Despite international efforts to reduce mercury emission to the environment, mercury contamination of tuna is stubbornly high

Mercury, a potent neurotoxin, poses significant health risks to humans, particularly to developing fetuses, young children, and adults exposed to it. Methylmercury, the form found in fish, is highly absorbable and can accumulate in organisms up the food chain. Predatory fish such as tuna, swordfish, and halibut often contain high concentrations of mercury due to biomagnification. Such fish is the main mercury exposure source for humans and therefore a global health concern. A significant part of mercury pollution primarily stems from human activities like coal burning, waste combustion, and cement production. The Minamata Convention on Mercury, enacted in 2017 by 140 countries, aims to mitigate mercury emissions globally, yet its direct impact on methylmercury concentrations in marine environments remains unclear. Understanding the factors influencing mercury levels in tuna, especially amidst climate change, is crucial for policymakers to minimize human exposure to this toxic substance. Most anthropogenic mercury releases are estimated to have occurred during the past five centuries. While anthropogenic mercury emissions have decreased since the 1970s in regions like Europe and North America, they have surged in Asia since the 1980s.

An international team of researchers recently published a comprehensive study assessing mercury contamination trends in tuna to evaluate the effectiveness of the Minamata Convention. Over a decade-long effort, they analyzed nearly 3,000 tuna samples collected from the Pacific, Atlantic, and Indian Oceans between 1971 and 2022. 

Focusing on skipjack, bigeye, and yellowfin tuna—constituting 94% of the global tuna catch—they observed that mercury levels remained largely unchanged despite global emissions reductions. In certain Pacific regions, skipjack tuna even exhibited increased mercury levels, correlating with rising emissions from Asia.

The researchers attribute tuna mercury contamination to ocean mixing processes, which stir up mercury deposited in deep ocean layers over decades. This legacy mercury resurfaces due to ocean dynamics, resulting in a delayed response to emission changes. However, the study's simplistic model lacks spatial resolution and excludes aquatic food webs, hindering the examination of local and regional impacts on mercury biomagnification. These intricate processes, coupled with the ongoing effects of climate change on ocean temperatures, further complicate predictions.

Consequently, the researchers suggest that only the most ambitious reduction policies would lead to a tangible decrease in tuna mercury contamination, aligning with the Minamata Convention's objectives.

The original publication

Related Studies:

J.E. Sonke, H. Angot, Y. Zhang, A. Poulain, E. Björn, A. Schartup, Global Change Effects on Biogeochemical Mercury Cycling. Ambio,  52/5 (2023)  853−876. DOI: 10.1007/s13280-023-01855-y

A. Médieu, A. Lorrain, D. Point, Are Tunas Relevant Bioindicators of Mercury Concentrations in the Global Ocean? Ecotoxicology, 32 (2023) 994-1009. DOI: 10.1007/s10646-023-02679-y

Y. Zhang, L. Zhang, S. Cao, X. Liu, J. Jin, Y. Zhao, Improved Anthropogenic Mercury Emission Inventories for China from 1980 to 2020: Toward More Accurate Effectiveness Evaluation for the Minamata Convention. Environ. Sci. Technol., 57/23 (2023) 8660−8670. DOI: 10.1021/acs.est.3c01065

Y. Zhang, P. Zhang, Z. Song, S. Huang, T. Yuan, P. Wu, V. Shah, M. Liu, L. Chen, X. Wang, J. Zhou, Y. Agnan, An Updated Global Mercury Budget from a Coupled Atmosphere-Land-Ocean Model: 40% More Re-Emissions Buffer the Effect of Primary Emission Reductions. One Earth, 6/3 (2023) 316−325. DOI: 10.1016/j.oneear.2023.02.004

A. Médieu, D. Point, T. Itai, H. Angot, P.J. Buchanan, V. Allain, L. Fuller, S. Griffiths, D.P. Gillikin, J.E. Sonke, L.-E. Heimbürger-Boavida, M.-M. Desgranges, C.E. Menkes, D.J. Madigan, P. Brosset, O. Gauthier, A. Tagliabue, L. Bopp, A. Verheyden, A. Lorrain, Evidence That Pacific Tuna Mercury Levels Are Driven by Marine Methylmercury Production and Anthropogenic Inputs. Proc. Natl. Acad. Sci. U.S.A., 119/2 (2022) 8. DOI: 10.1073/pnas.2113032119

R.V. Barbosa, D. Point, A. Médieu, V. Allain, D.P. Gillikin, L.I.E. Couturier, J.-M. Munaron, F. Roupsard, A. Lorrain, Mercury Concentrations in Tuna Blood and Muscle Mirror Seawater Methylmercury in the Western and Central Pacific Ocean. Mar. Pollut. Bull., 180 (2022) No. 113801. DOI: 10.1016/j.marpolbul.2022.113801

J. Shi, Y. Chen, L. Xu, Y. Hong, M. Li, X. Fan, L. Yin, Y. Chen, C. Yang, G. Chen, T. Liu, X. Ji, J. Chen, Measurement report: Atmospheric mercury in a coastal city of Southeast China – inter-annual variations and influencing factors, Atmos. Chem. Phys., 22 (2022) 11187–11202, DOI: 10.5194/acp-22-11187-2022.

