The Knox report: a review of the epidemiological evidence on fluoridation of water and cancer (1985)

An expert Working Party convened by the UK Department of Health and Social Security and led by Professor George Knox reported in 1985 on its evaluation of analyses of cancer data available at that time .

Members of the Working Party included some of the country’s leading cancer epidemiology experts from the Institute of Cancer Research, supported by colleagues from the Medical Research Council, the University of Birmingham Cancer Epidemiology Research Unit and the Water Research Centre.  They reviewed around 110 published papers and commissioned re-analyses of some of the most important data and results.

Naturally occurring and added fluoride are not linked to cancer, and fluoridation of drinking water is safe

In their report, Professor Knox and his team concluded: “We have found nothing in any of the major classes of epidemiological evidence which could lead us to conclude that either fluoride occurring naturally in water, or fluoride added to water supplies, is capable of inducing cancer, or of increasing the mortality from cancer.

“This statement applies both to cancer as a whole and to cancer at a large number of specific sites.  In this we concur with the great majority of scientific investigators and commentators in this field.  The only contrary conclusions are in our view attributable to errors in data, errors in analytical technique, and errors in scientific logic.

“The evidence permits us to comment positively on the safety of fluoridated water in this respect. The absence of demonstrable effects on cancer rates in the face of long-term exposures to naturally elevated levels of fluoride in water; the absence of any demonstrable effect on cancer rates following the artificial fluoridation of water supplies; the large human populations observed; the consistency of the findings from many different sources of data in many different countries; lead us to conclude that in this respect the fluoridation of drinking water is safe.”

They added: “The routine monitoring of public health has been an important feature of many fluoridation programmes, and has contributed to the confidence with which we can assert the safety of fluoridation with respect to cancer.  We recommend that such monitoring should continue.”

1. Knox G: Fluoridation of water and cancer: a review of the epidemiological evidence. HMSO. (1985)


“It is unrealistic in many fields to expect a study carried out in the 1970s necessarily to conform to the methodological standards judged appropriate in the 2000s.  Also, the quality of research published on the web and in other non-peer reviewed sources is unlikely to match that of research published in the standard scientific journals, and therefore generally carries little weight.”


“New studies are needed to investigate the bioavailability and absorption of fluoride from naturally fluoridated and artificially fluoridated drinking water, looking also at the influence of water hardness. This is particularly important because if the bioavailability is the same, many of the findings relating to natural fluoride can also be related to artificial fluoridation.”

Note: Following publication of the MRC report, the Department of Health commissioned a study to compare the bioavailability of naturally occurring and added fluoride in the water supply.
Click here to view a summary of results.