Last week, I was boating in the Toronto harbour with the Swim Guide team looking for signs of pollution. We saw – and smelled – a handful of things: the milky look of water contaminated with sewage, plastic bottles and bags, and algae. It got me thinking: what counts as pollution? How do you recognize it? And what do you do about it?  

This article will help you recognize common types of pollution, avoid getting sick from it, and protect others by reporting it and building case files in your watershed. 

If you see beach pollution, submit a pollution report to the Swim Guide. 

Beach pollution #1: Algae

Taken by Sarah Camp, flickr

How is it caused?

Algae exist naturally in the water, but can become numerous when excess nutrients are present. This is often caused by runoff from agriculture or residential practices (like fertilizing your lawn or using household products). 

How do you recognize it?

Algae can be green, yellowish-brown, or red. It might look like moss, thick stringy mats, or a floating slimy scum. Sometimes it looks like a blue-green algae bloom (which is extremely toxic).

Why are they bad?

Most of us don’t like running into slimy algae when we’re swimming. Aside from making swimming unenjoyable, it may also harbour bacteria or insects and can irritate your skin.

What do you do if you come into contact with one?

Rinse off. Avoid any activities on or near the water where you might inadvertently swallow the water.

Beach pollution #2: Blue-green algae

Photo by Roger Bunting

How is it caused?

Blue-green algae, which is a cyanobacteria, occurs naturally in lakes, rivers, and ponds, but can rapidly multiply in the right conditions. Blue-green algae needs similar conditions as true algae to grow: a combination of warm water, nutrients, and intermittent exposure to high light intensity.

How do you recognize it?

Blue-green algae can look like slicks of bright-green paint on the surface of the water. If the bloom is dispersed throughout the water, it often causes the water to look like pea soup. It also has a grassy or swampy smell.

Why is it bad?

Blue-green algae is extremely toxic for humans and animals. Contact with a bloom can cause rashes, blisters, and skin and mouth ulcers. Ingesting water that is contaminated with blue-green algae can lead to headaches, nausea, diarrhea, cramping, and vomiting. In more severe cases, ingesting contaminated water can lead to liver failure and even death.

What do you do if you come into contact with it?

Rinse with fresh water immediately if you think you’ve come into contact with blue-green algae. Avoid all contact with the water, especially any that could lead to ingestion. Don’t eat fish from a contaminated lake, and don’t drink water (even if it’s been boiled) from a contaminated water source.

If you think you’ve accidentally ingested contaminated water source, contact your local Poison Centre (Canada, US).

Beach pollution #3: Sewage

Where does it come from?

Sewage might be in the water because of a leak, CSO (Combined Sewer Overflow), or bypass from a sewage treatment plant. Generally, sewage is more likely to be in the water if there’s been an extreme weather event – like a heavy rainfall or snowmelt – because this can overwhelm systems and cause sewage to be diverted into the water.

How do you recognize them?

You’ll probably see not-so-nice things in the water, like tampons, disposable wipes, condoms, and other items that are flushed down the toilet (even if they shouldn’t be). The water may also be a different colour (usually milky looking) and you might see a “sewage front” making its way through the water.

Why is it bad?

Not only is sewage in the water or at the beach just plain gross, it causes bacteria like E. coli to become extremely elevated. Bacteria in the water are likely to make you sick: think gastrointestinal illness like vomiting and diarrhea, skin rashes, eye and ear infections, and low-grade fever.

What do you do if you come into contact with sewage?

Your symptoms will vary depending on the level of contact you had with the water.

If you had secondary contact (think spray over the edge of a boat), wash your skin with soap and water.

If you had primary contact (think swimming), you probably swallowed about 1 – 2.5 tablespoons of water per 45 minutes of swimming. Within a few days, you might start to develop symptoms indicating gastrointestinal illness. This will usually go away on its own. Keep yourself comfortable and drink lots of fluid until the symptoms subside.

If you’ve drank or ingested contaminated water, see your doctor.

Beach pollution #4Plastics pollution

Photo by Bill McDonald

How is it caused?

Microplastics get into our watersheds in two main ways: when beauty and hygiene products (those little beads in your soap or exfoliant) get washed down the drain, or when larger pieces of plastic (like water bottles or bags) get broken down by waves. Microplastics sit in the water column, attract toxins, and eventually get ingested by fish, birds, and/or humans.

How do you recognize it?

That’s a tough one. You might recognize plastic pollution by the larger pieces of plastic that are visible to the human eye: disposable water bottles, for example. But true microplastics are so small you usually can’t see them. Suffice it to say that if you’re swimming anywhere, there’s probably microplastics. 

Why are they bad?

A lot of reasons. Plastics often don’t degrade very quickly, and are persistent in the environment. Chemicals on the plastic are leeched into water and ingested by humans and animals, where they can potentially impact hormones and other systems. 

What can you do about it?

Stop adding to the problem. Make sure to recycle your plastics (this includes cigarette butts, which are a major contributor to plastics pollution) and avoid products that have microplastics (for a list of products that contain the beads, see this list). 

Beach pollution #5: Litter/garbage

Taken by Alder, flickr

How is it caused?

This one’s pretty self-explanatory: garbage can be the result of direct littering (on the beach or into the water), though garbage can also be blown longer distances through wind.

Why is it bad?

On the beach, garbage is not only unsightly, but can also attract rodents and insects. When garbage gets into the water, it can leech chemicals, leading to ground and water pollution.

What do you do if you come into contact with it?

Take a photo of it and report it to the Swim Guide. Organize a beach cleanup. Or just clean it up yourself.

Beach pollution #6:Oil

How is it caused?

Oil in the water is mainly caused by spills from industry, but can also come from ships, drains, and dumping.

How do you recognize them?

Because oil doesn’t dissolve in water, it usually forms a thick sludge in the water. You’ll probably see the streaks of it on the surface of the water – the little rainbow-like smears are telltale signs of oil. You may also smell kerosene or gasoline.

Why are they bad?

There are a range of things that can happen if you come into contact with oil. You can have a skin reaction from prolonged exposure, eye and ear infections, gastrointestinal illness (nausea, vomiting, diarrhea). Sometimes, with prolonged exposure and in highly polluted water, contact with oil can lead to liver or kidney disorders, respiratory ailments (if you’re regularly exposed), digestive disorders, and intestinal infections, like parasites, cholera, and hepatitis.

What do you do if you come into contact with one?

Wash your body with soap and water. Don’t use harsh detergents or solvents to wash oil from the skin.

If you accidentally ingest oil, call your local poison control centre. Do not smoke for at least 72 hours.


Do you have a common pollution problem in your watershed that we missed? Let us know! 

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