In this report, “mercury” refers to the chemical element in all forms, in contrast to the Minamata Convention, which distinguishes “mercury” from “mercury compounds.” The report reflects progress made by the scientific community, national authorities and organisations in better understanding mercury cycling (Chapter 2), atmospheric mercury emissions (Chapter 3), mercury levels in air (Chapter 4), atmospheric transport and fate (Chapter 5), releases to water (Chapter 6), and the cycling and methylation of mercury in the aquatic environment (Chapter 8). In addition to updating GMA 2013, new sections are included on observed levels of mercury in biota (Chapter 7) and observed levels and trends of mercury in humans (Chapter 9).
Key findings of highest policy relevance include:
- A new global inventory of mercury emissions to air from anthropogenic sources in 2015 quantifies global emissions from 17 key sectors at about 2220 tonnes.
- Estimated global anthropogenic emissions of mercury to the atmosphere for 2015 are approximately 20% higher than they were in updated estimates for 2010.
- Emissions patterns in 2015 are very similar to those in 2010.
- Stationary combustion of fossil fuels and biomass is responsible for about 24% of the estimated global emissions, primarily from coal burning (21%).
- Human activities have increased total atmospheric mercury concentrations by about 450% above natural levels.
- Artisanal and small-scale gold mining introduced about 1220 tonnes of mercury into the terrestrial and freshwater environments in 2015, but this amount cannot be reliably separated between discharges to soils and releases to water.
- Natural production of methylmercury in the oceans and in some lakes is often not limited by the input of inorganic mercury.
- Reductions in mercury emissions and resulting declines in atmospheric concentrations may take time to show up as reductions of mercury concentrations in biota.
- Mercury loads in some aquatic foodwebs are at levels of concern for ecological and human health.
- All people are exposed to some amount of mercury.