State officials have decided that exotic chemicals used in open-air Army tests at Dugway Proving Ground don't pose much threat to the general public.

So the Utah Air Conservation Committee gave temporary approval Thursday for the Army to use those chemicals during 10 open-air tests planned through Sept. 14. Some of the chemicals are obscurants - which cause smoke - and others simulate the characteristics of deadly chemical weapons.Approval to use the chemicals was held up last month when committee members and state health officials said they had never heard of many of the substances, and had no idea how toxic they are.

The committee was also upset when it learned that several of those chemicals had already been used in open-air tests without proper state permits.

So the committee asked David Thurman of the Utah Bureau of Epidemiology to study the chemicals on the Army's list and report on their characteristics.

He told the committee Thursday that he had some trouble finding out about some of the chemicals because the Army is about the only one that uses them, but he feels their use is safe, based on what he could find out from the Army and scientific computer data bases.

Thurman wrote to the committee, "I do not find evidence that any of these substances, as currently used or proposed for use, pose a significant hazard to the public health or to the environment outside of the Dugway Proving Ground test range."

But he warned several large "gaps of knowledge" exist about how toxic many of the chemicals are.

For example, he said he didn't even know the name of one of the chemicals because it is classified by the Army and referred to by a code name - EA5763.

He noted that the only specific information he could find about that chemical was an assessment from the Livermore National Laboratory that said its lethal dose in rats is 800 milligrams per kilogram of animal weight. He said the Army also assured him the substance is "not in the class of heavy metals recognized as highly toxic."

Several committee members asked the Army to consider giving more state health officials security clearance so they could openly talk about such substances, which Army representatives said they are anxious to do.

Thurman also told the committee that several of the chemicals used are dangerous - but more in the sense of the occupational risks that they pose to workers than from possible danger that clouds of the chemicals could make people off the base sick.

For example, he said, Dugway uses white phosphorus, which ignites spontaneously with air, and hexachloroethane, which irritates the lungs and has caused deaths of animals in studies.

Thurman said he believes such chemicals pose little threat to the general public because in visits to Dugway, he was assured that tests are conducted only when wind and other weather conditions are favorable. He said the Army also uses computers to predict where chemicals will spread - a practice which has been highly accurate and helped to ensure chemicals do not leave the base.

Of note, many of the chemicals that Thurman evaluated were used last year in tests of the sometimes controversial Bigeye nerve gas bomb.

The Pentagon admitted last week that many minor problems still exist with that bomb, and more redesign and tests will be needed to correct them. The Army now apparently has permission to use the chemicals needed for such tests.