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. 2025 Jan 24;11(3):e42261.
doi: 10.1016/j.heliyon.2025.e42261. eCollection 2025 Feb 15.

Seasonal analysis of indoor and outdoor ratios of PM2.5 and PM10 in Bangkok and Chiang Mai: A comparative study of haze and non-haze episodes

Wissanupong Kliengchuay  1 , Sarima Niampradit  1 , Narut Sahanavin  2 , William Mueller  3 , Susanne Steinle  3 , Miranda Loh  3 , Helinor Jane Johnston  4 , Sotiris Vardoulakis  5 , San Suwanmanee  6 , Walaiporn Phonphan  7 , John W Cherrie  3 , Kraichat Tantrakarnapa  1
Affiliations

Seasonal analysis of indoor and outdoor ratios of PM2.5 and PM10 in Bangkok and Chiang Mai: A comparative study of haze and non-haze episodes

Wissanupong Kliengchuay et al. Heliyon. .

Abstract

Particulate matter (PM) air pollution has been identified as one cause of human health impact with the estimated global 8.8 million attributable deaths. Thailand experiences haze episode every year, which can lead to high ambient concentrations of particulate matter in ambient air. This study aims to investigate the relationship of indoor and outdoor air quality in both haze and non-haze period in two cities in Thailand: namely Bangkok and Chiang Mai. We conducted the air quality sampling in various styles of house, with 17 houses in both urban and rural areas, between April to October 2019. The results indicated that the concentration of PM2.5 in indoor air in Bangkok were 19.85 and 11.40 μg/m3 for haze and non-haze period, respectively, whereas the PM10 concentrations were 32.124 and 17.49 μg/m3 for haze and non-haze period, respectively. The corresponding average of outdoor air concentrations were 26.26 and 16.68 μg/m3 for haze and non-haze, respectively. While the PM10 concentrations were 46.36 and 23.86 μg/m3 for haze and non-haze period, respectively. In Chiang Mai, it was observed that the mean concentration of PM2.5 in indoor was 106.80 μg/m3 and 5.52 μg/m3 for haze and non-haze periods, respectively. Regarding PM10, it was observed that the mean concentration in indoor was 118.54 μg/m3 and 9.74 μg/m3 for haze and non-haze periods, respectively. Indoor/Outdoor (I/O) ratios of PM2.5 varied in Bangkok average was 0.76 for haze and 0.68 for non-haze period. The I/O ratio in Chiang Mai was 0.91 and 1.16 for haze and non-haze episode, respectively. Indoor/Outdoor (I/O) ratios of PM10 varied in Bangkok average was 0.70 for haze and 0.73 for non-haze period. The I/O ratio in Chiang Mai was 0.92 and 0.96 for haze and non-haze episode, respectively Our findings indicated the influences of outdoor air quality on indoor air quality during both haze and non-haze episode. The intrusion of outdoor air in Chiang Mai to the houses caused a higher I/O ratio than Bangkok due to the characteristics of house and culture. The indoor air quality in terms of particulate matter were dominated by outdoor air quality. Thus, people should close doors/windows during the haze as well as non-haze episode to avoiding the pollutant accumulation.

Keywords: Haze episode; Indoor/Outdoor (I/O) ratios; Non-haze episode; PM2.5.

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Conflict of interest statement

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Kraichat Tantrakarnapa reports financial support was provided by Thailand Research Fund (10.13039/501100004396TRF) (RDG603009). Kraichat Tantrakarnapa reports financial support was provided by 10.13039/501100004704National Research Council of Thailand (10.13039/501100004704NRCT). John Cherrie reports financial support was provided by 10.13039/501100000265Medical Research Council (MRC). Reports a relationship with that includes:. Has patent pending to. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Fig. 1
Fig. 1
Map of the study area with house sampling sites (QGIS 3.22 Biatowieza).
Fig. 2
Fig. 2
Land-use characteristics in sampling sites area (QGIS 3.22 Biatowieza).
Fig. 3
Fig. 3
Representative land use areas for each type are marked by a circle with a 100-m radius around the house in a) Bangkok and b) Chiang Mai.
Fig. 4
Fig. 4
Daily concentrations of (a) PM10 and (b) PM2.5 in Haze and Non-haze episode.
Fig. 5
Fig. 5
I/O ratio of PM2.5 in (a) Bangkok house and (b) Ching Mai house in haze and non-haze episode.
Fig. 6
Fig. 6
Cumulative distributions function of PM2.5 I/O ratios and best curve fitting in (a) Bangkok in Haze episode, (b) Bangkok in non-haze episode, (c) Chiang Mai in Haze episode and (d) Chiang Mai in non-haze episode.
See this image and copyright information in PMC

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