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 rotife r, Brachionus calyciflorus. Compounds were selected to gain an underst anding of how structural components, especially the polar head groups, contribute to toxicity. Rotifers were exposed under static test condi tions to the 22 compounds for 2d. Exposure concentrations were verifie d analytically in the test system. Results demonstrate a relationship between alkyl chain length and toxicity within a surfactant class. Bet ween classes, N-containing amines and quaternary ammonium compounds ha d greatest toxicity, in general, followed by the nonionic compounds. A nionic compounds were typically least toxic. A good quality (R-2 = 0.8 6), three-variable, parametric OSAR model was developed using the ADAP T software package. The model contains one variable to account for the contribution of the hydrophobic tail group to observed toxicity (the number of sp(3)-hybridized carbons bonded to two other carbons [2SP3]) and two descriptors, the valence-corrected, fourth-order cluster inde x (X-4(C)V) and a count of the number of nitrogens in the molecule (NN ), to account for the contribution of the polar head group.