Health risk assessment and environmental impacts of heavy metals from informal e-waste recycling shops in Chattogram City, Bangladesh

Informal e-waste recycling has emerged as a significant source of heavy metal contamination in urban areas of Bangladesh; however, empirical research on its environmental consequences and associated health risks remains limited. This study aimed to determine the potential contamination of nine heavy metals in eight locations from informal e-waste recycling facilities in Chattogram City, Bangladesh. The sample populations were e-waste recycling workers from the exposed sites and a control site. Indoor air particulate matter, surface soil, groundwater, and drinking water, as well as blood and urine were sampled and analyzed. Results showed that the residues of the heavy metals in all samples from the exposed sites were significantly greater than those from the control site (p < 0.05), except that no significance was found for Cu and Pb in drinking water from the exposed and control sites. The residues of Cr and As in surface soil were higher than the screening levels. The residues of Cr, Pb, Ni, Hg, and Mn found in groundwater from the exposed sites exceeded the maximum allowable limits (MAL). The residues of Pb and Mn found in drinking water from both the exposed and control sites exceeded the MAL. The residue of Pb in groundwater showed a very high contamination factor (C_f^i > 6) at the exposed sites. The Pollution Load Index (PLI) of the heavy metals found in surface soil, groundwater, and drinking water exceeded 1, indicating a substantial influence of anthropogenic activities, which degraded the soil and water quality. The residue of Pb found in groundwater showed a considerable potential ecological risk (80 ≤ Eri < 160), and its geoaccumulation index (Igeo) was at 3 ≤ Igeo < 4, indicating heavy contamination in groundwater at the exposed sites. This study demonstrated that groundwater played a key role in enhancing distribution of heavy metals at the exposed sites. In assessing the non-carcinogenic risks, it was found that all the heavy metals detected in different environmental media of surface soil, groundwater, and drinking water posed no probability for causing the risks of concern to the e-waste exposed workers as the target hazard quotient (THQi) and the total target hazard quotient (TTHQ) for ingestion and dermal contact of the heavy metals were below the USEPA recommended value of 1. The calculated carcinogenic risks showed that the sum of total target risk (TTRsum) for dermal contact of Cr, Pb, and Ni in groundwater were higher than the USEPA recommended value of 1 × 10-4. Also, Cr detected in groundwater was considered the major contributor of the carcinogenic risks to potentially exposed workers through dermal contact based on its calculated target risk (TRder = 1.09E-4). Results in blood and urine demonstrated that the residues of the heavy metals in all samples from the exposed workers were significantly greater than those from the controls (p < 0.01), indicating substantial bioaccumulation resulting from internal exposure associated with recycling activities. The findings indicated that residues of Cr, Ni, As, Mn, and Zn in blood serum, blood plasma, and urine frequently exceeded the guideline values, indicating significant internal exposure of heavy metals. In assessing the non-carcinogenic risks, it was found that all the heavy metals detected in urine posed no probability for causing the risks of concern to the e-waste exposed workers as the target hazard quotient (THQi) and the total target hazard quotient (TTHQ) for ingestion of the heavy metals (3.88E-2) were below the USEPA recommended value of 1. The calculated carcinogenic risks showed that the target risk (TRi) and total target risk (TTR) for ingestion (7.06E-5) were below the USEPA recommended value of 1 × 10-4. Cr exhibited the highest value among the calculated total estimated daily intake of heavy metals detected in urine. Findings of this study would be of help to decision makers in strengthening laws and regulations on environmental pollution prevention and worker protection through enhancing compliance among the informal e-waste recycling facilities in Bangladesh.