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
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
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
"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
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
For many compounds in the report, experts have little
information on what amounts may be harmful or what they may do
"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
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
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
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
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
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
Tests on schoolchildren show that mercury exposure in the womb
can lower IQs, with memory and vocabulary particularly
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.
Copyright 2005 Los Angeles Times