Findings from a new report by the US American Centers for Disease Control and
Prevention (CDC) shows a significant decline in exposure to secondhand smoke
and continued decreases in children's blood lead levels. The report, which
tested 148 chemicals and heavy metals (the most substances measured to date),
also suggests the need for more research into health effects of exposure to low
levels of cadmium.
"This is the most extensive assessment ever of Americans' exposure to
environmental chemicals; it shows we're making tremendous progress, and that's
good news," said CDC Director Dr. Julie Gerberding. "Exposure to secondhand
smoke continues to plummet and blood lead levels in children are way down.
However, many challenges remain. CDC is steadfast in its commitment to health
protection, including protection from environmental threats."
Environmental groups stated that the report confirms that the American public
is exposed to widespread contamination by toxic chemicals, the effects of which
are largely unknown. "While [the] report is an important first step, it falls
short in recognizing the scale of chemical exposure to people and wildlife,"
stated Clif Curtis, director of World Wildlife Fund's (WWF) Global Toxics
Program. "WWF's own biomonitoring studies document that people are broadly
contaminated with a range of chemicals that are not measured in the new CDC
report such as brominated flame retardants and perfluorinated chemicals"
The report documents the ongoing assessment of the exposure of the U.S.
population to environmental chemicals using biomonitoring. According to CDC,
biomonitoring measurements are the most health-relevant assessments of exposure
because they measure the amount of the chemical that actually gets into people
from all environmental sources.
For this year's report, CDC's Environmental Health Laboratory measured 148
chemicals -- 38 of which have never been measured in the U.S. population --- or
their breakdown products (metabolites) in blood or urine. The samples were
collected from approximately 2,400 people who participated in CDC's National
Health and Nutrition Examination Survey (NHANES) from 1999 -2002. NHANES is an
ongoing national health survey of the general U.S. population. The report
provides exposure data on the U.S. population by age, sex, and race or
In addition to lead and cadmium, the report includes extensive data for such
chemicals as mercury, lead, cadmium, and other metals; phthalates;
organochlorine pesticides; organophosphate pesticides; pyrethroid insecticides;
herbicides; polycyclic aromatic hydrocarbons; dioxins and furans;
polychlorinated biphenyls; and phytoestrogens.
CDC conducts this research to learn more about the effectiveness of public
health interventions and better understand the health risks of exposure to
chemicals in the environment (present in air, water, food, soil, dust or other
environmental media such as consumer products).
Research separate from the report's findings is needed to determine the
relationship between levels of chemicals in the blood or urine and health
effects. The results presented in this and future reports will help set
priorities for research on human health risks resulting from exposure to
Curtis said that he hopes that CDC "will broaden its biomonitoring scope in
future reports to include the newly emerging, persistent and bioaccumulative
industrial chemicals to which we are all exposed. Tens of thousands of man-made
chemicals are at large, in our homes, our environment and in our bodies. Many
could be harmful and require closer study."
Exposure to Environmental Tobacco Smoke Decreases
Levels of a chemical called cotinine, which is a marker of exposure to
secondhand smoke in nonsmokers, have dropped significantly since levels were
first measured from 1988 to 1991. Compared with median levels for 1988-1991,
median cotinine levels measured from 1999-2002 have decreased 68 percent in
children, 69 percent in adolescents, and about 75 percent in adults. Still,
some populations remain at greater risk; the third report shows that
non-Hispanic blacks have levels twice as high as those of non-Hispanic whites
or Mexican Americans, and children's levels are twice as high as adults' levels.
Children's Blood Lead Levels Continue to Decline
New data on blood lead levels in children aged 1-5 years show that for
1999-2002, 1.6 percent of children aged 1-5 years had elevated blood lead
levels (levels of 10 micrograms per deciliter or greater -- the CDC blood lead
level of concern). This percentage has decreased from 4.4 percent in the early
"Lowering blood lead levels in children is one of the major environmental
health accomplishments of the past 30 years; however, CDC is still concerned
about exposure to lead from lead-based paint and lead-contaminated house dust,
soil and consumer products," said Dr. Jim Pirkle, deputy director for science
at CDC's Environmental Health Laboratory. "There is no safe blood lead level in
children. Children are best protected by controlling or eliminating lead
sources before they are exposed."
Exposure to Cadmium Merits Monitoring
Recent studies have shown that urine levels of the metal cadmium as low as 1
microgram per gram of creatinine may be associated with subtle kidney injury
and an increased risk for low bone mineral density. The report shows that about
5 percent of the U.S. population aged 20 years and older had urinary cadmium at
or near these levels. Cigarette smoking is the likely source for these higher
cadmium levels. More research is needed on the public health consequences of
these levels in people in this age group.
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