ILLINOIS — As temperatures begin to rise, the Illinois Environmental Protection Agency (Illinois EPA) and Illinois Department of Public Health (Illinois DPH) are reminding recreators to use caution in Illinois waterways this summer when harmful algal (cyanobacteria) blooms are possible. Cyanobacteria, also known as blue-green algae, are microscopic organisms that naturally occur in lakes, streams, and ponds. Rapid and expansive growth of cyanobacteria is referred to as a “bloom.” While most blooms are harmless, some produce toxic chemicals that can cause sickness or other health effects in exposed people and pets.
When a bloom producing toxins has been confirmed, local officials are advised to post appropriate signage to warn residents to avoid contact with affected waters. However, not all blooms are reported to state officials. Therefore, residents are advised to avoid contact with water that:
• looks like spilled, green or blue-green paint;
• has surface scums, mats, or films;
• has a blue or green crust at the shoreline;
• is discolored or has green-colored streaks; or
• has greenish globs suspended in the water below the surface.
Residents or local officials who suspect a cyanobacteria bloom may report the bloom to the Illinois EPA, which recently released a new Bloom Report Form Application accessible on computer or phone. The App and other reporting methods are available on the Illinois EPA website at https://www2.illinois.gov/epa/topics/water-quality/monitoring/algal-bloom/Pages/reporting.aspx.
Young children, the elderly, and people with compromised immune systems are most at risk to adverse health effects attributable to algal toxins. Individuals are most often exposed to algal toxins while swimming or participating in other recreational activities in and on the water. The most common routes of exposure are direct skin contact, ingestion of contaminated water, or inhalation of water droplets in the air (e.g., while water skiing or tubing). Symptoms of exposure to algal toxins include rashes, hives, diarrhea, vomiting, coughing, or wheezing. More severe symptoms may result from longer or greater amounts of exposure. If you are concerned you have symptoms that are a result of exposure to algal toxins, contact your health care provider or call the Illinois Poison Center at 1-800-222-1222.
Residents are also advised to keep pets out of water that may contain cyanobacteria. Do not allow pets to drink from the water or lick their fur after swimming in water containing a cyanobacteria bloom. Residents and pets that have contact with cyanobacteria should rinse with clean water as soon as possible. If pets experience symptoms that may be the result of exposure, contact a veterinarian immediately.
Activities near, but not in or on, a lake or river such as camping, picnicking, biking, and hiking are not affected. With all activities, wash your hands with soap and water before eating if you have had contact with lake water or shore debris.
For additional information about harmful algal blooms, please visit the Illinois EPA Harmful Algal Bloom website:
To report a human or animal illness from harmful algal bloom exposure, please visit the Illinois DPH Harmful Algal Bloom website: