UPDATED: Increased car traffic during SEPTA strike increased air pollution by 400 percent

    Traffic clogs I-676 in Philadelphia  during the SEPTA strike. (Katherine Blodgett via Twitter)

    Traffic clogs I-676 in Philadelphia during the SEPTA strike. (Katherine Blodgett via Twitter)

    The SEPTA strike in early November drove more commuters to their cars, and Philadelphia air quality suffered because of it.

    Updated Nov. 19, 2016 at 11 a.m.

    The SEPTA strike in early November drove more commuters to their cars, and Philadelphia air quality suffered because of it.

    New data show that the concentration of fine-particle air pollution during the morning rush for the four weekdays the strike lasted was about four times higher than before the strike. The average hourly maximum emission jumped from 5 micrograms per cubic meter to 20 micrograms per cubic meter during the strike.

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    Philadelphia Department of Public Health Deputy Commissioner Caroline Johnson said motor vehicles are a primary source of this contaminant.

    “Fine-particulate matter is a reflection of air pollution. It’s basically soot and chemicals and exhaust that’s produced by burning of fuels,” Johnson said.

    Five monitors around the city detected an increase in all other pollutants, as well. Fine-particulate matter can cause health problems, particularly in the heart and lungs, but Johnson said the relatively short spike during the strike shouldn’t be a major health concern.

    Instead, she said, it’s a reminder that driving has consequences.

    “The less we drive the better the air quality will be in Philadelphia,” Johnson said.  

    Drexel Assistant Professors Peter DeCarlo and Shannon Capps collected and analyzed meteorological data during the strike and found weather conditions could have also affected pollution concentration.

    Capps said the strike days were a little less windy than the comparative pre-strike days, meaning there was less wind to dilute emissions. Relative humidity was higher during the strike. More water in the air can ease the formation of fine particulate matter. Capps said it’s not clear exactly how much of the elevated pollution levels can be attributed to weather and how much to increased traffic.

    SEPTA’s buses, subways and trolleys provide commuters with about 900,000 rides a day.

    Editors note: This article was updated to reflect meterological data during the strike which was not reported at the time the story was filed.

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