An examination of the relationship between fluoridation of water and cancer mortality in 20 large US cities.

A comparison of mortality of 10 US cities with fluoridated water supplies compared with 10 non-fluoridated cities has been used as evidence that artificial fluoridation of drinking water causes cancer and has been widely publicised in New Zealand. Several deficiencies are noted in the analysis used by the investigators in this study and it is shown that appropriate analysis of the data from these cities yields additional evidence for the safety of fluoridation. This finding agrees with that from previous examinations of the same data in spite of the fact that they included an error in the mortality report from one city.