In North Carolina, a hazardous waste incinerator was having trouble meeting air quality requirements. But when local residents developed asthma-type ailments and blamed them on the burn plant, doctors didn't know what the trouble was.

The difficulty of identifying possible public health risks associated with incinerators is that "basically there's a large gap of information," said William A. Suk of the National Institutes of Health.Suk, who plans research that is funded by the NIH's National Institute of Environmental Health Sciences, met with Deseret News editors and reporters Wednesday. He was accompanied by Ronald O. Kagel, chairman of the Coalition for Responsible Waste Incineration, a nonprofit group of companies and academic institutions that support environmentally sound incineration of hazardous waste.

Suk and Kagel are attending the Second International Congress on Toxic Combustion By-Products, held through Friday at the University of Utah. The symposium has drawn 200 scientists from around the globe.

In the North Carolina case, Suk said, the state "thought EPA (the Environmental Protection Agency) was doing their job, and EPA thought they were doing their job" to make certain that the plant met all standards.

Because neither the public at large nor many physicians are very familiar with symptoms that could be caused by pollution, it is difficult to check whether health problems really are tied to environmental causes. "There is no education, or little education, teaching physicians about the problem," Suk said.

The National institute of Environmental Health Sciences has a program to educate the public about such difficulties.

"Let's face it - most people don't live near a hazardous waste site," he said. "If they do, they move." That makes it hard to track residents to see if long-term effects have shown up.

According to Kagel, who is an environmental quality consultant at the Dow Chemical Co. in Midland, Mich., modern requirements are stringent for incineration, and when carried out according to the legal requirements, experts believe it is safe.

Kagel stressed the advantages of incineration, saying that today, the preferred treatment of hazardous waste is "incineration - high-temperature, high-technology incineration."

Most organic combustible material can be incinerated, destroying most of the substances. "The incinerators are rigorously controlled by EPA," he said.

Federal standards require that material be destroyed to "four nines" - that is, 99.99 percent of the substance must be burned away. An EPA risk assessment expert has taken the position that "the 0.01 percent residue does not constitute a health hazard," he said. The remaining ash goes to a hazardous waste landfill.

"Obtaining a permit is a very, very difficult thing . . . Once a permit is obtained, the system is operating, it must go through some difficult tests."

Asked how the incinerator's safety can be verified, Kagel said, "There are continuous emissions monitoring on all incinerators operating right now." Monitoring is for many pollutants; for dioxins and furans, among the most hazardous material, the risk is not allowed to reach one in 100,000.

Americans generate 250 million tons of hazardous waste per year, he said. Of this, 50 million tons could be incinerated. But only about 1 percent of that is burned now, he said.

Asked about charges that building high-capacity commercial incinerators in Utah could make the state a dumping ground for hazardous material throughout the West, Kagel said his coalition "is made up of those people who generate the waste and burn it at their own facilities," not commercial incinerators.