Investigation of Indoor Nitrogen Dioxide (NO2) Exposure and Health Risk Assessment at a Cross-Border Checkpoint, Chiang Rai Province in Tourism Seasonality

Abstract

The inhalation of indoor nitrogen dioxide (NO2) is generated by traffic density and is associated with a risk to human health. The objective of this study was to assess indoor NO2 levels at the Chiang Khong District border crossing at the 4th Thai-Laos Friendship Bridge (Chiang Khong-Huay Xai) in Chiang Rai Province in order to evaluate indoor air quality in tourist season within the limits of a health risk assessment. Indoor NO2 samplings were collected by using a passive sampling method. The results for indoor NO2 concentrations in all sampling sites in the Chiang Khong District border ranged between 18.7±5.8 to 37.8±28.9 µg/m 3 . The highest indoor NO2 concentration was measured in April 2023 (25.1±10.8 to 88.3±30.6 µg/m 3 ) because the total number of tourists and vehicles passing at a cross-border crossing was the highest, which is peak season and Songkran festival in Thailand. Moreover, a significant correlation between indoor NO2 concentrations was found between the total number of vehicles and tourists (p<0.01). Indoor NO2 concentrations have been influenced by trucks and cars. The levels of indoor NO2 emitted by diesel-powered vehicles were obvious. Long-term Hazard Quotient (HQ) values in relation to non-carcinogenic hazards to human health caused by indoor NO2 exposure revealed that children had higher HQ levels than adults.