g o v e r n m e n t

EMERGING HEALTH CRISES IN CHILDREN Conference focuses on asthma and cancer as federal agencies gear up programs to address possible environmental causes

Bette Hileman C&EN Washington

M edical experts and policymakers met late last month in Washing­ton, D.C., to ponder two emerg­

ing health crises in children—asthma and cancer—and to grapple with govern­ment efforts to address them.

At this first national research confer­ence on children's environmental health, experts reported that death rates for asthmatic children—rising 6% a year-more than doubled between 1980 and 1993. Currently, nearly 5 million chil­dren, 7% of the population ages 18 or younger, have asthma, and their medical treatment costs $6.2 billion a year. "Asth­ma has become almost epidemic in this country," said Ruth A. Etzel, chief of the Air Pollution & Respiratory Health Branch at the Centers for Disease Control & Pre­vention in Atlanta.

Similarly, W. Archie Bleyer, chairman of the division of pediatrics of the M. D. Anderson Cancer Center in Houston, re­ported that cancer incidence among chil­dren under 19 is rising 1% a year. By 2000, one in every 900 people between the ages of 20 and 45 will be a cancer survivor, he said, and, if trends continue, the ratio by 2030 will be one in 250. Although 80% of pediatric cancer is cured, more children die of it than of any other disease.

The National Institute of Environmental Health Sciences (NIEHS) was the meet­ing's principal sponsor, although the meet­ing itself was organized by the Emeryville, Calif.-based Children's Environmental Health Network, a national project dedi­cated to pediatric environmental health.

Causes for the rapid rises in asthma and cancer are not known, researchers said. One hypothesis is that prenatal ex­posure to endocrine disrupting or other chemicals programs the developing fetus for cancer or asthma in early life.

Federal agencies have taken a number of steps to respond to these two crises

and to other pediatric health problems that may be related to environmental ex­posures. The Children's Cancer Group, a cooperative research group created by the National Institutes of Health, is col­lecting cancer data and organizing re­search on causes, prevention, and cures, Bleyer told conference attendees.

The Environmental Protection Agency has created a new center to provide a clearinghouse for research on children, EPA Administrator Carol M. Browner an­nounced at the meeting. The center will pull together various agency efforts in an attempt to focus attention on the envi­ronmental threats children face. And it will review existing standards to make sure they protect children.

Currently, only 5% of the federal medi­cal research budget is being spent on chil­dren, according to a soon-to-be-released White House report, titled "Children's Ini­tiative," on the federal commitment to re­search on children. So, to expand this now very meager medical research fund­ing, EPA will establish two national cen­ters of excellence on children's environ­mental health at existing universities, Browner said.

In addition, Browner said, EPA has proposed a large increase in the money it spends on protecting children's health. In fiscal 1997, $7.5 million of EPA's bud­get is specifically targeted at this area. For fiscal 1998, EPA has requested an in­crease to $15.4 million.

The rapidly rising asthma rates are puz­zling. "There is a linear relationship be­tween air particulate levels and hospitaliza­tions for asthma," said H. James Wedner, professor of medicine at Washington Uni­versity School of Medicine, St. Louis. But asthma is a multifactorial illness triggered not only by air pollution, but also by com­mon allergens and viral infections.

No one knows why in the industrialized world asthma became more prevalent in the late 1950s, and the upward trend has continued even as air quality has improved.

Claudio: prenatal exposure is a factor

Some researchers, such as Luz Claudio, a neurotoxicologist at Mount Sinai Medical Center in New York City, speculate that prenatal exposure to chemicals may cause the immune system to develop improper­ly. Others, such as Patrick Holt of TVW Telethon Institute for Child Health Re­search in West Perth, Australia, hypothe­size that exposure of the young child to a variety of microbial infections—as hap­pens in developing countries—may allow the immune system to mature faster and become more adept at fending off asthma. The prevalence of asthma seems to be lower in developing countries.

Although asthma is very common across the U.S., rates are higher in urban than in rural areas, and deaths torn asthma are con­fined mostly to the inner cities. Asthmatics can be helped greatly by reducing their total exposure to common allergens—such as dust mites, cats, cockroach antigens, and pollen—and by well-monitored medical treatment, Wedner said.

