High levels of sulfur dioxide detected again in Mon Valley

Higher than permitted levels of sulfur dioxide were detected Monday evening in the Mon Valley, according to an Allegheny County Department of Health announcement Tuesday afternoon.

The sulfur dioxide, or SO2, exceedance was detected at 10 p.m. Monday at the North Braddock air quality monitor, according to health department data. The monitor recorded an SO2 level of 82 parts per billion before dropping below the federal standard of 75 parts per billion later that evening.

The health department is considering enforcement action, according to the announcement.

SO2 is a colorless gas that could affect breathing and may aggravate respiratory and cardiovascular conditions, according to the health department. It smells like a match that has just been struck.

The health department is analyzing the data and will provide updates if new information is available, spokesman Ryan Scarpino said.

“While we are still investigating, at this time we have yet to find anything abnormal in our operations,” Meghan Cox, spokesperson for U.S. Steel, said in an e-mail.

The detection marks the seventh time health department air quality monitors detected SO2 levels that exceeded federal standards for hourly emissions since a Dec. 24 fire at Clairton Coke Works. The fire knocked out equipment used to remove SO2 from coke oven gas.

The last SO2 exceedance occurred Jan. 8.

Temperature swings have contributed to the region’s poor air quality this week as a weather event called an inversion traps polluted air closer to the ground, health department officials told the Tribune-Review Tuesday.

SO2 exceedances would not have been captured in the air quality index, or AQI, a measure of regional pollutants like ozone and particulate matter used by many weather apps or the federal Environmental Protection Agency’s AirNow.gov air quality site, according to a post by the health department on its Facebook page.

Jamie Martines is a Tribune-Review staff writer. You can contact Jamie at 724-850-2867, jmartines@tribweb.com or via Twitter @Jamie_Martines.