Pollution and Wastes

What is the Pollutant Standard Index?

The U.S. Environmental Protection Agency and the South Coast Air Quality Management District of El Monte, California, devised the Pollutant Standard Index to monitor concentrations of pollutants in the air and inform the public concerning related health effects. The scale measures the amount of pollution in parts per million, and has been in use nationwide since 1978.

PSI Index Health Effects Cautionary Status
0 Good
50 Moderate
100 Unhealthful
200 Very unhealthful Alert: elderly or ill should stay indoors and reduce physical activity.
300 Hazardous Warning: General population should stay indoors and reduce physical activity.
400 Extremely hazardous Emergency: all people remain indoors windows shut, no physical exertion.
500 Toxic Significant harm; same as above.


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