![]() ![]() Since temperatures over 84☏ are typically required for ozone to form, it’s much more prevalent in the summer than winter. Ozone is a harmful gas pollutant and key component of smog, created when precursor pollutants, nitrogen oxides (NO x), and volatile organic compounds (VOCs) react in warmer temperatures and sunlight. In addition to PM2.5 pollution, Chicago has also had difficulty complying with federal ozone standards. This ranking places Chicago air quality in a slightly worse position than Los Angeles air quality (12.7 μg/m 3), a city well known for its pollution challenges. Chicago had not experienced such high annual exposure levels since 2012.Ĭhicago PM2.5 pollution ranks worst in the state of Illinois for particle pollution and 79th nationally out of 1517 metropolitan areas in the United States. In 2019, Chicago averaged an annual PM2.5 level of 12.8 μg/m 3, thereby breaching both the WHO target and the US EPA target. The World Health Organization (WHO), meanwhile, employs a more stringent standard, recommending that exposure remain below 10 μg/m 3 annually. The US EPA recommends that annual PM2.5 exposure not exceed 12 μg/m 3. PM2.5 pollution is fine particle pollution with a range of chemical compositions that measures 2.5 microns in diameter or less. ![]() Fine particulate matter (PM2.5) and ozone represent two of the most common ‘main pollutants’ responsible for a city’s AQI due to the weight the formula ascribes to them for their potential harm and prevalence at high levels. The pollutant with the highest individual AQI becomes the ‘main pollutant’ and dictates the overall air quality index. The US Environmental Protection Agency (EPA) defines “moderate” air quality as air potentially unhealthy to sensitive groups including children, the elderly, and people with pre-existing cardiovascular or respiratory health conditions.ĪQI ratings are calculated by weighting 6 key criteria pollutants for their risk to health. In 2019, Chicago averaged an air quality index (AQI) of 52 (“moderate”). ![]()
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