Assessment of Air Quality Index for Cities and Major Towns in Tamil Nadu, India

Air Pollution may be defined as any atmospheric condition in which certain substances are present in such concentrations that they can produce undesirable effects on man and his environment. The Air Quality Index (AQI) is a reporting system and an important tool of risk communication. It informs the public about the level of ambient air quality, and the potential health risk it would impose. AQI converts complex air quality data of various pollutants into a single number (index value), nomenclature and colour. AQI is represented as numeric value varies from 0 to 500. If score is 0, it is the best air quality and if score is 500, it is the worst air quality. There are six AQI categories, namely Good, Satisfactory, Moderate, Poor, Very Poor, and Severe. Each of these categories is decided based on ambient concentration values of air pollutants and their likely health impacts. In Tamil Nadu, under National Ambient Air Quality Monitoring Programme, Ambient Air Quality (AAQ) is being monitored by Central Pollution Control Board in association with Tamil Nadu Pollution Control Board in 28 locations covering cities, major towns and major industrial areas viz. Chennai, Salem, Coimbatore, Madurai, Trichy, Cuddalore, Mettur, and Thoothukudi. The AAQ data from January 2015 to December 2015 for the above cities and towns is collected and AQI is calculated for four months covering four seasons (i.e.,) January (winter), May (summer), July (monsoon), November (post monsoon). Almost all the stations’ AQI fall under good and satisfactory category except Trichy where the majority of the days the AQI fall under moderate category. From the AQI of all the stations, it is observed that responsible pollutant is PM10. The other parameter (i.e.,) SO2 and NO2 fall under good category for all stations for all days. The higher value of PM10 is mainly due to vehicular pollution.