Releases of Mercury to Water

Mercury (Hg) is a naturally occurring metal that is used to manufacture products like fluorescent lights and dental amalgam. Mercury can be released directly to water from human activities like production of pulp and paper, processing of metals and from wastewater treatment plants.

Mercury can be transformed by microorganisms into methylmercury, a toxic form of mercury that is harmful to both humans and wildlife. Methylmercury can bioaccumulate in the food chain and enter our bodies through the ingestion of contaminated food. Mercury and its compounds are listed as toxic[1] according to the Canadian Environmental Protection Act, 1999 (CEPA 1999).

In 2011, the amount of Hg released to water was 351 kilograms (kg), an increase of 30%, or 81 kg, from 2010 and 8% (31 kg) lower than in 2003, the baseline year of this time series.

The increase in the amount of Hg released to water in 2011 from 2010 levels is attributable to one wastewater treatment plant, which released more mercury in its treated effluent in 2011 than in 2010, along with some mining facilities that reported Hg releases to the National Pollutant Release Inventory (NPRI) for the first time in 2011. The spike in 2005 is attributed to an unusually high amount reported to have been released by a single wastewater treatment plant.

Releases of mercury to water, Canada, 2003 to 2011

Releases of mercury to water, Canada, 2003 to 2011

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How this indicator was calculated

Note:  The indicator only includes the kilograms of Hg, including that released in substances containing Hg, reported in the National Pollutant Release Inventory (NPRI) based on the NPRI reporting criteria for releases of Hg and its compounds. As a result, the Hg releases represent only a portion of the releases of this toxic pollutant to water in Canada.
Source: Environment Canada (2013) National Pollutant Release Inventory Online Data Search - Facility Reported Data.

Sources of releases of mercury to water

Water, sewage and other systems--which includes wastewater treatment plants, water supply and irrigation systems, and steam and air-conditioning supply--released 49% (174 kg) of the total mercury released (351 kg) in 2011. Second were the pulp, paper and paperboard mills sector, representing 22.0% (77.1 kg) of the total. Slightly below the pulp, paper and paperboard mills, the metal ore mining industry ranked third, releasing 21.9% (77.0 kg) of the total.

Releases of mercury to water by source, Canada, 2011

Releases of mercury to water by source, Canada, 2011

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How this indicator was calculated

Note: The indicator only includes the kilograms of Hg, including that released in substances containing Hg, reported in the National Pollutant Release Inventory (NPRI) based on the NPRI reporting criteria for releases of Hg and its compounds. As a result, the Hg releases represent only a portion of the releases of this toxic pollutant to water in Canada. Categories follow the North American Industry Classification System (NAICS), except “Other Sources,” which represents a group of sources for which releases are not individually mentioned in this chart.
Source: Environment Canada (2013) National Pollutant Release Inventory Online Data Search - Facility Reported Data.

Releases of mercury to water by province and territory

Facilities in Ontario released the most mercury to water in 2011, representing 35% (121 kg) of the national total (351 kg). Mercury in Ontario came mainly from one wastewater treatment plant. Quebec facilities, namely metal ore mining facilities, were next, contributing 29% (101 kg) of the national total. Alberta ranked third, with 25% (89 kg) of the national release to water, originating mostly from a pulp, paper and paperboard mill and wastewater treatment plant.

Releases of mercury to water by province and territory*, Canada, 2011

Releases of mercury to water by province and territory*, Canada, 2011

View data for this chart
How this indicator was calculated

Note: The indicator only includes the kilograms of Hg, including that released in substances containing Hg, reported in the National Pollutant Release Inventory (NPRI) based on the NPRI reporting criteria for releases of Hg and its compounds. As a result, the Hg releases represent only a portion of the releases of this toxic pollutant to water in Canada.
* No facilities in Prince Edward Island, Yukon, the Northwest Territories or Nunavut reported releases of Hg to the NPRI for 2011.
Source: Environment Canada (2013) National Pollutant Release Inventory Online Data Search - Facility Reported Data.

Related indicators

Other information

[1] Section 64 of CEPA 1999 defines a substance as toxic if it is entering or may enter the environment in a quantity or concentration or under conditions that a) have or may have an immediate or long-term harmful effect on the environment or its biological diversity, b) constitute or may constitute a danger to the environment on which life depends, or c) constitute or may constitute a danger in Canada to human life or health.