KEYNOTE Is indoor environment a safe haeven to avoid air pollution?

Air pollution by particulate matter has aroused worldwide concerns. Ultrafine particles (UFP) are particularly in focus because of their potential health risk and capability of exchanging between indoor and outdoor... [ view full abstract ]

Air pollution by particulate matter has aroused worldwide concerns. Ultrafine particles (UFP) are particularly in focus because of their potential health risk and capability of exchanging between indoor and outdoor environments. Urban residents spend the majority of time in indoor environments, which, however, may not be a safe haven for staying away from outdoor air pollution.
Three representative types of functional area, i.e., school, office and home, in Guangzhou, China were selected as study sites. Indoor and outdoor UFP (14‒660 nm) at each site were simultaneously and consecutively monitored using a Scanning Mobility Particle Sizer with an automatic indoor/outdoor switch system in October 2014 and July 2015, which represent dry and wet weather seasons, respectively.
Among three functional areas, the highest UFP level occurred at home, and the indoor UFP concentrations were greater than those in outdoors. There was insignificant differences of UFP concentrations between dry and wet weather seasons, suggesting low efficacy for scavenging of UFP through wet deposition. The UFP concentrations peaked during rush hours, implicating motored vehicles as the major contributors to outdoor UFP, whereas human activities, such as cooking and smoking, were the major source of indoor UFP. It is interesting to note that the number concentrations of indoor UFP were positively correlated with outdoor UFP at schools and offices, suggesting that the exchange of UFP between indoor and outdoor environments was efficient. In addition, particles with the sizes of 50−100 nm predominated UFP deposited in both the tracheobronchial and alveolar regions.