Research Team Blames Catalytic Converters for Spread of Potential Toxin

Our efforts to clean up the environment by requiring catalytic converters on motor vehicles may have backfired, according to a new report from a research team that includes Old Dominion University oceanographer Peter Sedwick (pictured).

Findings published in the April 24 Early Edition of the Proceedings of the National Academy of Sciences report that trace amounts of the metal osmium, which can be very toxic under certain conditions, is increasingly prevalent in rain and snow, as well as rivers and oceans around the world. The researchers, led by Dartmouth University earth sciences professor Mukul Sharma, determined that the increases in osmium are manmade and claim that the manufacturing and use of catalytic converters is largely responsible.

The article was also the subject of a follow-up news story in the journal Nature.

"As part of my recent field sampling programs in the Sargasso Sea and the Antarctic Ocean, I had the opportunity to collect seawater and snow samples using specialized 'clean' techniques for the analysis of osmium," Sedwick said. "These samples, along with those from other global locations, were analyzed by Cynthia Chen and Mukul Sharma in professor Sharma's laboratory. Professor Sharma is a world expert on the geochemistry of osmium, and directed the research that produced the publication."

Sharma was quoted as saying in a Dartmouth publication: "It's interesting, maybe ironic, that we stopped adding lead to gasoline in the 1970s so that catalytic converters could be introduced to remove smog from car exhaust. Now we learn that using platinum in the converters is responsible for an increase in osmium. Fortunately, unlike lead, the concentration of osmium in water is extremely small and may not adversely affect biology."

Osmium is released naturally via volcanic vents and from some meteorites, but the researchers found that the naturally occurring forms of the element cannot explain the amounts they found in rain and snow and in samples from rivers, oceans and polar ice. There are other sources for manmade osmium, such as hospital incinerators, but the researchers say the greatest amount comes from smelters that produce the raw material to meet what Sharma called our "insatiable demand for platinum-based catalytic converters."

Sharma suggested that to remove any chance of osmium contamination "scrubbers" should be installed at production facilities that produce platinum. About 95 percent of the world's platinum is refined in South Africa and Russia, where no environmental laws control the emissions.

Sedwick, an assistant professor of ocean, earth and atmospheric sciences who joined ODU in 2008, has a research interest in the atmospheric input of trace elements to the surface ocean. Although he has a particular focus on iron, which is an essential trace nutrient required by marine phytoplankton, he said he hopes to continue collaborative work with Sharma on the geochemistry of osmium.