Exploring Air Pollution - B Watkins - Bog

Air pollution is defined as all destructive effects of any sources which contribute to the pollution of the atmosphere and/or deterioration of the ecosystem. Air pollution is caused by both human interventions and/or natural phenomena. It is made up of many kinds of pollutants including materials in solid, liquid, and gas phases. Air pollutions of indoors will not be specifically considered in this article.
The Pollutant Standard Index (PSI) is a numerical value and indicator of pollutants that is normally used to facilitate risk assessment. It is a numeric value between zero to 500. PSI is a guideline for reporting air quality Hence, it would provide a method of comparing the relative contribution of each pollutant to total risk.[21] The calculation of PSI is based on the concentration of five major air pollutants including particulate matters (PMs), sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and ozone (O3) in the air.
Air quality index (AQI) is defined as a measure of the condition of air relative to the requirements of one or more biotic species or to any human need. AQI is divided into ranges, in which they are numbered, and each range is marked with color codes. It provides a number from healthy standard level of zero to a very hazardous level of above 300 to indicate the level of health risk associated with air quality. Based on PSI, air quality is classified into six major indices, which is marked by color codes and each color corresponds to a different level of health concerns. Principally, green is defined as a color indicator for healthy air quality; while yellow, orange, red, purple, and maroon colors indicate as moderate, unhealthy for sensitive groups, unhealthy, very unhealthy, and hazardous air quality, respectively. These ranges and codes may differ in the different methods of classifications in different countries