Pollutant Standards Index

Pollutant Standards Index (PSI) is a numerical scale used for reporting the daily air quality with regard to human health and the environment. The PSI was developed by the United States Environmental Protection Agency (EPA) to provide a simple and uniform way to report levels of different pollutants in the air.

Overview

The PSI is calculated using measurements of five major air pollutants regulated by the Clean Air Act: ground-level ozone, sulfur dioxide, carbon monoxide, nitrogen dioxide, and particulate matter. Each of these pollutants has a different effect on human health and the environment, and the PSI provides a way to compare the levels of these pollutants in a standardized way.

Calculation

The PSI is calculated using a complex formula that takes into account the concentrations of the five pollutants. The formula gives more weight to pollutants that are present in higher concentrations. The PSI value can range from 0 to 500, with higher values indicating worse air quality.

Health implications

The PSI is used to provide information about the potential health effects of air pollution. For example, a PSI value of 100 for sulfur dioxide corresponds to a level that is considered harmful for sensitive groups, such as people with asthma. Higher PSI values indicate a greater potential for health effects.

Limitations

While the PSI is a useful tool for comparing air pollution levels, it has some limitations. For example, it does not take into account the effects of multiple pollutants combined. In addition, the PSI does not provide information about long-term exposure to air pollution.

See also

• Air Quality Index
• Air pollution
• Environmental health