Mutagenicity of size-fractioned airborne particles collected with Andersen low pressure impactor

Mutagenicity of size-fractioned airborne particles collected with a multi-stage fractioned sampler, an Andersen low pressure impactor, was measured by microsuspension assay using Salmonella typhimurium YG1024 strain (x 20 conc. bacterial solution). Fine particle samples showed mutagenicity with a good dose-response relationship under the conditions of both with and without a metabolic activation system (S9 mix). In generally, the activities without S9 mix were higher than those with S9 mix, and the highest activity per unit air volume was observed in the sample of 0.52 mum in diameter. Most of the negatives were observed in coarse particle samples. The size distribution of mutagenic activity per unit air volume was skewed to the smaller size range and had one peak at 0.52 mum, although that of mass concentration was bimodal, having two peaks bounded around 1-2 mum in diameter. The highest mutagenic activity per unit mass of particles in a series of fractioned samples was observed in the sample of less than 0.22 mum in diameter. It was suggested that ultrafine particles were more mutagenic than fine particles (PM 2.5-0.1), as if the mass concentrations of ultrafine particles were 10% or less than those of fine particles. It was also shown the Andersen low pressure impactor is very useful for studies of carcinogens and mutagens in suspended particles in ambient air.