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Improving Mercury Monitoring in the Marine Environment and in Seafood

Scientists are trained on sampling techniques to monitor contaminants in fish. (Photo: R. Cassi/IAEA)

The World Health Organisation (WHO) rates mercury as one of the top ten chemicals of major public concern, due in part to its persistence and tendency to accumulate in the environment and in organisms. In high concentrations, it can have devastating health effects with impacts on the brain and nervous system. With global seafood consumption nearly doubling in the past three decades and over 1 billion people around the globe relying predominantly on marine food sources for their protein intake, monitoring of mercury ocean concentrations is critical.

As a sign of the importance of addressing the issue of mercury in the environment, the Minamata Convention on Mercury was adopted by 128 countries in 2013. The Convention prohibits numerous mercury-emitting processes and products and calls for limits to mercury emissions. Once the convention is ratified, Member States will be required to establish and strengthen environmental mercury monitoring efforts. The IAEA Environment Laboratories have long worked with Member States to develop detection techniques and improve monitoring of mercury in the marine environment, as well as study the transfer of this toxic pollutant up the food chain.

Released through industrial activities, coal power plants and artisanal and small-scale gold mining, mercury makes its way into the marine environment through various pathways such as rainfall and surface water. “Bacteria in the water column and sediment change mercury to methylmercury, an extremely toxic element, which can have serious negative effects on organisms and tends to bioaccumulate as it is transferred up the food chain” said Dr Emiliya Vasileva, Research Scientist in the Marine Environmental Studies Laboratory of the IAEA Environment Laboratories.

Concentration levels of methylmercury in fish increase exponentially higher up in the food chain. In its 2013 report on mercury in the environment, UNEP listed red tuna as having a median methylmercury concentration of 470 µg/kg and other top predators like sharks and marlin up to 800 µg/kg. The concentrations in individual fish can vary based on where they lived, and can in some cases be even higher.

The Marine Environmental Studies Laboratory (MESL) of the IAEA Environment Laboratories in Monaco has been working for many years to increase Member States’ capabilities to detect mercury and various mercury species like methylmercury and study transfer processes up the food chain. This includes the development, validation and distribution of recommended analytical procedures for the determination of mercury and methyl mercury in marine environmental samples, as well as the organisation of training courses and proficiency tests on the determination of mercury and methyl mercury in environmental samples.

Furthermore, to help with such analyses, the IAEA Environment Laboratories produce reference materials, which include samples of sediment, fish and biota. These can be used as part of quality control procedures during analyses, to validate analytical methods and to establish traceability to internationally agreed references. Reference materials play an important role in increasing the accuracy and certainty of environmental mercury measurements.

A scientist preparing a sample for analysis. (Photo: R. Cassi/IAEA)