Blue-green Algae

Blue-green algae, also called cyanobacteria, are a type of microscopic bacteria that occur naturally in freshwater lakes, bays, ponds, rivers and streams usually beginning in late summer to early fall.

Under certain environmental conditions, these algae can grow rapidly and form large masses that are known as algae blooms. Some, but not all, blue-green algae blooms are considered harmful as they may produce toxins that can be harmful to the health of people and pets.

What to do if you Suspect Blue-green Algae

If you suspect there could be blue-green algae in a body of water you should take the following measures:

  • Don't drink the water
  • Don't swim or bathe in the water
  • Keep animals out of the water
  • Don't attempt to treat the water using chemicals or by boiling. This will cause the algae cell to break open and release the toxins that it contains. Water filtration jug systems are also ineffective at removing these toxins.
  • Don't touch or handle the algae
  • Report the suspected algae to:
    • Ministry of Environment Spills Action Centre at 1-800-268-6060
    • Niagara Region Public Health Department at 905-688-3762 or toll free 1-800-263-7248, or email Public Health

Learn how to identify blue-green algae.

Health Effects of Blue-green Algae

You can be exposed to blue-green algae by:

  • Direct skin contact (swimming)
  • Swallowing (drinking water)
  • Eating fish caught in water where blue-green algae occurs

Symptoms include:

  • Itchy, irritated eyes and skin
  • Headaches, fever, diarrhea, stomach pain, nausea, and vomiting
  • More serious effects such as liver damage may occur when large amounts are ingested

Blue-green Algae: Background, potential impacts to human health and safety of drinking water

Prevention of Exposure in Niagara

  • Municipal drinking water sources are routinely monitoring for the presence of algae and the harmful toxins they can produce during peak algae season
  • Advisories or warnings are issued to the public if there is any concern about the quality of drinking water
  • Beaches are visually monitored for the presence of algae
  • Beaches are posted with not to swim advisories if algae is suspected

If you don't have municipal water service and suspect blue-green algae in your drinking water source call Niagara Region Public Health Department 905-688-3762 or toll free at 1-800-263-7248.

About Algae and Drinking Water Treatment
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