Workers who clean and maintain chip-making equipment have the highest level of exposure to harmful chemicals in manufacturing plants, according to a report issued by an industry trade group.

However, there's insufficient evidence to link exposure to chemicals in chip plants to cancer, said the Semiconductor Industry Association's scientific advisory committee.

In the report, the committee recommended "that a rigorous epidemiologic study is desirable to evaluate the cancer risk to workers in the wafer fabrication areas."

The committee also recommended that chip companies "suspend any planned or periodic destruction of employment, work history, exposure assessment or medical records," according to a five-page executive summary released yesterday.

The document was made public after critics blasted the association for not releasing the entire report on Tuesday when it announced that the board had accepted the committee's recommendations and that it will begin a feasibility study before committing to a comprehensive study.

The rest of the inch-thick report probably won't be released because it mentions specific companies that agreed to disclose information on condition of confidentiality, said spokeswoman Molly Tuttle.

Dr. Joseph LaDou, director of the International Center for Occupational Medicine at the UC San Francisco, said he was more encouraged by the executive summary than the association's news release earlier in the week.

Still, he's concerned that the association might be dragging its feet by insisting on a feasibility study.

Tuttle said the association is working with member companies to prepare a plan, which needs the board's approval. "We're trying to do the right thing and make sure we're doing this appropriately," she said.