International study provides important benchmark for countries still using leaded gasoline

October 18, 1999

Switching to Unleaded Reduces Lead in People's Blood

A new study by Princeton University researchers demonstrates, for the first time, that it is possible to predict the extent to which switching from leaded to unleaded gasoline reduces the level of lead in people's blood. Lead levels where unleaded gasoline is used averaged about three micrograms per deciliter (ug/dL), well below the 10 ug/dL that is generally considered cause for concern in the United States.

The study will appear in the Nov. 15 print issue of the peer-reviewed journal Environmental Science & Technology, published by the American Chemical Society, the world's largest scientific society. It was published on the journal's web site on Oct. 1.

"Most countries still use leaded gasoline," according to the study's lead author Valerie Thomas, Ph.D., research scientist at Princeton's Center for Energy and Environmental Studies. Countries using the largest amounts of lead in gasoline include Nigeria, Indonesia, Saudi Arabia, Iraq and South Africa, according to Thomas. "Some of the highest concentrations of lead in gasoline are found in Africa, where there has been almost no progress in phasing lead out of gasoline," she adds.

Before this study, the research article claims, "there has been little ability to predict how blood lead levels will change, for a given population, as leaded gasoline is phased out."

In areas where lead has been removed from gasoline, blood lead levels typically fall to about three micrograms per deciliter (ug/dL), says Thomas. "In many of the locations studied, average population blood lead levels were above ten micrograms per deciliter before the reductions of lead in gasoline," she noted.

In the United States, the Centers for Disease Control and Prevention recommends 10 ug/dL as the threshold for taking action to reduce children's exposure to lead. U.S. blood lead levels in both adults and children have dropped more than 80 percent since the 1970s, according to the CDC.

The reduction to three ug/dL in the measured populations is an average, Thomas emphasizes. "Blood lead levels of individuals are distributed about the average. Even when the average blood lead level is three ug/dL, some individuals may have significantly higher exposures," according to Thomas.

Exposure to lead can cause numerous medical problems. Young children and infants are particularly susceptible to lead poisoning. They can have reduced IQs, learning disabilities and slow development as a result of exposure to lead.

Exposures to industrial emissions, lead-soldered food cans and lead-based paint also can contribute to elevated blood lead levels, says Thomas. However, she points out, "both the timing of the reductions, and data on air lead concentrations, indicate that reductions of lead in gasoline were a major cause of the reductions in lead exposure."

The study analyzed data from lead measurement studies in Belgium, Canada, Finland, Greece, Italy, Japan, Mexico, Nepal, New Zealand, South Africa, Spain, Sweden, Switzerland, the United Kingdom, the United States and Venezuela.

In some locations, even if leaded gasoline is eliminated other sources of lead contamination could cause blood lead levels to remain above three ug/dL, according to the article. "Nevertheless," says Thomas, "this study can be used as a guide by policy makers in countries still using lead in gasoline, allowing them to estimate roughly the effects of eliminating leaded gasoline."
-end-
(The on-line version of the research paper cited above is available on the American Chemical Society's ASAP (As Soon As Publishable) web site. Journalists desiring full access to papers at the ASAP site must submit their requests in writing to newsroom@acs.org in the ACS Department of News & Information.)

A nonprofit organization with a membership of nearly 159,000 chemists and chemical engineers, the American Chemical Society publishes scientific journals and databases, convenes major research conferences, and provides educational, science policy and career programs in chemistry. Its main offices are in Washington, D.C., and Columbus, Ohio. (http://www.acs.org)

American Chemical Society

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