A chemical commonly used to make rubber products may cause cancer in people exposed to fumes during the manufacturing process, British researchers said on Tuesday.

Workers exposed to 2-mercaptobenzothiazole, or MBT, at a rubber chemicals plant in North Wales were twice as likely to develop colon cancer and four times as likely to get bone marrow cancer compared to the general population, they said.

"Perhaps MBT should be handled with increased care as it may be a human carcinogen," Tom Sorahan of the University of Birmingham and colleagues said in the journal Occupational and Environmental Medicine.

The risk is probably limited to factory workers exposed to MBT when added to a mixture of chemicals eventually used as a component to make rubber products, he added.

"People using rubber goods wouldn't be exposed because MBT wouldn't be given off," Sorahan said. "The problem is for people manufacturing the MBT in industry."

Previous studies have suggested the chemical may cause tumors in mice, but the latest findings are some of the first to link MBT to cancer in humans, Sorahan told Reuters.

His team looked at death rates for 363 workers exposed to the chemical who had worked at the plant for at least six months between 1955 and 1984 and diagnoses of cancer from 1971 to 2005.

The risks also seemed to rise the longer a person was exposed to the chemical. But more research was needed to confirm the findings because the study included a relatively small number of workers, Sorahan added.

"This can only be confirmed one way or the other by doing large studies," he said.

(Agencies via China Daily January 21, 2009)