Mercury-containing dental amalgam, used to fill cavities, is set to be phased out globally by 2034 to reduce human exposure to the toxic heavy metal. The decision was taken by the 153 parties to the Minamata Convention on Mercury at the Sixth Conference of Parties (COP-6) that took place last week in Geneva.

While 50 countries, including the European Union’s 27 member states, have already phased out dental amalgam, typically a mix of liquid mercury and silver, many countries, including the United States, continue to allow the use of the amalgam in dental procedures. Mercury is a highly toxic element and exposure to even small quantities of it can cause developmental delays in children as well as affect the nervous, digestive and immune systems, according to the World Health Organization (WHO).

“Use of dental amalgam poses several challenges, including exposure to mercury of dental practitioners, also the cost challenges related to disposal of dental amalgam, and also mercury emissions from crematoria,” said Monika Stankiewicz, Executive Secretary of the Minamata Convention, a global treaty adopted in 2013 to protect both humans and the environment from the adverse effects of mercury. Alternatives to the amalgam include composite resin, glass ionomer, ceramics and gold.

Mercury in artisanal mining and cosmetics the focus of other COP6 initiatives

Stankiewicz spoke at a press conference on Monday, discussing the outcomes of COP6. Parties to the Convention also agreed to step up efforts to address mercury exposures in artisanal gold mining. They will also collaborate to reduce the availability of cosmetics with mercury. While such cosmetics are banned, they are available online, experts said. This year’s COP drew some 1000 in-person participants to Geneva as well as several thousand online.

The convention, named after the Japanese city of Minamata, alludes to the neurological disease that drew global attention to the issue in 1956, when several thousand Japanese residents of the city were diagnosed with symptoms of severe mercury poisoning, due to their consumption of fish and shellfish exposed to high methylmercury levels in wastewater emissions from a nearby chemical plant.

The Convention, adopted in 2013, came into force in 2017. Since the first Conference of the Parties in 2017, more restrictions on mercury use have progressively been added, based on the support and willingness of countries.

“The issue of dental amalgam has been discussed also in the past two COPs,” Stankiewicz said. “So, it’s a third COP that the parties have been negotiating the matter. And then each of the COPs, certain measures were adopted to dramatically reduce the use of dental amalgam. So, the convention already includes a number of measures that restrict the use.”

The decision to phase out dental amalgam worldwide received strong support from US Secretary of Health and Human Services Robert F Kennedy Jr, an environmental lawyer, who appeared before the COP’s opening session on 3 November via video link.

However, he also criticised the continued use of thiomersal, a preservative used in some vaccines that contains a derivative of mercury called ethylmercury.

“Why do we hold a double standard for mercury? Why do we call it dangerous in batteries, in over-the-counter medications, and makeup – but acceptable in vaccines and dental fillings,” Kennedy asked as the discussions kicked off on November 3. While the US FDA has recently banned the use of thiomersal, the WHO has continued to call it safe to use.

With regards to the phase out of amalgam, some countries at this year’s COP, including a bloc of African states, called for speeding up the timeline to ban the production, import and export of amalgam by 2030 – arguing that they lacked facilities to safely manage mercury waste. But they were met with resistance from other countries, including the United Kingdom and India, which considered the date as too ambitious. The UK allows for amalgam although its use is banned for children under the age of 15, pregnant or breastfeeding women.

Gold mining – a ‘just transition’

Countries also discussed new measures to phase out mercury use in artisanal and small-scale gold mining – an occupation that continues to draw poor communities in developing countries, given the high price of gold.

The discussions took place just before the UN climate change conference (COP30) convened Monday (10-21 November) in the Amazonian city of Belém – one of the world’s regions where artisanal and small-scale gold mining exposes communities and the sensitive rain forest that they inhabit to dangerous levels of mercury emissions.

Artisanal gold extraction involves mixing mercury with crushed rocks of gold ore, then heating the amalgam to vaporize the mercury, leaving the gold behind. The process exposes workers, including women and children, to severe health risks through inhalation of mercury vapor, as well as releasing methylmercury into the environment, which can bioaccumulate in the food chain. 

“The COP strengthened its commitment to addressing the challenges of artisanal and small-scale gold mining, otherwise referred to as ASGM, through acknowledging the need for a just transition for miners. So, this is supporting fair, inclusive and sustainable alternatives,” said Brenda Koekkoek, Senior Coordination Officer of the Minamata Convention.

While no specific decision was taken, parties to the convention agreed to support new technologies and other measures to phase out the use of mercury and related toxic exposures. This pathway, conference participants stressed, is preferable to banning ASGM altogether, which would turn the miners into criminals.

“This [discussion] does empower countries who have the mandatory obligation to develop national action plans under the Convention to consider measures of how they would look at the just transition (away from mercury use in artisanal mining) in their national action plans,” Koekkoek added.

WHO to help draw up a strategy for mercury phase-out in public health systems

For the next COP, scheduled in 2027, the WHO has been invited to prepare a strategy on mercury phase-out in cosmetics. This strategy would focus on advice to countries about measures to prevent the use, manufacture, import and export of mercury-contaminated cosmetics. “It could be then used domestically by parties, and also on that basis, prepare appropriate documentation to our COP in 2027,” Stankiewicz said.

WHO has been a longtime observer to the Convention, and historically active in measures such as phasing out mercury-containing thermometers and other medical devices used by health systems.

The parties to the convention also agreed to look more closely at the global mercury supply chain, sharing relevant information. An expert group has been constituted that would look more closely at the manufacture, use and trade in specific mercury compounds, as compared to elemental mercury, which has largely been the focus to date.

Image Credits: Unsplash/Navy Medicine, European Network for Environmental Medicine, Planet Gold .