Mutagenicity of suspended particulate matter divided in three sizes indoors

To clarify indoor air pollution, indoor and outdoor air samples were collected from 22 houses in Tokyo using a low-volume cascade impactor with a quartz fiber filter. Suspended particulate matter (SPM) was classified into three sizes: greater than or equal to 10 mum, 2.5-10 mum and less than or equal to 2.5 mum. The mutagenic compounds were extracted by the dichloromethane/sonication method. The solution was concentrated by NZ gas. Mutagenicity was determined by the microsuspension method, employing the Salmonella typhimurium (S. typhimurium) YG 1024 strain in the presence and absence of S9 mix. The samples showed generally higher mutagenicity in the absence of S9 mix than in its presence. Outdoor air tended to have higher or similar mutagenicity to indoor air. The smallest SPM (less than or equal to 2.5 mum) fraction showed the highest mutagenicity (revertants/m(3.) air). These results suggest that one of the main sources of high mutagenic SPM indoors is air entering from outdoors.