Dallas (Tex.) Morning News  [Printer-friendly version]
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