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An air quality index (AQI) is an indicator developed by government agencies [1] to communicate to the public how polluted the air currently is or how polluted it is forecast to become. [ 2 ] [ 3 ] As air pollution levels rise, so does the AQI, along with the associated public health risk.
The World Health Organization guidelines were most recently updated in 2021. [1] The guidelines offer guidance about these air pollutants: particulate matter (PM), ozone (O 3), nitrogen dioxide (NO 2), sulfur dioxide (SO 2) and carbon monoxide (CO). [2] The WHO first released the air quality guidelines in 1987, then updated them in 1997. [2]
AQI Mechanics An individual score is assigned to the level of each pollutant and the final AQI is the highest of those five scores. The pollutants can be measured quite differently. SO 2, NO 2 and PM 10 concentration are measured as average per day. CO and O 3 are more harmful and are measured as average per hour. The final AQI value is ...
Below is a list of 526 cities sorted by their annual mean concentration of PM2.5 (μg/m 3) in 2022. [1] [2] By default the least polluted cities which have fewest particulates in the air come first. Click on the arrows next to the table's headers to have the most polluted cities ranked first.
The following list of countries by air pollution sorts the countries of the world according to their average measured concentration of particulate matter in micrograms per cubic meter (μg/m 3). The World Health Organization's recommended limit is 5 micrograms per cubic meter, although there are also various national guideline values, which are ...
1-hour Not to be exceeded more than once per year 40 CFR 50.8: Primary 9 ppm (10 mg/m 3) 8-hour Not to be exceeded more than once per year 40 CFR 50.8: Ozone (O 3) Primary and Secondary 0.12 ppm (235 μg/m 3) 1-hour a: expected number of days per calendar year, with maximum hourly average concentration greater than 0.12 ppm, is equal to or less ...
PM 2.5 AQI of US monitors, calculated utilizing NowCast, courtesy US EPA PM2.5 AQI map, calculated utilizing NowCast, courtesy US EPA. The PM (particulate matter) NowCast is a weighted average of hourly air monitoring data used by the United States Environmental Protection Agency (USEPA) for real-time reporting of the Air Quality Index (AQI) for PM (PM 10 - particles less than 10 micrometers ...
An AQI is essentially a health protection tool people can use to help reduce their short-term exposure to air pollution by adjusting activity levels during increased levels of air pollution. Examples include Canada's Air Quality Health Index (AQHI) , [ 246 ] Malaysia's Air Pollution Index , and Singapore's Pollutant Standards Index .