Several studies have shown that exposure to fluoride can cause behavioural changes (Int Clin Psychopharmacol, 1994; 9: 79-82; Neurotoxicol and Teratol, 1995; 17: 169-77; Fluoride, 1996; 29: 187-8). At a 1998 conference on fluoride in Washington, Professor Roger Masters reported a link between the blood lead levels of 280,000 children in Massachusetts and the use of silicofluorides for water fluoridation; fluoride increases the toxic effects and absorption of lead. Both in Britain and in Georgia, behaviours associated with lead toxicity, such as violent crime, are more frequent in communities using silicofluorides than in areas not using them. At the same conference, Dr Phyllis Mullinix, a neuro toxicologist at Boston Children's Hospital, Massachusetts, reported results of a study using two steroids to treat childhood leukaemia, one of which had a fluorine atom in its structure. The steroid caused behaviour patterns typical of hyperactivity. A follow up study showed a significant drop in average IQ scores, compared with children using the non fluoride drug (Fluoride, 1998; 31: 175).