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Beware Toxic Algae Over the Fourth of July

Wednesday, July 1, 2020

Over the Fourth of July holiday, don’t act like the crowds recreating in Grand Lake St. Marys, Ohio. With area pools closed due to the pandemic, people are flocking to the lake to cool off, despite the state’s guidelines on social distancing and large gatherings. But there’s another reason to be cautious: The lake is currently experiencing a toxic algae outbreak, which can be dangerous to visitors, both human and animal alike.

Microcystin is one of the most common toxins produced by algae blooms in bodies of water. The Ohio Department of Health has issued a “red flag” warning for Grand Lake St. Marys, meaning that microcystin levels are at or above 20 micrograms per liter, or µg/L.

According to the department, a red flag advisory means that people should avoid all contact with the water, because it’s unsafe. The state considers recreation in water with an algae bloom to be safe for all ages only if microcystin levels are below 6 µg/L.

Algae outbreaks are triggered by nitrogen and phosphorus from fertilizer and animal manure that run off farm fields into water. When people touch, ingest or breathe in algae toxins, they can get sick. Microcystin can cause short-term problems like sore throat, nausea and vomiting. Long-term exposure can lead to more-serious health impacts such as liver failure and cancer.

Animals are also at risk – as of last summer, 32 animal deaths had been reported since 2010, and last summer alone, at least six dogs died after getting in or near contaminated bodies of water.

Grand Lake St. Marys has a long history of toxic algae outbreaks. EWG tracks news reports of blue-green algae blooms, which are actually tiny organisms called cyanobacteria, in our news report map, which goes back to 2010. The lake has had a toxic bloom every year since then, and there are many indications that blooms occurred even earlier.

But this lake isn’t the only body of water with an algae problem. So far in 2020, through the end of June, there have been 72 news reports of algae outbreaks across the country.

We know there are potentially many more blooms, since not every one receives news coverage. In fact, because of pandemic-triggered budget concerns, some states are cancelling or reducing monitoring for toxic algae. As EWG pointed out last summer, only 20 states test their bodies of water for algae toxins like microcystin in the first place.

If you plan to visit a lake or river – this weekend or any time this summer – keep an eye out for blooms. Before you get near the water, look for algae that is bluish-green or resembles pea soup. If you see either, stay out of the water and contact your local health department to see whether it has a record of toxic algae there.  

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