The newly discovered carcinogens are found in cigarette smoke, which is already known to be a major cause of bladder cancer, contributing to at least 50 percent of the approximately 60,000 cases in the United States every year.

All three of the new carcinogens, however, were also found to be risk factors for bladder cancer in nonsmokers. Although second-hand smoke is one source of exposure for non-smokers, the researchers say that it is very important to identify the other sources of exposure for nonsmokers.

"Identifying the non-smoking related sources of these [carcinogens] should become a high scientific priority," write the authors, who are led by Professor Steven R. Tannenbaum, the Underwood-Prescott Professor of Toxicology at MIT.

"This is very important from a public health point of view," said Tannenbaum, who holds appointments in the Biological Engineering (BE) Division and the Department of Chemistry. "It's much more effective to prevent cancer rather than treat it."

The team also identified six chemicals in the same chemical family that do not appear to be human carcinogens. Because they are chemically similar to their three noxious cousins, they could potentially lead to safer alternatives for the latter.

Authors of the paper from MIT are Tannenbaum, Paul L. Skipper, a BE principal research scientist, and Jinping Gan, a former graduate student. Their colleagues Manuela Gago-Dominguez, Kazuko Arakawa, Ronald K. Ross, and Mimi C. Yu are at the University of Southern California, Los Angeles.

In 1993 Tannenbaum and Skipper teamed up with Yu on the ongoing Los Angeles Bladder Cancer Study. Among other conclusions,
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Contact: Elizabeth Thomson
thomson@mit.edu
617-258-5402
Massachusetts Institute of Technology
7-Oct-2004