Air quality in Delhi: status and concerns.

Data on the status of air quality are presented for two locations in Delhi, the capital city of India, for 2013. Our study revealed that the levels of oxides of nitrogen (NOx), particulate matter of 10 or <10 μm aerodynamic diameter (PM10) and benzene exceeded the maximum permissible limits laid down in the National Ambient Air Quality Standards (NAAQS). On most of the monitoring days, the concentrations of PM10also exceeded the limits for 24 h averages stipulated by the NAAQS. This study also demonstrated that the concentration of pollutants varied with the season, peaking in dry season (winter) mainly because of the relatively stable meteorological conditions and recording the lowest values in the wet season (the rainy season) because of turbulence, strong winds, and rains. The post-monsoon season showed the contribution of local sources. The strong correlation among NOx, PM10, and benzene strongly suggests that motor vehicles are the major contributor to this pollution. Intervention by regulatory agencies is essential to improve the air quality of Delhi. [ABSTRACT FROM AUTHOR]