Guardian Corrections and clarifications

• A news story about health experts calling for a moratorium on water fluoridation said that some critics cite a number of possible negative associations of fluoridation, including “hyperthyroidism”. In fact fluoride may have a negative link with hypothyroidism, an underactive thyroid, not hyperthyroidism, which is an overactive thyroid. In the past it has been used to treat hyperthyroidism (Health experts call for halt in fluoridation of Britain’s water, 26 December, page 15).