Survey shows lead, tobacco exposure may be down in U.S., but blood and urine samples, awash with chemicals

Jul 23 2005

According to the latest U.S. government survey on chemical exposures, levels of lead have dropped dramatically, exposure to second-hand smoke is down and most women are not carrying unsafe levels of mercury.

The Centers for Disease Control and Prevention (CDC), released the third National Report on Human Exposure to Environmental Chemicals, on Thursday, and it has details on 148 different chemicals found in the blood and urine of 2,400 volunteers.

CDC director Dr. Julie Gerberding says however, it says virtually nothing about whether the chemicals pose any danger to people, and what the human health consequences are of these exposures.

Gerberding says research is needed in this area, and it could take years, as scientists look at disease in the population and correlate it with the findings of the regular CDC surveys, before any answers are provided.

The first report started in 1999, and this latest one has found 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.

Gerberding says the removal of lead from gasoline was the main reason for this decline, but as it is unknown what is a safe level, it is important to ensure that all children are free of lead exposure.

The report also looked at exposure to second-hand tobacco smoke, using a measure of a chemical called cotinine, a breakdown product of nicotine, and 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.

However the survey found that blacks and children still have higher levels than white adults.

The report also looked at mercury, specifically methylmercury, which makes its way into people most frequently when they eat contaminated fish, and levels in blood of above 58 micrograms per litre can cause nerve damage in developing foetuses.

Apparently none of the women in the survey had mercury levels that approached this level, but as 5.7 percent of the women had levels that were one-tenth of this, the CDC says it would seek studies to find out if these levels might affect a foetus.

The report also contains details on pesticides, weed killers, pollutants known as polycyclic aromatic hydrocarbons, dioxins, furans, polychlorinated biphenyls or PCBs and phytoestrogens, some of which are known carcinogens.

Gerberding says it is possible that some people may be genetically predisposed to be sensitive to some chemicals.

The American Chemistry Council has said that the mere detection of a chemical does not necessarily indicate a risk to health.

Toxicologist Tim Kropp of the Environmental Working Group, which conducts its own studies on chemicals, is particularly interested on the information on a class of chemicals called phthalates.

His group has been lobbying to force the cosmetics and plastics industries to at least label products that contain the compounds, which help make perfumes stick to the skin, makes plastic malleable and performs other functions.

They have apparently been found to affect the reproductive systems of some animals.

The report can be found online at http://www.cdc.gov/exposurereport/