Richard Clapp, a professor of environmental health at Boston University's School of Public Health, wrote the study that was published in Environmental Health, an online scientific journal.

"The findings reveal elevated cancers in manufacturing workers associated with solvents," Clapp said. "These cancers include brain, non-Hodgkin's lymphoma, and kidney."

The study examines data on the cause of death for 31,941 people who had worked for IBM Corp., and died between 1969 and 2001. Of the 27,272 men who died, there were 7,697 deaths from cancer, significantly higher than the 7,206 expected, according to national averages, the study said. Of 4,669 women, 1,667 had died of cancer, higher than the 1,454 expected according to averages.

IBM has dismissed the results of Clapp's study, saying it is based on inconclusive data and flawed methodology. IBM has been cleared in at least one major lawsuit by former employees who said they were exposed to dangerous chemicals on the job. (Extensive coverage of that landmark trial can be found here.)

Clapp acknoweldges there's no conclusive evidence that links the cancer deaths to the manufacturing facilities or chemicals used in the plants, and said the study had originally begun as part of the chemical-exposure lawsuit.

A court order required IBM to provide plaintiffs company documents. It included thousands of records detailing those deceased who had worked at IBM plants for at least five years. The lawyers for the plaintiffs gave the records to Clapp to search for patterns of excess mortality among the employees.

Despite claims in the newly published study, some industry watchers remain skeptical about the claims of direct linkage. "If you look at factories in the 1960s and 1970s, conditions at the facilities were less than desirable, but it still would be pretty difficult to prove the deaths were attributed to chemicals because so many more people smoked," said Len Jelinek, director and principal semiconductor analyst at research firm iSuppli Corp., El Segundo, Calif. "On the other hand, we now understand the physiological impact of some of the chemicals being used in fabrication facilities."

Jelinek said at one time fabrication facilities filtered air through large rooms to keep toxins out and equipment clean. Today, companies encapsulate equipment in the room, because it was too expensive to recycle air in such a large room.

"The way facilities operate in the past five years has changed dramatically," Jelinek said, suggesting the findings are suspect.