What is methylmercury
Methylmercury is formed from mercury by the action of bacteria that live in aquatic systems and in soils. Methylmercury production has been primarily attributed to different kinds of bacteria which do not need oxygen.
Mercury pollution is a major environmental issue, and mercury is considered one of the top ten chemicals of public health concern by the WHO. The problems caused by mercury are primarily a consequence of the formation and spread of methylmercury in aquatic ecosystems. Fish-eating predators including humans are exposed principally to methylmercury via the consumption of contaminated freshwater and marine fish.
Keep reading as we tell you more about Methylmercury, and Erik Björn, who VOTO supports in his research on the topic.
Erik Björn’s road from interested youth to Ph.D.
In secondary school, Erik chose to study an elective topic in environmental sciences with a large focus on chemistry. After the first class, the teacher said: “Bring your rubber boots next week, we will go out sampling on the lake!”. The student group brought their boots and collected samples and carried out different chemical measurements. Really without knowing exactly what to expect. At the end of the class the teacher said: “now go home, think, and try to explain your results. The one who comes up with the correct answer will get ice cream next week!”. No student managed to get the ice cream these first weeks.
But for Erik, the teacher’s approach turned out to be a starting shot that spurred curiosity and a desire to understand how the environment functions. Soon enough, the work in this secondary school class even included advanced environmental studies on mercury.
How methylmercury is formed
Part of the mercury will eventually reach oxygen-free environments, for example, in soils and sediment, where it can be converted into the more toxic form known as methylmercury. This process happens inside the cell of certain types of bacteria that thrive under oxygen-free conditions.
Natural and human caused oxygen free environments
Around the earth, oxygen-free environments are found naturally. These places are commonly called “dead zones” but they host organisms that can live without the presence of oxygen. A good example of this is the Dead Sea. Whilst some parts of the Baltic Sea are naturally oxygen free, these areas and/or depths that are impacted are changing due to some human activities. This transformation results in optimum conditions for the bacteria that cause formation of methylmercury, as they can live in low-oxygen waters.
In other words, the presence of oxygen in the water, would stop mercury from becoming methylmercury, which is more toxic and more easily absorbed by animals.
Mercury sources, natural and human
Mercury is spread globally to the environment via natural sources, such as volcanic eruptions. But also via human activities, predominantly coal combustion and small-scale gold mining. Since the industrial revolution, most of the spread of mercury has been related to humans. Mercury can be transported around the globe via the atmosphere and water.
In addition to the global sources, regional and local sources significantly impact mercury levels in local environments. One important example of local mercury sources is sediment contaminated by past industrial activities. Restoration to a pre-industrial level of such contaminated sites is critical to fulfilling several of Sweden’s national Environmental Quality Goals and Generation Goals.
Erik’s engagement in this field
There are two main reasons why Erik is engaged in this field. The curiosity and desire to understand processes in the environment that started in his secondary school studies are still there. He is also driven by the desire to contribute to something that is important. Working to reduce mercury pollution is one clear example.
How does methylmercury affect humans
Methylmercury is highly neurotoxic, and high exposure to it in the fetus can cause intellectual disabilities. Fetuses are particularly vulnerable to mercury exposure. Therefore, the Swedish National Food Administration has issued dietary advice for certain fish to pregnant women, those who are breastfeeding or are planning to have children
In addition to human health effects, mercury contamination also affects the ecosystem. In the Baltic Sea, mercury is ranked the second most severe biota contaminant by HELCOM
Mercury concentrations exceed sustainable environment target values in 95% of fish and virtually all mussel samples.
This project
The total number of contaminated sites is high in Sweden, especially along the Baltic Sea coast. There is a need for improved risk assessments of contaminated sediment, including understanding which factors control the formation of the highly toxic methylmercury. Mitigation actions must be prioritized for sites that constitute the most considerable risk.
Erik and his team will improve risk assessment of contaminated sediment along the Swedish Baltic Sea coast by identifying the critical factors controlling methylmercury formation in such environments.
First, Erik and his team will identify the processes that determine the availability of mercury that can be converted to methylmercury in each type of sediment. The second step is to then isolate the processes that control the activity, or productivity, of the bacteria responsible for methylmercury formation.
Voice of the Ocean (VOTO) is contributing to this project by providing fieldwork support and infrastructure. VOTO will supply vessels and personnel, which will extend the original fieldwork area to a substantial geographical range, encompasses a wider range of environmental conditions.
Based on this knowledge, Erik and his team will establish which of the two processes determines how much methylmercury is formed in the sediment.
These results will be necessary for improving the risk assessment of mercury-contaminated sediments, including predicting the effects of changes in the environment (e.g., due to eutrophication or climate change) and tailoring land use and water resource management in the vicinity of contaminated areas
The results will also be essential for optimizing remedial actions for contaminated sediments. From a broader perspective, the results will help ecosystems to recover more quickly from mercury pollution.
VOTO’s interest in this project
Ingestion of mercury has clear, long-term impacts on our health, and the Baltic Sea is renowned for its high mercury-levels. Understanding better what controls the spatial and temporal distribution of these toxic deposits, and the conversion rate to the methylmercury form, will help to guide future policy measures to both clean up and reduce our seas. Erik’s research is clearly motivated and his team is well set up to produce high impact results to the community. The contribution that VOTO is able to provide can substantially increase the geographical impact of the study and provides a more robust database for the team to analyse. We’re looking forward to seeing the results of our collaboration!