Results from the CDC survey on exposure to environmental chemicals.

The Third National Report on Human Exposure to Environmental Chemicals, released last July by the 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 also suggests the need for more research into health effects from exposure to low levels of cadmium.

For this third 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) during 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 ethnicity.

In addition to data on lead and cadmium, the report includes extensive data on chemicals such as mercury, and other metals; phthalates; organochlorine pesticides; organophosphate pesticides; pyrethroid insecticides; herbicides; polycyclic aromatic hydrocarbons; dioxins and furans; polychlorinated biphenyls; and phytoestrogens.

The results presented in this and future reports will help set priorities for research on human health risks resulting from exposure to environmental chemicals.

Exposure to Environmental Tobacco Smoke Decreases

Median levels of a chemical called cotinine, which is a marker of exposure to secondhand smoke in nonsmokers, have dropped significantly since the first measurements were made in 1988-1991; by 68 percent in children, 69 percent in adolescents, and about 75 percent in adults. Still, some populations remain at greater risk; the most recent 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 one to five years of age show that for 1999-2002, 1.6 percent of the children had elevated blood lead levels (concentrations of 10 [micro]g/dL or greater are defined as the CDC level of concern). This percentage has decreased from 4.4 percent in the early 1990s.

"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 CDCs Environmental Health Laboratory. "There is no safe blood lead level in children. Children are best protected by controlling or eliminating lead sources before exposure occurs."

Exposure to Cadmium Merits Monitoring

Recent studies have shown that urine levels of the metal cadmium as low as 1 [micro]g 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 20 years of age and older has urinary cadmium at or near these levels. Cigarette smoking is the likely source of these higher cadmium levels. More research is needed on the public health consequences.

The Third National Report on Human Exposure to Environmental Chemicals and an executive summary are available online at www.cdc.gov/exposurereport.