The Ohio River is free from harmful levels of toxic algae after more than a month of recreational public health advisories, according to the Kentucky Energy and Environment Cabinet.
The cabinet lifted recreation public health advisories along the Ohio River on Thursday after recent water samples showed a decline in toxic algae.
The algae first formed in late September when drought conditions paired with hot temperatures produced blooms along a 300-mile stretch of the Ohio River. The blooms resulted in the cancellation of the Great Ohio River Swim in Cincinnati and the swimming portion of Louisville’s Iron Man Competition.
“We’ve been testing for more than a month and after the Iron Man competition we’ve continued to test to make sure that we could tell people, recreational users of the river, when they could safely return,” Mura said. “And the algal blooms have finally cleared up.”
Blue-green algae can produce a toxin known as microcystin that’s harmful to people, and especially to pets. When touched or consumed, the toxin can cause stomach pain, nausea, vomiting and other health effects.
The algal blooms were growing throughout the river, often appearing as green, paint-like scum on the surface. The highest sample seen this year was greater than 5,000 micrograms per liter on October 9 in Madison, Indiana. That was 625 times higher than the recreational advisory threshold in Kentucky and Indiana.
But recent wet weather has helped return the river to normal, Mura said.
“We’ve had more flow because of the rains and we’re not getting the intense sunlight and heat we were getting that caused these blooms,” he said.
Kentucky officials said that although samples are below the hazardous concentrations, people should still avoid waters with visible algal blooms.