Dallas (Tex.) Morning News, July 22, 2006


Rules on cancer-causing chemicals add margin of safety, agency says

[Rachel's introduction: The new EPA cancer guidelines are "not protective of children," says Philip Landrigan, professor of pediatrics and community and preventive medicine at Mount Sinai School of Medicine in New York City. "It's an example of the administration failing the most vulnerable members of our society."]

By Sue Goetinck Ambrose

For years, scientists have warned that government safety standards leave children too exposed to cancer-causing chemicals.

Last year, the Bush administration took action. But many experts say the new guidelines may offer only one-tenth the protection that children need from the chemicals most dangerous to them.

The U.S. Environmental Protection Agency, which issued the guidelines, says they add an extra margin of safety to already stringent standards. But some public health specialists note that while some chemicals are 100 times more toxic to children than adults, the EPA's new guidelines assume the worst chemical is only 10 times as bad.

The new guidelines are "not protective of children," said Philip Landrigan, professor of pediatrics and community and preventive medicine at Mount Sinai School of Medicine in New York City. "It's an example of the administration failing the most vulnerable members of our society."

The need for special protection for children was widely recognized more than a decade ago, after a 1993 report from the National Academy of Sciences concluded that pesticides probably posed greater risks to children than adults. But it wasn't until March 2005 that the EPA issued the guidelines, officially known as the Supplemental Guidance for Assessing Susceptibility From Early-Life Exposure to Carcinogens.

The guidelines are used primarily by the EPA to set standards for acceptable chemical exposure levels in various settings, such as in air or drinking water or at waste cleanup sites.

Until the early 1990s, many scientists say, the idea that children may have an extra sensitivity to some chemicals was not widely appreciated, Dr. Landrigan said.

"I don't think there was deliberate inaction," he said. "The consciousness of children's susceptibility just wasn't there."

Children are not miniature adults when it comes to chemical exposures. They have their own behaviors -- playing close to the ground, putting dirty hands to their mouths -- that distinguish them from adults. Children also eat, breathe and drink more per pound of body weight than adults and differ in how they metabolize foreign chemicals that enter the body.

And in recent years, scientists have become aware of a deeper difference between children and grown-ups: The rapid development of children both before and after birth can make them more susceptible to harm from chemicals.

Scientists suspect that a child's swift growth can leave less time to repair chemical damage to cells or genes, creating populations of cells with dormant, tumor-causing alterations that can erupt into a cancer later in life. Indeed, studies in lab animals have shown that exposure to certain chemicals before birth or early in life can cause cancer in adulthood.

Each year, about 700 new chemicals enter the market, according to a 2005 government report. Not all of those will be directly tested for their potential health effects. And when a chemical is tested for its ability to cause cancer, the research generally is conducted on adult lab animals, not juveniles.

"Virtually all the data that are now used for cancer risk projection are based on these studies that exclude the period of greatest vulnerability," said Dale Hattis, a geneticist and toxicologist at Clark University in Worcester, Mass.

To create the new guidelines, the EPA examined the few published studies that do exist -- some dating to the 1960s -- on cancer-causing chemicals given to juvenile animals. Of 50 chemicals identified by the EPA as causing cancer after early-life exposure, adequate comparisons between juvenile and adult exposure existed for only 18. And of those, the EPA focused its efforts on 12 chemicals that appear to cause cancer by creating mutations in genes.

The EPA calculated how potent each of the 12 chemicals was in its ability to create tumors in juveniles vs. adults. Some chemicals were almost 10 times more potent in adults. But the EPA found that others were more than 100 times more potent in juveniles.

Studies limited

Few of the known cancer-causing chemicals -- the government lists more than 230 known or probable cancer-causing substances -- have been compared in studies on younger and older animals. So the EPA took, in essence, a one-size-fits-all approach to devise its new policy for all untested chemicals. To account for the wide range of potencies, the agency chose to use a value known as the geometric mean, which is similar to an average.

For the potencies of the 12 chemicals, the geometric mean was 10 -- and the EPA used that number in its guidelines. For children under age 2, for example, the EPA said acceptable carcinogen levels for any untested chemicals should be set 10 times lower than they would have been before the guidelines were issued. For children between 2 and 16, the acceptable levels should be three times lower.