A. Médieu, D. Point, A. Receveur, O. Gauthier, V. Allain, H. Pethybridge, C.E. Menkes, D.P. Gillikin, A.T. Revill, C. Somes, J.  Collin, A. Lorrain, Stable Mercury Concentrations of Tropical Tuna in the South Western Pacific Ocean: An 18-Year Monitoring Study. Chemosphere, 263 (2021) No. 128024. DOI: 10.1016/j.chemosphere.2020.128024

C.-M. Tseng, S.-J. Ang, Y.-S. Chen, J.-C. Shiao, C.H. Lamborg, X. He, J.R. Reinfelder, Bluefin Tuna Reveal Global Patterns of Mercury Pollution and Bioavailability in the World’s Oceans. Proc. Natl. Acad. Sci. U. S. A. , 118/38 (2021) No. e2111205118. DOI: 10.1073/pnas.2111205118

Y. Zhang, S. Dutkiewicz, E.M. Sunderland, Impacts of Climate Change on Methylmercury Formation and Bioaccumulation in the 21st Century Ocean. One Earth, 4/2 (2021) 279−288. DOI: 10.1016/j.oneear.2021.01.005

D. Cossa, J. Knoery, M. Boye, N. Marusczak, B. Thomas, P. Courau, F. Sprovieri, Oceanic Mercury Concentrations on Both Sides of the Strait of Gibraltar Decreased between 1989 and 2012. Anthropocene, 29 (2020) No. 100230. DOI: 10.1016/j.ancene.2019.100230

C.X. Li, J.E. Sonke, G. Le Roux, N. Piotrowska, N. Van der Putten, S.J. Roberts, T. Daley, E. Rice, R. Gehrels, M. Enrico, D. Mauquoy, T.P. Roland, F. De Vleeschouwer, Unequal Anthropogenic Enrichment of Mercury in Earth’s Northern and Southern Hemispheres. ACS Earth Space Chem., 4/11 (2020) 2073−2081. DOI: 10.1021/acsearthspacechem.0c00220

D.G. Streets, H.M. Horowitz, Z. Lu, L. Levin, C.P. Thackray, E.M. Sunderland, Global and Regional Trends in Mercury Emissions and Concentrations, 2010−2015. Atmos. Environ., 201 (2019) 417−427. DOI: 10.1016/j.atmosenv.2018.12.031

Amina T. Schartup, Colin P. Thackray, Asif Qureshi, Clifton Dassuncao, Kyle Gillespie, Alex Hanke, Elsie M. Sunderland, Climate change and overfishing increase neurotoxicant in marine predators, Nature, 572 (2019) 648-650. DOI: 10.1038/s41586-019-1468-9

K. Marumoto, N. Suzuki, Y. Shibata, A. Takeuchi, A. Takami, N. Fukuzaki, K. Kawamoto, A. Mizohata, S. Kato, T. Yamamoto, J. Chen, T. Hattori, H. Nagasaka, M. Saito, Long-Term Observation of Atmospheric Speciated Mercury during 2007−2018 at Cape Hedo, Okinawa, Japan. Atmosphere, 2019, 10/7 (2019) 362. DOI: 10.3390/atmos10070362

H. Kim, K. Lee, D.-I. Lim, S.-I. Nam, S.H. Han, J. Kim, E. Lee, I.-S. Han, Y.K. Jin, Y. Zhang,  Increase in Anthropogenic Mercury in Marginal Sea Sediments of the Northwest Pacific Ocean. Sci. Total Environ., 654 (2019) 801−810. DOI: 10.1016/j.scitotenv.2018.11.076

L.S.P. Nguyen, G.-R. Sheu, D.-W. Lin, N.-H. Lin, Temporal Changes in Atmospheric Mercury Concentrations at a Background Mountain Site Downwind of the East Asia Continent in 2006−2016. Sci. Total Environ., 686 (2019) 1049−1056. DOI: 10.1016/j.scitotenv.2019.05.425

