Indoor and outdoor air pollution in Tokyo and Beijing supercities

Since automobile exhaust and coal combustion exhaust are the major sources of suspended particulate matter (SPM) and airborne pollutants in many countries, SPM and polycyclic aromatic hydrocarbons (PAH) in indoor and outdoor air were measured using the new portable samplers (AND sampler) around a main road and in residential areas of Tokyo and Beijing. The results showed that the relationship between the airborne particle concentration in indoor air and outdoor air varied with the aerodynamic diameter of the particles. The concentration of SPM in indoor air increased in proportion to that in outdoor air. The concentration of PAH and mutagenic activity in air also varied with the aerodynamic diameter of the particles. Fine particles exhibiting an aerodynamic diameter of <2 mu m contained high concentrations of PAH and mutagens. The concentrations of benzo(k)fluoranthene, benzo(a)pyrene [B(a)P], and benzo(ghi)perylene in indoor air increased in proportion to those in outdoor air around a main road and in residential areas of Tokyo and Beijing. The results showed that fine particles seemed to be more harmful to humans than coarse ones. In the winter season, the SPM and sulfur dioxide concentration in indoor and outdoor air in residential areas of Beijing was approximately 4 to 5 times higher than that around a main road of Tokyo. The B(a)P concentration in outdoor air in residential areas of Beijing was approximately 15 times higher than that in residential areas around a main road of Tokyo. Since the concentration of SPM and PAH in indoor air increases in proportion to that in outdoor air, it is reasonable to make efforts to reduce SPM and PAH generated by automobile exhaust in Tokyo and coal combustion exhaust in Beijing.