Seasonal trends, meteorological impacts, and associated health risks with atmospheric concentrations of gaseous pollutants at an Indian coastal city.

This study presents surface ozone (O3) and carbon monoxide (CO) measurements conducted at Bhubaneswar from December 2010 to November 2012 and attempts for the very first time a health risk assessment of the atmospheric trace gases. Seasonal variation in average 24 h O3 and CO shows a distinct winter (December to February) maxima of 38.98 ± 9.32 and 604.51 ± 145.91 ppbv, respectively. O3 and CO characteristics and their distribution were studied in the form of seasonal/diurnal variations, air flow patterns, inversion conditions, and meteorological parameters. The observed winter high is likely due to higher regional emissions, the presence of a shallower boundary layer, and long-range transport of pollutants from the Indo-Gangetic Plain (IGP). Large differences between daytime and nighttime O3 values during winter compared to other seasons suggest that photochemistry is much more active on this site during winter. O3 and CO observations are classified in continental and marine air masses, and continental influence is estimated to increase O3 and CO by up to 20 and 120 ppbv, respectively. Correlation studies between O3 and CO in various seasons indicated the role of CO as one of the O3 precursors. Health risk estimates predict 48 cases of total premature mortality in adults due to ambient tropospheric O3 during the study period. Comparatively low CO concentrations at the site do not lead to any health effects even during winter. This study highlights the possible health risks associated with O3 and CO pollution in Bhubaneswar, but these results are derived from point measurements and should be complemented either with regional scale observations or chemical transport models for use in design of mitigation policies.