The impact of incense burning on indoor PM2.5 concentrations in residential houses in Hanoi, Vietnam

Abstract Incense burning is a common cultural and religious practice in many Asian countries, including Vietnam. However, there is scarce information about the impact of incense burning in the residential indoor environment. In this study, we quantified the concentrations of PM2.5 indoor and outdoor and assessed the influence of incense burning on indoor air quality at residential houses in Hanoi, Vietnam. Three AirVisual Pro monitors were used to simultaneously and continuously measure PM2.5 concentrations, both indoor and outdoor for one week at each of 32 urban residential homes. Over 47 % of the homes had a daily average indoor PM2.5 concentration greater than 50 μg/m3, the recommended guideline in Vietnam. The daily average indoor PM2.5 concentration in the homes was 52.1 ± 33.9 μg/m3, while the corresponding outdoor concentration was 54.4 ± 37.6 μg/m3. These values were significantly higher in homes that burnt incense, with mean concentrations in a room during an incense burning event being 201.3 ± 132.2 μg/m3 with a 1 min-average peak of 825.5 μg/m3. Multiple linear regression analysis showed that, incense burning increased the geometric mean of indoor PM2.5 concentration by 120 %, after adjusting for other factors. Our results indicated the need for raising public awareness on the impact of incense burning on air quality in household environments.