Evidence gathered over 60 years about adding fluoride to drinking water has failed to convince some people this major public health initiative is not only safe but helps to prevent tooth decay.
Myths about fluoridated water persist. These include fluoride isn’t natural, adding it to our water supplies doesn’t prevent tooth decay and it causes conditions ranging from cancer to Down syndrome.
Now the National Health and Medical Research Council (NHMRC) is in the process of updating its evidence on the impact of fluoridated water on human health since it last issued a statement on the topic in 2007.
Its draft findings and recommendations are clear cut:
NHMRC strongly recommends community water fluoridation as a safe, effective and ethical way to help reduce tooth decay across the population.
It came to its conclusion after analysing the evidence and issuing a technical report for those wanting more detail.
Here are four common myths the evidence says are wrong.
1. Fluoride isn’t natural
Fluoride is a naturally occurring substance found in rocks that leaches into groundwater; it’s also found in surface water. The natural level of fluoride in the water varies depending on the type of water (groundwater or surface) and the type of rocks and minerals it’s in contact with.
Fluoride is found in all natural water supplies at some concentration. Ocean water contains fluoride at around 1 part per million, about the same as levels of fluoridated drinking water in Australia.
There are many places in Australia where fluoride occurs naturally in the water supply at optimum levels to maintain good dental health. For example, both Portland and Port Fairy in Victoria have naturally occurring fluoride in their water at 0.7-1.0 parts per million.
The type of fluoride commonly found in many rocks and the source of the naturally occurring fluoride ion in water supplies is calcium fluoride.
The three main fluoride compounds generally used to fluoridate water are: sodium fluoride, hydrofluorosilicic acid (hexafluorosilicic acid) and sodium silicofluoride. All these fully mix (dissociate) in water, resulting in the availability of fluoride ions to prevent tooth decay.
So regardless of the original compound source, the end result is the same – fluoride ions in the water.
2. Fluoridated water doesn’t work
Evidence for water fluoridation dates back to US studies in the 1940s, where dental researchers noticed lower levels of tooth decay in areas with naturally occurring fluoride in the water supply.
This prompted a study involving the artificial fluoridation of water supplies to a large community, and comparing the tooth decay rates to a neighbouring community with no fluoride.
The trial had to be discontinued after six years because the benefits to the children in the fluoridated community were so obvious it was deemed unethical to not provide the benefits to all the children, and so the control community water supply was also fluoridated.
Further reading: How fluoride in water helps prevent tooth decay
Since then, consistently we see lower levels of tooth decay associated with water fluoridation, and the most recent evidence, from Australia and overseas, supports this.
The NHMRC review found children and teenagers who had lived in areas with water fluoridation had 26-44% fewer teeth or surfaces affected by decay, and adults had 27% less tooth decay.
A number of factors are likely to influence the variation across populations and countries, including diet, access to dental care, and the amount of tap water people drink.