"Given the totality of the evidence, Stericycle should be shut down now, not after months of investigation," he said.
The Utah Department of Environmental Quality (DEQ) recently slapped Stericycle, a large Illinois-based company, with violation notices for exceeding its limits on emissions of nitrogen oxide, as well as dioxins and other hazardous air pollutants.
DEQ has recently revised the notice, imposing stiffer penalties and mandating provisions to deter future violations of emission standards.
"It is a priority to pursue this process with all diligence. In fact, the Division of Air Quality is closely scrutinizing Stericycle to ensure compliance," said DEQ director Amanda Smith. "If Stericycle does not comply with the conditions outlined in the [notice of violation], DEQ will pursue all legal options to revoke its permit."
Plant manager Steven McOmber referred requests for comment to Stericycle's corporate office, which did not immediately return a phone message
In a press statement released shortly after Wednesday's rally, the governor expressed concern over Stericycle's bypass emissions, but it was not clear whether he would use his executive authority to close the plant.
"Our agencies are pursuing penalties to the fullest extent of the law," said Ally Isom, Herbert's deputy chief of staff, in an email to reporters. "With all the state and our partners are doing to improve air quality, it is distressing when one entity [Stericycle] appears less committed to doing its part."
North Salt Lake Mayor Len Arave said the time might be coming when it will be best for Stericycle to cease operations in his community, but he was not willing to endorse his constituents' call to shut down the plant.
Incineration of medical waste is no longer the standard and the vast majority of such facilities have been closed around the nation in recent years.
"While thousands of communities are cleaner, in Utah things have gotten worse," Dr. Ellie Brownstein, a pediatrician, said. That's because hospital waste from eight nearby states is shipped to the North Salt Lake incinerator.
"This is an industry that shouldn't exist. If they were to clean up their act and promise to never do this again, that's still not enough, because the cleanest incinerator there is still a serious public health hazard," Moench said. "The evidence of the public health threat is what's in the blood of the people there. No one is monitoring that. What is in the breast milk of the mothers there? No one is monitoring that."