ILLINOIS — In preparation for summer weather and higher temperatures, the Illinois Environmental Protection Agency (Illinois EPA) and Illinois Department of Public Health (Illinois DPH) have issued their annual reminder for individuals to use caution when recreating on Illinois waterways, as harmful algal (cyanobacteria) blooms are possible on any body of water. 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 adverse health effects in exposed people and pets.

Illinois EPA has published the 2023 Harmful Algal Bloom Program which includes routine monitoring and event response information. Routine monitoring includes several streams, lakes, and lake beaches throughout Illinois. Event response investigates credible reports of a potential cyanobacteria bloom. The Illinois EPA has also created a new online Harmful Algal Bloom Dashboard that displays information submitted through the public Illinois Bloom Report Form and has a map of blooms that have been reported to Illinois EPA, investigated, and confirmed.

If a bloom producing toxins is 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 a body of 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 through the Bloom Report Form App, which is accessible by computer or phone. The App and other reporting methods are available on the Illinois EPA website at https://epa.illinois.gov/topics/water-quality/monitoring/algal-bloom/reporting.html.

Individuals most at risk for adverse health effects attributed to algal toxins include young children, the elderly, and people with compromised immune systems. 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 a 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, swim in the water, or lick their fur after being in contact with 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: https://epa.illinois.gov/topics/water-quality/monitoring/algal-bloom.html