A study of Hill Air Force Base workers that showed a few excess cancers over a 36-year period needs to be followed up by an examination of just what substances employees were exposed to, Sen. Or-rin Hatch, R-Utah, says.

The National Cancer Institute will later this year look at the possible link between certain specific solvents used in aircraft maintenance operations at Hill.A Hatch aide said that statistically the results of the initial cancer institute study only "raise a suspicion" but do not tell Hill workers if they are at risk, who is at risk, what substances may be hazardous under the conditions in which they are used at the base, or what levels of exposure are risky.

Scientists know from past studies that certain solvents are dangerous at high exposure levels, but stringent rules on their use have reduced the hazard to workers, particularly in recent years.

Hatch told reporters Wednesday that the results of the first study "are still being analyzed. Utah people are healthier than the average in the United State, and this study tells us workers at Hill are even more healthy than the Utah average."

The report showed an overall death rate among workers at Hill only 92 percent of that for the Utah population as a whole.

"But there may be some increase of a few types of cancer among these workers," Hatch said. "There may be some suggestion of that. We need to do more study of the particular exposures before we can know for sure."

The statistics used by National Cancer Institute involve very small numbers that may be skewed by chance, a Hatch aide said. Where the expected numbers of cancers are 1.8 and the number found is three, over more than 30 years, factors other than occupational exposure may be involved.

One of the tables showed that workers with up to five years of service at Hill were at higher risk than those who had worked there for longer periods. Such data would not support a finding that occupational factors affected the chance of developing cancer.