Officials with the Iowa Department of Natural Resources (IDNR) say they have identified a hepatotoxin, called microcystin toxin, in Green Valley Lake near Creston in Union County.

Microcystin toxin is released by blue-green algae or cyanobacteria
Cyanobacterial blooms can form in warm, slow-moving waters that are rich in nutrients such as fertilizer runoff or septic tank overflows. Blooms can occur at any time, but most often occur in late summer or early fall.

Symptoms may take hours or days to show up in people, but normally show up within one week after exposure. Symptoms of microcystin exposure/poisoning include
• Rash, hives, or skin blisters (especially on the lips and under swimsuits).
• Gastrointestinal symptoms such as stomach pain, nausea, vomiting, diarrhea, severe headaches, and fever.
• Runny eyes and nose, cough, and sore throat, pleuritic pain, asthma-like symptoms, or allergic reactions.
• Exposure to large amount of microcystin can cause liver damage.

Swimming in the lake should be avoided. If you do swim, do not ingest the water, and wash thoroughly before you leave.