POLLUTION LOCATOR|Definitions of Criteria Air Pollutant Health Risk Measures



PERSON-DAYS IN EXCEEDANCE
A measure for identifying areas where large numbers of people are exposed to unhealthy air quality. The number of days when monitored concentrations of a criteria pollutant exceed a National Ambient Air Quality Standard (NAAQS) is multiplied by the total number of people living in the affected area. Person-days in exceedance is the conventional risk measure used to compare areas with poor air quality. While it does not provide a characterization of the kinds of health effects an exposed population may experience as a result of poor air quality, it does provide a population-weighted indicator of the potential extent of criteria air pollutant-related health effects.