Pollution Standards Index (PSI, Signapore) and Air Quality in other Major Cities, Measurement


By Michael J. Lynch, University of South Florida, FL


The Pollution Standards Index (PSI) is an air pollution index used in Singapore to access air quality. The PSI was previously used in the US, which changed to the Air Quality Index (AQI) in 1999. Links to air quality measures for other cities appear at the end of this entry.

The PSI includes a measure of six air pollutants: sulfur dioxide; nitrogen dioxide; carbon monoxide; fine particle matter (PM 2.5); and particle matter (PM 10).

The PSI scale ranges from 0-500. The scale is used to alert the public concerning poor air quality conditions. Each range in the PSI corresponds with health effects that may affect people’s activity levels. A PSI between 0-50 is classified as “good” and has no health restrictions; a PSI from 51-100 is classified as “moderate” air pollution, and such conditions should have no serious detrimental impacts for the general public; a PSI between 101-150 is classified as “unhealthy for sensitive groups”, meaning that the general public is unlikely to be affected by the level of air pollution, but that sensitive groups with preexisting conditions should exercise caution with respect to expose to outdoor air; a PSI between 151 and 200 is classified as “unhealthy,” and it is at this level that members of the general public may begin to feel the negative effects of high levels of air pollution; a PSI between 201-300 is classified as “very unhealthy,” and triggers an emergence health warning to the general public; and a PSI between 301-500 is classified as “hazardous,” resulting is a health alert advisory.

Many large cities throughout the world have air quality indexes used to alert the public when air pollution is serious enough to cause a public health hazard. An example of these indexes for cities around the world may be found HERE.

Some city specific indexes are as follows:

Beijing Beijing
Hong Kong Hong Kong
Shanghai Shanghai

You may search for city specific data on this page: City Air Quality Data.

Further Reading


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