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UPDATED: Yet Another H2S Exceedance & More Unhealthy Air for Mon Valley, ACHD Responds

This story was updated at 10:32 a.m. Wednesday to include a statement issued by the Allegheny County Health Department.

Another day, another air quality exceedance for the Mon Valley.

For the second straight day, concentrations of hydrogen-sulfide (H2S) at Allegheny County Health Department’s air quality monitor in Liberty exceeded the state 24-hour average standard of 0.005 ppm on Tuesday. The average concentration there was 0.007 ppm.

Hydrogen sulfide is a colorless gas most commonly recognized by its “rotten egg” smell.

“While H2S at Liberty was pretty bad yesterday, the 24-hour average concentration at North Braddock was just 0.001 ppm – and that required rounding up,” GASP staff attorney Ned Mulcahy noted. “I really can’t explain it, but the same thing is happening today. H2S at Liberty averaged 0.023 ppm from 10 p.m. – 7 a.m. but over the same time period at North Braddock the average was just 0.004 ppm.”

Based on numbers published shortly before this story, the 24-hour average h2s concentration at Liberty will exceed the state standard again today, making four such exceedances in five days.

And that’s not all of today’s air quality concerns.

Levels of fine particulate matter (pm2.5), were high enough at one point this morning to earn the Liberty-Clairton the distinction of worst air quality in the country per Levels are expected to drop through the day but by how much is unclear.

GASP will continue to monitor the data and will update this report if there is an exceedance for either H2S or fine particulate matter (PM2.5).

Following the publication of this story, ACHD issued the following statement via its Allegheny Alerts system:

Starting last evening, air quality readings for PM2.5 at the Liberty Monitor increased and have remained elevated. This is unusual and unexpected because the air dispersion forecast was for fair air quality yesterday evening and fair for this morning.The Health Department contacted US Steel regarding these unhealthy air quality readings and was informed that they took their three oldest batteries off line sometime in the past 12 hours. However, ACHD is requesting additional information from the company to understand the situation.While we continue to work with US Steel, we are issuing an Air Pollution Watch for the Mon Valley. The forecast for the next 24-hours indicates that the PM2.5 levels will likely exceed the 24-hour standard for the Mon Valley.Young children, the elderly, and those with respiratory problems, such as asthma, emphysema, and bronchitis, are especially vulnerable to the effects of air pollution and should limit outdoor activities during this time.We have requested that US Steel delay bringing the batteries online until air quality improves and we have a better understanding of what caused the unhealthy situation. 

Editor’s Note: These exceedances come on the heels of a Notice of Violation issued by ACHD to U.S. Steel regarding concentrations of hydrogen-sulfide. You can read more about that here.

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