Municipal Affairs and Environment

Blue-Green Algae: Frequently Asked Questions

Drinking Water

  1. Can the tap water from my public water supply contain blue-green algae and/or its toxins?
  2. Is there a regulation or guideline that recommends a maximum safe level of microcystin in drinking water?
  3. What about smaller treatment systems and private supplies?
  4. Can I cook using water with blue-green algae in it?
  5. What about using contaminated water for washing?
  6. Does renal dialysis treatment put me at higher risk for exposure to blue-green algal toxins?

1. Can the tap water from my public water supply contain blue-green algae and/or its toxins?

Exposure to blue-green algae or blue-green algae toxins is unlikely if your drinking water source is a public water supply. If blue-green algae are detected in a public water supply, treatment plants can remove them in a number of ways. Conventional water treatment facilities can remove the cells by adding chemicals that bind them together. As the cells clump together, they become heavier and fall to the bottom of the reservoir or tank, where they can be easily filtered out.

It is important to remember that drinking water that is not treated may pose risks far beyond those associated with blue-green algae. All natural surface waters contain bacteria, algae, viruses and other pathogens that, if consumed, may pose health risks to humans, pets and other domestic animals. No one should ingest raw lake or pond water at any time.

^ Top of Page

2. Is there a regulation or guideline that recommends a maximum safe level of microcystin in drinking water?

The Health Canada Guideline recommends a maximum acceptable concentration of 0.0015 mg/L (1.5 ug/L) for total microcystins in drinking water, based on the toxicity of microcystin-LR. This guideline is believed to be protective of human health against exposure to other microcystins (total microcystins) that may also be present. It is a conservative value, as it is derived on the basis of daily consumption of microcystin-LR over a full year. Visit Health Canada's web site for more information on cyanobacterial toxins-microcystin-LR. Opens in new window

^ Top of Page

3. What about smaller treatment systems and private supplies?

Small drinking water systems with modest treatment facilities and private supplies with either no treatment or minimal water treatment systems are less likely to have the specialized equipment to effectively filter and treat water during blue-green algae blooms. The treatment methods most commonly used by this sector are for the most part, ineffective against blue-green algae contamination.

^ Top of Page

4. Can I cook using water with blue-green algae in it?

Boiling water does not remove blue-green algal toxins and cooking with contaminated water is not advised. While the odour and appearance of blue-green algae make its presence relatively easy to identify, it is impossible to know from observance of the water whether blue-green algal toxins are present.

^ Top of Page

5. What about using contaminated water for washing?

If there is another source of water available do not use blue-green algae contaminated water for washing clothes or dishes. If no alternative supply is available, wear rubber gloves to avoid direct contact with the water. Bathing or showering in contaminated water should also be avoided, as toxins can cause skin irritation and rashes.

^ Top of Page

6. Does renal dialysis treatment put me at higher risk for exposure to blue-green algal toxins?

While the level of microcystins allowed for drinking purposes will not adversely affect the health of most people, patients undergoing renal dialysis treatment may be more susceptible to the associated health risks. Because dialysis patients may receive dialysis two or three times per week (exposure to more than 300L of water per week), there is potential for dialysis patients to be exposed to elevated levels of these toxins.

Conventional surface water treatment processes are usually effective in removing the algal cells, but are not very effective at removing or destroying dissolved toxins, particularly from supplies that contain high levels of organic material. Specialized surface water treatment processes can reduce the toxin levels to below the drinking water guideline, but these levels (0.1-0.5 µg/L) are still of concern for dialysis patients. Dialysis patients should confirm with their local municipality or dialysis treatment provider that blue-green algae toxins have not been detected in the water being used for dialysis.

^ Top of Page

Last Updated:
This page and all contents are copyright, Government of Newfoundland and Labrador, all rights reserved.