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Thursday Marked Fourth Straight Day of Hydrogen Sulfide Exceedances in the Mon Valley

Updated: Mar 25

The values in red denote exceedances of PA’s 24-hour H2S standard of 0.005 ppm.

Thursday marked the fourth straight day of air quality exceedances in the Mon Valley, with hydrogen sulfide (H2S) concentrations again exceeding the Pennsylvania standard at Allegheny County Health Department’s Liberty monitor – the 24-hour average H2S concentration was 0.009 ppm at the Liberty monitor. The PA standard is 0.005 ppm.

That means there were H2S exceedances at the Liberty air quality monitor in five of the last nine days.

An H2S exceedance was also noted at the North Braddock air quality monitor (24-hour average concentration of 0.006 ppm), the third such infraction in nine days.

“This week, in addition to all of those H2S exceedances, Allegheny County also experienced its first exceedance of the health-based standard for particle pollution,” GASP Executive Director Rachel Filippini said. “Despite all that, the health department issued zero communications to the public to give them a heads up about this latest bout of bad air so they could take measures to mitigate exposure.”

GASP again is calling on ACHD to better utilize the county Alert system and its social media channels to better inform the public on air quality issues that could impact their health. 

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