F. Wang, P.M. Outridge, X. Feng, B. Meng, L.-E. Heimbürger-Boavida, R.P. Mason, How Closely Do Mercury Trends in Fish and Other Aquatic Wildlife Track Those in the Atmosphere? - Implications for Evaluating the Effectiveness of the Minamata Convention. Sci. Total Environ., 674 (2019) 58−70. DOI: 10.1016/j.scitotenv.2019.04.101

P.M. Outridge, R.P. Mason, F. Wang, S. Guerrero, L.E. Heimbürger-Boavida, Updated Global and Oceanic Mercury Budgets for the United Nations Global Mercury Assessment 2018, Environ. Sci. Technol., 52/20 (2018) 11466−11477. DOI: 10.1021/acs.est.8b01246

H. Angot, N. Hoffman, A. Giang, C.P. Thackray, A.N. Hendricks, N.R. Urban, N.E. Selin, Global and Local Impacts of Delayed Mercury Mitigation Efforts. Environ. Sci. Technol., 52/22 (2018) 12968−12977. DOI: 10.1021/acs.est.8b04542

Y. Tang, S. Wang, Q. Wu, K. Liu, L. Wang, S. Li, W. Gao, L. Zhang, H. Zheng, Z. Li, J. Hao, Recent decrease trend of atmospheric mercury concentrations in East China: the influence of anthropogenic emissions, Atmos. Chem. Phys., 18 (2018) 8279–8291. DOI: 10.5194/acp-18-8279-2018.

B. Zheng, D. Tong, M. Li, F. Liu, C. Hong, G. Geng, H. Li, X. Li, L. Peng, J. Qi, L. Yan, Y. Zhang, H. Zhao, Y. Zheng, K. He, Q. Zhang, Trends in China’s Anthropogenic Emissions since 2010 as the Consequence of Clean Air Actions. Atmos. Chem. Phys., 18/19 (2018) 14095−14111. DOI: 10.5194/acp-18-14095-2018

P.E. Drevnick, B.A. Brooks, Mercury in Tunas and Blue Marlin in the North Pacific Ocean. Environ. Toxicol. Chem., 36/5 (2017) 1365−1374. DOI: 10.1002/etc.3757

D.G. Streets, H.M. Horowitz, D.J. Jacob, Z. Lu, L. Levin, A,F.H. ter Schure, E.M. Sunderland, Total Mercury Released to the Environment by Human Activities. Environ. Sci. Technol., 51/11 (2017) 5969−5977. DOI: 10.1021/acs.est.7b00451

F. Sprovieri, N. Pirrone, M. Bencardino, F. D’Amore, F. Carbone, S. Cinnirella, V. Mannarino, M. Landis, R. Ebinghaus, A. Weigelt, E.-G. Brunke, C. Labuschagne, L. Martin, J. Munthe, I. Wängberg, P. Artaxo, F. Morais, H. de M.J. Barbosa, J. Brito, E. Cairns, C. Barbante, M. de C. Diéguez, P.E. Garcia, A. Dommergue, H. Angot, O. Magand, H Skov, M. Horvat, J. Kotnik, K. Read, L.M. Neves, B.M. Gawlik, F. Sena, N. Mashyanov, V. Obolkin, D. Wip, X.B. Feng, H. Zhang, X. Fu, R. Ramachandran, D. Cossa, J. Knoery, N. Marusczak, M. Nerentorp, C. Norstrom, Atmospheric Mercury Concentrations Observed at Ground-Based Monitoring Sites Globally Distributed in the Framework of the GMOS Network. Atmos. Chem. Phys., 16/18 (2016) 11915−11935. DOI: 10.5194/acp-16-11915-2016

C.-S. Lee, M.E. Lutcavage, E. Chandler, D.J. Madigan, R.M. Cerrato, N.S. Fisher, Declining Mercury Concentrations in Bluefin Tuna Reflect Reduced Emissions to the North Atlantic Ocean. Environ. Sci. Technol., 50/23 (2016) 12825−12830. DOI: 10.1021/acs.est.6b04328

Jozef M. Pacyna, Oleg Travnikov, Francesco De Simone, Ian M. Hedgecock, Kyrre Sundseth, Elisabeth G. Pacyna, Frits Steenhuisen, Nicola Pirrone, John Munthe, and Karin Kindbom, Current and future levels of mercury atmospheric pollution on a global scale, Atmos. Chem. Phys., 16/19 (2016) 12495-12511. DOI: 10.5194/acp-16-12495-2016

D.C. Evers, S.E. Keane, N. Basu, D. Buck, Evaluating the Effectiveness of the Minamata Convention on Mercury: Principles and Recommendations for next Steps. Science of The Total Environment, 569−570 (2016) 888−903. DOI: 10.1016/j.scitotenv.2016.05.001

