Municipal Affairs and Environment

Blue-Green Algae: Frequently Asked Questions

Recreational Water

  1. Can water containing blue-green algae blooms be used for recreational activities?
  2. What is Health Canada doing to ensure the quality of recreational water?
  3. Can I eat fish from contaminated water?

1. Can water containing blue-green algae blooms be used for recreational activities?

Recreational activity is not recommended when a blue-green algae bloom is visible. Researchers generally agree that between 30 and 50 per cent of algae blooms are harmless because they contain only non-toxic species of blue-green algae. However, blooms containing even one species of toxic blue-green algae may be dangerous. Since there is no immediate way to tell if a particular bloom is toxic, samples have to be analyzed in a laboratory before a body of water can be declared safe.

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2. What is Health Canada doing to ensure the quality of recreational water?

Health Canada has developed recreational water quality guidelines for blue-green algae in fresh water bodies, which recommend a maximum of 100,000 cells/mL of total cyanobacteria in water, and a maximum of 20 µg/L total microcystins. For more information, visit Health Canada's Guidelines for Canadian Recreational Water Quality Opens in new window. Information specific to cyanobacteria is found in section 6 of the Guidelines.

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3. Can I eat fish from contaminated water?

Microcystins can accumulate in the tissues of fish, particularly in the viscera (liver, kidney, etc.), and in shellfish. Levels in the tissues depend upon the severity of the bloom in the area where the fish or shellfish are living. Caution should be used when considering the consumption of fish caught in areas of a water body where major blue-green algae blooms occur; in particular, the viscera of the fish should not be eaten.

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