Blue-green algae occur naturally in bodies of water in low numbers. During prolonged hot weather algae can become abundant, discoloring water and forming scums-particularly in warm, shallow areas. Some blue-green algae produce toxins. These pose health risks to people and animals if exposed in large enough quantities. Symptoms of toxin exposure may include allergic reactions or eye, skin, nose, and throat irritation. Ingesting large amounts of water containing blue-green algae toxins has resulted in liver and nervous system damage in laboratory animals, pets, livestock and people.

People, pets and livestock should avoid contact with water that has scums on the surface or is discolored-blue-green, yellow, brown or red. If contact does occur, wash with soap and water or rinse thoroughly with clean water. Swimming, bathing or showering with water not visibly affected by a blue-green algae bloom is not expected to cause health effects. If symptoms of toxin exposure develop, stop using the water and seek medical attention.

Individuals should not drink untreated surface water. Home boiling, disinfecting (chlorine or UV), and filtering do not remove algal toxins. When using surface water to wash dishes, rinse with bottled water. In addition to toxins, untreated surface water may contain bacteria, parasites or viruses known to cause illness.

For additional information, including information in Spanish, go to:

NY Health Department

NY DEC