PM2.5 bound polycyclic aromatic hydrocarbons in an Indian residential indoor air environment and their health risk

Polycyclic Aromatic Hydrocarbons (PAHs), a group of semi-volatile organic pollutants with 2-7 aromatic rings are emitted in association with particulates/gases from incomplete combustion. They are persistent and affect human health adversely. This is the first study wherein PM2.5 bound PAHs from 8 different indoor air pollution sources, namely dhoop (DH1, DH2), incense sticks (IS1, IS2), cigarette, mosquito coil and solid fuels 'coal and wood', that are widely used in South-Asian countries were studied. Their emission rates and concentration profiles were compared. Dhoop was studied for the first time and found to be emitting the highest quantity of total PAHs. FLA/(FLA + PYR) ratio rightly indicated ingredients like wood and grass as sources. However, other ratios indicated petrogenic/coal origin, while BaP/(BaP + CHR) and BaA/(BaA + CHR) ratios were not reported earlier. The highest Toxicity Equivalent Concentration and Mutagenic Equivalent Concentration were estimated for DH2 and the lowest for cigarette smoke. The maximum Inhalation Lifetime Cancer Risk equal to 1.85 x 10(-05) (adults) was observed for DH2, exceeding the WHO guidelines. These inferences will help in optimizing the indoor sources' combustion duration and formulating manmade indoor sources. They will assist in identifying high-risk indoor environments, causative sources and control mechanisms.