Concentrations of PCDD/Fs and dl-PCBs in ambient air in Hanoi, Vietnam, between 2017 and 2021, and health risk assessments.

The concentrations and seasonal and temporal variations in polychlorodibenzo-p-dioxins/polychlorodibenzofurans (PCDD/Fs) and dioxin-like polychlorobiphenyls (dl-PCBs) in ambient air from November 2017 to September 2021 were investigated via passive air samplers containing polyurethane foam (PUF) discs in three residential areas: the Cau Giay (CG) urban, Quang Minh (QM) industrial-suburban, and Ba Vi (BV) rural areas, Hanoi, Vietnam. The average total toxic equivalents (TEQs) of PCDD/Fs and dl-PCBs (∑TEQs), using WHO-TEFs, were highest in the QM area (506 fg WHO-TEQ/PUF day) and ranged from 317 to 752 fg WHO-TEQ/PUF day. Compared to that in the QM area, the average ∑TEQs were lower in the CG area, ranging between 372 and 615 fg WHO-TEQ/PUF day with an average value of 482 fg WHO-TEQ/PUF day. The average ∑TEQs were lowest in the BV area, ranging from 121 to 414 fg WHO-TEQ/PUF day with an average of 231 fg WHO-TEQ/PUF day. PCDD/F and dl-PCB air pollution increased during spring and winter. The highest seasonal average ∑TEQs in the CG area was 534 fg WHO-TEQ/PUF day in winter. The highest average ∑TEQs in the QM and BV areas were 653 and 280 fg WHO-TEQ/PUF day in spring, respectively. The average daily dose (ADD) values of PCDD/Fs and dl-PCBs through inhalation for adults in the three areas were minimal (9.9-96.2 fg WHO-TEQ/kg body weight (BW)/day) and below the 10% threshold of the tolerable daily intake (TDI) value recommended by the WHO (100-400 fg WHO-TEQ/kg BW/day). For children, the ADD values (15.1-244 fg WHO-TEQ/kg BW/day) were less than and within 10% of the recommended TDI value.