Use of the Daphnia magna test to estimate the toxicity of the ozonation by-products of phenols and chlorophenols

The toxicities of the ozonation products of 18 phenols were assayed with th e Daphnia magna 24-hour toxicity test. The toxicities of the ozonation prod ucts of eight individual chlorophenols, and a mixture of them, are signific antly lower than the toxicities of untreated solutions of chlorophenols. Fo r some other phenols, including ordinary phenol (oxybenzene), toxicity incr eased during ozonation, and the formation of very toxic products was observ ed.