Indoor PM2.5Exposure during haze and non- haze episodes in a residential microenvironment of Dhaka: A comparative study

Haze is a common meteorological phenomenon during winter in Dhaka. This study was conducted to evaluate the exposure variation of fine particulate matter i.e. PM2.5 in a residential home of Dhaka under haze and non-haze weather. Indoor PM2.5 samples were collected during January- February, 2020, using a filter- based air sampler. Six heavy metals (Fe, Mn, Cu, Zn, Pb and Cr) were analysed using atomic absorption spectrophotometer. The 24- hour average haze- time indoor PM2.5 concentration was 139 ± 57.7 μgm-3, whereas that during non- haze period was 96.3 ± 17.7 μgm-3, both significantly exceeding the WHO guideline value. Haze- time PM2.5 concentration in the sampling home was 1.44 times higher than its non- haze counterpart, suggesting that outdoor PM2.5 particles probably entered the household via ventilation and infiltration, thereby degrading the indoor air quality. The concentration of heavy metals increased by 1.32 to 71.3 times during haze, with Zn contributing the highest to PM2.5. Hazard index (HI) for children and adults during haze was 31.19 and 13.68, respectively, indicating severe non- carcinogenic risk. Total cancer risk during haze (6.22× 10-4) and non- haze (4.66× 10-4) exceeded the USEPA threshold (1× 10-4). Exposure to elevated indoor PM2.5 levels during haze increased the probability of cancer incidence from 1 in 2146 individuals, to 1 in 1608 individuals. Backward air mass trajectory analysis suggested that transboundary source contributed to aerosols during haze formation. Findings of this study revealed the severity of indoor air pollution in Dhaka, emphasizing effective control strategies. Dhaka Univ. J. Sci. 74(1): 27-35, 2026 (January)