Chemical Used in Tires Tracks Pollution

BOSTON — A type of chemical used to help make automobile tires last longer has given scientists a tool they can use to try to trace the source of some water pollution.

Researchers at the Lawrence Livermore National Laboratory at the University of California found unusual chemicals in sediment at the bottom of the San Francisco Bay while studying pollution in that body of water.

“We found a compound there we didn’t recognize at first,” said Robert B. Spies, a marine environmental scientist who headed the research. “It started a little detective story.”

The researchers, who reported their findings in a recent edition of the British science journal Nature, eventually identified the chemicals as benzthiazoles. The substances are used in the manufacture of tires to prolong the life of the tires and prevent oxidation, which can cause the rubber to crack.

Tires wear slowly as cars move along streets, depositing small amounts of rubber on the pavement. When it rains, the water apparently washes off some of the deposits, which contain the benzthiazoles.

Also washed off are other pollutants from a variety of sources, such as car exhaust and oil, Spies said. These often end up polluting nearby streams, rivers and other bodies of water.

“This street runoff is a source of pollution to a lot of water bodies,” said Spies in a telephone interview.

The researchers realized the presence of benzthiazoles could therefore be used to trace the source of such pollutants when they are found.

“The significance of this is it acts as a tracer for street runoff,” said Spies. “This compound can act as a marker for the sources. If you find the compound in, say, San Francisco Bay or Boston Harbor, you know it came from the streets.”

The substance itself has not been shown to pose a major hazard to marine life, but it is usually accompanied by other toxic substances that can be hazardous.

“The value is that when regulators are tying to clean up an area, such as San Francisco Bay, the first thing you want to know about is where is it coming from,” said Spies.

“Is it coming from industrial discharges or somewhere else? Street runoff is a point source that is suspected to be a major source of contaminants,” he said.

Once the source of pollution is identified, officials can take steps to try to intercede, he said.

“This compound is a major step is understanding where the pollutants come from,” said Spies.