Assessing the risk posed by a substance to human health can be a tremendous scientific challenge. Gathering scientifically sound data on exposure, evaluating all possible adverse outcomes and the levels needed to reach such effects, assessing the uncertainties surrounding the issue, can take years, decades, even generations. Once all that work is done, however, the process is usually fairly simple. A simple comparison of what is believed to be a safe level and what is believed to be out there does the job.
In many cases, the decisions that follow the conclusions reached by the risk assessment are even more challenging than the assessment itself. This is commonly the case when more than one risk are to be compared at once and against each other, or when the costs and benefits of a certain decision need to be weighed. In these cases, the lines between scientific, political and moral principles start getting blurred.
Probably no human health issue could better exemplify this than Water Fluoridation, or the addition of fluoride to the drinking water supply as a preventive treatment against tooth decay.
In early the 20th century, tooth decay was a major health issue with nearly every individual across most age groups in the United States presenting the disease. (Centers for Disease Control, 1999). No effective measures were available at the time. Those “treated” for the disease by tooth extraction, would soon develop gastrointestinal problems due to poor mastication. Those who didn’t get the treatment, commonly developed serious oral infections and in many cases died of septicemia (Selwitz et al.).
Epidemiological studies in the 30’s and 40’s uncovered a correlation between a dental condition known as “Colorado Brown Stain” and lower incidence of dental caries. Patients with Colorado Brown Stain were usually restricted to areas of naturally high levels of fluoride in water. The teeth of these individuals, although were stained with yellow/brown spots, presented significantly lower numbers of caries. (Ripa, 1993)
The Colorado Brown Stain would later been known as dental fluorosis and its underlying causes would be linked to the reaction of the hydroxyapatite in the teeth enamel with the fluoride on the water to form a harder and more pH-resistant fluoride-rich variant (Aoba and Fejerskov, 2002).
A few years after that discovery, in 1945 the city of Grand Rapids, Michigan, would become the first city in the world to supplement their municipal water supply with fluoride salts. Many US cities followed shortly. The phenomena would make it across the boarder in only one year, and in 1946 Brantford, ON would become the first Canadian city to adopt this strategy.
Since then thousands of cities across the world have opted for this health policy, and currently 16,412 US cities, serving 62.2% of the US population provide some sort of water fluoridation (Bailey W et al., 2008). Other countries suchas United Kingdom, Ireland, Australia and, as mentioned, Canada join the US on this effeort. Some other European countries such as Germany or Finland, implemented water fluoridation for a number of years, but eventually ceased their programmes.
In 1999, The Centre for Control Deaseases in the United Sates, named Water Fluoridation one of the Ten Great Public Health Achievements in the 20th Century (Centers for Disease Control, 1999). The controversy surrounding the real effectiveness, safety and even morality of the policy still continues and it could also be placed among the most contentious public health topics of the century.
During the next weeks, I will explore the different aspects of this controversial issue. From the more scientific aspects such as the physiological and microbiological processes involved in tooth decay and tooth re-mineralization, the toxicological effects of fluoride, or the exposure levels (both from natural and human sources) to the more socio-political and moral views around the topic.
Aoba, T., Fejerskov, O., 2002. Dental Fluorosis: Chemistry and Biology. Critical Reviews in Oral Biology & Medicine 13, 155-170.
Bailey W, Duchon K, Barker L, W., M., 2008. Populations receiving optimally fluoridated public drinking water – United States, 1992–2006. Morbidity and Mortality Weekly Reports 57, 737–741
Centers for Disease Control, 1999. Achievements in Public Health, 1990-1999: fluoridation of drinking water to prevent dental caries. Morbidity and Mortality Weekly Reports, 933-940.
Ripa, L.W., 1993. A half-century of community water fluoridation in the United States: review and commentary. Journal of public health dentistry 53, 17-44.
Selwitz, R.H., Ismail, A.I., Pitts, N.B., Dental caries. The Lancet 369, 51-59.