Children's Cancer
New toxins suspected as cancer rate rises in children...
by John H. Cushman, Jr.

The rate of cancer among American children has been rising for decades.  Although the reasons remain unclear, many experts suspect the increase may be partly the result of growing exposure to new chemicals in the environment.

That suspicion, while still unproved, is beginning to shape federal research priorities and environmental strategies.

Depending on which types of cancer are counted, and in what age groups among the nationís youth, the rate of increase has amounted to nearly 1 percent a year, according to the National Cancer Institute.  Over a few decades, that has meant striking double-digit increases.

Childhood cancer is still far less common than cancer in adults, and its very rarity makes it especially hard to discern what might be causing the increase.  Its creeping spread has also been masked by better news, as recent medical gains have made it much more likely that a child with cancer will survive.

But childhood cancer, even when its young victims are cured, can inflict wrenching costs on children and their families, whether its toll is measured in financial, emotional or physical terms.  Patients can suffer permanently from brain damage, stunted growth or secondary cancers later in life, partly as a result of radiation and chemical therapies.

And today, according to experts in the field, a newborn child faces a risk of about 1 in 600 of contracting cancer by age 10.

In the United States, cancer is diagnosed each year in an estimated 8,000 children below the age of 15.  Cancer, although it kills fewer children than accidents do, is the most common form of fatal childhood disease, accounting for about 10 percent of all deaths in childhood.

The increases surprise even people who are predisposed to think the worst about the ill effects of chemical pollution.

"I had not realized that the numbers were going up that way," said Karen Florini, a lawyer specializing in health issues at the Environmental Defense Fund.  "I think it indicates a very disturbing trend that we had better get to the bottom of."

Acute lymphoblastic leukemia in boys and girls increased 27 percent between 1973 and 1990; since then, the rate in boys has declined, but it is still rising in girls.  Brain cancer, or glioma, increased nearly 40 percent from 1973 to 1994.  These two forms of cancer account for most of the disease in children.

Other forms of cancer, such as the form of bone cancer called osteogenic sarcoma and the kidney cancer known as Wilmsí tumor, have also been rising, although the numbers of cases remain so small that the trends may not be statistically significant.

The increases are big enough that better diagnosis and reporting of the diseases are unlikely to be the principal explanation, experts say; childhood cancer is such a serious ailment that it is usually detected.

Although the causes are not known and are probably many, some experts say, toxins in the air, food, dust, soil and drinking water are prime suspects.

So with the Clinton administration putting a high priority on issues of childrenís health and the environment, and with Congress last year overwhelmingly approving new laws taking childrenís exposures into account when setting standards for pesticide residues in food and contaminants in drinking water, federal authorities are moving to review the epidemiological data much more closely and to review environmental regulations that may help fight the trend.

At a meeting in Washington two weeks ago, a team assembled by the Environmental Protection Agency drafted a research plan that could steer millions of dollars toward better understanding the problem, beginning next year.

"The increases are too rapid to reflect genetic changes, and better diagnostic detection is not a likely explanation," said Dr. Philip Landrigan, a pediatrician who directs the division of environmental medicine at the Mount Sinai School of Medicine in New York City and who is the senior adviser to a new office of childrenís health at the EPA "The strong probability exists that environmental factors are playing a role."

Not all environmental factors involve pollution.  Landrigan said that changes in life style, especially diet, must also be considered and may play some role.  Viruses may be implicated in some cancers, but there is scant evidence.

Instead, he and many other experts are inclined to examine the estimated 75,000 new synthetic chemicals introduced in the last half century, the emissions from cars, the pesticides in foods and in neighborhoods, the runoffs in drinking wateróthe whole collection of chemicals out there, mostly untested for toxicity to humans, let alone for possible cancerous effects in children.

If their suspicions prove to be well foundedóand that could take many years to determineóit could usher in a new generation of tighter controls on pesticides, toxic wastes and other chemicals based on the theory that it may take less of a carcinogen to afflict a child or a fetus, that their health may be affected by combinations of chemicals and that their needs ought to come first in dictating pollution controls.

But first, an expansion of federally supported research is likely.

"Iím talking about new research on air pollutants, water pollutants and pesticides and their effects on children," said Carol Browner, the administrator of the EPA, "and new testing guidelines that routinely incorporate childrenís issues into EPAís risk assessments.  Iím talking about moving beyond the chemical-by-chemical approaches of the past, and instead looking at a childís total cumulative risk from all exposures to toxic chemicals."

