Mortality rates (for blacks and whites only) in 24 cities with fluoridated and 22 with non-fluoridated water supplies in the United States were compared for the years 1969-1971. During these three years 570,671 deaths occurred in the cities with fluoridated water; the 1970 reference population in those cities was 15,972,817. The figures for the cities with non-fluoridated water were 351,053 and 11,106,746 respectively, so that the crude death rates for all causes were 1190.9 (fluoridated) and 1053.6 (non-fluoridated) per 100,000 person-years. Adjustments for age, sex and race reduced differences for some causes and removed them for others. Further correction, using analyses of covariance for city characteristics that influence mortality, gave adjusted death rates for all causes of 1123.9 and 1137.1, and for malignant neoplasms 195.3 and 196.9, in the cities with fluoridated and non-fluoridated water respectively. I found no evidence of a harmful effect of fluoridation.
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