The concentrations are especially high in children, a national study says.
By Marla
Cone, L. A. Times Staff Writer
July 22, 2005
In the largest study of
chemical exposure ever conducted on human beings, the U.S. Centers for Disease
Control and Prevention reported Thursday that most American children and adults
were carrying in their bodies dozens of pesticides and toxic compounds used in
consumer products, many of them linked to potential health threats.
The report documented bigger doses in children than in adults of many chemicals,
including some pyrethroids, which are in virtually every household pesticide,
and phthalates, which are found in nail polish and other beauty products as well
as in soft plastics.
The CDC's director, Dr. Julie L. Gerberding, called the national exposure report
— the third in an assessment that is released biennially — a breakthrough that
would help public health officials home in on the most important compounds to
which Americans are routinely exposed.
The latest installment, which looked for 148 toxic compounds in the urine and
blood of about 2,400 people age 6 and older in 2000 and 2001, is "the largest
and most comprehensive report of its kind ever released anywhere by anyone,"
Gerberding said. Findings were broken down by age group and race.
At Thursday's news conference, CDC officials emphasized the good news: Steep
declines were found in children's exposure to lead and secondhand cigarette
smoke.
Lead levels in children have dropped significantly over several years, which
Gerberding called an "astonishing public health achievement" attributable
largely to its removal from gasoline and paint.
About 1.6% of young children tested from 1999 to 2002 had elevated levels of
lead, which could lower their intelligence and damage their brains, compared
with 88.2% in the late 1970s and 4.4% in the early 1990s.
But the discovery of more than 100 other substances in humans, particularly
children, distressed environmental health experts.
"The report in general shows that people — kids and adults — are exposed to
things that aren't intended to be in their body," said Dr. Jerome A. Paulson, an
associate professor of pediatrics at the George Washington University School of
Medicine and Health Sciences who specializes in children's environmental health.
"In and of itself, that is a concern. Whether it's harmful or not we can't tell
from this particular study."
The new data in the 475-page report reveal how "we have fouled our own nest,"
Paulson said. "We contaminated the environment sufficiently that there are
measurable amounts of potentially toxic substances in people — kids and adults."
The CDC did not try to gauge the health threat the chemicals might pose. A
measurable amount of a compound in a person's body does not mean it causes
disease or other damage, the agency noted.
For many compounds in the report, experts have little information on what
amounts may be harmful or what they may do in combination.
"We are really at the beginning of a very complicated journey to understand the
thousands of substances we are exposed to," said Thomas Burke, associate
professor at the Johns Hopkins Bloomberg School of Public Health.
The discovery of pyrethroids in most people is especially important, as no one
had looked for them in the human body before. Pyrethroids are synthetic versions
of natural compounds found in flowers, and they have been considered safer than
older pesticides, such as DDT and chlordane, that build up in the environment
and have been banned in the United States.
But in high doses, pyrethroids are toxic to the nervous system. They are the
second most common class of pesticides that result in poisoning. At low doses,
they might alter hormones. The compounds are used in large volumes in farm and
household pesticides and are sprayed by public agencies to kill mosquitoes.
Pyrethroids "were a step forward [from DDT and other banned pesticides], but now
we're beginning to understand that while they don't persist in the environment,
many of us are exposed," Burke said. "We don't quite know what those levels
mean."
Eleven of 12 phthalates tested were higher in children than adults. All of the
phthalates but one are used in fragrances. In animal tests, and in one recent
study of human babies, some of the compounds have been shown to alter male
reproductive organs or to feminize hormones.
Representatives of the chemical and pesticide industries praised the study,
saying that human biomonitoring is the best available tool to measure exposure.
They echoed the CDC in saying that discovery of the chemicals in the human body
did not automatically mean they posed a threat.
The report demonstrates "that exposure to these man-made and natural substances
is extremely low," said American Chemistry Council spokesman Chris VandenHeuvel.
The CDC's Gerberding said that "for the vast majority" of the 148 chemicals in
the report, "we have no evidence of health effects."
Many toxicologists and environmental scientists disagree.
Studies of animals, and in some cases people, suggest that most of the compounds
can affect the brain, hormones, reproductive system or the immune system, or
that they are linked to cancer. "These are some bad actors," Burke said.
Many of the compounds have not been studied sufficiently to know what happens
with chronic exposure to low doses. "No evidence of health effects does not
imply that they are not harmful," Paulson said. "It just means we don't know one
way or another."
Environmental groups have called for U.S. law to require chemical companies to
test industrial compounds more comprehensively, a proposal similar to one that
the European Parliament is to debate in the fall.
The evidence that many contaminants amass in children more than in adults could
mean that they are exposed to larger amounts — perhaps from crawling, breathing
more rapidly or putting items in their mouths — or that their bodies are less
able to cope with or metabolize them.
In the womb and in the first two years after birth, children undergo
extraordinary cell growth, from brain neurons to immune cells, so there are more
opportunities for toxic compounds to disrupt the cells, Paulson said. Animal
tests show that fetuses and newborns are the most susceptible to harm from many
chemicals.
In the CDC study, one of every 18 women of childbearing age, or 5.7%, had
mercury that exceeded the level that the U.S. Environmental Protection Agency
deemed safe to a developing fetus.
Tests on schoolchildren show that mercury exposure in the womb can lower IQs,
with memory and vocabulary particularly impaired.
The CDC plans to expand the national chemical report to more than 300 compounds
in two years and about 500 in four years. An estimated 80,000 chemicals are in
commercial use today.