March 21, 2001 -- Thanks to advances in technology, scientists are now able to get a much more accurate picture of how many substances in the environment accumulate in the human body -- and at what levels. The findings are mixed: Levels of lead and tobacco-related chemicals have dropped substantially in recent years, but a chemical used in soap and cosmetics is surprisingly prevalent.
The complete findings were released today by the CDC. The CDC obtained the information in 1999 by measuring blood and urine levels of 27 chemicals in people from 12 U.S. locations.
Of these substances, 24 were measured for the first time, and three -- lead, cadmium, and cotinine -- have been measured previously. The new data will serve as a yardstick for comparing future tests.
Researchers tracked four categories of exposures: metals (such as lead, mercury, and cadmium), tobacco smoke, organophosphate pesticides, and phthalates (compounds used in soap, shampoo, hairspray, nail polish, and flexible plastics). In the future, they plan to add more environmental chemicals to the list, with the goal of reaching 100 in four years. Ultimately, they will break the findings down by age, sex, race, ethnicity, income level, and urban/rural residence status of the participants.
Among the positive findings: Efforts to ban public smoking seem to have resulted in a measurable reduction in harmful tobacco smoke exposure. Levels of cotinine, the chemical left over after the body breaks down tobacco, decreased fourfold in 1999, the report says, when compared with data from prior years. Also, lead levels in children continued to decline in 1999, the data show.
These success stories are important to note, says Eric Sampson, PhD, of the CDC's Environmental Laboratory.
"Blood lead levels for children aged 5 and younger keep going down, [showing that we are] successful in limiting children's exposure to lead," he says. Nevertheless, he warns, lead poisoning among children is still a major concern, especially for those who live in homes built before 1950 and those exposed to lead-contaminated dust.
In a bit of a surprise, blood levels of two of the seven phthalates measured -- diethyl phthalate (DEP) and dibutyl phthalate (DBP) -- were found to be higher than levels of other phthalates that are produced in greater quantity. Further research is needed to explain this finding, researchers say.
Mercury, a metal known to be harmful to young children and pregnant women, was measured for the first time. Although no previous data exist for comparison, the levels were higher than had been predicted, which is a cause for some concern, according to information presented at the Washington, D.C., press conference where the report was introduced.
At this conference, Philip Landrigan, MD, professor of pediatrics at Mount Sinai School of Medicine in New York City, called the report a "wake-up call."
"Americans are being exposed to an array of toxic chemicals, many of which can and should be avoided," says Landrigan, an expert on children and pesticides.
But Jeff Steir, associate director of the American Council of Science and Health in New York City, urges caution in interpreting and analyzing the new report.
"It is important not to overplay the significance of tests whose purpose it is to find extremely low, or 'trace,' levels of chemicals in the blood," he tells WebMD. "The mere presence of chemicals, be they natural or manmade, do not indicate any negative health consequences. In toxicology, it is the dose that makes the poison," he says.
"The real danger takes place when workers are exposed to certain chemicals at high levels over long periods of time," Steir adds.