By far the biggest known disadvantage of amalgam fillings is the release of mercury into the environment.
As things currently stand, the main risk of mercury amalgam poisoning comes not from the fillings in your own teeth, but from other people’s old fillings that aren’t disposed of correctly.
This study states that dental amalgam is often the largest source of mercury in municipal wastewater, and it also contributes towards mercury pollution in the soil and air.
Most of this comes directly from dental clinics, but mercury can also end up in the environment through the burial or cremation of deceased people who had silver tooth fillings.
Why is this a problem?
Waste mercury enters the food chain through fish and seafood.
The elemental form of mercury used in teeth fillings is relatively stable. But if this mercury makes its way into the environment it can be converted into toxic methylmercury.
This easily enters the food chain, particularly through fish and seafood, and it’s in this way that humans become exposed to mercury in its most harmful form.
Banning dental amalgam is one way to stop this problem, but until that happens, the next best solution is to ensure it’s disposed of properly.
Some countries have implemented strict regulations for the disposal of dental amalgam. For instance, as of 1 January 2018, EU dentists must have amalgam waste collected by an authorised waste management company. Elsewhere, particularly in developing countries, amalgam can end up in general waste with no special treatment.
The Minamata Treaty of 2013 brought together 140 countries in a commitment to reduce the amount of mercury released into the environment from sources including dental amalgam, batteries and cosmetics.
This led to the introduction of new EU legislation in 2018 which, among other things, prohibits the use of dental amalgam in children under 15 and pregnant and breastfeeding women, unless there is a specific medical need for it.
Some campaigners have used this to fuel the argument that dental amalgam is unsafe to use, but it must be stressed that the legislation stems from environmental (rather than health) concerns.