To reveal the contamination levels of ambient air with particulate matter and mutagens in Japan and the influence of their long-range transport from the Asian continent, we collected airborne particles at 10 sites, from rural sites to metropolitan areas, in central and western areas of Japan for a year, from July 2008 to June 2009. The fluctuation patterns and levels of airborne particle concentration were similar among the 10 sites, and remarkable increases of the concentrations were seen on a few sampling dates, including March 16 and 17, 2009. Most airborne particles collected at the 10 sites showed mutagenicity toward Salmonella typhimurium
YG1024 without a mammalian metabolic system (S9 mix) in the Ames test. The mutagenicity levels were quite different among the sampling sites, and the levels seemed to be dependent on the extent of urbanization and industrialization of the subject areas. At Yurihama, a rural site on the west coast of Japan, the mutagenicity level of airborne particles was low, but the particles collected on March 16 and 17, 2009, showed relatively high mutagenicity, >40 revertants/m3
, in YG1024 without S9 mix. Airborne particles collected on March 16 and 17, 2009, at most sites showed relatively high or high mutagenicity, >80 revertants/m3
, in YG1024 without S9 mix. High coefficients of correlation were found between the concentration and mutagenicity of airborne particles collected in spring, from March to May, for many sites. The results of back trajectory analysis indicated that air masses for March 16 and 17, 2009, had moved from the Asian continent to Japan. The arrival of Asian dust in central and western areas of Japan on those days was reported by the Japan Meteorological Agency. These results suggest that the arrival of mutagens accompanied by Asian dust could be evidently found at Yurihama on March 2009.