August 12, 1994 Contact: Robert Irion (408/459-2495)

CONTROLS OF LEAD EMISSIONS ARE PAYING OFF IN THE OCEAN, ACCORDING TO MEASUREMENTS ALONG U.S.-MEXICO COAST

FOR IMMEDIATE RELEASE

SANTA CRUZ, CA--Ocean waters at the border between California and Mexico contained far less lead in the late 1980s than in the mid 1970s despite substantial increases in population and sewage disposal, according to new research by scientists at the University of California, Santa Cruz.

Geochemists Sergio Sanudo-Wilhelmy and Russell Flegal found three times less lead in seawater samples collected at the border in 1988 than other researchers had measured near the same spot in 1973. They attribute this decline to strict controls in the United States over lead emissions into the environment, especially the ban against leaded gasoline.

The team's study also reveals that further down the coast of Baja California, most of the lead in the water comes not from the U.S. but from increasing Mexican emissions. Although the levels of lead in the ocean are now low, they could rise off Mexico and in other parts of the globe as developing countries burn more and more leaded gas, the researchers warn.

"Industrialized countries are controlling their release of lead into the environment, and it's having an effect--the ocean is responding and cleaning itself over very short timescales," says Sanudo-Wilhelmy. "But we don't know what the effects will be from Third World countries. Their lead inputs could start being more of a problem."

Sanudo-Wilhelmy and Flegal published their findings in the current issue (August 1994) of the journal Geochimica et Cosmochimica Acta. Flegal is a professor of earth sciences at UCSC. Sañudo-Wilhelmy was a graduate student under Flegal when he conducted the study; he now is an assistant professor of marine sciences at the State University of New York at Stony Brook.

Flegal, who served on a National Academy of Sciences panel that investigated lead's toxic effects in the environment, says lead levels globally are declining as industrialized nations--by far the biggest lead "offenders" in the past--clean up their acts. In the U.S., he notes, "We're seeing lead levels go down in humans, in the air, in Great Lakes sediments, and in Wisconsin peat bogs. This study is another piece of evidence that emission controls are working.

"This is a success story," Flegal continues. "We're discharging much more effluent into the ocean, but the quality of the effluent has improved. That's good news."

Sanudo-Wilhelmy and Flegal collected their samples at numerous locations from San Diego southward along 200 miles of Baja California in June 1988 and June 1989. They used ultraclean collection and analysis techniques that limited any additional lead contamination to less than one part per trillion. The researchers compared their results to those obtained by Clair Patterson of the California Institute of Technology, who analyzed seawater along the southern California coast in 1973. Toxicologists regard Patterson's measurements (published in 1976) as the first reliable figures for lead in coastal waters.

At the one location where the 1988 data and Patterson's study overlapped--near the border between the U.S. and Mexico--lead levels dropped from 36 to 12 parts per trillion. Other recent data along the southern California coast, not published as part of the new study, also reflect this threefold decline, says Sañudo-Wilhelmy. The decrease occurred despite a 42 percent increase in the population of the surrounding area and a 21 percent increase in wastewater discharges.

The threefold drop in environmental lead levels from the mid 1970s to the late 1980s shows up in several other ways, Sañudo- Wilhelmy notes. For instance, lead deposited each year in ocean sediments in the same region declined from 4.5 to 1.6 milligrams per square meter. According to the U.S. Department of the Interior, lead released into the atmosphere in the U.S. dropped from 189,000 to 55,000 tons per year, due largely to eliminating lead from gasoline. (Other industrial activities, such as coal-fired smelting, still put lead into the air.)

Of the lead the researchers did detect in their samples, nearly half came from upwelling--lead deposited into the ocean elsewhere, transported in deep currents, and brought up to the surface again near the coast. To trace the origins of this lead, the team analyzed the ratios of subtly different atomic varieties called isotopes. The ratios they found were typical of lead from Asian countries bordering the North Pacific.

Along the Baja California coast, lead levels ranged from 4 to 7 parts per trillion--lower than the levels measured near the U.S.- Mexico border. However, an isotopic analysis showed that most of this lead comes from industrial emissions in Mexico. "As we move south, we see mainly Mexican lead, probably 90 percent of which is from leaded gasoline," says Sanudo-Wilhelmy.

Finally, the researchers note in their article the relatively high (25 parts per trillion) levels of lead they measured within San Diego Bay. All wastewater discharges into San Diego Bay stopped in 1964, but not before the bay's sediments were contaminated with lead and other trace metals. Now, it appears these contaminants may continually cycle back and forth between the sediments and the water. "Lead concentrations in semi-enclosed bays and estuaries may remain elevated for decades," the researchers write, "while lead concentrations in coastal waters may be rapidly reduced within a period of months."

This release is also available on UC NewsWire, the University of California's electronic news service. To access by modem, dial (209) 244-6971.

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