The in-traffic microenvironment can enhance personal exposure to fine particulate matter (PM). With this study, we aimed to calibrate a DustTrak instrument (DustTrak 8533 DRX Aerosol Monitor, TSI Incorporated, Shoreview, MN, USA) and low-cost sensors (AS-LUNG-P sensors) and then assess inhalation exposure to PM_2.5 and PM₁ for different commuters in central areas of Ho Chi Minh City (HCM). The DustTrak instrument and low-cost sensors were calibrated using a gravimetric method under side-by-side conditions. Relationships between the DustTrak signals and PM concentrations measured by the gravimetric method were identified using simple linear regression models for PM_2.5 (R² = 0.998, p-value < 0.05) and PM₁ (R² = 0.989, p-value < 0.05). Meanwhile, PM concentrations determined by the AS-LUNG-P sensors and the gravimetric method were correlated using two-segmented linear regressions. To obtain the corresponding two-segment regression equations, the response of the AS-LUNG-P sensors was compared with the corrected DustTrak data. The coefficient of variation (CV) evaluated for all sensors was smaller than 10%, indicating that the data were applicable for particle assessment. For inhalation exposure assessment, the results showed that commuters using open transport modes, such as bikes, motorbikes, and walking, were exposed to more PM than those using closed transport modes (e.g., cars). Specifically, the bicyclists had the highest inhaled doses of PM among the open transport groups. PM exposure levels in the morning were higher than in the afternoon. Additionally, exposure levels to PM concentrations rapidly increased when passing through intersections of major roads and moderately decreased when using surgical facemasks.

Mercury (Hg) is a global pollutant that has gained monumental attention in recent decades due to its neurotoxicity and great bioaccumulation features. The atmosphere plays a key role in the movement of Hg in the environment, and residential combustion is a significant contributor to atmospheric Hg. However, there is a severe lack of research on the impact of Hg emissions from residential combustion in Southeast Asia (SEA). This study focused to illustrate the contribution of residential combustion on the level of total gaseous mercury (TGM) in a tropical megacity in southern Vietnam by conducting a short field campaign in February 2023. The mean TGM concentration during the study period was 2.27 ± 0.81 ng m^-3, in which daytime TGM level (7 am – 7 pm, 2.56 ± 0.80 ng m^-3) was significantly higher than at night (7 pm – 7 am, 1.58 ± 0.28 ng m^-3), which could be attributed to local burning activities. The TGM concentration was also increased because of the increase in burning activities (i.e. burning joss paper and incense) during the Lantern Festival. Backward trajectory analysis suggested the domination of regional background air mass in the study area, implying that TGM concentration variation is mostly associated with local influences. We estimated that residential combustion caused a rise of around 70% in TGM concentration at the sampling site. Overall, this is the first study to illustrate the importance of Hg emissions from residential combustion in urban SEA region, laying a background for upcoming studies in atmospheric Hg in this region.