Indoor PM2.5 concentrations in various retail stores in an urban city: Levels, sources and health risk assessment

This study provides information about PM 2.5 indoor–outdoor mass concentrations, indoor/outdoor ratios (I/O) and health risks associated with PM 2.5 inhalation in seven various retail stores: photocopy centre, bakery, restaurant, hairdresser, dry cleaner, grocery store and hotel. Simultaneous indoor and outdoor measurements were performed in all retail stores in both summer and winter seasons, weekdays and weekends, and also during busy and less-active hours to obtain a realistic exposure assessment. According to the results, indoor PM 2.5 levels in the winter season were comparatively higher than those measured in the summer season. The highest PM 2.5 concentrations were measured at the hairdresser (3076.0 ± 1345.5 µg/m 3 ) and restaurant (2138.1 ± 636.4 µg/m 3 ) in each sampling period in winter. I/O ratios of >1 were obtained at the hairdresser (7.3–72.3) and restaurant (1.6–17.3) in the winter season and at the hairdresser (1.3–12.7) and dry cleaner (1.1–1.7) in the summer season in all measurement periods. Quite high indoor PM 2.5 concentrations and consequently high I/O ratios indicated a strong contribution from indoor sources rather than infiltration of ambient air. Non-carcinogenic health risks due to PM 2.5 exposure were evaluated by estimating hazard quotient (HQ) values, and all HQ values were above the acceptable limit of 1 defined by US EPA for the photocopy centre, hairdresser and dry cleaner in both seasons. The results showed that indoor activities at the retail stores were significant for indoor PM 2.5 levels as well as occupational health risks faced by employees at retail stores.