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Public health efforts in the United States have helped reduce the amount of chemicals from secondhand cigarette smoke and lead in the body, although they are still too high in many people, federal officials reported Friday.

The Centers for Disease Control and Prevention took blood and urine samples from 2,500 people in 1999 and 2000 and tested for 116 different chemicals, including metals, pesticides, insect repellants and disinfectants.

In the early 1990s, 4.4 percent of children ages 1 to 5 had elevated levels of lead, but that dropped to 2.2 percent in 1999-2000.

Lead poisoning — which can occur when children ingest lead-based paint or drink lead-heavy water — can cause learning disabilities, and behavioral problems.

There was more good news: In most people, the level of exposure to dioxins — which have been linked to cancer and liver disease — was too low to detect.

To gauge the effect of secondhand smoke, the CDC tested for nonsmokers for cotinine, a product of nicotine after it enters the body. Levels dropped by 75 percent for nonsmoking adults and 58 percent for children in 1999-2000 compared with the early 1990s, the CDC said.

But blacks had more than twice the cotinine levels of whites or Mexican-Americans, the CDC said. And cotinine levels for children were twice as high as levels for nonsmoking adults.

CDC officials believe children's exposure to chemicals from secondhand smoke may be higher because public health efforts in the 1990s primarily focused on reducing secondhand smoke in adult areas, such as in the workplace. In addition, CDC officials said, children may absorb more from their environment than adults.

"What we are looking at now is that we have now a group we need to specifically target and think of new things to do to reduce their exposure" to secondhand smoke, said Dr. Jim Pirkle, deputy director of science for the CDC's National Center for Environmental Health.

For many of the chemicals in the report, more research is needed to find out whether the levels measured can cause health problems, the CDC said.

Levels of exposure to DDT among Mexicans were three times as high as for other groups. But levels were lower than those detected in smaller, earlier studies.

The report cautions that the presence of a toxin does not necessarily mean a person is in danger.

"Just because people have an environmental chemical in their blood or urine does not mean that the chemical causes disease. The toxicity of a chemical is related to its dose or concentration. Small amounts may be of no health consequence," it reads.

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