Chemical characteristics and mutagenic activity of PM₂.₅ at a site in the Indo-Gangetic plain, India

Abstract

Airborne fine particulate matter PM2.5 was collected from May 2010 to December 2012 at Agra, a semi-urban site in north-central India. PM2.5 samples were chemically characterized for 16 polycyclic aromatic hydrocarbons by gas chromatography. PM2.5 values varied between 8.4 and 300 µg m(-3) with 55% of the values exceeding the 24h average NAAQ (National Ambient Air Quality) standard of 65 µg m(-3). Particle associated total PAHs ranged between 8.9 and 2,065 ng m(-3) with a mean value of 880.8 ng m(-3) during the sampling period, indicated an alarming level of pollution in Agra. Strong relationship was observed between PM2.5 and total PAHs (r=0.88), suggesting an increasing PAHs concentration with increasing PM2.5 mass. On a mass basis 3-ring and 4-ring compounds were dominant. Seasonal variation in mass concentration of PAHs was observed with high concentration in winter followed by post monsoon, summer and monsoon. This seasonal pattern could be attributed to differences in source strength and climatic conditions. PAHs concentration were also observed to be negatively correlated with the meteorological parameters i.e. temperature, solar radiation, relative humidity and wind speed. Molecular diagnostic ratios revealed vehicular emissions and combustion of wood and coal as the probable sources. The estimated carcinogenicity of PAHs in terms of benzo(a)pyrene toxic equivalency (B[a]PTEQ) was assessed and confirmed that benzo[a]pyrene was the dominant PAH contributor (3.64%). Health risk of adults and children by way of PAHs was assessed by estimating the lifetime average daily dose (LADD) and corresponding incremental lifetime cancer risk (ILCR) using USEPA guidelines. The assessed cancer risk (ILCR) was found to be within the acceptable range (10(-6)-10(-4)). The particulate samples indicated the presence of both base pair and frame shift mutagens using TA98 and TA100 strains of Salmonella typhimurium. Enhanced mutagenic response was observed in the presence of enzyme activation.

Keywords: Diagnostic ratios; Health risk; Mutagenicity; PM(2.5); Polycyclic aromatic hydrocarbons.