By Peter Montague
Cancers diagnosed in children younger than 15 are increasing at about 1% per year in the US. (Charles W. Schmidt, "Childhood Cancer: A Growing Problem", Environmental Health Perspectives Vol. 106, No. 1, January 1998, pp. A18-A23.) Cancers are now the second leading cause of death among children (after accidents).
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" (Schmidt). Childhood cancer really is increasing.
Two kinds of childhood cancers account for 50% of all cases: leukaemias (cancers of the blood-forming organs), and brain cancers. Leukaemias seem particularly likely to strike children younger than two, and brain tumours occur most often in children younger than six.
In adults, cancers occur after a delay of seven to 20 years (or more) from the time of exposure to cancer-causing agents. 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. 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 ionising radiation. A study of 32,000 twins in 1985 showed that those who had leukaemia were twice as likely to have been exposed to X-rays as were healthy children. Other studies have confirmed these findings.
Exposure to electromagnetic fields from power lines and from wiring in homes has been studied for its effects on childhood leukaemia, with mixed results. Some studies show a relationship, others show none.
It is conceivable that some childhood leukemia is caused by one or more viruses. Viruses cause leukaemias in cats, chickens, and cattle, so there is no reason to rule out humans.
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". 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 leukaemias, lymphomas, neuroblastomas and brain cancers have all been linked to pesticides in recent years.
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, fungi and weeds in homes, lawns, and gardens, can expose children.
People in the US put an estimated 28.5 million kilograms of pesticides and 126.6 million kilograms of disinfectants into their homes each year. Recent studies estimate that between 78% and 97% of families in the midwestern US use pesticides in and around the home. A study of indoor air in homes in Jacksonville, Florida, detected pesticides in the air in 100% of the homes.
A recent review article described 31 studies of pesticides and childhood cancers reported during 1970-1996. The review concluded, "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 ..."
Several different kinds of exposure of children to pesticides have been studied:
1) Father's exposure to pesticides while the mother is pregnant: "Childhood brain cancer and leukemia were the most studied, with fairly consistent, moderate increases in risk."
2) "Farm residence was associated with brain cancers, neuroblastoma, retinoblastoma, non-Hodgkin's lymphoma, and Wilms' tumor to varying degrees."
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 ..."
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."
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 residues in a home offered some surprising results. A home was professionally treated with chlorpyrifos, 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 US. It is a potent nerve poison — six grams 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. 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 people's shoes, bring pesticides into the home from outdoors. Without sunlight to help break them down, pesticides can remain on carpets for long periods.
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 leukaemias 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. 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).
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.
[From Rachel's Environment & Health Weekly. Like Green Left Weekly, Rachel's is a non-profit publication which distributes information without charge on the internet and depends on the generosity of readers to survive. If you are able to help keep this valuable resource in existence, send your contribution to Environmental Research Foundation, PO Box 5036, Annapolis, Maryland 21403-7036, USA. In the United States, donations to ERF are tax deductible.]