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Particulate pollution has emerged as a serious environmental health concern in Pakistan.The use of biomass fuels in traditional stoves produces high levels of indoor air pollutants. In Pakistan, 94% of rural and 58% of urban households depend on biomass fuel. This study investigates variations in indoor/outdoor concentrations of particulate matter during various activities for three different micro-environments in Pakistan. At a rural site, the average indoor/outdoor ratios for PM 10 , PM 2.5 and PM 1 , in kitchens using biomass fuels were 3.80, 4.36 and 4.11, respectively. A large variation was recorded in the mass concentration of particulate matter during cooking with concentrations in the range 4,000 to 8,555µg/m 3 . In a living room at rural site, the average indoor/outdoor ratios for PM 10 , PM 2.5 and PM 1 were 1.74, 2.49 and 3.01, respectively. At the urban site, the average indoor/outdoor ratios for same size fractions were 1.71, 2.88 and 3.47, respectively. Cooking, cleaning and smoking were identified as principal contributors to the high indoor levels of particulate matter. This study showed considerably high concentrations of particulate matter, particularly in kitchens using biomass fuels, as compared to living areas. Thus women and children face the greatest exposure due to the amount of time they spend in the kitchen. Practical ImplicationsIn the developing world, particulate air pollution both indoor and outdoor is a substantial health hazard to public. The very high concentrations of particulate matter in both rural and urban sites, particularly in kitchens using biomass fuels emphasize the severity of this issue in Pakistan The women and children are extensively at risk due to amount of time spent in kitchens. This state of affairs calls for a large scale intervention to reduce the exposure to indoor air pollution.

The concentration and size distribution of bacterial and fungal aerosol was studied in 15 houses. The houses were categorized into three types, based on occupant density and number of rooms: single room in shared accommodation (type I), single bedroom flat in three storey buildings (type II) and two or three bedroomed houses (type III). Sampling was undertaken with an Anderson six-stage impactor during the summer of 2007 in the living rooms of all the residential settings. The maximum mean geometric concentration of bacterial (5,036 CFU/m 3 , ± 2.5, n=5) and fungal (2,124 CFU/m 3 , ± 1.38, n=5) aerosol were in housing type III. The minimum levels of indoor culturable bacteria (1,557 CFU/m 3 , ±1.5, n=5) and fungal (925 CFU/m 3 , ±2.9, n=5) spores were observed in housing type I. The differences in terms of total bacterial and fungal concentration were less obvious between housing types I and II as compared to type III. With reference to size distribution, the dominant stages for culturable bacteria in housing types I, II and III were stage 3 (3.3-4.7 μm), stage 1 (7 μm and above) and stage 5 (1.1-2.1 μm), respectively. Whereas the maximum numbers of culturable fungal spores were recovered from stage 2 (4.7-7 µm), in housing type I, and from stage 4 (2.1-3.3 μm) in both type II and III houses. The average geometric mean diameter of bacterial aerosol was largest in type I (4.7 μm), followed by type II (3.89 μm) and III (1.96 μm). Similarly, for fungal spores, type I houses had the highest average mean geometric diameter (4.5 μm), while in types II and III the mean geometric diameter was 3.57 and 3.92 μm, respectively. The results indicate a wide variation in total concentration and size of bioaerosols among different residential settings. The observed differences in the size distributions and concentrations reflect their variable airborne behaviour and, as a result, different risks of respiratory exposure of the occupants to bioaerosols in various residential settings.