Temporal variations in airborne PCDD/F and dl-PCB concentrations surrounding the dioxin-remediated areas in Da Nang, Vietnam, and health risk assessments

The air pollution levels from polychlorodibenzo-p-dioxins/polychlorodibenzofurans (PCDD/Fs) and dioxin-like polychlorobiphenyls (dl-PCBs) in three residential areas located north, west, and south of the Da Nang airport were determined by using passive air samplers containing polyurethane foam (PUF) discs with 3-month sampling intervals from 2017 to 2020. The total toxic equivalents (∑TEQs) of the PCDD/Fs and dl-PCBs, using WHO₂₀₀₅-TEFs, were highest north of the airport (134 to 10610 fg WHO-TEQ/PUF day, with an average of 1108 fg WHO-TEQ/PUF day). The ∑TEQs were lower west of the airport, between 159 and 381 fg WHO-TEQ/PUF day and averaged 230 fg WHO-TEQ/PUF day. The lowest ∑TEQs occurred south of the airport, with ranges of 76 and 331 fg WHO-TEQ/PUF day and an average of 152 fg WHO-TEQ/PUF day. Construction activities, including excavation and transportation of dioxin-contaminated soil north of the airport, have increased airborne PCDD/F and dl-PCB contamination and health risks. The average daily doses of PCDD/Fs and dl-PCBs through inhalation (ADD_A) for residents located north of the airport were the highest (10.9 to 3434 fg WHO-TEQ/kg BW/day and average: 597 fg WHO-TEQ/kg BW/day). Residents located west of the airport faced lower health risks (13–123 fg WHO-TEQ/kg BW/day and average: 39 fg WHO-TEQ/kg BW/day). Residents south of the airport were exposed to a minimum of 6.2–107 fg WHO-TEQ/kg BW/day, with an average of 28 fg WHO-TEQ/kg BW/day. The maximum and average ADD_A values for residents north of the airport exceeded 10% of the tolerable daily intake (TDI) recommended by the WHO (100–400 fg WHO-TEQ/kg BW/day). In comparison, all the ADD_A values for residents located west and south of the airport were less than and within 10% of the TDI.