The Contribution of Outdoor Fine Particulate Matter to Indoor Air Quality in Bangkok Metropolitan Region, Thailand – Are Indoor Dwellers Safe?

Objective: This study aimed to analyze the relationship between indoor and outdoor fine particulate matter (PM2.5) concentrations and to characterize factors that may contribute to domestic PM2.5 concentrations, including smoking, printer/copier, and cooking activities. Methods: We measured the ambient and indoor PM2.5 concentrations from 7 sampling sites in Bangkok Metropolitan and vicinity area, Thailand by using PM2.5 concentrations sensor (SN-GCHA1, Panasonic Photo & Lighting Co., Ltd). Real-time PM2.5 concentrations, temperature, and relative humidity (RH) measurements were recorded hourly for two consecutive days during February 20th to March 2nd, 2018. We collected real-time indoor and outdoor PM2.5 mass concentrations at the same time. Factors influencing domestic PM2.5 production in the indoor environment were recorded. Results: The mean indoor PM2.5 concentrations from each site ranged from 20.05-45.85 μg/m3 and the mean outdoor PM2.5 concentrations ranged from 9.42-56.56 μg/m3. The ambient and indoor PM2.5 mass concentrations curves tended to fluctuate in a similar trend. There was a significantly positive correlation between the average ambient and the average indoor PM2.5 mass concentrations in all studied places. The correlation coefficient (r) varied from 0.6 to 0.833. Five from seven sites demonstrated a strong correlation (r ≥ 0.7), whereas, two from seven sites demonstrated a moderate correlation (0.5 ≤ r < 0.7). The average indoor/ambient PM2.5 concentration ratio from each place ranged from 0.37 to 3.57. Conclusion: The indoor PM2.5 concentrations are correlated with the ambient PM2.5 concentrations. The concentrations of PM2.5 in most sampling sites were higher than the recommended threshold. Hence, indoor dwellers are still at risk for health impacts from PM2.5. Besides public management of the ambient PM2.5, the interventions dealing with the indoor PM2.5 should be promoted concurrently