The Four New Groupings of ATH Substances - Substance-Specific Context

Mercury and its compounds

Mercury (and its compounds) has been on the NPRI substance list since the program's inception, at the 10-tonne manufacture, process and otherwise use reporting threshold. In the year 2000, the NPRI reporting threshold for mercury was reduced to five kilograms.

Several initiatives and agreements have been developed for both international and domestic action to reduce anthropogenic mercury releases. Mercury, which has been classified as a CEPA toxic (Schedule I of CEPA 1999), is included on the soon to be ratified United Nations Economic Commission for Europe Aarhus Protocol on Heavy Metals as a toxic with the potential for long-range transport through the atmosphere, and on the North American Commission for Environmental Cooperation (CEC)'s North American Regional Action Plan on Mercury.

While much of the atmospheric mercury deposited within Canadian territory comes from outside our borders, Canadian emissions are nevertheless important. Domestic initiatives, such as the Canada-wide Standards process, are necessary to ensure that Canada reduces its own releases of mercury into our environment.

Mercury and mercury compounds are a significant concern because they are known to cause environmental and health impacts. Everyone is exposed to some level of mercury in air, water and food. In the general population, the major sources of mercury exposure are through fish and shellfish consumption and from dental amalgam. Minor methyl-mercury exposure can occasionally occur from handling contaminated soil or drinking contaminated well water. Mercury bioaccumulates in humans and wildlife such as fish, loons and otters; as a result, governments have set guidelines on the quantity of fish we should consume. The main effects of human exposure to mercury are understood to be neurological and renal (kidney) disturbances. Chronic exposure to mercury, especially the organic form of methyl-mercury, can cause damage to the brain, spinal cord, kidneys, liver and developing fetus.

Anthropogenic Sources

A number of industrial processes contribute to mercury releases. The largest sources in Canada are:

• metal mining and smelting,
• waste incineration, and
• coal-fired power plants.

Other sources of mercury arise from:

• chloralkali plants,
• mineral ores processing,
• steel manufacturing,
• petroleum refining, and
• fossil fuel combustion.

As a result of the lowered reporting threshold for the year 2000, there is an apparent increase in mercury releases despite the reductions achieved through the initiatives mentioned above. This change is the result of the increased number of facilities that are now required to report mercury releases. As a consequence, the actual decrease in releases is not reflected in the NPRI data.

Mercury enters the environment during the life cycle of a range of consumer, medical and industrial products such as:

• fluorescent lamps,
• dental amalgams,
• fever thermometers,
• thermostats,
• electrical switches,
• pressure sensing devices, and
• blood pressure reading devices.

Canada-wide standards for fluorescent lamps and dental amalgam waste have been developed in order to reduce releases from these product sources.

Natural Sources

Mercury is an element and a natural part of our universe. It has been identified in the sun and found in meteorites and moon rocks. On the Earth, natural deposits of mercury are relatively rare and are generally found as cinnabar, a vermilion red ore that contains up to 86% mercury. Mercury may be released during volcanic eruptions and forest fires, and from a range of other natural sources such as fresh waters, oceans, plants, soils, and rocks. When mercury previously deposited from anthropogenic releases is re-emitted from the environment, it is not considered a natural source.