At a press conference convened at the Salt Lake County government building, activists also renewed calls on Gov. Gary Herbert to close the plant, arguing the study he recently ordered into its health impacts on surrounding communities is of little value. Preliminary reports based on 10-year-old soil samples found scant traces of dioxins, one of Stericycle's pollutants causing the most concern.
A meaningful epidemiological investigation will take too long and could forestall action against a polluter that has already been caught trying to deceive state regulators and the public, according to Foxboro resident and mother Alicia Connell, a co-founder of Communities for Clean Air, a local group that formed to fight incineration.
"The governor's actions are bewildering to us. The health study does not change the reality of the situation," Connell said. "The communities around Stericycle are determined that the incinerator be closed down. We will do whatever it takes to make that happen."
She added, "There are companies offering new, safer, cleaner options. This should remove the final barrier to correct the mistake made 25 years ago when the incinerator was approved."
At Thursday's conference in the county council's chambers, Connell was flanked by representatives of such companies. They described their on-site methods of using chemicals and ozone to disinfect medical waste, which can then be dumped in municipal landfills in a shredded form.
But the strongest remarks Thursday were directed at the state.
"The governor is allowing Stericycle to operate until they are proven unsafe beyond any doubt. A wealth of existing research and the anecdotal evidence from residents in the area is more than enough to demand a safer, conservative, precautionary approach," said Brian Moench, a co-founder of the physicians group.
"Living near an incinerator, or having your body contaminated with incinerator toxins originating miles away, statistically increases your chance of many types of serious diseases," he said. "We don't need to wait for a study specific to Utah to confirm that."
Utah Department of Health officials said it is too early for anyone to dismiss the study.
"I would caution people to not read too much in this first phase. What we found was a validation of the need to look further into the potential health impacts," spokesman Tom Hudachko said.
Herbert ordered the three-tier study of the plant's emissions of dioxins and furans last month in the face of mounting community pressure and allegations from state regulators. They allege the plant exceeded its emission limits, failed to report excess emissions and rigged stack tests, all in violation of its permit.
The company, which is contesting the alleged violations, did not respond to phone messages left at its corporate offices in Illinois.
The Health Department this week released the first phase of the study, called a technical assist, which explained the ways dioxins pollute the environment and harm people.
This class of toxic chemicals are generated by the burning of many types of materials. They drop out of smoke quickly so they don't pose much of an exposure risk through inhalation. But they can contaminate soil and break down slowly, according to the report by Craig Dietrich, a toxicologist with the department's environmental epidemiology program.
Human exposures typically occur through food because plants take up the chemical.
The Davis soil samples did not show alarming levels of dioxin, including the one taken near Stericyle's five-acre compound, now surrounded by the Foxboro subdivision. According to Hudachko, the study team is poised to collect six fresh samples fanning out from the plant.
"Based on what those sample show there might be a need to home in on certain areas. This is essentially a first pass," he said.
But the physicians group lambasted the soil study, arguing dioxins don't persist in soil because they eventually vaporize and the plant emits plenty of other toxic materials. Stericycle's permit allows the North Salt Lake plant to emit each year up to 9.5 tons of hazardous pollutants, including mercury and lead.
Focusing on dioxin amounts to "cherry picking" data in a way that de-emphasizes the threat Stericycle poses to public health, the doctors said.