Urban air quality in most megacities has been found to be critical and Kolkata Metropolitan City is no exception to this. An analysis of ambient air quality in Kolkata was done by applying the Exceedance Factor (EF) method, where the presence of listed pollutants’ (RPM, SPM, NO2, and SO2) annual average concentration are classified into four different categories; namely critical, high, moderate, and low pollution.

Exposure to fine particles is measured using metrics such as mass concentration (MC), number concentration (NC) and surface area concentration (SAC). This study aims to find correlation between the three metrics in outdoor environments of a city – city periphery, city centre and on-road. Simultaneous real-time mass, number and surface area concentration measurements were conducted in these environments. Arithmetic means, peak concentration values, and regression coefficients were determined to find relation between the three metrics.