Subject: #588: Children's Cancer and Pesticides
. ---March 5, 1998--- .
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. CHILDREN'S CANCER AND PESTICIDES .
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CHILDREN'S CANCER AND PESTICIDES
Cancers diagnosed in children younger than 15 are increasing at
about one percent per year in the U.S.[1] Cancers are now the
second leading cause of death among children (after accidents).
An estimated 7800 children in the U.S. were diagnosed with new
cancers in 1995.[2] Part of this increase results from better
diagnosis and better recording of cases by state and federal
agencies, but "taken together they cannot explain the magnitude
of the increases that have been observed over the last several
decades."[1] In other words, childhood cancer really is
increasing.
Two kinds of childhood cancers account for 50% of all cases:
leukemias (cancers of the blood-forming organs), and brain
cancers. Leukemias seem particularly likely to strike children
younger than age two, and brain tumors occur most often in
children younger than age six.
In adults, cancers occur after a delay of seven to 20 years (or
more) between the time of exposure to cancer-causing agents and
the manifestation of a cancer. However, in the case of childhood
cancers, these delays are often much shorter. This makes it seem
as if many childhood cancers occur in children who are somehow
predisposed to get the disease. If they are exposed to a
carcinogen before or shortly after birth, their disease manifests
quickly. Perhaps the predisposition is inherited, or perhaps it
is caused by something in the environment.
The best-established environmental cause of cancers in children
is ionizing radiation. A study of 32,000 twins in 1985 showed
that those who had leukemia were twice as likely to have been
exposed to x-rays as were healthy children.[3] Other studies
have confirmed these findings.
Exposure to electromagnetic fields (EMFs) from power lines and
from 110-volt wiring in homes has been studied for its effects on
childhood leukemia, with mixed results. Some studies show a
relationship, others show none.[4] The connections between EMFs
and cancer need to be clarified by further study.
It is conceivable that some childhood leukemia is caused by one
or more viruses. Viruses cause leukemias in cats, chickens, and
cattle, so there is no reason, on the face of it, to rule out
humans.[1]
Certain chemicals also might be related to childhood cancers.
Unfortunately, there is a "conspicuous absence of information on
chemical exposures and toxicity relating to children."[1]
Neither government nor the chemical corporations have seen it as
their job to discover whether chemicals are harming children.
Nevertheless, several studies have shown a link between childhood
cancers and pesticides. Childhood leukemias, lymphomas,
neuroblastomas, and brain cancers have all been linked to
pesticides in recent years. (See REHW #333, #559.)
Children are exposed to pesticides by many routes. No-pest
strips, pet collars, and shampoos (for pets, and in some cases
for the children themselves, for head lice), plus routine use of
pesticides against rodents, insects, funguses, and weeds in
homes, lawns, and gardens can expose children.
Americans put an estimated 62.7 million pounds (28.5 million
kilograms) of pesticides and 278.5 million pounds (126.6 million
kilograms] of antimicrobials (disinfectants) into their homes
each year.[5] Recent studies estimate that between 78% and 97%
of families in the midwestern U.S. use pesticides in and around
the home.[6] A study of indoor air in homes in Jacksonville,
Florida detected pesticides in the air in 100% of the homes.[7]
A recent review article described 31 studies of pesticides and
childhood cancers reported during the period 1970-1996. The
review concluded that, "In general, results from leukemia studies
suggest that no-pest strips and frequent use of pesticides in the
home may be strongly associated with childhood leukemia..."[6]
Several different kinds of exposure of children to pesticides
have been studied:
1) Father's exposure to pesticides while the mother is pregnant:
"Collectively, these studies suggest an increase in risk of brain
cancer, leukemia, Wilms' tumor, Ewing's sarcoma, and germ cell
tumors associated with paternal occupational exposure to
pesticides prior to and during pregnancy.... Childhood brain
cancer and leukemia were the most studied, with fairly
consistent, moderate increases in risk."[6]
2) "Farm residence was associated with brain cancers,
neuroblastoma, retinoblastoma, non-Hodgkin's lymphoma, and Wilms'
tumor to varying degrees."[6]
3) "Few studies have evaluated no-pest strips or pesticides used
on pets; however, those [few] studies, as well as studies of
pesticide use in the home, have reported fairly consistent
associations for exposure during childhood and the risk of brain
cancer and leukemia, despite their [the studies'] small size."[6]
4) "In general, professional extermination and use of garden
pesticides were less likely to show positive effects than the use
of other home pesticides for most childhood cancers; however, the
risk of Wilms' tumor and lymphoma was elevated with professional
extermination use during childhood and brain cancer was elevated
with termite extermination during pregnancy."[6]
The authors make the important point that careful studies, in
which pesticide exposure is actually measured (rather than
estimated or assumed) are much more likely to reveal a
significant relationship between pesticides and childhood
cancers. When a father's exposure to pesticides is estimated,
based on his job title, for example, the resulting study is
likely to show less effect of pesticides on childhood disease
compared to a careful (and expensive) study in which the father's
exposure to pesticides is measured. Very few studies of
pesticides actually go to the trouble (and expense) of measuring
exposures. The clear implication is that, if funds were
available for better studies, we would have more bad news about
the relationship of pesticides to childhood cancers.
A recent study of pesticides and childhood brain cancers has
revealed a strong relationship between brain cancers and
compounds used to kill fleas and ticks.[7] The specific
chemicals associated with children's brain cancers were
pyrethrins and pyrethroids (which are synthetic pyrethrins, such
as permethrin, tetramethrin, allethrin, resmethrin, and
fenvalerate), and chlorpyrifos (trade name: Dursban).
A recent, careful study of chlorpyrifos (Dursban) residues in a
home offered some surprising results.[5] A home was
professionally treated with chlorpyrifos (trade name: Dursban),
following the ventilation recommendations printed on the
government-approved label. The residues were then measured on
the surface of a dresser and on the surfaces of children's
plastic toys and cloth toys for two weeks. Chlorpyrifos is the
most commonly used pesticide in the U.S. It is a potent nerve
poison --a fifth of an ounce is sufficient to kill an adult.
To the researchers' surprise, the measurable residues of
chlorpyrifos continued to increase for a week after the initial
treatment. They discovered that the pesticide was entering the
air, then slowly settling out onto plastic and cloth surfaces,
especially children's toys. Based on their measurements of toys,
they estimated a typical child's exposure to chlorpyrifos from
this one application: it was six to 21 times as high as the
recommended "safe" dose. Thus we learn that government "safe"
standards for pesticides in the home are based on unrealistic
estimates of the amounts of pesticides that will remain in the
home after treatment. Chlorpyrifos was measurable in this
particular home for 2 weeks after the initial application.
This chlorpyrifos study estimated exposure based on pesticide
residues on toys alone. Other studies have shown that pesticides
are also retained on carpeting, and on pets. Furthermore, pets,
and peoples' shoes, bring pesticides into the home from outdoors.
Without sunlight to help break them down, pesticides can remain
on carpets for long periods. These routes of exposures were not
considered in the chlorpyrifos study just described. Thus even
this careful study may have underestimated actual exposures that
children encounter.
We often hear it said that the burden of proof is on the
pesticide companies to show that their products are harmless to
humans before they can be marketed. But this is clearly not the
case. Dozens of studies have now shown that several classes of
pesticides are associated with brain cancers and leukemias in
children, yet those products continue to be sold in enormous
quantities and the pesticide companies continue to mislead the
public by claiming that their products are entirely "safe." The
burden is clearly on the public to show that specific children
have been harmed by specific pesticide applications. Because
cancers are delayed, showing cause and effect is all but
impossible. Thus do the chemical corporations have their way
with our children, while government looks on approvingly. No,
the burden of proof of harmlessness is not on the corporations,
it is on us. This should be reversed.
To really put the burden of proof onto the pesticide
corporations, prior to marketing they should be required to post
a bond, to cover the damage that their products might do. As
decades passed, if no damage came to light, they could get part
or all of their bond back (with interest). (See REHW #586 and
#510.) How large should the bond be? We might begin to estimate
a fair amount by asking a random sample of mothers, "How much
money would you accept in return for us giving your child a brain
cancer?" Their answers could provide a basis for beginning to
estimate the true costs of this problem.
--Peter Montague
(National Writers Union, UAW Local 1981/AFL-CIO)
===============
[1] Charles W. Schmidt, "Childhood Cancer: A Growing Problem,"
ENVIRONMENTAL HEALTH PERSPECTIVES Vol. 106, No. 1 (January 1998),
pgs. A18-A23. This article mistakenly says that childhood
cancers are increasing at 10% per year. For the correct estimate,
see footnote 2, below. See also REHW #559.
[2] Carol L. Kosary and others, editors, SEER CANCER STATISTICS
REVIEW, 1973-1992 TABLES AND GRAPHS [NIH PUBLICATION NO. 96-2789]
(Bethesda, MD: National Cancer Institute, 1995), Table I-3, pg.
17.
[3] E.B. Harvey and others, "Prenatal x-ray exposure and
childhood cancer in twins," NEW ENGLAND JOURNAL OF MEDICINE Vol.
312, No. 9 (February 28, 1985), pgs. 541-545.
[4] Many studies are cited in Martha S. Linet and others,
"Residential exposure to magnetic fields and acute lymphoblastic
leukemia in children," NEW ENGLAND JOURNAL OF MEDICINE Vol. 337,
No. 1 (July 3, 1997), pgs. 1-7.
[5] Somia Gurunathan and others, "Accumulation of Chlorpyrifos on
Residential Surfaces and Toys Accessible to Children,"
ENVIRONMENTAL HEALTH PERSPECTIVES Vol. 106, No. 1 (January 1998),
pgs. 9-16.
[6] Julie L. Daniels and others, "Pesticides and Childhood
Cancers," ENVIRONMENTAL HEALTH PERSPECTIVES Vol. 105, No. 10
(October 1997), pgs. 1068-1077.
[7] Janice M. Pogoda and Susan Preston-Martin, "Household
Pesticides and Risk of Pediatric Brain Tumors," ENVIRONMENTAL
HEALTH PERSPECTIVES Vol. 105, No. 11 (November 1997), pgs.
1214-1220.
Descriptor terms: pesticides; burden of proof; precautionary
principle; chlorpyrifos; dursban; cancer statistics; carcinogens;
children; ionizing radiation; x-rays; electromagnetic fields;
emfs; viruses; no-pest strips; pets; pet collars; leukemia;
wilm's tumor; brain cancer; ewing's sarcoma; farming;
occupational safety and health; agriculture; lymphoma; fleas;
ticks;
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