"What it's telling you is that, on average, children are more susceptible and that tenfold is the average," said Dr. Lynn Goldman, professor at the Johns Hopkins Bloomberg School of Public Health in Baltimore and a former assistant administrator at the EPA under the Clinton administration. "But by applying this factor, they may not be sufficiently protective."

It's likely, she said, that many carcinogens -- if they were specifically tested -- would be more than 10 times as potent in juveniles, just like the chemicals in the EPA analysis found to be more than 100 times as potent in young animals.

"You don't want to stop here and say 10 is right," she said. "That should be the starting point to make sure we aren't underprotecting kids from a whole series of chemicals."

The chemical industry has its own perspective on the EPA guidelines - at least one industry group said it thinks the EPA's guidelines are based on faulty science.

"There are fundamental problems with the dataset," said Rick Becker, a toxicologist with the American Chemistry Council. "There's very limited data across the board to show that there's increased susceptibility" in children.

He argues that the EPA should be responsible for testing whether chemicals actually are worse for juveniles.

"You shouldn't base decisions on science that isn't supported by the data," he said.

Dr. Landrigan dismissed Dr. Becker's reasoning.

"They're ignoring the vast body of literature that children are more susceptible than adults," he said.

The EPA says it will incorporate new information on chemicals' effects on juveniles, should it become available.

"We didn't choose the chemicals that were tested," said Martha Sandy, a toxicologist at California's state EPA. "We're depending on what's out there in the literature. We don't know about other chemicals that we're exposed to that haven't been tested."

As a result, Dr. Sandy said, the guidelines essentially are an educated guess for any chemicals that haven't been tested. If some of the studies analyzed by the EPA simply hadn't been done, Dr. Sandy said, the default factor could have come out lower or higher.

Another shortcoming is that the studies weren't originally designed to measure the relative potencies for juveniles vs. adults, scientists said. So even choosing the best calculation to capture the broad range of potencies is a matter of scientific debate.

Environmental officials from California and Connecticut, for example, have said that for their states' own guidelines, they are likely to use calculations that end up offering more protection than the EPA's federal guidelines.

In theory, the EPA could have proposed a higher adjustment factor for children, one that would account for the higher potencies seen in the animal studies. This would cover more chemicals that are the worst for juveniles but overprotect for chemicals that don't seem to pose any increased risk.

Bill Farland, a top official in the EPA's office of research and development, predicted that there would not be many chemicals that would need more stringent regulation to protect children.

Further, he said of the new guidelines, "We're adjusting something that was already... protective."

Prenatal exposure

But other scientists said it's unfortunate that the EPA guidelines don't address prenatal exposure to potentially harmful chemicals. Studies have shown that exposure to chemicals in utero can influence adult health. For example, women whose mothers took the anti- miscarriage drug DES were more likely to develop vaginal cancer in their 30s.

"The policy that the EPA put in place does not address prenatal exposure but clearly... that's an important time and needs to be thought about," said Tracey Woodruff, an EPA scientist who participated in the study that led to the new guidelines. She made her comments in a lecture at the National Academy of Sciences this year.

And the EPA's guidelines only cover chemicals thought to cause cancer via genetic mutations.

"We don't quite have enough information to look at any [other] group of chemicals as a whole," Dr. Woodruff said.

Others disagree. Dr. Henry Anderson, a medical officer at the Wisconsin Division of Public Health, led the advisory committee assigned to evaluate the guidelines while they were still in draft form. He said the EPA could have addressed chemicals that trigger cancer in ways other than via mutations.

"The EPA said... for the other carcinogens that don't work through that [mutation] mechanism, we aren't going to change anything," Dr. Anderson said in an interview. "We came at it the other way."

In fact, scientists are beginning to understand that while genetic mutations definitely contribute to cancerous growth, other kinds of changes to the genetic blueprint can be just as harmful.

One type of such change reprograms genes without actually causing a mutation. Just like mutations, these so-called epigenetic changes can encourage the rampant growth that's the hallmark of cancer cells. One new theory even holds that epigenetic changes -- not mutations -- are the first missteps on the long road from healthy tissue to cancer.

The debate over the guidelines raises another, broader issue, said Clark University's Dr. Hattis -- a cost-benefit analysis of what risks are acceptable, given the conveniences that chemicals offer and the costs associated with avoiding any potential harm from them.

"You might want to impose more burden on the responsible parties to achieve confidence that you should be more protective," he said. "But all that is a discussion... that has not been really engaged in by risk managers or the public."

E-mail sgoetinck@dallasnews.com