Dr. Jim Pirkle, deputy director for science at the CDC, said previous CDC studies from 1991 to 1994 estimated 4.4 percent of U.S. children aged 1 to 5 years had toxic blood lead levels. The current study, with data from more than 2,000 people taken in 1999 and 2000, estimated only 2.2 percent of children had a toxic lead level.

The new study of Americans' environmental "body burden" of environmental chemicals also showed the levels of cotinine - a marker for secondhand tobacco smoke - had decreased by 58 percent in children, 55 percent in adolescents and 35 percent in adults since the early 1990s, Pirkle said at a telephone news conference.

CDC scientists suggested the declines were tied partly to increased public awareness of the toxins and the dangers they posed to children.

Pirkle said there was cause for concern because children had cotinine levels more than twice as high as adults. But Dr. Richard Jackson, director of the CDC's Center for Environmental Health, stressed that children ate, drank and breathed two to three times as much, proportionally, as adults, which might partially account for their higher levels.

"(The CDC report) identifies chemicals that are actually getting into Americans and how much of each chemical is getting in," Jackson said.

'HUGE DIFFERENCE' FOR PUBLIC HEALTH

"I know that this kind of information makes a huge difference for public health workers on the front line of environmental health problems every single day," Jackson said in a telephone news conference from Atlanta. "The report tells us whether efforts to reduce exposure to environmental chemicals are really working."

The CDC report was the second in a series, but this version tested Americans' blood and urine for 116 environmental chemicals - known as their "body burden" of chemicals - up from 27 chemicals surveyed in a CDC report released two years ago.

"This kind of information is what moves the science forward to answer those health effect questions, and by finding out what (chemicals) are in people and what levels are typical in the population, we're moving a lot of studies forward that will give us that information much faster," Jackson said.

At a later telephone news conference organized by the National Environmental Trust, Dr. Peter Orris and others applauded the scope of the report and said it provided support for the further regulation of environmental chemicals.

"It would appear that regulation and in fact the outright elimination of certain chemicals works," said Orris, director of the Occupational Health Services Institute at the University of Illinois.

Noting reported decreases in levels of lead, PCBs, dioxin and DDT, Orris said, "These are all examples of regulatory action on the part of the government which we not only can applaud but we now have data indicating that this works and in an effective means of social policy."

Another study, released by the Environmental Working Group and the Mt. Sinai School of Medicine, tested nine volunteers for the presence of 210 industrial compounds, pollutants and other chemicals, and detected traces of 167 chemicals.