Play Live Radio
Next Up:
0:00 0:00
Available On Air Stations

CDC Warns About Health Risks Of More Algae Blooms, But Data On Algae In Austin Lakes Is Still Scarce

A researcher holds a sample of algae.
Michael Minasi
Brent Bellinger, lead reservoir ecologist for City of Austin, holds up a sample of a non-toxic type of algae found in Lady Bird Lake on Sept. 9.

When toxic blue-green algae was first reported in Austin in 2019, it struck fear into the hearts of dog owners. In its first year detected in Lady Bird Lake, the slimy stuff claimed the lives ofat least five dogs that had ingested it while swimming. Since then, it has been a recurring problem in lakes around the region.

But while the risk posed to dogs was clear, less is known about the algae’s potential impact on humans. A report released this month from the Centers for Disease Control and Prevention began to fill in those blanks, but still leaves many questions without clear answers.

The study is a nationwide attempt to catalog emergency room visits related to all kinds of toxic algae from 2017 to 2019. It found that respiratory problems were the most common reason people went to the ER after touching or ingesting algae. Gastrointestinal and neurologic illness was also reported, as were skin problems. The study doesn't mention any deaths after coming into contact with algae.

The study doesn't provide much detail about the specific risks related to the kind of algae found in Central Texas. It doesn't specify whether the ER visits were prompted by exposure to blue-green algae — the kind found in Lady Bird Lake, also known as cyanobacteria — or toxic "red tide" algae, which blooms on the coasts.

“As the number of blooms increases annually, the likelihood of negative health outcomes (e.g., respiratory or gastrointestinal illness) from exposure also increases."
Centers for Disease Control and Prevention

Of the 321 cases analyzed, only eight occurred in Health and Human Service Region 6, which includes Texas, Arkansas, Louisiana, New Mexico and Oklahoma.

The City of Austin said it is aware of only one potential case of human algae poisoning, but noted the symptoms may have been caused by other pathogens.

"We know of one reported ER visit that the patient’s family said might be related to harmful algae," Stephanie Lott, a spokesperson for the City's Watershed Protection Department, wrote in an email to KUT. "The City of Austin investigated the incident and did not find any toxins in algae at that location. Based on the available information, the City was not able to either confirm or rule out that harmful algae was the cause."

She said there isn't a formal tracking system in the state, so the city is relying on people calling 311 to report potential incidents.

It's unclear what type of algae was to blame for the ER visits tracked in the CDC report. The report stated that a large percentage of those visits were the result of one massive red tide event in the Southeast in 2018.

The report authors noted the number of cases is likely an undercount. The study had access to data for only 70% of ER visits that occurred in that timeframe. It also relied on patients to self-report that they had been exposed to some kind of algae.

Insofar as the number of algae blooms correlates to the number of people who get sick, the authors said they believe more people are likely to be affected by algae in the future.

“As the number of blooms increases annually, the likelihood of negative health outcomes (e.g., respiratory or gastrointestinal illness) from exposure also increases,” the report says.

Algae Blooming

Researchers said there is one big reason the number of algae blooms is increasing: We are feeding the algae.

In Austin, for example, cyanobacteria appeared after a massive flood swept runoff into Lady Bird Lake containing septic waste and agricultural and residential fertilizers. All those things contain phosphorus, which the algae needs to grow.

That’s why reducing fertilizer use and improving land and agricultural management are crucial to combatting cyanobacteria.

The CDC report also observes that global warming is likely to bring more algae blooms, as cyanobacteria thrives in warmer waters.

Locally, the City of Austin has initiated an algae-monitoring program and websiteto warn people where it is being detected. Austin’s Watershed Protection Department is also testing a program to starve the algae out of parts of the lake.

In the meantime, swimmers should be cautious in local waterways, especially during warmer seasons.

Brent Bellinger, lead reservoir ecologist for the city, said the algae is most dangerous when ingested, but can also irritate the skin.

“We recommend if you see large clumps of algae ... to just kind of avoid those areas,” he told KUT earlier this year. “You never want to gulp the water.”

Got a tip? Email Mose Buchele at Follow him on Twitter @mosebuchele

If you found the reporting above valuable, please consider making a donation to support it. Your gift pays for everything you find on Thanks for donating today.

Mose Buchele focuses on energy and environmental reporting at KUT. Got a tip? Email him at Follow him on Twitter @mosebuchele.
Related Content