Review of the environmental toxicity of quaternary ammonium halides.

This paper summarizes all available information on the environmental toxicity of quaternary ammonium compounds (QACs). Ten-minute contact kills of bacteria occur at 50-333 mg/liter. These chemicals are acutely toxic at approximately 1 mg/liter to invertebrates and fish and toxicity is occasionally as low as 0.1 mg/liter; no-effect levels are generally 10 times lower than LC50 values. Toxicity to invertebrates and fish appears to be relatively independent of structure; the compounds studied, which have a large variety of structures, are all toxic at approximately the same order of magnitude. The QACs tested inhibited plant growth at 3-5 mg/liter. Predictions of toxicity to QACs are made based on knowledge of structure-activity relationships.