Lead, Tobacco Exposure Down in U.S., Survey Finds
WASHINGTON Levels of lead have dropped dramatically, exposure to second-hand smoke is down and most women are not burdened by unsafe levels of mercury, according to the latest U.S. government survey on chemical exposures.
The third National Report on Human Exposure to Environmental Chemicals, released Thursday by the Centers for Disease Control and Prevention, has details on 148 different chemicals found in the blood and urine of 2,400 volunteers.
But it says virtually nothing about whether the chemicals pose any danger to people, CDC director Dr. Julie Gerberding said.
"More important, what are the human health consequences of those exposures?" Gerberding asked during a news conference.
This is where research is needed, and finding those answers will take years as scientists look at disease in the population and correlate it with the findings of the regular CDC surveys, first started in 1999.
The latest report finds that 1.6 percent of U.S. children have elevated blood lead levels, compared to 4.4 percent in 1991-94 and 88.2 percent in 1976 to 1988.
"We don't know what is a safe level, so we continue to strive to ensure that all children are free of lead exposure," Gerberding said, noting that the removal of lead from gasoline was the main reason for the decline.
The report, found on the Internet at http://www.cdc.gov/exposurereport/, also looked at exposure to second-hand tobacco smoke, using a measure of a chemical called cotinine, a breakdown product of nicotine.
It found that cotinine levels in blood have fallen 68 percent in children aged 4 to 11 from a previous 1988-to-1991 test period, by 69 percent in 12- to 19-year-olds and by 75 percent in adults aged 20 to 74.
But blacks and children still have higher levels than white adults, the survey found.
SAFE LEVELS OF MERCURY
The report also looked at mercury, specifically methylmercury, which makes its way into people most frequently when they eat contaminated fish.
Levels in blood of above 58 micrograms per liter can cause nerve damage in developing fetuses. "None of the women in the survey has mercury levels that approached this level," Gerberding said.
But 5.7 percent of the women had levels that were one-tenth of this, and the CDC said it would seek studies to find out if these levels might affect a fetus.
The report also contains details on pesticides, weed killers, pollutants known as polycyclic aromatic hydrocarbons, dioxins, furans, polychlorinated biphenyls or PCBs and phytoestrogens.
Some are known carcinogens, such as dioxins and PCBs.
Gerberding said some people may have a genetic predisposition to be sensitive to some chemicals.
"So it is not just a matter of are you exposed to a chemical or not but how does your body or your unique composition respond to that chemical," she said.
"As the CDC cautions, the mere detection of a chemical does not necessarily indicate a risk to health," the American Chemistry Council said in a statement.
Toxicologist Tim Kropp of the Environmental Working Group, which conducts its own studies on chemicals, said he was interested on the information of a class of chemicals called phthalates.
His group has lobbied to force the cosmetics and plastics industries to at least label products that contain the compounds, which help make scents stick to the skin, make plastic malleable and perform other functions. They have been found to affect the reproductive systems of some animals.
"If you look at the phthalate metabolites, the large majority of phthalate material comes from fragrances and cosmetics," Kropp said in a telephone interview.