Efforts to curb exposure to secondhand tobacco smoke in the United States have paid off dramatically, according to a new report from the Centers for Disease Control and Prevention (CDC) in Atlanta. That's just one conclusion from a report, released today, that presents the first data on the general population's exposure to 24 environmental chemicals.
CDC's goal was to create a baseline range of chemical exposure for a cross section of the country's population. With this baseline in hand, researchers will be able to determine whether a person has had an unusually high exposure to an environmental chemical, a necessary first step in determining whether a chemical exposure may have caused birth defects or other health effects. In 1999, researchers from CDC's National Health and Nutrition Examination Survey (NHANES) visited 12 locations across the country, collecting blood and urine samples from 3800 people. CDC analyzed the samples for traces of 27 chemicals, including toxic metals, cotinine (a marker for tobacco smoke), and metabolites of malathion and other pesticides. They also looked for metabolites of phthalates--chemicals found in soap, shampoo, hair spray, and other household products--which cause reproductive damage in laboratory animals.
The researchers found good news in two cases for which earlier data existed. Blood levels of cotinine dropped 75% compared to a 1991 NHANES survey. "It's really striking," says Richard Jackson, director of CDC's National Center for Environmental Health (NCEH). Average lead exposure has also dropped. For children age 1 to 5, blood levels fell from 2.7 to 2.0 micrograms per deciliter (µg/dL). (A level of 10 µg/dL is associated with harmful effects on children's learning and behavior.)
Most of the other compounds, in contrast, have never been measured in the general population. It's not clear whether the baseline levels represent a health risk, says Jim Pirkle of NCEH's Division of Laboratory Sciences. But already the measurements are providing clues for further investigation. The levels of two phthalates stand out among the rest, so CDC researchers are concentrating on figuring out how they get into the body.
Public health experts welcome the report. "History was made today," said John Balbus of George Washington University in Washington, D.C., at a press conference. "It's a small but significant step." CDC plans to increase the number of chemicals it tests to 100 within 4 years, but even that is a tiny fraction of the tens of thousands in use today.