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Air Pollution Sources By The Numbers

(Joseph Gottlieb, CTO, Thursday, May 7, 2020)

If you have been outside during March or April (or if you have listened to the news), you have probably seen how clear the air is outside. It’s not just perception – all of the indicators point to the air being significantly cleaner than this time last year. Clearly, there were a lot less cars driving in March and April than is normal, but there were also a lot of shuttered businesses as well – both contribute to reduced air pollution. Given that, let’s look at the primary sources of air pollution in the US; the data is from EPA’s 2019 report (also in chart below; pollution reduction levels vary by area, and are from various sources):

  • Carbon Monoxide (CO) – The greatest air pollution ingredient by weight, constituting 54% of all air pollution. Transportation is the greatest contributor to CO, producing 35.8% of all CO. During COVID-19, drops of CO between 16% and 25%.
  • Ammonia (NH3) – Ammonia represents about 3% of all air pollution by weight, with only 2.8% coming from transportation (nearly 94% of ammonia is produced by industrial processes)
  • Nitroxen Oxides (NOx) – Nitrogen Oxides make up about 10% of air pollution by weight, with transportation being the greatest source at 32.3%. During COVID-19, NOX levels decreased anywhere from 20% to 25%.
  • Particulate Matter (PM2.5 and PM10) – PM10 is particulate matter of 10 microns or smaller, while PM2.5 (a subset of PM10) is particulate matter of 2.5 microns or smaller. PM10 (which includes PM2.5) represents 14% of air pollution ingredients by weight; transportation produces 10.2% of all PM10 in air pollution.
  • Sulfer Dioxide (SO2) – SO2 represents 8% of air pollution by weight, with only 1% of it being produced by transportation.
  • Volatile Organic Compounds (VOC) – VOCs represent 11% of air pollution by weight; nearly 12% of all VOCs are produced by transportation (primarily gasoline and diesel vapors).

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