A Department of Health study found no increased rate of asbestos-associated cancer among those living within a two-mile radius of two former vermiculite plants in downtown Salt Lake City. And although the study found significantly increased rates of respiratory and lung cancers there, they doubt the processing plants caused the cancers.

People who worked at the plants and their household members, though, were likely exposed to asbestos at levels that could cause concern, health officials say. Now they're hoping that former employees of the two vermiculite facilities will contact them so they can see whether working directly with the material had adverse health effects.

Vermiculite is the fluffy, shiny material in ceiling insulations and potting soils, although it starts life as an ore that only becomes fluffy when it expands and pops, somewhat like popcorn.

Concern about the vermiculite processed in Utah arose because much of it came from a mine in Libby, Mont., which was contaminated with asbestos, said Wayne Ball, a Utah Department of Health toxicologist. When the vermiculite pops, a process called "exfoliation," asbestos can be released. The Libby mine was closed in 1990.

With help from the Agency for Toxic Substances and Disease Registry, state health departments nationwide have been looking at cancer rates near facilities that processed asbestos-contaminated vermiculite. Salt Lake had two of them: Vermiculite Intermountain, 333 W. 100 South, operated from 1941-86. Intermountain Products Inc., 733 W. 800 South, had a short run, from 1985-87.

But the Utah Department of Health study of cancer data between 1973 and 2000 found that within a two-mile radius of the VI facility, rates of the two primary cancers related to asbestos exposure, mesothelioma and asbestosis, were no higher than in other parts of the state. Conversely, lung and respiratory cancers were 50 percent higher, "and we don't know why," Ball said.

When an environmental agent is the cause, he said, trends can be spotted. There was no upward or downward trend on respiratory cancer rates over the 28-year time period studied, from 1973-2000. "It was elevated, but consistent. We don't know what was happening, but because mesothelioma was not increased, we don't feel these facilities contributed to lung cancer rates in the area," he said.

The report, available online at www.health.utah.gov/enviroepi, said that the former VI site, now a Utah Power and Light substation, commercial parking lot and small businesses, poses no public health risk now. Most of the site had been cleaned up when the researchers were writing their report and the last remaining contaminated soil beneath asphalt was to be remediated by the end of 2006. The Environmental Protection Agency finished cleanup of the IP site in December 2004.