Mercury in the environment

Mercury is a toxic substance that can have negative effects on our health and the environment.

Mercury production

Mercury pollution is produced by:

  • natural sources, such as volcanic activity and forest fires
  • human activities, such as the burning of coal, metal mining and waste incineration (all of which contribute to a large portion of mercury pollution)

Ontario has the highest level of mercury emissions into the air of all the Canadian provinces. In 2014, Ontario accounted for 28% of national emissions, at 1.2 tonnes. That same year, the US emitted 50 tonnes of mercury and in 2010, China emitted 537.9 tonnes of mercury.

Effects of mercury on the environment

Mercury released into the air can remain there for six to 12 months and wind can carry it long distances. This means that the mercury emitted to the air in one country can travel to another country. 40% of airborne mercury deposited in Ontario comes from current global emissions created by human activity. The United States and China form a part of the two largest source regions for airborne mercury originating from human activity that is deposited in Ontario.

Once mercury gets into the environment, it remains there for a long time. Micro-organisms found in water, wetland and soil, typically convert mercury to methylmercury, a highly toxic form. Methylmercury can build up in fish, shellfish and other animals that are higher up the food chain.

It is important that we understand where mercury pollution comes from and what its effects are, so that we can take appropriate action to reduce it. We also need to understand how the increase in extreme weather events as a result of climate change, food web changes related to invasive species and changes in water chemistry could increase mercury pollution in Ontario.

Read more about sources of mercury.

Health effects and how to reduce exposure

Mercury and our health

Mercury exposure can affect our health. It can cause damage to the nervous system and kidneys, and may also cause cancer.

Mercury can be found in several forms in the environment. Each form of mercury has different chemical properties that govern how soluble, reactive, and toxic it is.

Humans are mainly exposed to methylmercury, the most toxic form, through consumption of fish and seafood.

Minamata disease is a neurological syndrome caused by severe mercury poisoning, which includes symptoms such as:

  • the loss of full control of bodily movements
  • numbness in the hands and feet
  • general muscle weakness
  • narrowing of the field of vision
  • damage to hearing and speech

Protect yourself and our environment

Some steps you can take to reduce exposure to mercury and prevent mercury from entering the environment are to:

  • regularly check what amounts of Ontario fish are safe to eat in the Guide to Eating Ontario Fish
  • eat small fish over larger fish (a general rule)
  • eat fish such as perch or whitefish rather than predatory fish such as walleye, trout or pike
  • deposit your used but unbroken fluorescent light bulbs at your local municipality or retail outlet (since they contain a small amount of mercury)
    • if your light bulb is broken, call the municipality or the retail outlet to ask about collection options. Read about safe cleanup of mercury from a broken fluorescent bulb
  • dispose of mercury switches, such as the ones found in older cars, through the Switch Out program
  • dispose of your mercury thermostats through the Thermostat Recovery Program (formerly Switch the Stat)

Read more information on mercury, including mercury in the food chain and how it affects our health.

How Ontario is taking action on mercury

Progress so far

Ontario has made significant progress on reducing mercury emissions thanks to initiatives such as closing coal-fired power plants. Overall, mercury emissions in the province have been reduced by more than 90% since 1990. Today, the majority of mercury deposited in Ontario comes from sources outside our borders.

While provincial mercury emissions and ambient levels of mercury show long-term patterns of decline, Ontario will continue to do more, such as working with federal and other partners on improving environmental monitoring, modeling and science to better understand and minimize the presence and impacts of mercury on Ontario, and protect human health and the environment.

Mercury labelled as a toxic substance

Under Ontario’s Toxics Reduction Act, mercury must be reported. Manufacturing and mineral processing facilities are required to examine how and why they use or create prescribed toxic substances and consider opportunities for reduction.

The Toxics Environment Map provides information to the public on which facilities are using mercury, and any reduction options they are implementing.

Mercury in our water

Ontario is taking a number of actions to reduce mercury in our water, including:

  • closing coal-fired power plants and decreasing emissions from waste disposal and industrial sources, which lowered the levels of pollutants in Great Lakes fish. Recently however, some mercury levels in fish appear to be increasing.
  • providing Ontarians with advice on safe consumption of fish with our Guide to Eating Ontario Fish. This advice is based on data from our world-class fish monitoring program. We're always looking to update and improve on the science used to generate fish consumption advice, such as:
    • monitoring contaminants in fish by sampling various sizes and species
    • sampling new locations
    • taking part in research on topics like the impacts of multiple chemicals
  • designated mercury a Chemical of Concern in the Canada-Ontario Agreement on Great Lakes Water Quality and Ecosystem Health. As a result, governments will prioritize actions to ensure releases of the substance are reduced or eliminated within the Great Lakes Basin.
  • developing and implementing sediment management strategies in Great Lakes Areas of Concern where we have identified sediment mercury issues (such as St. Lawrence River (Cornwall) and St. Clair River).

Read our Water Quality in Ontario Reports.

Mercury in our air

Ontario is taking a number of actions to reduce mercury in our air, including:

  • reducing human mercury emissions into the air in Ontario by over 74% between 1990 and 2014, by decreasing emissions from closing coal fired power plants, waste disposal and industrial sources.
  • banning coal-fired electricity generation in the province in 2015 – a first in North America. Experts agree that getting rid of coal has made Ontario’s air cleaner and saved the province $4.4 billion per year in health, environmental and financial impacts.
  • regulating contaminants released to air by various sources, including local industrial and commercial facilities. The regulation limits exposure to substances that can affect human health and the environment. For more information, visit Rules on Air Quality and Pollution in Ontario.

Read our Air Quality in Ontario Reports.

Mercury in our soil

Ontario has developed and implemented regulations and standards for the clean up and redevelopment of brownfields (i.e. former industrial sites). These include a formal process to develop site-specific standards and requirements related to the identification of mercury in soil, ground water and sediment, and appropriate management measures to ensure any mercury concerns are identified and appropriately addressed.

Reducing national and global mercury emissions

A number of global actions to fight the release of mercury include: