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#588 - Children's Cancer and Pesticides, 04-Mar-1998

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;