Water fluoridation, the controlled addition of fluoride into the public water supply, is the tooth decay-preventing method with the lowest environmental footprint, according to a new study. Over a third of the world’s population has access to water fluoridation, and while there’s a lot of science documenting its effectiveness on teeth, there’s been no data on its environmental impact yet. But there’s good news.

Fluoride is a naturally occurring mineral that can help prevent tooth decay in the right amount. It’s present in varying amounts in water sources such as rivers, lakes, and even the ocean. Before teeth erupt, the fluoride taken in makes tooth enamel (the hard surface) stronger — and after they erupt, fluoride helps rebuild weakened tooth enamel and reverses decay.

Water fluoridation is used around the world on the principle that adding fluoride to drinking water can prevent cavities. In the US, almost 75% of the population has access to fluoridated water services, but the practice is exceedingly rare in most of Europe and Asia. Despite being a controversial topic, water fluoridation (at the advised level) isn’t toxic or harmful and has been shown to prevent tooth decay. The new study not only backs that up but also shows that the process is surprisingly green.

The impact of water fluoridation

Trinity College Dublin researchers collaborating with University College London quantified the environmental impact of water fluoridation for a single five-year-old child over a one-year period and compared this to the use of fluoride varnish and toothbrushing programs, which are implemented in schools around the world.

“As the climate crisis starts to worsen, we need to find ways of preventing disease to reduce the environmental impact of our health systems. This research clearly demonstrates the low carbon impact of water fluoridation as an effective prevention tool,” Brett Duane, lead author of the study and Trinity researcher, said in a statement.

To understand the environmental impact, the researchers carried out a life-cycle assessment by measuring the combined travel, weight, and amount of all products and processes involved in the three preventive programs: toothbrushing, fluoride varnish, and water fluoridation. The data was then used to calculate environmental outputs.

The results showed that water fluoridation had the lowest impact in all environmental categories studied (carbon footprint, amount of water used, and amount of land used), and the lowest disability-adjusted life years impact when compared to all other methods. In other words, not only was it the most eco-friendly approach, it was also the most efficient for protecting teeth. The study also found that water fluoridation had the greatest return on investment.

Considering cost effectiveness, environmental sustainability, and clinical effectiveness, the researchers argue that water fluoridation should be the preventive intervention of choice in much more places around the world. The study strengthens the case for countries to implement water fluoridation programs to reduce dental decay, especially in vulnerable groups, they said.

“Water fluoridation has been deemed safe by a number of different government bodies and provides significantly more benefit than any potential harm. This paper adds further positive data around water fluoridation by emphasizing its comparatively low environmental footprint compared to other established preventive programs,” the researchers wrote.

Worldwide, the Irish Republic and Singapore are the only countries that implement mandatory water fluoridation. The US also has a large-scale fluoridation program, as do Malaysia and Singapore. Several other country have a minority of their water supply fluoridated.

The study was published in the British Dental Journal.