Characteristics and health impacts of PM_2.5-bound PCDD/Fs in three Asian countries

Polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) were ubiquitous, persistent chemical compounds attached to particulate matter in the atmosphere. We aimed to study the characteristics of these pollutants in atmospheric PM_2.5 of three Asian countries, including Taiwan (Taipei), Thailand (Chiang Mai), and Vietnam (Hanoi). We carried out a source apportionment analysis to determine significant PCDD/F contributors in these areas. Multiple media model was conducted to access the health impact assessment. The PM_2.5 concentration in Taipei (n = 7), Chiang Mai (n = 20), and Hanoi (n = 10) were 18.4 ± 6.21 μg/m³, 133 ± 49.5 μg/m³, and 88.1 ± 12.6 µg/m³, respectively. The PCDD/Fs level in Hanoi was 92.4 ± 67.3 fg I-TEQ/m^3, and in Taipei and Chiang Mai was 5.01 ± 2.39 fg I-TEQ/m³ and 14.4 ± 13.1 fg I-TEQ/m³, respectively, which showed that the higher PM_2.5 concentration was not necessary to follow with higher PCDD/Fs level. In all three cities, the effect of traffic on ambient PCDD/F level was significant (23-25 %). However, we also observed the specific sources of PCDD/Fs in each city during the sampling periods, namely long-range transport (Taipei, 55 %), Biomass/open burning (Chiang Mai, 77 %), and industrial activities (Hanoi, 34 %). In the carcinogenic risk estimation, the highest median total carcinogenic risk was in Hanoi (5.87 × 10^-6), followed by Chiang Mai (1.06x10^-6), and Taipei (2.95 × 10^-7). Although diet was the major absorption pathway, the food contributor of exposure differed among the three areas due to the difference in food consumption composition.