The biggest pollutants threatening Canadian lakes

Algae bloom

Canada many lakes, rivers, streams, and other bodies of water make up 7 percent of the world’s renewable freshwater. Unfortunately, the biggest threat to fresh water is rooted in human development. Generally, water is considered “polluted” when people can’t drink it or fish can’t survive in it, and I can almost guarantee that we all know of at least one beach that is controlled by a sign dictating whether it is safe to swim in the waters or not. Of all the polluted waters in the world, Lachine Canal in Quebec is the second image on Wikipedia’s “Water Pollution” page. Lake Ontario and Lake Erie have a particularly bad reputation, but most unfortunate was probably last year, when Lake Winnipeg was named the most threatened lake in the world. Pollutants can enter our lakes through a variety of different ways. Here, we’ve listed some of the biggest pollution threats to Canadian lakes, along with some suggestions to help reduce your impact.

Plastic debris

When we see the occasional piece of plastic debris, garbage, or discarded clothing item washing up on shore, this pollution problem isn’t exactly a secret. Plastic allegedly accounts for 80 to 90 percent of ocean pollution, and studies suggest that the Great Lakes could be in even worse shape. Samples from Lake Erie suggested that there are between 1,500 and 1.7 million tiny plastic particles per square mile, which is a 24 percent higher concentration than samples taken in areas of the Atlantic Ocean. The most common pieces are so small that they can only be seen under a microscope, measuring under two-tenths of an inch. At the very least, this is a problem with pollution misconceptions and visibility, but also the food chain. Fish are known to mistake the particles for food and gobble them up. The chemicals transfer from the plastic to the fish, and then potentially to whoever or whatever eats the fish.

How to reduce your plastic footprint: Reduce your use of ‘everyday’ items that have easy, re-usable replacements, including water bottles, plastic bags, and food containers. This list provides ideas to get you started, and some will even save you money in the long run. It’s win-win.

Agricultural runoff 

Agricultural runoff is a big problem for Canada’s lakes because of the nitrates used in fertilizers and pesticides, particularly phosphorus. High levels of phosphorus are a problem that many thought was cured in the ’60s, when it was discovered that phosphorus in detergents was turning Canada’s lakes green. For years, the reduction of chemical detergents suggested a pollution turnaround, and some of the most badly affected waters, such as Lake Erie, were brought back to relatively good health. In recent years, however, the visible damage has returned in the form of toxic, invasive algae blooms that feed on the nitrates and take up thousands of kilometres of freshwater space in Lake Erie, Lake Winnipeg, and others throughout North America. The swaths of algae force suffocating fish and underwater lifeforms to migrate farther into waterways, searching for food and oxygen. The presence of pesticides has also been linked to reproductive failures in fish. Today, most of the phosphorus that feeds that algae comes from farmland runoff. Both global warming and modern factory farming practices seem to be to blame for this, as mass fertilizations overhead by plane are not uncommon and as the occurrence of heavy rainfalls have increased significantly in the last 60 years.

How to reduce harmful runoff: While new technology and equipment can be expensive, some suggest that the overhaul of modern farming practices is the only way to go. Simple practices in conservation, like testing soil for chemical levels, or adding G.P.S.-guided machinery that shows where fertilizers have been distributed, are a few ideas that have been brought up. Other new equipment puts fertilizer in the ground at an earlier stage, rather than sprinkled on top in the winter months.


One of the greatest chemical threats to the Great Lakes is the presence of pharmaceutical compounds. At the base level, sewage treatment plants are not designed to treat or filter pharmaceuticals, and recent studies have shown that it is effecting amphibian lifestyle and reproductive cycles. Recent studies conducted in Canadian lakes have shown that fish populations significantly decrease when exposed to even small levels of estrogen—a common hormone in birth control pills. The male fish were so effected in fact, that they started to grow female reproductive properties like eggs. It is suggested that other common medications—antibiotics and antibacterials—could result in resistant strains of bacteria that could then be passed on through fish or wildlife consumption. Most samples of Canadian lakes have shown relatively low levels of these pharmaceuticals, but the impact on fish and wildlife is evident.

How to properly dispose of medications: The Government of Canada has this handy info guide on how to safely dispose of your pills and potions. (Rule number one? Don’t flush medicine down the toilet or sink.)

Synthetic fragrances

Synthetic fragrances can be found almost anywhere these days, but are most commonly found in hygiene and cosmetic products, including multiple everyday items like perfumes and colognes, makeup, detergents, and cleaning products. Due to their prominent use, traces of the chemical compounds used to make these scents have been found in the fatty tissues and milk of humans and animals. There are over 300 chemicals in fragranced products and many are not listed or disclosed, but fragrances with “musks” are the most hazardous. The chemical compounds are lipophilic, which means that they typically combine and dissolve better into oily liquids than water, and subsequently means that the fragrant remnants, which arrive through air, water, or urban runoff, are there to stay in the form of nasty sewage sludge buildup.

How to use fewer fragrances: Switch to naturally-scented products, environmentally friendly cleaners, and second-guess the routine use of smelly personal hygiene products. Do you really need to wear cologne today?

Oil sands operations

In the past couple of years, numerous studies have come out stating that the environmental and health risks of Alberta’s oil sands were previously underestimated. Mining, processing, and huge mechanical vehicle traffic are a few of the more obvious negative projects of the biggest industrial project on earth, but there are also problems that occur simply from the mass amounts of dust and evaporation from tar sand tailing ponds that eventually end up in our lakes. A disturbing study released by top Canadian scientists last year showed toxic hydrocarbon levels in six area lakes, some already reaching warning levels,  20 times more damaged than when the mines were first built.

How more damage can be prevented: For ways to help at home, decreasing your dependence on oil and non-renewable resources is where it starts and ends. For most of us, that means less reliance on cars, taking advantage of public transit, walking, biking, or carpooling. The rest will be left to higher levels of government.

Human waste

Environment Canada disclosed in 2012 that Canada dumps over 150 billion litres of untreated and under treated waste water into our waterways every year. As a vast country of widely varying town and population sizes, municipal and public water treatment  facilities are proposed, constructed, and operated at the provincial level. For the many arctic communities that don’t have the infrastructure, this means waste is dumped directly into the waterways, without filtration or treatment. However, this is also the case in some major urban centres, such as Halifax, where old treatment systems failed long ago, in Richmond, B.C., where there was a raw spill from sewer system overflow, or Lake Winnipeg, which was named the most threatened lake in 2013 for sewage discharge and agricultural runoff. Faulty or old systems mean that even when there is adequate water waste treatment, storm water can cause overflow, allowing raw sewage to spill directly into our lakes (and rivers, and oceans).

How to reduce the waste: After stating that 850 facilities across Canada require upgrades, the Government of Canada released a plan to repair and replace the most high-risk facilities starting in 2020, and reaching the low-risk by 2040. However, these system upgrades will not apply to facilities in the far north.