Bioaccessibility and risk assessment of potentially toxic elements in indoor dust of an industrial city in Eastern India

The study investigated the seasonal variability, bioaccessibility, and human exposure risks associated with potentially toxic elements (PTEs) in indoor dust of Durgapur, one of the largest industrial cities in West Bengal State of India. Indoor dust samples from over 80 households in 15 residential areas were collected over three seasons of the year and the samples were analyzed for the PTEs by inductively coupled plasma optical emission spectroscopy (ICP-OES). The annual average concertation was found to be high for Fe (50331 ± 9017 mg kg -1 ) followed by Mn (1571 ± 895 mg kg -1 ), Zn (303 ± 214 mg kg -1 ), Cu (139 ± 67 mg kg -1 ), Cr (111 ± 65 mg kg -1 ), Pb (70.4 ± 55 mg kg -1 ), Ni (40.0 ± 23 mg kg -1 ), Cd (2.66 ± 2.3 mg kg -1 ). The total PTEs content in the dust was found to be higher in the winter. The bioaccessibility of PTEs was found to vary from 6.5% to 62.1%, in the order of Zn > Cu > Cd > Pb > Ni > Cr > Mn > Fe. The bioaccessibilities of Cr, Fe, Ni, and Zn were higher during the monsoon, while Cu and Mn exhibited high bioaccessibilities in the summer, and Cd and Pb were most bioaccessible during the winter. Geo-accumulation Index (I geo ) was higher for Cd, followed by Pb and Zn. Principal component analysis coupled with XRD results revealed two potential sources for PTEs viz iron and steel industries (Cr, Fe, Mn and Ni) and vehicular emission (Cd, Cu, Pb and Zn). Both empirical and probabilistic approaches to assessing human health risk showed that there is no potential exposure risk from these elements. The probabilistic approach is more conservative than the empirical method. Among the different PTEs, Fe had a higher hazard quotient but was within the limit. The use of bioaccessible fractions for risk assessment had marginally decreased the hazard quotient. Therefore, it is recommended to use a conservative risk assessment, employing total PTEs with a probabilistic model. • Dust composition (mg/kg): Fe, Mn > 1000; Zn, Cu, Cr > 100; Pb, Ni > 10; Cd > 1.0. • Order of bioaccessibility (6.5-62.1 %): Zn > Cu > Cd > Pb > Ni > Cr > Mn > Fe. • Content of all elements was more in winter followed by summer and monsoon. • Sources are steel industry (Cr, Fe, Mn, Ni) and traffic emission (Cd, Cu, Pb, Zn). • No exposure risk from bioaccessible and total elemental content.