She promised to pursue better interdisciplinary and collaborative studies of suspected environmental causes and mechanisms of childhood cancer, an initiative that was endorsed at the agencyís conference.

Industry representatives who attended the meeting, though, cautioned against the governmentís moving too fast to react to such sketchy scientific information.

"It doesnít appear that anyone really knows yet what the causes are," said Nancy Doerrer, vice president for scientific and policy programs at the American Industrial Health Council, which represents a diverse group of manufacturing companies.

"Yes, there may be some role for environmental causation for childhood cancer," she said.  "But there is also a role for life style, and the prenatal vitamin supplementation during pregnancy also seems to be very important in preventing some cancers."

Ms. Doerrer said that the EPA was acting properly by announcing that it would select a few major regulations for scientific review to determine whether they adequately protected children.

"But to take too much action without really studying the problem would be wrong," she said.  "You are seeing lots of language being written into proposed regulations and legislation that is intended to protect susceptible populations.  That seems to be the new buzzword."

The group also recommended developing a National Childhood Cancer Registry, which would contain information such as exposure histories and family health data, and for better techniques for screening chemicals suspected of making children sick.

A cancer registry, which would be a comprehensive database seeking to include information on practically every child with cancer in the country, would be "a difficult thing to accomplish," said Dr. Robert Amler, chief medical officer at the Agency for Toxic Substances and Disease Registry, a federal agency based in Atlanta.

A first step might be to pool the data that already exist elsewhere, such as extensive information the agency has collected to track people exposed to cancer-causing chemicals at Superfund sites.

The childhood cancer registry would improve scientistsí chances of finding significant associations between exposures to harmful chemicals and the incidence of cancer, he said.

"Most studies of cancer in children have led to hypotheses, and in some cases have confirmed or furthered these hypotheses, but almost every study carries with it very important limitations," he said.  "These intrinsic limitations make it difficult for scientists and policy makers to tell the public what these studies really mean in terms of real risks to children."

Already, using new legal authority, the EPA is taking the risks to children into account in setting standards for food and water safety.

The Food Quality Protection Act, which became law last year, gave the EPA 10 years to review its limits on pesticide residues on food.  The agency is starting with what it thinks are the riskiest chemicals: the organophosphate, carbameate and organochlorine classes, as well as with other chemicals that may cause cancer in humans.

But Dr. Lynn Goldman, the assistant administrator for pesticides and toxic substances, said that although scientists have adequate information to screen most drugs, food additives and pesticides, they lack even basic toxicity data for most of the agencyís list of about 3,000 industrial chemicals produced in the highest volumes each year, many of them found in consumer products and in the workplace.

"The problem with childhood cancer, of course, is that we really do not know what causes most of it," she said.  "As we are working through screening the pesticides and tightening up the standards, we would hope that we are reducing the risks for children, but we really canít be sure."

Many studies have explored the possible role of environmental toxins in childhood cancer.  Studies have cited possible links between cancer in children and their exposures to pesticides, their parentís exposures to chemicals at work and other factors.

In a study published in The American Journal of Public Health in February 1995, researchers suggested that "use of home pesticides may be associated with some types of childhood cancer."

The study examined 252 children in whom cancer was diagnosed in the Denver area between 1976 and 1983 and 222 control subjects, and it interviewed their parents about household pesticide use.  It found some evidence that yard treatments might be associated with soft tissue sarcomas, and that pest strips containing insecticide might be associated with leukemia.

But the researchers conceded that the measures of actual exposure in studies like this are crude, and called for further research to show "what exposures, if any, are associated with which particular childhood cancers."

Another study, published in The Archives of Environmental Contamination and Toxicology in 1993, found associations between brain cancer in Missouri children and the use of pesticides in homes and yards. 

But here, too, the researchers conceded weaknesses, including small sample sizes, potentially inaccurate memories of pesticide use, and a lack of detailed verification of childrenís actual exposures to the pesticides. 

Clinicians said that there were many measures already known that may prevent cancers in children, just as in adults.

"Donít smoke, donít expose your kids to cigarette smoke, use sunscreen, donít expose kids to radon and asbestos," said Dr. Sophie Balk, a pediatrician at the Jacobi Medical Center, a public hospital in the Bronx.

Copyright 1997 The New York Times Company

printable version

close this window

 

Protect All Children's Environment