Medical Research Council report (2002)

Taking account of York review and other evidence

In 2002, a working group set up by the Medical Research Council published the findings of its own analysis – Water Fluoridation and Health – of the earlier review of fluoridation studies undertaken by a team at the University of York. (1)  In addition, the MRC group looked at other evidence that had not been included or taken into account by York.

No association between cancer mortality rates and fluoridation

With regard to any possible link between fluoridated water and cancer, the MRC group said in its report: “Several studies have analysed data sets from ten fluoridated and ten non-fluoridated cities in the USA.  With the exception of the analysis by Yiamouyiannis and Burk, which did not adjust appropriately for sex, age and ethnic group, none of these analyses has suggested that overall cancer mortality rates were positively associated with fluoridation.

“Similar analyses in other areas in the US, and in the UK and elsewhere, have not shown any differences in total cancer rates between fluoridated and non-fluoridated populations, or between populations with water supplies naturally high or low in fluoride.  Some ecological studies have looked specifically at bone cancer or at osteosarcoma, and have not observed any associations with water fluoridation.”

The MRC working group highlighted a study (Hoover et al, 1991) which, they believed, should have been included in the analysis of cancer data undertaken by the York team.  The study – one of the largest of its kind ever undertaken – analysed the patterns of cancer deaths in 1.2 million men and 1.1 million women in fluoridated and non-fluoridated communities during 35 years before and 35 years after fluoridation started.  It found that fluoridation did not increase the risk of death from cancer for either men or women compared with the risk before fluoridation, or compared with non-fluoridated populations.

High level of reassurance concerning safety

The MRC report concluded: “Overall, the current evidence does not support the hypothesis that exposure to artificially fluoridated water causes an increase in the risk for cancer in humans…Furthermore, studies of cancer rates in relation to variations in naturally occurring fluoride levels provide information on lifetime exposure and the absence of any detectable adverse effects of fluoride in these studies provides a high level of reassurance concerning safety.”

Recognising that any effect of fluoridated water on bone health could be important in public health terms, the MRC working group looked at the studies reviewed by the York team on hip fracture rates.  It concluded that the evidence to date suggested there was no effect.

The MRC group also considered suggestions of possible effects on other aspects of general health and concluded that there was no evidence to support any such association.  Click here for a pdf of the full MRC report.

1. Medical Research Council (2002): Working group report: Water fluoridation and health.