Infiltration of fine particles in urban daycares.

Abstract

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 50day-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 0.86h-1 ). However, fine particle deposition rates were lower for naturally ventilated rooms (0.67±0.43h-1 ) compared with air-conditioned ones (1.03±0.55h-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.