Also known as trace elements,and toxic metals.
What are they?
Heavy metals are metallic elements and metalloids with high density relative to water and can be toxic or poisonous at low concentrations.
Low-level exposure to heavy metals through consumption or contact can induce organ damage, and some are known or suspected human carcinogens. Certain metals, including copper and chromium, are essential for body function at certain concentrations but quickly become toxic beyond a biological threshold.
Examples of heavy metals that can be found in water are: lead, arsenic, mercury, thallium, cadmium, and chromium.
Are heavy metals in water regulated in Alberta?
Yes, heavy metals are regulated in Alberta in several ways. The Environmental Quality Guidelines for Alberta Surface Waters identify threshold levels of heavy metals for protection of aquatic life and for agricultural uses.
There are provincial and federal regulations concerning the correct disposal and management of industrial wastes, electronic waste, and mine tailings because these can contribute heavy metals to the water system. Regulations for reclamation of decommissioned mine sites also relate to heavy metals as these sites can be significant sources of heavy metal contamination in groundwater and surface water over the long term.
Are heavy metals in my water?
Heavy metals can be dissolved in water. However, in the Bow River Basin, heavy metals (if present) are found in low concentrations.
Water treatment generally removes metals from drinking water, but some risks can exist from old pipe networks. Read more about lead in drinking water on the page "Do you feel mis-LEAD by your water?"
What are the impacts on human health?
Heavy metals can be highly toxic. When they are present in water at higher concentrations they can cause serious damage to human health. For example, high levels of arsenic are found in groundwater in some areas of British Columbia, China, and the United States. In Bangladesh, the amount of arsenic in the drinking water has resulted in a long-standing health crisis.
Lead is one example of a heavy metal that occurs naturally in rocks and soil, but is much more common in human-made materials. Lead is found in various products including paint, dinnerware and food items (almost all food has some traces of lead). In the past, water pipes were made with lead – and lead was also added to gasoline. We are exposed to lead every day and almost none of that exposure comes from the water we drink (drinking water quality regulations require less than 0.01 mg/litre of lead).
In higher quantities, lead is toxic to humans. It can accumulate in the body, including in developing bones. In children, high levels of lead in drinking water leading to blood lead levels between 11 and 30 micro-grams per decalitre have resulted in slower cognitive abilities and learning, and altered behaviour. Higher lead levels in water can also cause skin disorders and hair loss.
What are the impacts on the environment?
Heavy metals can also be toxic for animals. Where there are higher concentrations of heavy metals in water, aquatic life can experience biological difficulties. In Canada there is a federal standard of thresholds for acceptable concentrations of various heavy metals called the Canadian Water Quality Guidelines for the Protection of Aquatic Life (Table 1: Pg. 25 to 38).
How do heavy metals get into the water?
Although heavy metals occur naturally in rocks and soil, very few enter the water system from natural sources. Human use of heavy metals, and mining and refining processes, are the main sources of heavy metals in water.
Increased human exposure to heavy metals in water comes from activities such as mining, smelting, metal corrosion, and use of metal-containing compounds in domestic and agricultural applications. Heavy metals get into the air through various ways, and when they fall with rain or snow they frequently end up in waterways. This is a particularly common route for mercury entering the water system.
In 2016, the U.S. City of Flint, Michigan, gained global attention due to lead entering the drinking water via lead water pipes. Lead has not been used in new Canadian water service lines since 1975, however there are lead water pipe systems in use around the world that were installed before the risks to human health were fully understood. Lead pipes can corrode when water has a certain temperature, standing time, pH and hardness. Lead dissolves most easily in water that is soft and acidic.
What can we do about heavy metals in the water?
If you are concerned about lead in your tap water you can have it tested by a lab.
Treatment plants may use processes to remove heavy metals before the treated water is returned to the river. You can check treatment process information by taking the virtual tour of the Calgary wastewater treatment plants or by exploring the website of the Alberta Capital Region Wastewater Commission.
Today the practice of adding lead to gasoline, paint, toys, and utensils has been reduced or eliminated around the world.
Although heavy metals cannot be degraded or destroyed, they can be absorbed or trapped and become less harmful to animals and people. Certain plants have been scientifically shown to remove heavy metals from water and soils. By ensuring we protect wetlands and riparian areas we can help keep heavy metal contamination out of our water systems.
Where can I find more information?
Ali, H., Khan, E., & Sajad, M. (2013). Phytoremediation of heavy metals—Concepts and applications. Chemosphere, 91(7), 869-881. http://dx.doi.org/10.1016/j.chemosphere.2013.01.075
Tchounwou, P. B., Yedjou, C. G., Patlolla, A. K., & Sutton, D. J. (2012). Heavy Metals Toxicity and the Environment. EXS, 101, 133–164. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4144270/
Solomon, F. (2008, April). Impacts of metals on aquatic ecosystems and human health. Retrieved from: http://www.infomine.com/library/publications/docs/mining.com/Apr2008c.pdf
Government of Canada (1992). Canadian Drinking Water Quality: Guideline technical Document – Lead. https://www.canada.ca/en/health-canada/services/publications/healthy-living/guidelines-canadian-drinking-water-quality-guideline-technical-document-lead.html