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 WHO2005-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.

Ambient air monitoring around the dioxin remediation site in Da Nang, Vietnam, using passive air samplers.

The concentrations and temporal variations of polychlorodibenzo-p-dioxins and polychlorodibenzofurans (PCDDs/PCDFs) in ambient air between March 2013 and February 2017 were investigated by passive air samplers containing polyurethane foam (PUF) disks in the dioxin remediation area using in-pile thermal desorption (IPTD) technology at Da Nang airport, Vietnam. The PCDD/PCDF concentrations in ambient air at each site depended on the location of the emission sources and the wind direction, the dioxin contamination level of excavated materials, the periods of excavation and transport, and the operation of the IPTD treatment system. The PCDD/PCDF concentrations were the highest in the former Agent Orange mixing and loading area (AOMLA), which was the closest to the IPTD system, with total toxic equivalent (TEQ) values ranging from 0.437 to 15.3 pg/PUF/day. The total TEQ concentrations in the Sen Lake area ranged from 0.138 to 2.41 pg/PUF/day. The lowest concentration of PCDDs/PCDFs occurred in the northern perimeter area, with total TEQ values ranging from 0.164 to 0.972 pg/PUF/day. The decreasing trend of the PCDD/PCDF concentrations in ambient air was confirmed over time at all three monitoring sites, among which there was a strong decrease in the former AOMLA after February 2015. Residents living near the Da Nang airport were at a low risk of being exposed to PCDDs/PCDFs through inhalation during remediation project implementation, while residents living close to the former AOMLA faced elevated risks with an average daily dose of PCDDs/PCDFs through inhalation ranging from 0.017 to 0.82 pg TEQ/kg body weight/day.

Antibodies to Highly Pathogenic A/H5Nx (Clade 2.3.4.4) Influenza Viruses in the Sera of Vietnamese Residents.

To cause a pandemic, an influenza virus has to overcome two main barriers. First, the virus has to be antigenically new to humans. Second, the virus has to be directly transmitted from humans to humans. Thus, if the avian influenza virus is able to pass the second barrier, it could cause a pandemic, since there is no immunity to avian influenza in the human population. To determine whether the adaptation process is ongoing, analyses of human sera could be conducted in populations inhabiting regions where pandemic virus variant emergence is highly possible. This study aimed to analyze the sera of Vietnamese residents using hemagglutinin inhibition reaction (HI) and microneutralization (MN) with A/H5Nx (clade 2.3.4.4) influenza viruses isolated in Vietnam and the Russian Federation in 2017-2018. In this study, we used sera from 295 residents of the Socialist Republic of Vietnam collected from three groups: 52 samples were collected from households in Nam Dinh province, where poultry deaths have been reported (2017); 96 (2017) and 147 (2018) samples were collected from patients with somatic but not infectious diseases in Hanoi. In all, 65 serum samples were positive for HI, at least to one H5 virus used in the study. In MN, 47 serum samples neutralizing one or two viruses at dilutions of 1/40 or higher were identified. We postulate that the rapidly evolving A/H5Nx (clade 2.3.4.4) influenza virus is possibly gradually adapting to the human host, insofar as healthy individuals have antibodies to a wide spectrum of variants of that subtype.