Ambient Air Quality of Major Indian States and Cities: A Spatiotemporal Analysis

This study evaluated the trends and shifts of the ambient air quality standards of the most polluted states and cities of India with respect to air quality parameters, e.g., nitrogen dioxide (NO2), sulfur dioxide (SO2), suspended particulate matter (SPM), and respirable suspended particulate matter (RSPM). The choice of air quality parameters was based on the guidelines of the National Air Quality Monitoring Programme of India. Besides evaluating the long-term trends and the major shift points along the last few decades, the study also analyzed the variation in air quality parameters across the seasons since burning of crop residue during certain seasons plays a significant role as a primary source of particulate pollution. Multiple cities within each state were analyzed separately to evaluate their spatial pattern, while each city was also analyzed based on residential and industrial locations. The obtained results were compared against the National Ambient Air Quality Standards of India to determine the air quality status quo. The results suggested considerable variation across the states and among the adjacent cities within the same state. The difference in slope (rate) of the detected trends between the residential and industrial locations was also noteworthy. Post-monsoon and winter seasons showed the higher presence of SPM and RSPM. The obtained results may be helpful for a country like India, which is currently the third largest emitter of greenhouse gases. The increasing rate of diseases related to poor lung functionality across many cities in India can also be correlated with the increasing trends of particulate pollutants. Such analyses, as presented in this study, may also be helpful in the stringent implementation of the Air (Prevention and Control of Pollution) Act of India as well as the air quality monitoring programs.