Toxicity of the insecticide permethrin and some degradation products towards algae and cyanobacteria

Abstract

Toxic effects of the pyrethroid insecticide permethrin and ten of its degradation products were determined for the growth, photosynthesis and acetylene-reducing ability of two species of green algae and three species of cyanobacteria (blue-green) algae). Permethrin was relatively non-toxic in all systems, except for the growth of the cyanobacterium Anabaena inaequalis, where it had an EC 50 of 1·5 to 5·0 ppm (μg ml −1). From two to five of the degradation products were significantly more toxic than permethrin. The most toxic metabolites were 3-phenoxybenzaldehyde and 3-phenoxybenzyl alcohol, followed by benzoic acid, 3-hydroxybenzoic acid and 3-phenoxybenzoic acid. The EC 50 values of these compounds were as low as 1·4 ppm, although most were in the range 30 to 70 ppm for photosynthesis and acetylene reduction and 2 to 6 ppm for growth. The green algae were generally less sensitive than the cyanobacteria to these toxicants. Combinations of permethrin and selected metabolites were tested against A. inaequalis and yielded both synergistic, antagonistic and additive interaction responses, depending upon the actual test system.