Blue-green Algae

Blue-green algae, or cyanobacteria (Government of Ontario), are microscopic organisms that naturally live in lakes and streams, usually in low numbers. In warm, shallow, undisturbed water that receives plenty of sunlight, they can multiply rapidly. When they do, they form blooms that discolor the water or create floating rafts or scum on the surface.

Toxins

• Some blue-green algae produce toxins that can harm people and animals when exposure occurs in large amounts.
• Swallowing water, touching skin, or inhaling airborne droplets containing high levels of these toxins while swimming, bathing, or showering can negatively affect your health.

If you draw water from a waterway with a blue-green algae bloom, monitor the bloom’s location.

• If the water does not show visible signs of a bloom, swimming and household use—such as bathing or showering—are not expected to cause health effects.
• However, some individuals are especially sensitive to even low levels of algal toxins and may experience mild symptoms, including skin, eye, or throat irritation, or allergic reactions.

What should you do if you suspect blue-green algae?

• Do not drink from the affected surface water, even if it has been treated.
• In-home treatments—such as boiling, disinfecting with chlorine or UV, or using water filtration units—do not remove blue-green algal toxins.
• People, pets, and livestock should avoid direct contact with water that is discoloured or has scum on the surface.
  • If contact does occur, wash with soap and water or rinse thoroughly with clean water to remove algae.
• Do not eat the liver, kidneys and other organs of fish caught in the water body. Be cautious about eating fish caught in water where blue-green algae blooms occur.  To learn more about eating fish in Ontario Lake visit: Guide to Eating Ontario Fish (ontario.ca).