Pollutant Standards Index
Pollutant Standards Index (pronunciation: puh-loo-tuhnt stan-dards in-deks, etymology: derived from English words "pollutant", "standards" and "index") is a standard measurement used to provide the public with an easily understandable metric of air quality. It is based on the levels of five major air pollutants regulated by the Clean Air Act: ground-level ozone, particle pollution (also known as particulate matter), carbon monoxide, sulfur dioxide, and nitrogen dioxide.
Definition
The Pollutant Standards Index (PSI) is an index that provides a standardised way of measuring and reporting the air quality in a specific location. It is calculated based on the concentrations of five major air pollutants: ground-level ozone, particle pollution, carbon monoxide, sulfur dioxide, and nitrogen dioxide. The PSI value can range from 0 to 500, with higher values indicating worse air quality.
History
The PSI was first developed and used by the United States Environmental Protection Agency (EPA) in 1976. It was later replaced by the Air Quality Index (AQI) in 1999, which includes additional pollutants and has a slightly different calculation method.
Calculation
The calculation of the PSI involves determining the sub-index for each of the five pollutants, based on their 24-hour average concentrations. The highest sub-index is then taken as the PSI for that day. The sub-indices are calculated using linear segments between breakpoints, which are set at levels of health concern.
Interpretation
The PSI is divided into six categories, each associated with a different level of health concern: Good (0-50), Moderate (51-100), Unhealthy for Sensitive Groups (101-150), Unhealthy (151-200), Very Unhealthy (201-300), and Hazardous (301-500).
See Also
External links
- Medical encyclopedia article on Pollutant Standards Index
- Wikipedia's article - Pollutant Standards Index
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