Polycyclic aromatic hydrocarbon exposure during commuting: A comparative analysis of Bus and Tuk-Tuk in Phnom Penh

¹ Research and Innovation Center, Institute of Technology of Cambodia, Russian Federation Blvd., P.O. Box 86, Phnom Penh, Cambodia
² Faculty of Chemical and Food Engineering, Institute of Technology of Cambodia, Russian Federation Blvd., P.O. Box 86, Phnom Penh, Cambodia
³ Faculty of Geoscience and Civil Engineering, Institute of Science and Engineering, Kanazawa University, Kanazawa, Ishikawa, 920-1192, Japan
⁴ Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki 852-8521, Japan

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

This study evaluated and compared the levels of exposure to PM2.5 and selected polycyclic aromatic hydrocarbons (PAHs) among commuters using two common transportation modes, city buses and Tuk-Tuks, in Phnom Penh, Cambodia. Sampling was conducted over 14 days using personal air samplers worn by commuters to capture the in-vehicle pollutant concentrations. The results showed that the Tuk-Tuk commuters consistently experienced significantly higher exposures than the bus commuters. The average PM2.5 concentration in Tuk-Tuks was 115.9 ± 36.3 μg/m³, compared with 76.0 ± 39.7 μg/m³ for buses. PAH exposure also followed this trend, with Tuk-Tuk commuters exposed to average PAH concentrations of 23.40 ± 6.70 ng/m³, whereas bus commuters were exposed to 4.88 ± 1.43 ng/m3. Among the PAHs analysed, benzo[ a ]pyrene (BaP), indeno[1,2,3-cd]pyrene (IDP), and benzo[ ghi ]perylene (BghiP) were the most dominant compounds. Diagnostic ratios consistently identified liquid fossil fuel combustion as the primary source of pollution. The higher exposure associated with Tuk-Tuk usage is attributed to its open-air design, which offers minimal protection against ambient pollutants, in contrast to the relatively enclosed environment of city buses. This study highlights the urgent need for improved air quality management and urban transportation planning in Phnom Penh. Interventions should focus on promoting cleaner transportation alternatives and implementing stricter emission regulations to safeguard commuter health.