Blue-green algal blooms bring health risks

Posted 10/2/19

NAPLES — “We know that blue-green algae isn’t just something that is in the water. It is something that can affect our health. We’re dealing with old organisms that go back almost 3.5 billion …

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Blue-green algal blooms bring health risks


NAPLES — “We know that blue-green algae isn’t just something that is in the water. It is something that can affect our health. We’re dealing with old organisms that go back almost 3.5 billion years,” explained Florida Surgeon General Dr. Scott Rivkees at the Sept. 24 meeting of the Department of Environmental Protection Blue Green Algae Task Force.

Making up for a meeting delayed by Hurricane Dorian in August, the task force met Sept. 24 and Sept. 25 at Florida Gulf Coast University.

Cyanobacteria is the oldest life form on the planet. Some — not all — species of cyanobacteria can produce toxins. But cyanobacteria that can produce toxins do not always do so.

Florida is not alone in dealing with this problem, he said. “More than half of the states in the United States are dealing with the issue as are other countries.”

Health effects for blue-green algae toxins have been recognized for almost 1,000 years, he said.

“Cyanobacteria do not always produce toxins,” said State Toxicologist Dr. Kendra Goff. “You can’t tell by looking.

“Our message has been: If you see a bloom, stay out of it,” she said.

There are many pathways in which cyanobacteria toxins can impact humans, she explained. The severity of that impact depends on the type and duration of the exposure.

One way Floridians are likely to be exposed is through direct skin contact during recreational activities. Humans can also inhale toxins, she explained, which happens most often when the water is disturbed by water skiing or power boating.

Incidental ingestion can happen while swimming, she said. Water used as a drinking water source can also contain cyanobacteria, but the treatments done to the public water supply destroy the toxins.

Dr. Goff said low levels of toxins have been found in fish. She explained the fillet or muscle of the fish does not have the toxin level that is harmful to human health. Fish organs, such as the liver, can accumulate higher levels of toxins. Shellfish can also accumulate higher levels of some cyanotoxins.

“In Florida, most of our data is from self-reported illnesses,” she said. “Most common are rashes and eye, nose and throat irritation.”

A compounding factor is when cyanobacterial blooms decompose, the foul smelling gas hydrogen sulfide is released, she explained. This gas can cause the same symptoms as the toxins. That makes it harder to determine if the symptoms are actually from toxin exposure, said Dr. Goff.

She said animals have become ill from drinking water that contains cyanotoxins.

The Department of Health’s message continues to be “if you see cyanobacteria blooms, then stay out of the water,” said Dr. Goff. “This is a message that is repeated in other states as well.”

This year, DOH has placed signs in public access areas around the state when cyanobacteria blooms were seen. It takes time to get the toxin data, she said. The signs are put up when blooms are present even before the test results about toxins are available.

Signs are also used in the Florida Healthy Beaches program to warn the public about high levels of fecal bacteria in the water along Florida’s coastline.

“Can you swim in the water? If the area is free of signs and you see no blooms, you can swim,” she said.

Dr. James Sullivan, of Florida Atlantic University, suggested freshwater near recreation areas be regularly tested for toxins just as water is tested at beaches for fecal bacteria. He said cyanobacteria can be present and not visible to the human eye.

What is ‘recreational contact’?
Dave Whiting, of the FDEP Division of Environmental Assessment and Restoration explained state standards vary in regard to toxins levels that trigger warnings.

The World Health Organization (WHO) previously set the safe level for recreational contact at 10 micrograms of microcystin per liter of water.

In late spring, the Environmental Protection Agency came out with criteria for swimming.

EPA came up with a “tolerable daily dose” that someone can be exposed to without incurring adverse effects, said Mr. Whiting.

“They specifically in this case looked at children, ages 6 to 10, who would be recreating in the water,” he explained. Young children would be the most at risk because they are the ones who spend the most time in the water, and incidentally ingest the most surface water while they are in the water, Mr. Whiting explained. In setting the tolerable daily dose, the EPA also considered the average body weight of a child ages 6-10.

EPA set the safe level for recreational contact at a magnitude of 8 micrograms per liter.

By comparison, EPA set the standard for drinking water at 1 microgram per liter.

More study needed
Dr. Michael Parsons of Florida Gulf Coast University said the visual message is a good first line of defense for public safety.

“If you see a surface scum, that means something is going on,” said Dr. Parsons. Just because you see a surface bloom doesn’t mean there are toxins, he added, but the public should be encouraged to be cautious.

Dr. Sullivan said DEP should establish best practices guidelines for water sampling.

“We need to know the environmental drivers so we can understand these blooms,” said Dr. Sullivan. “We also need to understand what controls toxicity. Just because an organization is capable of making toxin does not mean it is going to make toxin. The type of toxin it makes and the toxicity of what it produces does vary with the environment. Along with knowing the environmental drivers, we need to know who the environmental drivers are which affect toxicity as well.”

He said there is a lot of research already available but added that research on other water bodies may not apply to Lake Okeechobee.