Okland Construction went to the Utah Air Quality Board in May and received a variance from the usual dust opacity rules for Saturday's implosion. Bird said the exception was granted because there was no practical way to control dust from the implosion.

But additional requirements are in place, to create a dust-impact zone where people other than the project workers will be excluded, he said. Members of the public won't be allowed back into that zone until crews have cleaned the surfaces.

Bird said that he would prefer that people watch the implosion on television rather than in person. When the implosion happens, he added, "there will be dust in excess of those dust requirements that we have in our rules."

No asbestos or other toxic material remain in the building, Bird said.

But Dr. Brian Moench, president of Utah Physicians for a Healthy Environment, said his group is concerned about the dust issue: "I don't know what the answer is, but particles of dust can be a significant hazard when they're inhaled in the lungs."

While the group has focused mostly on air pollution from fossil-fuel burning, it also worries about the effects of dust pollution.

"Particles of dust, regardless of the source, can be a significant public health hazard," he said. That can be true whether the inhaled dust is from soil, pulverized rock or cement material.

State air-quality regulations are insufficient to protect public health, particularly when it comes to construction dust, Moench said.

"They're not designed to address this kind of situation at all," he said. "The air-quality regulations aren't strict enough as it is, but they really don't address these acute and short-term situations well at all."

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E-mail: bau@desnews.com