Drop reported in levels of some harmful chemicals
By Lisa M. Krieger
San Jose Mercury News
There is good news about the bad things that lurk in our bodies, according to the newest and most comprehensive survey of Americans’ exposure to pollutants.
A nationwide sampling of bodily fluids shows a decline in the levels of lead, some pesticides, and other chemicals known to be harmful to our health.
But the survey also poses new questions, because it offers the first-ever evidence of exposure to previously unmeasured chemicals. Because their health impact is not well understood, further study is planned.
The report, released by the federal Centers for Disease Control and Prevention on Thursday, uses the emerging science of biomonitoring—detecting what pollutants make their way into our bodies. After decades of testing soil, water, food and air, scientists now are studying pollution in people.
There are efforts in California to conduct a similar study of state residents.
Technological advances have made it possible to detect a wider array of chemicals in the body at much lower levels than before. The first round of CDC testing in 2001 looked for 27 chemicals. The second study, released in 2003, expanded to 116 chemicals.
This new study examined 148 chemicals, 30 of which had never been sought before. About 2,500 Americans of various ages and ethnic groups were tested. Results were not broken down by state or region. By the end of the decade, more than 470 chemicals in the human body will be studied by the CDC.
“It provides the missing data that we’ve needed,’’ said Dr. Julie Gerberding, director of the CDC. “It is a giant step forward in understanding exposure—and what are the health consequences of exposure?
“It is important to reassure people that for the vast majority of chemicals, there is no evidence of health effects,’’ said Gerberding.
For less-studied chemicals, she said, “it will tell us where to focus our lens.’’
Specifically, the CDC survey found:
Levels of toxic lead in the blood of young children have continued to decline. This decrease shows that efforts to reduce lead exposure in children have been successful—and it is a reminder that a few children are still living in homes with lead-contaminated paint. A drop in levels of a cancer-causing byproduct of nicotine called cotinine is thought to reflect a reduction in exposure to secondhand cigarette smoke, due to regulatory crackdowns on smoking. Three once widely used pesticides, discontinued in the 1970s and 1980s, were virtually undetectable. Aldrin, endrin and dieldrin were used to kill insects in cotton and corn crops. Mercury remains present in the blood of some people, probably due to eating fish or shellfish that accumulate mercury from their environments. But the mercury was found in concentrations thought to be too low to cause fetal defects. About 5 percent of tested women of child-bearing age had mercury levels that were suspicious but not dangerous. Those people will be monitored.Several findings will trigger closer study, such as the fact that chemicals called pyrethyroids—used in insect foggers and sprays, flea dips for pets and termite treatments—were found to be present in almost everyone.
In addition, troubling levels of a chemical called cadmium, linked to kidney damage, was found in about 5 percent of adults. Cigarette smoking is the likely source for this metal.
An inventory of chemicals in the body is important because it can serve as a yardstick in the future, revealing when things are really wrong, according to Gerberding. For example, if someone is concerned that they may have experienced high exposure to a chemical, they can compare their personal exposure levels to the U.S. standards. If their levels are higher than the national norms, that could indicate a problem.
Critics say that the CDC survey is useful but does not go far enough—and they urge broader study on the state level. A bill to create a California biomonitoring program was defeated this week in a key Assembly committee, but could be reconsidered later this session.
“While today’s report is an important first step, it falls short in recognizing the scale of chemical exposure to people and wildlife,’’ said Clif Curtis of the World Wildlife Fund, which conducts its own biomonitoring studies, in a statement. “People are broadly contaminated with a range of chemicals that are not measured in the new CDC report.’’
But others say the survey proves there is no need for alarm. Critics of the state-funded study say that California should focus on specific workplace exposures and not test the general population.
“As expected, there are low levels’’ of exposure, said Robert Krieger, a toxicologist with the University of California-Riverside. “And they’re not cause for concern for anybody.’’ A government survey “causes anxiety and even changes in behavior because of simple detection of things that don’t pose a threat. People get afraid.
“We live in a chemical world,’’ he said.
(In accordance with Title 17 U.S.C. Section 107, this material is distributed without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes.)
Posted by: Paul on July 22, 2005 at 21:39:55