USG Interiors, LLC will pay a $6,253 fine for air quality violations at its Cloquet ceiling tile plant.

The Minnesota Pollution Control Agency said USG more than doubled its emission limits in late 2019.

The facility manufactures acoustical ceiling tiles through a process that involves combining a variety of raw materials into a slurry that is dried, cut and coated. The process requires an air-quality permit, with limits on emission of nitrogen oxides, carbon monoxide, volatile organic compounds and particulate matter.

The pollutants can cause respiratory and cardiovascular illness in humans, according to the MPCA, and nitrous oxide is the main contributor to ground-level pollution that causes visibility issues.

USG previously paid a $59,000 fine and agreed to three enforcement steps, including a compliance and testing plan approved by the MPCA, after the company self-reported 32 air-quality violations or missed equipment tests between July 2014 and October 2016.

An MPCA report on enforcement actions settled in the first half of 2020 also included a $6,800 fine for Bunes Septic Service of Grand Rapids for "improper land application of sewage."

The now-shuttered ERP Iron Ore Plant 4 in Grand Rapids, Rajala Mill Co. in Bigfork and Ogston's Body & Paint in Duluth were all fined less than $5,000 for air-quality violations, while Lakehead Trucking in Duluth was fined less than $5,000 for a subsurface sewage treatment system violation, the MPCA said.