Mercury
Why is mercury so harmful to humans? What do we need to do to safeguard human health from mercury poisoning? And where does the Minamata Convention on Mercury come into all of this?
How does mercury get into lakes?
Mercury is emitted into the environment from many natural and human-made sources. Industrial processes can release mercury as a by-product into the atmosphere. For example, a coal-burning power plant could release mercury into the air in its fumes. Mercury can travel long distances in the atmosphere—even across oceans and continents—before finally settling on lakes and rivers.
How does mercury affect human health?
Methylmercury is the organic form of mercury that is harmful to humans and many other animals. It has no known function in our bodies.
Once mercury enters bodies of water, bacteria convert it into this toxic form, which is then carried up the food web into top predator species like sport fishes. When people eat those fishes, they also ingest the methylmercury contained in them. Once the mercury is in our bodies, it is not easily excreted, meaning that it accumulates over time.
Mercury poisoning, or Minamata disease (named after the Japanese town in which it was first documented), comprises a wide range of physical and mental symptoms. These symptoms can include hair loss, muscle weakness/paralysis, organ damage, loss of senses, depression, and even death.
What has IISD-ELA taught us about the impact of mercury on freshwater lakes?
Fish are an important source of protein for humans—many people around the world depend on them. Even so, given the risks, they should be eaten in moderation. Real impacts can only be made, however, by reducing the amount of mercury that enters ecosystems, and ultimately humans.
Systems can recover when mercury stops being added. Just ask the scientists at IISD Experimental Lakes Area who, in a highly controlled experiment, intentionally added small amounts of traceable mercury to a lake to see how it moved through the ecosystem and food web. Predictably, the amount of mercury found in the fish increased.
When they stopped adding mercury, the amount found in fish decreased, suggesting that reducing the amount of mercury that enters the atmosphere may have a significant impact on the amount of methylmercury that ends up in fish (and, therefore, humans). It should be noted, however, that the response time will vary considerably between lakes.
What is the Minamata Convention on Mercury?
The Minamata Convention on Mercury is an international treaty designed to protect humans from mercury poisoning by reducing the amount of mercury released into the environment. Now ratified by 75 countries, it bans new mercury mines, limits products containing mercury, and controls mercury release into air, land, and water.
What needs to happen now?
First, given that this is a borderless problem (mercury emitted from a power plant in Asia can end up in an American lake), we need all countries to ratify the treaty so the international community can get to work on implementation.
As with all international efforts, making mercury history will require regional actions.
In Canada, for example, reducing mercury emissions means action at the federal and provincial levels. The federal government must show leadership in regulating activities, such as hydroelectric reservoir development mining and logging, that release mercury into the air, land, or water. Ontario’s recent ban on coal-fired electricity generation, a major mercury contributor, demonstrates the potential that the provinces have to take action to curb mercury release.
It should come down to all of us, too. While governments and industries move to phase out products containing mercury, public awareness campaigns should inform people of the dangers to the environment and the safe disposal of consumer products.