P.E. Drevnick, C.H. Lamborg, M.J. Horgan, Increase in Mercury in Pacific Yellowfin Tuna: Mercury in Yellowfin Tuna. Environ. Toxicol. Chem., 34/4 (2015) 931−934. DOI: 10.1002/etc.2883

H.M. Amos, J.E. Sonke, D. Obrist, N. Robins, N. Hagan, H.M. Horowitz, R.P. Mason, M. Witt, I.M. Hedgecock, E. Corbitt, E.M. Sunderland, Observational and Modeling Constraints on Global Anthropogenic Enrichment of Mercury. Environ. Sci. Technol., 49/7 (2015) 4036−4047. DOI: 10.1021/es5058665

C.H. Lamborg, C.R. Hammerschmidt, K.L. Bowman, G.J. Swarr, K.M. Munson, D.C. Ohnemus, P.J. Lam, L.-E. Heimbürger, M.J.A. Rijkenberg, M.A. Saito, A Global Ocean Inventory of Anthropogenic Mercury Based on Water Column Measurements. Nature, 512/7512 (2014) 65−68. DOI: 10.1038/nature13563

H.M. Amos, D.J. Jacob, D.G. Streets, E.M. Sunderland, Legacy Impacts of All-Time Anthropogenic Emissions on the Global Mercury Cycle. Global Biogeochem. Cycles, 27/2 (2013) 410−421. DOI: 10.1002/gbc.20040

R.P. Mason, A.L. Choi, W.F. Fitzgerald, C.R. Hammerschmidt, C.H. Lamborg, A.L. Soerensen, E.M. Sunderland, Mercury Biogeochemical Cycling in the Ocean and Policy Implications. Environ. Res., 119 (2012) 101−117. DOI: 10.1016/j.envres.2012.03.013

D.G. Streets, M.K. Devane, Z. Lu, T.C. Bond, E.M. Sunderland, D.J. Jacob, All-Time Releases of Mercury to the Atmosphere from Human Activities. Environ. Sci. Technol., 2011, 45/24 (2011)  10485−10491. DOI: 10.1021/es202765m

X.W. Fu, X.B. Feng, G. Zhang, W.H. Xu, X.D. Li, H. Yao, P. Liang, J. Li, J. Sommar, R.S. Yin, N. Liu, Mercury in the Marine Boundary Layer and Seawater of the South China Sea: Concentrations, Sea/Air Flux, and Implication for Land Outflow. J. Geophys. Res., 115/D6 (2010) No. D06303. DOI: 10.1029/2009JD012958

L.-E. Heimbürger, D. Cossa, J.-C. Marty, C. Migon, B. Averty, A. Dufour, J. Ras, Methyl Mercury Distributions in Relation to the Presence of Nano- and Picophytoplankton in an Oceanic Water Column (Ligurian Sea, North-Western Mediterranean). Geochim. Cosmochim. Acta, 74/19 (2010) 5549−5559. DOI: 10.1016/j.gca.2010.06.036

C.A. Choy, B.N. Popp, J.J. Kaneko, J.C. Drazen, The Influence of Depth on Mercury Levels in Pelagic Fishes and Their Prey. Proc. Natl. Acad. Sci. U. S. A. 106/33 (2009) 13865−13869. DOI: 10.1073/pnas.0900711106

E.M. Sunderland, D.P. Krabbenhoft, J.W. Moreau, S.A. Strode, W.M. Landing, Mercury Sources, Distribution, and Bioavailability in the North Pacific Ocean: Insights from Data and Models. Global Biogeochem. Cycles, 23/2 (2009) GB2010. DOI: 10.1029/2008GB003425

N.E. Selin, D.J. Jacob, R.M. Yantosca, S. Strode, L. Jaeglé, E.M. Sunderland, Global 3-D Land-Ocean-Atmosphere Model for Mercury: Present-Day versus Preindustrial Cycles and Anthropogenic Enrichment Factors for Deposition. Global Biogeochem. Cycles, 11/2 (2008) 13. DOI: 10.1029/2007GB003040

F.J.G. Laurier, R.P. Mason, G.A. Gill, L. Whalin, Mercury Distributions in the North Pacific Ocean
20 Years of Observations. Mar. Chem., 90/1 (2004) 3−19. DOI: 10.1016/j.marchem.2004.02.025

A.M.L. Kraepiel, K. Keller, H.B. Chin, E.G. Malcolm, F.M.M. Morel, Sources and Variations of Mercury in Tuna. Environ. Sci. Technol., 37/24 (2003) 5551−5558. DOI: 10.1021/es0340679

Atmospheric Mercury Network, AMNet

European Monitoring and Evaluation Program, EMEP

UN environment programme: Global mercury assessment

UN Environment Programme: Minamata Convention on Mercury

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