Although California phased lead out of gasoline about eight years ago, it will continue to wash into the San Francisco Bay for the next 50 to 100 years, scientists say.
University of California, Santa Cruz scientists published the 10-year-study in Tuesday's issue of Proceedings of the National Academy of Sciences in Washington.
The tetraethyl lead that was added to cars in the 1960s has polluted the air and water and is still found in the Sacramento and San Joaquin rivers, which flow to the Sacramento Delta and the San Francisco Bay, according to the study.
Lead can harm the nervous, reproductive and blood-producing systems of the body even at low levels. But the scientists say the lead that flows into the bay is less than that found in drinking water and does not threaten anyone's health.
The reason the lead will stick around for so long is because a large volume fell as air pollution in the Central Valley and the bay, the scientists said.
In the 1960s and 1970s, cars emitted about 33,000 tons of lead that found its way into the Sacramento and San Joaquin rivers. About 80 percent of the lead in the North and Central Bay areas comes from those cars. The rest is from hydraulic gold mining that took place during the Gold Rush. In the South Bay, that split is about 90 percent to 10 percent.