Some factory workers have worried about their health.Getty

A paper suggesting that IBM factory workers are at higher risk of contracting cancer has been published after more than two years of controversy and a court battle.

The study, by professor of environmental health Richard Clapp of the Boston University School of Public Health, Massachusetts, is an analysis of nearly 32,000 people employed by IBM for at least 5 years who died between 1969 and 2001. It suggests that workers died from certain cancers, such as brain, kidney and skin cancers, at significantly higher rates than seen in the general US population.

The paper, now published in Environmental Health¹, has had a turbulent history. The study was spurred by a lawsuit in Santa Clara County, California, in which two former IBM employees said that the working conditions had affected their health. As part of this trial, the plaintiffs' attorneys obtained a computerized file of work history and mortality at IBM facilities. They commissioned Clapp to analyse the data and Clapp also acted as an expert witness in the case. But his results, which did not link specific chemicals to cancer risk, were not allowed into evidence by the court. IBM won the case.

Clapp's results were originally submitted to Clinics in Occupational and Environmental Medicine for publication in 2004. But the journal refused to publish it, saying the paper was original research unsuited to a journal that publishes reviews. The refusal prompted accusations that the journal had actually succumbed to pressure from IBM (see 'Scientists cry foul as Elsevier axes paper on cancer mortality').

IBM lawyers argued in part that the data were only released for use in the court case. Clapp says a New York court gave him the go ahead this spring to finally publish the work.

Chemical concerns

The study is the largest published thus far that examines whether people working in computer manufacturing could have higher rates of cancer, and is part of wider concerns about the health of workers in the semiconductor industry (see 'Semiconductor industry: Chipping in').

The study shows, for example, that male manufacturing workers were around 60-80% more likely to have died from cancers of the kidney, skin, brain and central nervous system.

Clapp's research does not pinpoint the specific chemicals or toxins that might be responsible for the increased cancers because there was no detailed information on which chemicals each person was exposed to in the company data. Workers in computer and semiconductor manufacturing are thought to be exposed to various chemicals, metals and sources of electromagnetic radiation.

Contradicting reports

"Dr. Clapp prepared his study as a paid expert witness in support of unsuccessful litigation against IBM," said IBM in a statement yesterday. "It is based on flawed methodology and woefully incomplete data." Clapp says that his study was carried out using standard statistical techniques.

IBM says that Clapp's conclusions are contradicted by an IBM-funded study of more than 126,000 employees at three facilities; several papers were published on this work. IBM says this showed that workers at the three sites had lower overall mortality and cancer incidence rates than the general population.

Occupational-health expert Joseph LaDou of the University of California, San Francisco, who backs Clapp's study, says the IBM funded study did indicate an increased risk of certain cancers.

Other similar studies are already under way, including one led by the Semiconductor Industry Association examining more than 200,000 industry workers.

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• References

  1. Clapp R. W., Environmental Health, published online (2006).