Fine particles (PM2.5) in residential areas of Lucknow city and factors influencing the concentration

Urban populations are exposed to a high level of fine and ultrafine particles from motor vehicle emissions which affect human health. To assess the hourly variation of fine particle (PM2.5) concentration and the influence of temperature and relative humidity (RH) on the ambient air of Lucknow city, monitoring of PM2.5 along with temperature and RH was carried out at two residential locations, namely Vikas Nagar and Alambagh, during November 2005. The 24 h mean PM2.5 concentration at Alambagh was 131.74 mu g/m(3) and showed an increase of 13.74%, which was significantly higher (p < 0.05) than the Vikas Nagar level. The 24 h mean PM2.5 on weekdays for both locations was found to be 142.74 mu g/m(3) (an increase of 66.23%) which was significantly higher (p < 0.01) than the weekend value, indicating that vehicular pollution is one of the important sources Of PM2.5. The mean PM2.5 at night for all the monitoring days was 157.69 mu g/m(3) and was significantly higher (p < 0.01) than the daytime concentration (89.87 mu g/m(3)). Correlation and multiple regressions showed that the independent variables, i.e., time, temperature, and RH together accounted for 54%, whereas RH alone accounted for 53% of total variations of PM2.5, suggesting that RH is the best influencing variable to predict the PM2.5 concentration in the urban area of Lucknow city. The 24 h mean PM2.5 for all the monitoring days was found to be higher than the NAAQS recommended by the US-EPA (65 mu g/m(3)) and can be considered to be an alarming indicator of adverse health effects for city dwellers.