Researchers design a new method to assess inconsistencies in mercury trade data for artisanal and small-scale gold mining


The Minamata Convention (MC) aims to restrict and limit trade in mercury, a highly toxic pollutant. While most countries involved in artisanal and small-scale gold mining (ASGM), the largest source of mercury pollution, are MC parties, its effectiveness has remained unclear. Researchers have now developed a new method for examining inconsistencies in global mercury trade data based on estimating and comparing mercury input from ASGM activities to total mercury available domestically.

Mercury (Hg) emissions are extremely toxic and can have widespread and long-term effects on human health. Hg can accumulate in soil and water bodies and enter the food web through staple crops such as rice and seafood. The largest source of Hg emissions is artisanal and small-scale gold mining (ASGM) industry, which involves the extraction of gold conducted by miners or companies with limited investment and production, and uses Hg to amalgamate gold ores.

In light of this, the Minamata Convention (MC) on Hg Control came into force in 2017 with the aim of ending the trade and domestic production of mercury. The MC asks its signatories to stop all trade in metallic Hg, to restrict the opening of new primary Hg mines, to stop the domestic production of Hg by 2032 and to stop the production and trade of products containing added Hg (such as Hg thermometers and vapor lamps) by 2020.

While 137 countries are currently party to the CM, its effectiveness remains uncertain. Inconsistencies often exist in global trade data and lead to difficulties in Hg monitoring and MC assessment. While the supply chains of the ASGM sector are severely restricted and dried up, the demand for Hg may not have diminished. This gap between supply and demand could lead to informal or illegal trade routes for Hg, such as mislabelling, smuggling and the black market.

In this context, an international team of researchers from Japan, Chile and Canada has now studied this question in depth. In their study published in the journal Resources, conservation and recycling, the team investigated the effect of MC on global Hg flux using a method to detect inconsistencies in mercury flux data. The study was led by Dr Yingchao Cheng of the National Institute for Environmental Studies (NIES) in Japan and involved contributions from Dr Kenichi Nakajima and Dr Keisuke Nansai of NIES, Professor Jacopo Seccatore of the University Adolfo Ibañez in Chile, from Professor. Marcello M. Veiga from the University of British Columbia, Canada, and Professor Masaki Takaoka from Kyoto University, Japan.

Their method of examining inconsistencies in global Hg trade data is based on estimating the input of Hg (the Hg that enters the fusion process and is lost with amalgam waste and combustion) from countries with ASGM activities and on the comparison of this quantity of intake to the total Hg available at the national level (apparent consumption of Hg). “By tracking Hg flows that have changed significantly after the MC came into effect, we can filter out trade routes of interest. This not only helps us see which trade activities have stopped or decreased, but puts also highlight the potentially illegal and informal flows of mercury use that emerged after MC,” says Dr. Cheng.

The study was carried out in 39 countries across four regions. The team identified inconsistencies in mercury trade statistics in Africa, Central and South America, and some Asian countries. Countries that are party to the MC have shown a reduction in metal Hg trade, and those with National Action Plans (NAPs) have demonstrated clear active measures to control the flow of Hg. “Our results underscore the importance to manage global flows of Hg hidden under ASGM activities to enforce good Hg management. We believe that the design and implementation of NAPs is an important step in this direction,” notes Dr Nakajima.

Asian countries, however, have lagged behind other regions in reducing Hg trade. in Hg have emerged since 2017.

Hg flow monitoring for the ASGM industry is essential for safe Hg management. While inconsistencies in trade data complicate the task, this new method helps to alleviate many of these issues and ensures that nations are spending their resources more effectively to target and expose high-risk trade routes and practices. Such advances in Hg management will reduce human exposure to mercury, making it easier for people to not only obtain clean gold, but also lead better lives.


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