Claudio is directing a NIEHS-funded project that aims to understand and re­duce asthma problems in children living in New York City's South Bronx area. The South Bronx has a large concentra­tion of waste management facilities-such as sludge treatment plants and med­ical waste incinerators—and extremely high asthma rates.

Claudio's program seeks to find corre­lations between outdoor pollution levels and asthma hospitalizations, and to train nurses in asthma management. "Neigh­borhood residents are not used solely as study subjects," she explained, "but as collaborators in the project, which seeks to address their needs and concerns."

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g o v e r n m e n t

The cancer incidence data collected recently by NIH's Children's Cancer Group startled even experts in the field, Bleyer said. Previously, a peak in inci­dence was thought to occur for children between the ages of three and six. But Bleyer found peaks before age one and again between the ages of two and three.

When increases in cancer rates for people of all age groups are compared, the rate for children under age five is ris­ing fastest, Bleyer said. Most of the in­crease is attributable to acute lympho­blastic leukemia, and to brain and ner­vous system tumors. "The cause of the infant leukemia may be an environmental exposure of the parent," he postulated.

"There is a fundamental difference between environmental exposure in a developing system and a mature sys­tem,'' John A. McLachlan, director of the Tulane Xavier Center for Bioenvironmen-tal Research at Tulane University in New Orleans, told the meeting. For example, "If you start giving the synthetic estro­gen diethylstilbestrol (DES) to a month-old mouse and continue throughout its lifetime, you never get any effect,'' he said. But if DES is given to a pregnant mouse or human, it alters gene expres­sion in the fetus permanently, and caus­es abnormalities in the reproductive tract of the offspring.

Therefore, exposure to estrogenic and other hormone disrupting chemicals are much more important for the fetus than for the adult, McLachlan explained. Adverse effects in the offspring can be produced by very small doses of some chemicals if they are given at a critical time during pregnancy.

Because of these considerations, risk as­sessments of chemicals have to change, insisted Philip J. Landrigan, chief of the Department of Community Medicine at Mount Sinai Medical Center. "Previous risk assessments have been based on protect­ing 21-year-old white males," he said. "In the past, we dosed 'teenage' or adult ani­mals for two years, then sacrificed the ani­mals. That simply misses the point." Ani­mals need to be dosed in the womb, by exposing the mother, and then followed into old age, he said.

And to tease out the causes of child­hood diseases, Landrigen said, large longi­tudinal prospective studies that follow the child from conception into adulthood, measuring chemical exposures in the par­ents and in the child, and measuring other possible causes of disease are needed.

At the meeting, Lynn R. Goldman, as­sistant EPA administrator for prevention,

Goldman: children will be protected

pesticides, and toxic substances, dis­cussed several new or revised laws and regulations that will help protect chil­dren's health. Two examples are the re­newed Safe Drinking Water Act and the new Food Quality Protection Act, both passed last year. These laws require that pesticides and other likely chemicals be tested for hormonal disruption activity. Still another effort is EPA's chemical test­ing guidelines issued in 1995 that incor­porate children into risk assessment.

The Food Quality Protection Act re­quires that cumulative exposures to pes­ticides—from food, water, residences, lawns—be taken into account when pes­ticides are registered. Pesticides with a common mechanism of action must be considered as a group using a weight-of-evidence approach. "It is the first act that says children will be protected," Goldman explained.

Another EPA effort to protect chil­dren's health is the proposed stricter air quality standards for ozone and particu­late matter. EPA argues that tighter stan­dards would result in 250,000 fewer cas­es of aggravated asthma annually.

In addition, Goldman noted, EPA will be attempting to revise the Toxic Sub­stances Control Act. Apart from pesticides, EPA currently requires testing of very few of the 3,000 to 5,000 new chemicals intro­duced to the market each year.

And to put even more emphasis on children's health, this spring, the White House will sponsor a conference on chil­dren and the developing brain. "Presi­dent Clinton has made [children's health] a top priority," Goldman said. "Some say we are moving too quickly. I say it's long overdue."^

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