This International Standard speci?es a method for the determination of the lethal effects of toxicants to Thamnocephalus platyurus test organisms after 24 h exposure. A second method (rapid test) is described in Annex A for the determination of sublethal effects after a very short exposure time (1 h).The methods are applicable to:a) chemical substances which are soluble or which can be maintained as stable suspensions or dispersions under the conditions of the test;b) industrial or sewage ef?uents, treated or untreated, if appropriate after decantation, ?ltration or centrifugation;c) fresh waters;d) aqueous extracts;e) toxins of blue-green algae.This Intern