Water samples from Nepewassi Lake have tested positive for blue-green algae (cyanobacteria), said the Sudbury and District Health Unit.

The sample from Nepewassi Lake contained a species of the algae that can produce toxins.

“Water contaminated with blue-green algal blooms has an unsightly pea-soup appearance and foul smell,” said Allan McDougall, an environmental support officer with the Sudbury and District Health Unit. “Visible algal blooms can produce toxins; therefore, using or drinking the water should be avoided.” 

The highest concentrations of toxins are usually found in blooms and scum on the shoreline. These dense accumulations pose the greatest potential risks to people and pets. Toxins can irritate the skin and, if ingested, can cause diarrhea and vomiting.

At high enough levels, toxins can cause liver and nervous system damage.

Blue-green algae might also be observed in other parts of the lake. Because the blooms are not anchored, they can move from one location to another through wind and water action. Also, new blooms can appear.

All residents on the lake should be vigilant for blooms in their area.

The Sudbury and District Health Unit advises people using lakes and rivers to be on the lookout for algal blooms. If blooms are visible:
-Avoid using the water for drinking, bathing, or showering, and do not allow children, pets, or livestock to drink or swim in the water.
-Residents with shallow drinking water intake pipes that might pump in blue-green algae should be cautious.
-Residents should not boil the water because boiling the water may release more toxins into the water.
-Residents should avoid cooking with the water because food may absorb toxins from the water during cooking.
-Residents should exercise caution with respect to eating fish caught in water where blue-green algal blooms occur. Residents should not eat the liver, kidneys, and other organs of fish caught in the water.
-Do not treat the water with a disinfectant like bleach. This may break open algae cells and release toxins into the water.
-Residents should not rely on water jug filtration systems as they do not protect against the toxins.

On lakes and rivers where blue-green algal blooms are confirmed, people who use the surface water for their private drinking water supply may wish to consider an alternate, protected source of water.

For more information, call the Sudbury and District Health Unit at 705-522-9200, ext.398.