Study Finds Lower Level of Old Toxins but New Trends Are Worrying
By ANDREW C. REVKIN
The broadest study yet of toxic chemicals that Americans absorb in their bodies showed a continuing decline in the clearest threats, like lead, pesticides and tobacco residues, but turned up numerous other findings that federal scientists and other experts called troublesome yesterday.
The study tested blood and urine collected in 1999 and 2000 from more than 2,000 volunteers chosen as a representative slice of the American population. It determined that almost 8 percent of the roughly 50 million American women ages 16 to 49 had blood levels of mercury exceeding 5.8 parts per billion, the precautionary standard set by the Environmental Protection Agency.
Federal health officials said the danger level for mercury was 10 times that high, a level not found in any of the women in the study. But they said the finding justified a greater effort to find ways to cut women's exposure to mercury, which at high levels can cause birth defects and other problems. Much of the mercury exposure is likely to accumulate through eating fish.
It is the second such study by the federal Centers for Disease Control and Prevention, but in examining 116 chemicals it greatly expands on the first report, published in 2001, which looked for only 27.
Health researchers, environmental campaigners and industry representatives hailed the report as a vital tool in trying to discern, or rule out, health effects from chemicals in the environment.
"This allows us to begin connecting the dots," said Dr. Patricia Butterfield, a researcher and professor of nursing at Montana State University. "We can begin in the next generation of citizens to understand these issues and make science-based decisions."
The study, the Second National Report on Human Exposure to Environmental Chemicals, was posted at www.cdc.gov/exposurereport yesterday.
Because the study measured exposures by age, sex and ethnic background, it could help public health officials focus their priorities, officials and experts said. For example, it found that all other population groups, including children, had blood levels of mercury well below the government safety limit.
Future surveys will be published every two years.
Among other findings, the new study disclosed that children had higher levels of residues from secondhand smoke, some pesticides and plastics than adults, and that Mexican-Americans have three times the levels of a DDT residue of other Americans.
The children's higher levels of residues could be a result of several factors, federal scientists said. For one, children eat, drink and breathe three times as much as adults pound for pound.
More work should be done to understand the DDT levels in Mexican Americans, scientists from the disease control agency said. The pesticide has long been banned in the United States and since 1997 has been phased out in Mexico. The study did not differentiate between native-born Americans of Mexican descent and Mexican immigrants.
The study used new methods able to detect the slightest traces of chemicals in the blood and urine. Tests were run to check for dozens of constituents or breakdown products of pesticides and plastics as well as long-lived compounds that are now largely banned but persist in the environment.
Already, federal officials said, the smaller 2001 survey has borne fruit.
They cited a recent investigation of a cluster of childhood leukemia cases in Fallon, Nev. Investigators sifted for clues to any link to 132 chemicals, said Dr. James L. Pirkle, the deputy director for science at the federal laboratories that conducts the studies. A significant finding was that levels of tungsten, a toxic metal, were higher locally than in the 2001 general overview of the population. Now the researchers can try to determine whether tungsten levels can be linked to the leukemia, he said.
The new study echoed the 2001 study's findings on DDT; tobacco residue, called cotinine; lead; and other toxic compounds that have been measured for many years. All concentrations have continued to drop in all age and ethnic groups, according to the new study.
Cotinine is a compound left behind after the body breaks down cigarette smoke and is used as an indicator of exposure to a host of other cigarette ingredients that can cause cancer and other diseases.
The new study found that children had more than double the level of cotinine found in nonsmoking adults. The researchers said this was probably because most efforts to curtail smoke exposure had occurred in workplaces and public spaces, not the home.
Environmental and chemical industry groups had different reactions to the report yesterday.
Environmental campaigners highlighted the need for more work to reduce chemical releases into the environment and more research on risks.
Industry groups said the data showed the robustness of humans, whose longevity and health have been steadily improving even with trace exposures like those measured in the new research.
Source: The New York Times