Assessment of metal contamination and the associated human health risk from dustfall deposition: a study in a mid-sized town in India.

It is evident from the past studies that dust fallout is a severe concern due to its impact to urban air quality and public health. This study mainly examines the spatial and seasonal variation of dustfall at ambient levels and chemical characterization of its insoluble fraction for Kharagpur Town, India. Dustfall samples were collected monthly for 1 year (July 2014 to June 2015) from four sampling sites. The results showed that the maximum dustfall deposition is found during summer (March to June) and in the range of 2.01 ± 0.36 to 15.74 ± 3.83 ton km-2 month-1, and minimum deposition is during monsoon season (July to October) in the range of 0.42 ± 0.72 to 7.38 ± 5.8 ton km-2 month-1. Selected metals like Sc, V, Cr, Co, Ni, Zn, Y, Zr, Ce, Hf, and Pb were analyzed using the high-resolution inductively coupled mass spectrometer (HR-ICP-MS) technique, and the contamination level of heavy metals was assessed using the geoaccumulation index (Igeo) and enrichment factor (EF). To estimate the sources for the metallic contaminants, principal component analysis (PCA) was conducted. The US EPA health risk assessment model was applied to determine the hazard index and hazard quotient values. The results show the significant level of enrichment for Pb (EF = 41.79) and Cr (EF = 4.39). The Igeo values point out moderate contamination by Pb (Igeo = 2.01) and Cr (Igeo = 1.6) in Kharagpur Town. This study suggests that in the context of noncancer risk of heavy metals as determined by the hazard index (HI) and hazard quotient (HQ) values, ingestion is the main source of exposure to dust in adults and children followed by dermal contact. Considering the inhalation route, carcinogenic risk level of Cr, Co, and Ni for adults and children is lower than the EPA's safe limit (10-6 to 10-4), indicating that cancer risk of these metals due to exposure to dustfall in Kharagpur is negligible.