Mercury is a naturally occurring element that is also present in the environment as a result of human activities. Water bodies can be contaminated with mercury from industrial sources, such as pulp and paper mills, and from the soil when large reservoirs are created by hydro-electric dams. Methyl mercury is considered the most toxic form of mercury to human health and is formed when bacteria interact with mercury present in water and plants. Methyl mercury accumulates up the food chain, and predatory fish generally represent the main source of exposure from the diet. Very high prenatal exposure to methyl mercury may have adverse effects on child neurodevelopment based on evidence from historical methyl mercury poisoning incidents following consumption of contaminated food (bread in Iraq, fish in Minamata Bay Japan) and epidemiological studies of populations with high dietary methyl mercury exposure from consumption of marine mammals or large predatory fish. Health-based guideline values for methyl mercury in hair and blood have been established to monitor individual and population-level exposure, and to establish maximum levels (MLs) for mercury in retail fish. These guideline values help Canadians maintain their exposure to methyl mercury within safe levels. Surveys of total and methyl mercury in retail fish are conducted, as needed, to assess dietary exposure to mercury and ensure the continued applicability of the Canadian MLs and consumption advice for mercury in fish sold in Canada species. If a potential concern to human health is identified, immediate and appropriate action will be taken.
Learn about the Canadian Total Diet Study (https://www.canada.ca/en/health-canada/services/food-nutrition/food-nutrition-surveillance/canadian-total-diet-study.html)
Search through Health Canada's food contaminant data on CANLINE (https://open.canada.ca/data/en/dataset/01c12f93-d14c-4005-b671-e40030a3aa2c)