Although drugs and chemicals pose “unique” health risks to children, identifying such risks and determining how--and if--federal health and environmental guidelines should be changed to accommodate children remains problematic, experts say.
The medical and environmental experts attending a forum here on the similarities and differences in health risks faced by children and adults concluded that a growing body of scientific evidence suggests that children, and especially fetuses and newborn infants, may be especially vulnerable when exposed to certain chemicals and drugs.
But far more needs to be known, they said, before federal policymakers can overhaul health and safety standards that are based on the assumption that children absorb, metabolize, and excrete substances in the same ways as adults.
“I think that we can agree that, in some ways, children are fundamentally different from adults,” said Ruth A. Etzel, chief of the air-pollution and respiratory-health-activity section at the U.S. Centers for Disease Control. “Our risk assessment fails and falls short as long as it does not take into account these fundamental differences between children and adults, just as it fails when it does not take fundamental differences between animal models and humans into account.”
The conference, the first on the subject to be sponsored by the U.S. Environmental Protection Agency, comes at a time when many advocates have been pushing for more stringent safety standards as a way to protect children.
Debate over whether federal environmental standards adequately protect children became heated in early 1989, when an environmental group charged that Alar, a chemical used by some growers to enhance crispness in apples, posed a special health risk to children.
In a report that caused dozens of school districts to temporarily stop serving apples, the National Resources Defense Council argued that the EPA’s health standard for Alar did not account for children eating proportionately more of the fruit than adults do. (See Education Week, March 22, 1989.)
At the conference, many of the more than 150 medical experts and environmental scientists in attendance argued that children are exposed to, as well as process, chemicals and drugs in different ways from adults.
Because their lungs, brains, and other bodily functions are still developing, children eat and breathe proportionately more per kilo of weight than adults, they said. Children also have a gastro-intestinal tract with a different pH balance, possibly have more porous skin, and are still developing their excretion system, they said.
The experts noted that children typically behave in ways that may also increase their exposure to certain pesticides. In addition to eating proportionately more and different kinds of foods, children put dirt and other items into their mouths, and spend more time outdoors, they said.
“It cannot be overemphasized that we have to come to a better understanding of how children behave in order to understand and estimate their exposure to chemicals in [their] world,” said Ellen Silbergeld, an adjunct associate professor of toxicology at the University of Maryland’s medical school.
As a result of these differences, Joseph V. Rodricks, a principal with ENVIRON Corporation in Arlington, Va., estimated that children absorb proportionately three times as much of a substance on an average exposure as do adults.
This is also true, he said, for lead. Adjusted for size and weight, infants up to 2 years of age who eat lead-laden products absorb five times as much of the metal, which has been linked with learning disabilities, as do adults, he said. By the time the child is 6 or 7, the proportion drops to twice as much, Mr. Rodricks said.
Presentations at the conference suggested that adults and children have dramatically different reactions to many common drugs and chemicals.
For instance, while Ritalin often successfully calms hyperactive children, they said, it does not have the same effect on adults. And while Phenobarbital successfully controls seizures in adults, the same drug causes some children to become hyperactive, it was noted.
In some cases, the scientists said, children may be more resilient than adults. For example, young children who take overdoses of medicines containing acetaminophen, the active ingredient in some non-aspirin pain killers, are less likely to die than adults who take overdoses.
And for other substances, the experts said, there appear to be few differences between children and adults in how they are affected. They noted that clinical tests of the drug AZT have shown it to cause virtually the same improvements and side effects in both adults and children who are infected with the virus that causes AIDS.
Experts at the conference said that much more needs to be known before the federal government can revise its safety standards, including more clinical tests of drugs and chemicals that examine the issues most salient to child development.
Such tests would examine, they said, whether there are specific critical periods, such as puberty, in which children may be especially vulnerable, and whether substances cause subtle, non-toxic effects.
For instance, they noted, children who have been exposed to lead at even very low levels have been shown to have lower IQ’s.
“We shouldn’t always automatically assume that children are going to be more sensitive,” said Jonathan R. Bell, an official in the British ministry of agriculture, fisheries, and food. “While it’s right to examine the differences between children and adults, I think its premature to draw too many conclusions.”
