Relative sensitivity of three terrestrial invertebrate tests to polycyclic aromatic compounds

In a project investigating the ecotoxicity of polycyclic aromatic compounds (PACs), we have previously reported on the sublethal toxicity of eight PACs to springtails (Folsomia fimetaria) and enchytraeids (Enchytraeus crypticus). The model substances included four polycyclic aromatic hydrocarbons (PAHs) and four N-S-O-heterocyclics. Here, new data are presented on the effects of PACs on the survival and growth of the earthworm Eisenia veneta, showing that, in general, earthworm growth was reduced at PAC concentrations above 25 mg/kg soil dry weight. The E. veneta tests were performed using the same soil type and very similar test conditions as for the F. fimetaria and E. crypticus tests, thus providing a good opportunity to compare the sensitivity of these three organisms. Species sensitivity was examined using the 50% reduction in survival (LC50 values) and no-observable-effect concentrations (NOEC values) for growth or reproduction as endpoints. The difference between the least and most sensitive species was generally much larger for LC50 values as compared to the NOEC values, suggesting a higher degree of uncertainty when extrapolating from one species to another for the LC50 data. For the NOEC data, relatively small differences in sensitivity was observed, but as a rather consistent pattern, F. fimetaria was the most sensitive and E. crypticus the least sensitive species. However, one substance (acridine) showed specific toxicity toward E. veneta, which was more sensitive than the two other species by more than one order of magnitude.