This study evaluated the interrelations between indoor and outdoor bioaerosols in a bedroom under a living condition. Two wideband integrated bioaerosol sensors were utilized to measure indoor and outdoor particulate matter (PM) and fluorescent biological airborne particles (FBAPs), which were within a size range of 0.5‐20 μm. Throughout this one‐month case study, the median proportion of FBAPs in PM by number was 19% (5%; the interquartile range, hereafter) and 17% (3%) for indoors and outdoors, respectively, and those by mass were 78% (12%) and 55% (9%). According to the size‐resolved data, FBAPs dominated above 2 and 3.5 μm indoors and outdoors, respectively. Comparing indoor upon outdoor ratios among occupancy and window conditions, the indoor FBAPs larger than 3.16 μm were dominated by indoor sources, while non‐FBAPs were mainly from outdoors. The occupant dominated the indoor source of both FBAPs and non‐FBAPs. Under awake and asleep, count‐ and mass‐based mean emission rates were 45.9 and 18.7 × 106 #/h and 5.02 and 2.83 mg/h, respectively. Based on indoor activities and local outdoor air quality in Singapore, this study recommended opening the window when awake and closing it during sleep to lower indoor bioaerosol exposure.

Singapore is a tropical country with a high density of day‐care facilities whose indoor environments may be adversely affected by outdoor fine particle (PM2.5) air pollution. To reduce this problem requires effective, evidence‐based exposure‐reduction strategies. Little information is available on the penetration of outdoor PM2.5 into day‐care environments. Our study attempted to address the following objectives: to measure indoor infiltration factor (Finf) of PM2.5 from outdoor PM2.5 and to determine the building parameters that modify the indoor PM2.5. We collected indoor/outdoor 1‐min PM2.5 from 50 day‐care classrooms. We noted mean Finf ± SD of 0.65 ± 0.22 in day‐care rooms which are naturally ventilated and lower Finf ± SD values of 0.47 ± 0.18 for those that are air‐conditioned: values which are lower than those reported in Singapore residences. The air exchange rates were higher in naturally ventilated rooms (1.47 vs 0.86 h−1). However, fine particle deposition rates were lower for naturally ventilated rooms (0.67 ± 0.43 h−1) compared with air‐conditioned ones (1.03 ± 0.55 h−1) presumably due to composite rates linked to the filters within the split unit air‐conditioners, higher recirculation rates, and interior surfaces in the latter. Our findings indicate that children remaining indoor in daycares where air‐conditioning is used can reduce their PM2.5 exposures during outdoor pollution episodes.

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To date, exposure studies linking dust-mite allergens with asthma and allergic morbidities have typically relied on sampling from representative locations in the home for exposure assessment. We determine the effects of differing microenvironments allergen exposures on asthma and asthma severity among 25 case and 31 control preschool children in Singapore. Blo t 5 allergen levels in various niches from the children's home and day-care microenvironments as well as their Blo t 5 time-weighted concentrations were determined. Eosinophilic cationic protein (ECP) levels from the children's saliva as markers for airway inflammation were obtained. Salivary ECP levels were higher in children with asthma than those without and the strength of association increased with higher salivary ECP levels. Although there was no relationship between time-weighted Blo t 5 concentrations with salivary ECP levels among the controls, a positive statistically significant relationship was noted among cases, demonstrating the effects of cumulative exposure on asthma severity. Avoidance measures to reduce Blo t 5 allergen exposure should include all microenvironments that asthmatic children are exposed throughout the day. K E Y W O R D Sallergen, microenvironment exposure, preschool children, salivary ECP, tropics