In soil, water and sediment, inorganic mercury is converted to methylmercury. The main contamination sources are e.g. coal combustion, smelting plants, sewage sludge and waste dumps.
Mercury can be absorbed from the soil or via water. In the tobacco plant, mercury occurs in an inorganic form. Measurable levels of mercury are usually not found in tobacco.
Methylmercury accumulates in fish and high levels are found in large predatory fish.
Mercury is not classified as carcinogenic by WHO. The EPA has classified mercuric chloride and methylmercury as possible carcinogens.
Swedish snus and foodstuffs
100 g of fish and shellfish contain 13 micrograms of mercury, which corresponds to the content in 54 (x) 24 g cans of Swedish snus.
There are EU-wide limits for mercury in certain foods, including fish. (http://www.slv.se). Mercury was assigned a GOTHIATEK limit in 2016.