The Eastern Ontario Health Unit (EOHU) issued an alert about blooms of blue-green algae in some rivers and lakes in Eastern Ontario. Residents who use surface water as their drinking source or who go swimming in local rivers or lakes should be cautious if there is blue-green algae in the water.

Blue-green algae blooms, also known as cyanobacteria blooms, may have toxins harmful to humans and other animals. The blooms are a natural occurrence around the world and tend to appear in warm, shallow, undisturbed water that gets lots of sunlight and is also rich in phosphorus and nitrogen. Animal and human waste and many fertilizers contain these two chemicals and can increase the chance of blue-green algae blooms if they get into local lakes and streams through surface runoff or leaching through the ground.

Cyanobacteria toxins can cause skin irritation and, if swallowed, result in diarrhea and vomiting. High-level concentrations of the toxin can cause damage to the liver and nervous system.

The EOHU urges residents living near lakes and streams or going out for boating or fishing trips to watch for algae blooms in the water. Dense blooms make the water resemble pea soup and can appear in shades of blue, blue-green, yellow, brown, or red.

Large blooms may include solid-looking clumps of algae. Fresh blooms may smell like fresh-cut grass while older blooms smell like rotting garbage.

Anyone who lives anywhere near where a suspected bloom exists should avoid using any surface water for drinking, cooking, bathing or showering. They should not allow children, pets, or livestock to swim in or drink the water. Clean water and soap should be used to scrub off any water that may contain blue-green algae that has come in contact with the skin. 

Boiling such water does not remove the toxins and may cause the algae to release more toxins. Water-jug filtration systems are not designed to screen out the toxins. Furthermore, using chlorine bleach or other disinfectants will cause the algae cells to break open and release toxins into the water.

Finally, one should not eat any fish caught in water where blue-green algae blooms exist. Nor should any fish organs coming from such waters be used as bait or fertilizer as they have absorbed the toxins.

The Ministry of Environment has more information on blue-green algae at http://www.ontario.ca/environment-and-energy/blue-green-algae.