Seasonal Variation and Sources of Polycyclic Aromatic Hydrocarbons (PAHs) in Indoor and Outdoor Air in a Semi Arid Tract of Northern India

PAHs concentration in particulate and gas phase was investigated in indoor and outdoor air of urban residential and roadside homes in a semiarid region of India. Samples were collected during winter and summer season (Nov 2006-Jun 2007). In particulate phase at roadside homes the annual mean concentration of PAHs in indoor was 5.53 to 952.28 ng/m(3), in outdoor it ranged 15.47 to 1036.79 ng/m(3) whereas at urban residential homes the particulate PAHs concentration range was 4.10 to 826.73 ng/m(3) (indoor) and 8.32 to 826.73 ng/m(3) (outdoor). The annual mean concentration of gaseous phase PAHs ranged from 2.75 to 90.34 ng/m(3) indoors, 2.29 to 113.56 ng/m(3) outdoors at roadside homes. In urban residential homes it ranged 2.64 to 87.58 ng/m(3) in indoor, 4.79 to 51.83 ng/m(3) in outdoor respectively. Significant seasonal variations of total PAHs concentrations were observed with higher levels during winter season period. The average BaP equivalent exposure, calculated by using toxic equivalent factors was approximately 8.99 ng/m(3) (indoors) and 14.03 ng/m(3) (outdoors). Principal component analysis (PCA) revealed that in indoor the most common sources of PAHs were cooking, smoking, incense burning whereas in outdoor PAHs mainly generated from petrol and diesel combusted fuel and diesel exhaust from generator sets.