Pitakchon Ponsawansong1,2,3, Tippawan Prapamontol This email address is being protected from spambots. You need JavaScript enabled to view it.1, Kittipan Rerkasem1, Somporn Chantara4, Kraichat Tantrakarnapa5, Sawaeng Kawichai1, Guoxing Li6, Cao Fang3, Xiaochuan Pan6, Yanlin Zhang This email address is being protected from spambots. You need JavaScript enabled to view it.3

1 Research Institute for Health Sciences, Chiang Mai University, Chiang Mai, Thailand
2 PhD Degree Program in Environmental Science, Environmental Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai, Thailand
3 Yale-NUIST Center on Atmospheric Environment, Nanjing University of Information Science and Technology, Nanjing, China
4 Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai, Thailand
5 Department of Social and Environmental Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
6 Department of Occupational and Environmental Health Sciences, School of Public Health, Peking University, Beijing, China

Received: February 7, 2023
Revised: May 30, 2023
Accepted: July 4, 2023

 Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.

Download Citation: ||https://doi.org/10.4209/aaqr.230030  

Cite this article:

Ponsawansong, P., Prapamontol, T., Rerkasem, K., Chantara, S., Tantrakarnapa, K., Kawichai, S., Li, G., Fang, C., Pan, X., Zhang, Y. (2023). Sources of PM2.5 Oxidative Potential during Haze and Non-haze Seasons in Chiang Mai, Thailand. Aerosol Air Qual. Res. 23, 230030. https://doi.org/10.4209/aaqr.230030


  • The first Thai evidence of PM2.5 and its source contributions to oxidative activity.
  • DTT assay shows PM2.5 chemical compositions' oxidative potential in Chiang Mai.
  • Biomass burning dominates PM2.5 and DTTv activity in haze episodes.


Dithiothreitol (DTT) assay is an acellular technique used to investigate the oxidative potential (OP) of chemical substances bound on PM, which may potentially lead to oxidative stress after exposure. In this study, the source contributions of 16 high priority polycyclic aromatic hydrocarbons (PAHs), designated by the United States Environmental Protection Agency (U.S. EPA), and 10 species of water-soluble inorganic ions bound on PM2.5 and their OP were investigated using DTT assay. The 24-hr ambient PM2.5 samples were collected throughout 2018–2019 and the analyzed OP was compared during haze episodes, which generally occurs in the dry season, and non-haze rainy season in the Chiang Mai-Lamphun basin. During haze episodes, DTTv activity was positively correlated with 4–5 rings PAHs including fluoranthene (Fla) pyrene (Pyr), benzo[a]anthracene (BaA), chrysene (Chr), benzo[b]fluoranthene (BbF) and benzo[k]fluoranthene (BkF) with coefficient ranging from 0.327 to 0.545, p = 0.002 to 0.009 (Pearson’s correlation). Inorganic ions, particularly NH4+, SO42–, and NO3, which are the tracers of secondary inorganic aerosol (SIA), were positively correlated with DTTv activity (r = 0.394 to 0.659. p = 0.000 to 0.047; Spearman’s correlation). Positive matrix factorization (PMF) indicated the biomass burning factor had the highest contribution (57.9%) to PM2.5 during haze episodes, followed by SIA (26.2%), and vehicle exhausts (7.8%). Furthermore, multiple linear regression (MLR) showed that biomass burning was the highest contributor to DTTv (43.0%). These results suggest that during haze episodes, higher levels of PM2.5 and its chemical compositions play a crucial role on OP, particularly DTTv activity, which may induce oxidative stress in human body.

Keywords: Air pollution, Biomass burning, Dithiothreitol assay, Oxidative potential, Particulate matter

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