Tooth filling materials Dental amalgams & alternative materials

7. What is the environmental risk of the use of dental amalgams and alternative materials?

• 7.1 Does mercury released by the use of amalgams pose a risk to the environment ?
• 7.2 What is the environmental impact of alternative tooth filling materials?

7.1 Does mercury released by the use of amalgams pose a risk to the environment ?

Methylmercury can accumulate along the food chain © Aurileide Alves

Mercury occurs naturally in the environment in different chemical forms. Elemental mercury is the form used in dental amalgams. Forms more commonly found in nature are inorganic mercury and organic mercury.

Most of the mercury in the environment comes from natural sources such as emissions from volcanoes and soil erosion. However, over the last several centuries the levels of mercury in the environment have increased because of human activity. The widespread use of mercury and its compounds in a number of industries has resulted in larger releases of mercury into the atmosphere. Mercury is present in many cosmetics, medicinal products and medical devices including dental amalgam. Moreover, some mercury compounds – especially the organic form methylmercury – have accumulated in the aquatic food chain.

Mercury from dental amalgam can end up in the soil, atmosphere, surface water and ground water through several routes, including wastewater discharges from dental practices, and emissions to air and soil resulting from the cremation or burial of individuals with dental amalgam fillings.

The amount and the type of mercury released from dental clinics vary widely across the EU depending on levels of usage of dental amalgam and on how the wastewater is treated before it is discharged.

Wastewater released by dental clinics could increase the concentration of inorganic mercury in water bodies. The added risk for aquatic organisms is considered low.

Sludge from plants that treat such wastewater present a low risk for soil-dwelling organisms.

The main concern with emissions to water is related to the well-known potential of methylmercury – an organic form of mercury – to bioaccumulate (build up inside an organism) and biomagnify (build up along the food chain). All forms of mercury can accumulate in organisms, but methylmercury is taken up at a faster rate than other forms and bioaccumulates to a greater extent. As a result, methylmercury can become increasingly concentrated in aquatic organisms and result in high levels of exposure for fish-eating animals and for humans. Some of the inorganic mercury present in wastewater from dental clinics, for instance, will be converted into methylmercury before its release (up to 0.2% of the total mercury) but also once it reaches the environment. How quickly this conversion takes place depends on the characteristics of the ecosystem and is highly variable. Though estimates are available of the amounts of mercury released by the use and disposal of dental amalgams in the European Union, it is not possible to say what proportion of the risk associated with organic mercury present in the environment is due to releases from amalgams.

At present it is not possible to do a complete risk assessment to human health and the environment of the use of mercury in dental amalgam. In general, the added risk to aquatic and soil organisms from the contributions of dental mercury to the total mercury is considered to be low. Improvements in the treatment of waste water from dental clinics and amalgam waste has generally reduced this environmental exposure. Further studies are needed to assess the environmental effects of burial and cremation of bodies containing amalgam on soils. More...

7.2 What is the environmental impact of alternative tooth filling materials?

Some of the small organic molecules (monomers) that are used to make the resin base for alternative tooth filling materials are derived from well known chemicals – notably methacrylic acids and glycidyl ethers. Therefore, although data on the toxic effects of these new materials on animals and on the environment are not available, major effects can be extrapolated. For instance, exposures to high levels of a particular type of resin base are expected to cause skin irritation and, if inhaled, are likely to harm the liver and the nervous system.

The available information is too limited to assess the relative effects of dental amalgams and their alternatives on the environment. To assess the full environmental impact it would be necessary not only to determine the risk of environmental contamination and its harmful effects on environmental organisms, but also other environmental effects. More...