Screening Legacy and Emerging Organic Pollutants in the Contaminated Soil of Dhaka, Bangladesh

Abstract

The current understanding on the legacy and emerging organic pollutants in the soil of Bangladesh remains limited. Inadequate disposal practices, particularly in e-waste, landfills, and industrial operations, may lead to the pervasive presence of persistent organic pollutants (POPs) and polycyclic aromatic hydrocarbons (PAHs) in the country. This study aimed to systematically investigate the concentration, sources, and risk assessment of halogenated flame retardants (HFRs), polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), organochlorine pesticides (OCPs), chlorinated paraffins (CPs), and PAHs in the contaminated soil of Dhaka's dumpsite, e-waste, and industrial areas collected in 2017. The total concentration of investigated pollutants averaged at 4793.1 ± 4041.9 ng g-1 dw, with the following order: ∑44CPs (4110.6 ± 4141.1 ng g-1 dw) > ∑16PAHs (421.5 ± 490.5 ng g-1 dw) > ∑16HFRs (190.3 ± 537.5 ng g-1 dw) > ∑209PCBs (43.5 ± 73.5 ng g-1 dw) > ∑50PCNs (17.7 ± 21.0 ng g-1 dw) > ∑27OCPs (9.4 ± 9.6 ng g-1 dw). The e-waste site exhibited the highest total concentration of the target pollutants, reaching 12,670.3 ng g-1 dw. CPs were the predominant contributors, accounting for averages of 81.8 ± 32.2%, 70.5 ± 37.0%, and 68.5 ± 21.5% to waste landfills, e-waste, and industrial sites, respectively. A comprehensive analysis of 209 PCB congeners revealed their primary origin from Aroclor-PCBs, with minor contributions from unintentionally-produced PCBs. The highest incremental lifetime carcinogenic risk (ILCR) occurred in e-waste sites, contributed by dl-PCBs, with a maximum value of 5.9 × 10-5 for adults exhibiting the limit 1.0 × 10-6 set by the U.S. EPA. The non-carcinogenic hazard quotients (HQ) were much lower, suggesting no significant risk from the investigated pollutants. Our findings highlight the importance of proper waste management and regulated e-waste recycling to mitigate potential hazardous risks to the Bangladeshi population.