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Blue-green algae blooms appeared earlier and on more lakes this summer than usual. Learn more about these blooms and the health risks they can pose.

Contact information
For information on Lakes in Wisconsin, contact:
Wisconsin DNR Lakes
Division of Water
Bureau of Water Quality
Blue-Green Algae Contacts

Blue-Green Algae

Drinking Water Concerns

Can I be exposed to blue-green algae or blue-green algal toxins through my drinking water?

Exposure to blue-green algae or blue-green algal toxins is unlikely if your water is provided by a municipal drinking water agency. For most Wisconsin residents and tourists, drinking water is provided by underground water sources that do not contain blue-green algae or blue-green algal toxins. While Lake Michigan and Lake Superior serve as water supplies for many communities on or near those lakes, there is no reason to worry since the water is pumped from far offshore, in deep water areas that are not affected by blue-green algal blooms.

Rainbow Lake in Waupaca County and Lake Winnebago are the only two Wisconsin inland lakes that serve as water supplies for area communities (Appleton, Neenah, Menasha, and Oshkosh). While blue-green algae blooms may occur on these lakes in summer, studies have shown that blue-green algal toxins are removed by the local utilities' routine water treatment processes.

Keep in mind that 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 post health risks to humans, pets, and other domestic animals. No one should ingest raw lake or pond water at any time.

How do water treatment plants deal with blue-green algae?

While most municipal drinking water treatment plants with surface water supplies do not regularly monitor for algal toxins, they do use treatment techniques that would remove the toxins if they were present. Conventional water treatment facilities can remove the cells of algae and other growing organisms by adding chemicals that bind them together. As the cells clump together, they become heavier and fall to the bottom of settling basins. Additional removal is obtained by filtration and through the use of activated charcoal. Studies conducted by scientists from the University of Wisconsin and the State Laboratory of Hygiene in the late 1990s did not detect any significant concentrations of algal toxins in the finished drinking water of several communities using Lake Winnebago as their water supply.

Can I treat my water at home to remove blue-green algae and their toxins?

There are a number of home water treatment options available to provide filtered water. Some of these systems include an activated charcoal step that will help remove certain chemicals like algal toxins if maintained and operated properly. However, variability in the design of the products on the market and in the operation and maintenance by homeowners prevent state health officials from declaring these products fail-safe.

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

No. Boiling water does not remove blue-green algal toxins. Because it is impossible to detect the presence of toxins in water by taste, odor or appearance, you are better off assuming they may be present.

What about using water with blue-green algae for washing?

If blue-green algae are visible, try to find a better source of water for washing food (i.e., fruits, vegetables, etc.), dishes, and clothes. Also avoid bathing or showering in water containing blue-green algae, as skin contact with the blue-green algae may lead to skin irritation or other adverse health effects.