Future trends in environmental mercury concentrations: implications for prevention strategies

Abstract

In their new paper, Bellanger and coauthors show substantial economic impacts to the EU from neurocognitive impairment associated with methylmercury (MeHg) exposures. The main source of MeHg exposure is seafood consumption, including many marine species harvested from the global oceans. Fish, birds and other wildlife are also susceptible to the impacts of MeHg and already exceed toxicological thresholds in vulnerable regions like the Arctic. Most future emissions scenarios project a growth or stabilization of anthropogenic mercury releases relative to present-day levels. At these emissions levels, inputs of mercury to ecosystems are expected to increase substantially in the future, in part due to growth in the legacy reservoirs of mercury in oceanic and terrestrial ecosystems. Seawater mercury concentration trajectories in areas such as the North Pacific Ocean that supply large quantities of marine fish to the global seafood market are projected to increase by more than 50% by 2050. Fish mercury levels and subsequent human and biological exposures are likely to also increase because production of MeHg in ocean ecosystems is driven by the supply of available inorganic mercury, among other factors. Analyses that only consider changes in primary anthropogenic emissions are likely to underestimate the severity of future deposition and concentration increases associated with growth in mercury reservoirs in the land and ocean. We therefore recommend that future policy analyses consider the fully coupled interactions among short and long-lived reservoirs of mercury in the atmosphere, ocean, and terrestrial ecosystems. Aggressive anthropogenic emission reductions are needed to reduce MeHg exposures and associated health impacts on humans and wildlife and protect the integrity of one of the last wild-food sources globally. In the near-term, public health advice on safe fish consumption choices such as smaller species, younger fish, and harvests from relatively unpolluted ecosystems is needed to minimize exposure risks.

Figure 1

Percent contribution of European anthropogenic emissions to total (wet plus dry) annual mercury deposition in the GEOS-Chem model (v. 9- 01- 03). Average for meteorological years 2004–2005.

Figure 2

Projected primary anthropogenic mercury emissions in 2050 (panel a) and resulting changes in atmospheric deposition relative to 2015 (panel b). Year 2050 mercury emissions scenarios are from Streets et al. [34] based on IPCC projections and adjusted biomass burning for consistency with Streets et al. [9]. These scenarios are bounded by AIB representing a “business-as-usual” scenario with rapid economic growth, while B2 represents a best-case scenario without mercury specific controls (environmental sustainability initiatives and widespread implementation of control technology). The legacy component of deposition is driven by reemissions of previously deposited anthropogenic mercury from oceanic and terrestrial ecosystems. Panel (b) is based on the modeling analysis of Amos et al. [8].