Water pollution: A silent threat in southern Alberta
For the past four years, the World Wildlife Fund (WWF) has worked with community organizations, water agencies, First Nations, researchers, governments and industry to gather data on the health of Canadian watersheds.
Researchers looked at the levels of certain pollutants in rivers — such as chloride, phosphorus or heavy metals — and compared them to the guidelines or standards set by provincial and federal governments. They also looked at long-term trends in the levels of these substances. The assessment of the South Saskatchewan River watershed had some disturbing news – pollution levels are “very high”.
The report cited evidence of every type of pollution in our watershed, with agricultural runoff and pollution from municipal and industrial sites creating the greatest concern. Pipeline leaks are also a concern in three of the four sub-watersheds.
Under the Canadian Environmental Protection Act 1999, a substance is considered 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.” (CEPA 1999)
Toxic substances can have different effects on human health and the environment. A substance that might be dangerous to wildlife in low levels might have no effect on people even at much higher levels. The opposite is also true: some substances can do more harm to humans than to the environment.
Under CEPA, Health Canada and Environment and Climate Change began to categorize the approximately 23000 substances on Canada’s “Domestic Substances List” to make sure that any substance that could potentially affect human health (Health Canada) or the environment (Environment Canada) was evaluated.
The intent was to identify substances suspected of being either persistent (chemical substances that take a very long time to break down in the environment), bio-accumulative (chemical substances that can be stored in the organs, fat cells or blood of living organisms and remain for a long time), or inherently toxic to the environment (chemical substances that are known or suspected, through laboratory and other studies, to have a harmful effect on wildlife and the natural environment on which it depends).
Many of the listed substances provide substantial benefits to society. They are used to manufacture products that increase productivity, save lives, and make modern life convenient e.g., cars, textiles, paper, medical supplies, and food packaging. Nevertheless, there are legitimate and growing concerns over the environmental and human health effects of long-term chronic exposures to contaminants found in our air, soils, water, consumer products, and bodies.
According to Alberta Agriculture, herbicides, insecticides and other chemical pollutants which enter lakes and rivers degrade through chemical processes such as photodegradation and biological degradation by microbes. Some toxic substances, however, can also be absorbed and retained by aquatic organisms (bioaccumulation) either directly from the water or consumed with food.
Contaminants that are not degraded can be passed on in the food web with each predator accumulating the pollutant of the organisms it had eaten (biomagnification). Biomagnified toxins or pollutants can result in major problems further up the food web. For example, double-crested cormorants in the Great Lakes basin have had bill deformities from the bioaccumulation of the insecticide DDT (Environment Canada 1995). Further, the mortality of waterfowl and other wild birds has increased because of decreased egg shell strength and the consumption of sport fish has been limited or banned in certain areas due to the bioaccumulation of pollutants.
Mercury is of particular concern because of its toxicity to aquatic organisms and its adverse effects on human health. Deposits occur naturally in all types of rocks, and human sources of mercury to the aquatic environment include industrial and municipal discharges, atmospheric deposition or industrial emissions and leaching from landfill sites. In May of this year, CTV reported that residents of the Grassy Narrows reserve in Ontario have suffered from mercury poisoning ever since a paper mill in Dryden dumped 9,000 kilograms of the toxic heavy metal into the English-Wabigoon River system in the 1960s.
A report authored by five experts and released last year suggested mercury could still be leaking into the river system. Despite some cleanup efforts, mercury concentrations in the area haven’t decreased in 30 years. Dangerous levels are still present in sediment and fish, causing ongoing health and economic impacts in Grassy Narrows and the Wabaseemoong First Nation.
In the environment, particularly lakes, waterways and wetlands, mercury can be converted to a highly toxic, organic compound called methylmercury through biogeochemical interactions.
Methylmercury, which is absorbed into the body about six times more easily than inorganic mercury, can migrate through cells which normally form a barrier to toxins. It can cross the blood-brain and placental barriers, allowing it to react directly with brain and fetal cells.
According to the Government of Canada’s webpage describing mercury in the food chain, almost all mercury compounds are toxic and can be dangerous at very low levels in both aquatic and terrestrial ecosystems. Because mercury is a persistent substance, it can bioaccumulate in living organisms, inflicting increasing levels of harm on higher order species such as predatory fish and fish-eating birds and mammals through biomagnification. Although the long-term effects of mercury on whole ecosystems are unclear, the survival of some affected populations and overall biodiversity are at risk.
In 2009, the Alberta government published a report entitled “Human Health Risk Assessment: Mercury in Fish, Rivers and Lakes, Southern Alberta“. The report discusses a fish sampling survey conducted in 2006 in some rivers and lakes of southern Alberta.
The main objectives of this program were to a) repeat the survey of mercury residues in fish in the South Saskatchewan basin that was done in 1982 – 83; b) evaluate whether fish consumption advisories are still needed and assess potential human health risk; c) determine if any of a subset of emerging contaminants may also be a concern; and d) determine the state of aquatic ecosystem health in Southern Alberta, as described in the Water for Life Strategy. This report was followed up by one published in 2016, “Mercury in Fish: In Alberta Water Bodies 2009–2013”.
The Government of Alberta has been issuing and reviewing fish consumption advisories for fish caught from local waterbodies in Alberta since the 1990s.
Fish consumption advisories apply to local subsistence consumers, recreational anglers and residents who eat fish caught from these waterbodies. The advisories inform the public about any potential health hazards they may encounter when eating specific types of fish.
Visit the MyWildAlberta website for a list of waterbodies with Fish Consumption Advisories related to mercury as well as for dioxin and furan, two toxic substances released into the environment through burning organics and waste-water discharges from industrial sites.
If you would like to learn more about surface water quality in Alberta, Alberta Environment and Parks has an excellent web page that defines surface water quality, provides an historical perspective on provincial monitoring and issues, and outlines ongoing activities. If you are at all interested in water quality, it is well worth your time.