BALTIMORE (AP) — Maryland environmental regulators are asking Baltimore's single largest source of industrial air pollution to cut nitrogen oxides omission by about one-fifth, as well as commission a study to determine if it can clean its exhaust more aggressively.

The Baltimore Sun reports a regulation proposed Friday would require the Wheelabrator Baltimore incinerator to reduce emissions of the harmful pollutant by about 200 tons (181 metric tons) a year.

The incinerator burns most of the region's trash, but isn't being held to same standard as Montgomery County's facility, as it's older and less sophisticated.

State environmental regulators and Wheelabrator officials have been in talks over the emissions for three years, as the state works to bring the region in compliance with federal ozone pollution limits.

A public hearing on the proposal is scheduled for Sept. 21.

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Information from: The Baltimore Sun, http://www.baltimoresun.com