Highly sensitive mutation assay for mutagenicity monitoring of indoor air using Salmonella typhimurium YG1041 and a microsuspension method

A highly sensitive mutation assay for indoor mutagenicity monitoring was investigated by a combination of Salmonella typhimurium YG strains and the microsuspension method, Tester strains were YG1024, YG1029, YG1041 and YG1042. YG1041 gave the highest sensitivity in the mutagenicity test for the extracts of airborne particulates. The sensitivity of the microsuspension assay using S.typhimurium YG1041 in the absence of S9 mix was similar to 200 times higher than that of the preincubation assay using strain TA98, which has been widely used for mutagenicity monitoring of airborne particulates outdoors. Furthermore, a significant correlation was observed between mutagenicities determined by the microsuspension assay using S.typhimurium YG1041 and TA98, where mutagenicity assay was carried out for airborne particulates collected by a high volume sampler for 24 h every 12 days for 1 year. This new method was also useful for indoor mutagenicity monitoring in which a small amount of airborne particulates was collected by a low noise sampler for 12 h each of 6 consecutive days. The monitoring showed that mutagenicity in the daytime is generally higher than that in the night and that smoking is an important factor in increasing mutagencity in indoor air.