Trends of particulate matter in four cities in India

Particulate matter (PM) in all the four Metropolitan cities in India are higher than the prescribed standards of Central Pollution Control Board, India as well as WHO guidelines. Over last 10 years various changes in fuel quality, vehicle technologies, industrial fuel mix and domestic fuel mix have taken place resulting in changes in air quality in these cities. A set of time series analysis methods viz. t-test adjusted for seasonality, Seasonal Kendall test and Intervention analysis have been applied to identify and estimate the trend in PM10 and total suspended particles (TSP) levels monitored for about 10 years at three monitoring sites at each of the four cities in India. These tests have indicated that overall PM10 levels in all four metro cities have been decreasing or stationary. The distinct trends for the monthly averages of PM10 concentrations at Parel, Kalbadevi in Mumbai and Thiruvattiyar in Chennai for the period 1993–2003 were declining by 10%, 6% and 5% per annum, respectively. This is ascribed to a shift in the magnitude and spatial distribution of emissions in the city. However, the monthly averages of TSP do not have a clear trend over the period 1991–2003.