IBM has blasted a study that claims to link higher cancer rates among its employees to the chip manufacturing facilities in which they work. 

The study, published in the scientific journal Environmental Health, was written by Dr Richard Clapp from Boston University. 

It alleges that employees working in facilities that manufacture computer equipment are more likely to develop certain forms of cancer, including brain, kidney and breast cancer.

The basis for the study was an IBM "corporate mortality file" obtained in 2002 as part of a lawsuit against the company filed by former employees. The file contained over 31,000 mortality files listing causes of death of former IBM employees.

The study concluded that "mortality was elevated due to specific cancers and among workers more likely to be exposed to solvents and other chemical exposures in manufacturing operations".

IBM questioned the validity of the report in a statement to vnunet.com. 

"Dr Clapp prepared his study as a paid expert witness in support of unsuccessful litigation against IBM. It is based on flawed methodology and woefully incomplete data," the company said.

IBM also pointed to a study conducted by Harvard University and the University of Alabama at Birmingham which it claims showed that IBM employees had lower cancer and mortality rates than the general population.

Former IBM employees have repeatedly alleged a link between cancer and the chemicals used in the chip lithography process.

IBM won a lawsuit in 2003 against a group of former employees who worked in the company's clean rooms in the 1970s and 1980s and alleged a link between their ailments and the chemicals to which they were exposed.