Montgomery County’s waste incinerator has polluted the air with toxic emissions beyond what the state allows, but for how long isn’t yet clear.

Officials also don’t know the extent to which elevated levels of toxic emissions may have endangered people’s health. The county is expecting to hire an outside expert to investigate the cause of the violation and the risks it posed.

Annual testing from September showed that one of the county facility’s three boilers was emitting excessive amounts of dioxins and furans, highly toxic pollutants that can cause cancer, reproductive and immunological problems, among other health issues.

Results from two days of testing showed the Dickerson facility was releasing an average of about 83% more dioxins and furans than allowed under state law.

“We have no idea how long this was going on,” County Executive Marc Elrich, a critic of trash incineration who has long promised to close the facility, said Wednesday.

After receiving test results in early November, Reworld, the company operating the incinerator, reported its findings to the state Department of the Environment and received a “notice of violation.”

An inspection of the problematic boiler revealed a tear in pollutant-trapping filter.

After completing repairs, the company conducted another test of the boiler on Dec. 1 and found that the concentration of dioxins and furans released fell within the allowable limit.

What’s next?

Reworld is in the process of verifying whether the filter tear caused the elevated levels of toxic pollutants, how it tore and how long the boiler unit was malfunctioning, according to the county Department of Environmental Protection.

Company spokesperson Linda Ribakusky said in a statement that the Reworld “has a strong track record of operating its facilities up to 99% below federal emission guidelines and maintaining continuous compliance with emissions standards.”

Elrich, though, said problems with the incinerator go far beyond this emissions violation.

“This aging facility that relies on outdated technology can be a threat to public health and the environment,” he said. “For decades, this incinerator has been one of the county’s largest pollution sources.”

County staff have in recent weeks been reviewing proposals from private companies to haul waste to regional landfills. A contract would present a major step toward closing the incinerator.

The County Council will have to sign off on any agreement. Elrich has been at odds with some council members over how to change county waste management, but the two sides agree the incinerator should be closed because of the health, environmental and financial risks it presents.