Content of the opinion
Dental amalgam, an alloy of mercury and silver, has been in use for over 150 years for the treatment of dental cavities due to its excellent mechanical properties and durability. Dental amalgam is the second largest use of mercury in the EU, after its use in the chlor-alkali industry. Mercury emissions from dental cabinets are also subject to EU water legislation, as mercury is classified as a priority hazardous substance according to the Water Framework Directive.
The aim of this new Opinion is to evaluate, in light of the new information available since 2008, if a modification of the scientific assessment of the environmental risks and indirect health effects of mercury in dental amalgam, is necessary.
The potential concentration of mercury in surface water has been estimated considering three possible scenarios (worst, average and best case scenario) and compared with the environmental quality standards as set up in the EU legislation in order to identify concentrations which might exceed these standards and may indicate risk to the aquatic ecosystem.
Worst and best case represent extreme scenarios but likely to occur in Europe, at least at local level.
Another main concern from the contribution of dental amalgam to the total anthropogenic emissions of mercury into the environment is related to the potential of this metal to bioaccumulate and biomagnify through the food chain, resulting in high levels of exposure for top predators (including humans) and associated risk for secondary poisoning.
Only for the worst case scenario, under extreme local conditions (maximal dentist density, maximal mercury use, absence of separator devices), SCHER concludes that mercury concentration might be above the safe threshold established by the European legislation with a potential consequential risk to the aquatic ecosystem, bioaccumulation and the risk for secondary poisoning in humans. This risk depends, however, on the methylation rate of inorganic mercury which may differ with exposure conditions.
SCHER suggests that compliance with the Water Framework Directive’s threshold for mercury would contribute to the safeguard of the ecosystem and also contribute to the prevention of human health effects.
With regard to Hg-free alternatives for dental use, SCHER concluded that information available does not allow a sound environmental risk assessment to be performed.