Guidance has been updated on a number of chemicals: asbestos, bentazone, chromium, iodine, manganese, microcystins, nickel, silver, tetrachloroethene and trichloroethene. Guidance has also been added for chemicals not previously assessed in the Guidelines: anatoxin-a and analogues, cylindrospermopsins and saxitoxins. The new guidance on organotins has replaced the prior guidance focused on dialkyltins. With these updates, the guideline values for tetrachloroethene and trichloroethene have been revised while new guideline values for cylindrospermopsins, manganese, microcystins, and saxitoxins have been established . Updated information on cyanobacteria has been included, introducing an alert level framework for early-warning and to guide short-term management responses. Guidance has also been updated in the sections on adequacy of water supply, climate change, emergencies, food production and processing, and radiological aspects, particularly on managing radionuclides when exceeding WHO screening values and guidance levels.