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Hydrogen Sulfide Limits Repeatedly Violated in Mon Valley

Updated: Feb 21

Comments made to the Allegheny County Board of Health by Sue Seppi, Sep. 13, 2017

Waking up in the morning or the middle of the night to “rotten egg odors” is not an uncommon event in Allegheny County, especially in or downwind of the Monongahela Valley.

That smell very likely comes from hydrogen sulfide (H2S), whose odor is perceptible by most at a very low concentration. Of course, there are other disagreeable outdoor odors, but the H2S odor is so unpleasant and common that Pennsylvania has required H2S in the ambient air to be below .005 parts per million (ppm), averaged over 24 hours. This standard has been adopted and is enforceable by the Allegheny County Health Department (ACHD) Air Quality Program.

The World Health Organization states, “in order to avoid substantial complaints about odor annoyance among the exposed population, hydrogen sulfide concentrations should not be allowed to exceed 7 µg/m3 (0.005 ppm), with a 30-minute averaging period.” Pennsylvania’s more lenient averaging time of 24 hours allows for considerably higher hourly H2S levels.

High hourly concentrations usually occur at night or early morning during our region’s frequent atmospheric inversions, when pollutants get trapped in chilled ground level air. H2S is also heavier than air, so it may stick close to the ground at breathing level.

Recently, the public received a new option— to not just hold their noses but to report these window-slamming odors to the ACHD Air Program with the Smell PGH app, developed by the CREATE Lab at Carnegie Mellon University. The Smell PGH app recorded 396 specific “rotten egg” odor complaints between September 29, 2016 and September 5, 2017.

Additional “rotten egg” malodor complaints likely were made directly to the ACHD Air Quality Program or to Smell PGH, but with the smell description on the app left blank.

Most of the time there are consequences which force improvements when air quality standards are breached, but for the 24 hour H2S standard in the Mon Valley, not so much. This standard, even with the generous 24 hour averaging period, has been significantly violated at the air pollution monitor in Liberty: YearViolations of .005 ppm standard 2017 through 9/535 201641 201587 201449 201328 201265

Is the Allegheny County Air Quality Program paying enough attention to excessive hydrogen sulfide or other odor issues? Some citizens in the Mon Valley area have resorted to litigation, recently suing U.S. Steel in part because of “noxious odors” alleged to be caused by U.S. Steel’s Clairton Coke Plant air emissions.

Recently the Pennsylvania Supreme Court affirmed a broad interpretation of Article 1 Section 27 of the Pennsylvania State Constitution. Section 27 affirms a Pennsylvania citizen’s right to clean air and the preservation of the aesthetic values of the environment.

GASP urges the Board of Health to require the County Air Quality Program to do better—to develop and implement a plan to eliminate violations of the H2S standard and to be held accountable for improvement. Odor is the most recognizable part of air quality. We’ll never really be worthy of our high rankings on the “Most Livable Cities” or other lists until we must achieve healthy, agreeable air quality.

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