Properties of Indoor Particles Collected in Japanese Homes

Due to the heightened ambient PM2.5 levels, the whole citizen of Japan, especially dwellers in Fukuoka Prefecture, start to make attention to the particulate matter (PM) of indoor environments. This study was aimed to thoroughly estimate the characteristics of indoor PM collected in five Japanese homes located in Fukuoka Prefecture. Simultaneous indoor measurements of PM were intensively made at five homes using filter-pack samplers, particle counters, and PM2.5 monitors for a day in springtime, 2012. Major ionic and carbonaceous components were also analyzed. The time series fluctuation of PM number concentration was gradually decreased by 6 AM and then it was rapidly increased by 8 AM in all indoor sites. The maximum level of PM2.5 was measured at the morning time (8 AM-9 AM) when the resident’s behavior was fast and strenuous. The Indoor/Outdoor (I/O) ratio for the giant PM larger than 5.0 μm was 1.16. It was possible to identify PM types and estimate the resident’s behavior through the comparison the theoretically calculated and the measured retention times for several types of PM in an indoor site. The theoretically reconstructed mass concentration of PM2.0-0.3 suggested that the portion of PM2.5 in indoor was quietly occupied by PM0.3 or the PM inherently originated from indoor environment.