Health effects of PM2.5 exposure on short-term international travellers to Thailand

Abstract

BACKGROUND: Thailand has increased in popularity as a top travel destination but there are concerns regarding significant seasonal levels of particulate matter 2.5 (PM2.5) that are 2.5 μm or smaller in diameter, which may affect the health of travellers during periods of high air pollution. The aim of this study was to examine the prevalence of short-term health effects and the association between exposure to PM2.5 and adverse health outcomes among international travellers. METHODS: A cross-sectional study was conducted in Bangkok and Chiang Mai, Thailand, between February and May 2024 during a period of high pollution levels. Data were collected via online questionnaires distributed at the international airports in both cities. Travellers aged 20 or older visiting during this polluted season were included, excluding those staying longer than 6 months. PM2.5 levels were obtained from the Thai Pollution Control Department from February to May 2024. RESULTS: Among 617 participants, 63.5% were male, 75.2% (n = 464) visited Bangkok and 66.1% (n = 408) were from North America/Canada. Tourism was the primary purpose of travel for 81.4% (n = 502). Mean PM2.5 levels were 30.5 μg/m3 [standard deviation (SD) = 13.2] in Bangkok and 65.9 μg/m3 (SD 32.0) in Chiang Mai. Travellers who visited Chiang Mai reported significantly more short-term health symptoms than those who visited Bangkok (58.8% vs 0.4%, P < 0.001). Among Chiang Mai visitors, respiratory symptoms were most common (46.4%), followed by eye (20.3%) and skin issues (11.1%). Reporting from participants who reduced outdoor activities during periods of high pollution were associated with a 69% lower level of symptoms [adjusted odds ratio (aOR) = 0.31, 95% confidence interval (CI): 0.1-0.7]. CONCLUSIONS: A majority of travellers reported health symptoms during their visit to Thailand during high-pollution seasons. Limiting outdoor activities appeared to mitigate these effects. Pre-travel advice should highlight the health risks associated with air pollution and emphasize preventive measures for minimizing exposure.