Estimating the toxicity of ambient fine aerosols using freshwater rotifer Brachionus calyciflorus (Rotifera: Monogononta)

The toxicity of atmospheric fine particulate matter (PM_2.5) in Atlanta is assessed using freshwater rotifers (Brachionus calyciflorus). The PM-laden quartz filters were extracted in both water and methanol. Aerosol extracts were passed through a C-18 column to separate the PM components into hydrophobic and hydrophilic fractions. Toxicity data reported in the units of LC₅₀ (concentration that kills 50% of the test population in 24 h) shows that ambient particles are toxic to the rotifers with LC₅₀ values ranging from 5 to 400 μg of PM. The methanol extract of the aerosols was substantially more toxic (8 ± 6 times) to the rotifers compared to the water extracts. A sizeable fraction (>70%) of toxicity was found to be associated with the hydrophobic fraction of PM. However, none of the bulk aerosol species was strongly correlated with the LC₅₀ values suggesting a complicated mechanism of toxicity probably involving synergistic interactions of various PM components. Highlights We assessed the toxicity of ambient particulate matter (PM) using B. calyciflorus.Ambient PM is toxic to the rotifers with LC₅₀ values ranging from 5 to 400 μg of PM.Water-insoluble PM components are more toxic than the water-soluble components.Toxicity was largely (>70%) associated with the hydrophobic components of PM.