Risk management strategy for products containing mercury: chapter 3


Mercury is a naturally occurring element that can be released to the atmosphere from natural sources or through human activities. Once mercury enters water bodies it can be converted through biological activity to a highly toxic, organic compound called methylmercury. Fish, aquatic mammals and waterfowl can absorb and build up methylmercury as they feed in affected water bodies.

3.1 Harmful Effects on Human Life or Health

In most chemical forms, mercury is a neurotoxin which can cause damage to the brain, central nervous system, kidneys and lungs. The severity of mercury's toxic effects depends on the form and concentration of mercury and the route of exposure.2

Methylmercury, one of the most toxic mercury compounds, readily enters the brain. In adults high levels of exposure to methylmercury can lead to health effects such as personality changes, tremors, changes in vision, deafness, loss of muscle coordination and sensation, memory loss, intellectual impairment, and in extreme cases even death.3

Unborn children may receive some of the maternal mercury body burden as mercury can cross the placental barrier.4 Children can suffer neurodevelopmental problems due to exposure while in the womb. Affected children may exhibit reduced coordination and growth, lower intelligence, and seizures. A recent study indicates that as many as 60,000 babies born in the United States each year could be at risk of neurodevelopmental delays due to in-utero exposure to methylmercury.5

3.2 Harmful Effects on the Environment or its Biological Diversity

The long-term effects of mercury on whole ecosystems are unclear, the survival of some affected populations and overall biodiversity could be at risk. For example, 20 milligrams of mercury, the amount contained in many common products, mixed evenly in a body of freshwater, could contaminate as much as 770 000 litres beyond safe limits for the protection of aquatic life (0.026 micrograms of mercury per litre of water).6

Mercury converted to methylmercury through biological activity which is a fat-soluble organic compound that can accumulate in living organisms7 and biomagnifies up the food chain.8 Piscivorous (fish eating) predators such as loons, merganser ducks, osprey, eagles, herons, and kingfishers are examples of species that can have high concentrations of methylmercury. Wildlife exposed to high levels of methylmercury is at risk of harm. Depending on level of exposure, effects can include slower growth, reproductive failure, the development of abnormal behaviors that can affect survival techniques9 and mortality.

2 Health Canada - Mercury and Human Health Fact Sheet, September 2004

3 Health Canada - Mercury and Human Health Fact Sheet, September 2004

4 WHO - Elemental Mercury and Inorganic Mercury: Human Health Aspects.

5 2003 US National Academy of Sciences - Toxicological Effects of Methylmercury (2000)

6 Canadian Council of Ministers of the Environment (CCME) - Canadian Water Quality Guidelines for the Protection of Aquatic Life.

7 Arctic Monitoring Assessment Programme - Mercury Fact Sheet, January 2005

8 UNEP - Global Mercury Assessment, 2003

9 U.S. EPA - Mercury Study Report to Congress, 1997

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