Size distributions of mutagenic compounds and mutagenicity in atmospheric particulate matter collected with a low-pressure cascade impactor

Size distributions of nine polycyclic aromatic hydrocarbons (PAHs), 2-nitrofluoranthene (2-NF) and mutagenicity in atmospheric particulate matter (PM) were measured by using a low-pressure cascade impactor in Saitama, Japan. PM was separated into 12 fractions of different sizes as follows: <0.11, 0.11–0.19, 0.19–0.29, 0.29–0.48, 0.48–0.68, 0.68–1.2, 1.2–2.1, 2.1–3.5, 3.5–5.1, 5.1–7.6, 7.6–11 and >11 μm. PAHs and 2-NF in PM were analyzed by gas chromatography/mass spectrometry with electron impact ionization (GC/EI-MS) and with negative ion chemical ionization (GC/NCI-MS), respectively. Mutagenicity of PM was determined by Ames test using Salmonella typhimurium strains TA98 and YG1024 under the conditions of both with and without S9 mix. The size distribution of PM was bimodal with peaks at 0.48–0.68 μm and 3.5–5.1 μm, while size distributions of total PAHs, individual PAHs, 2-NF and mutagenicity were unimodal with a peak at 0.48–0.68 μm. Nearly 87–95% of these compounds and 88–100% of mutagenicity were found in fine particles, and 2.9–5.8% of these compounds and 5.1–5.9% of mutagenicity were found in ultrafine particles. On the other hand, PAHs, 2-NF and mutagenicity per unit mass of PM increased as the particle size became smaller. The highest contents of PAHs, 2-NF and mutagenicity per unit mass of PM were observed in the fraction of <0.11 μm (ultrafine particle) or 0.11–0.19 μm.