Effects of surfactants on the rotifer,Brachionus calyciflorus, in a chronic toxicity test and in the development of qsars

The toxicity of a range of surfactant and surfactant-related compounds was investigated in the 2-d whole life cycle bioassay with the rotifer, Brachionus calyciflorus. Compounds were selected to gain an understanding of how structural components, especially the polar head groups, contribute to toxicity. Rotifers were exposed under static test conditions to the 22 compounds for 2d. Exposure concentrations were verified analytically in the test system. Results demonstrate a relationship between alkyl chain length and toxicity within a surfactant class. Between classes, N-containing amines and quaternary ammonium compounds had greatest toxicity, in general, followed by the nonionic compounds. Anionic compounds were typically least toxic. A good quality (R2 = 0.86), three-variable, parametric QSAR model was developed using the ADAPT software package. The model contains one variable to account for the contribution of the hydrophobic tail group to observed toxicity (the number of sp3-hybridized carbons bonded to two other carbons [2SP3]) and two descriptors, the valence-corrected, fourth-order cluster index (4XvC) and a count of the number of nitrogens in the molecule (NN), to account for the contribution of the polar head group.