-0730],
August, 1995), pg. 75.
 SCIENCE AND JUDGMENT IN RISK ASSESSMENT (Washington, D.C.:
National Academy Press, 1994). See Chapter 11.
Descriptor terms: science magazine; hormones; endocrine
disrupters; hormone disrupters; pesticides; synergism;
endosulfan; chlordane; wildlife; detergents; plastics; our stolen
future; theo colborn; john peterson myers; new york times;
gina kolata; gulf war syndrome; radiation; tobacco; cigarettes;
asbestos; risk assessment; toxicity testing;
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