New peril emerges from lakes’ algae warnings
K-State expert says blue-green blooms produce cancer-causing poison
After print deadline, both Marion Reservoir and Marion County Lake were placed under blue-green algae warnings through Aug. 3.
A family of five splashed and paddled in the Marion County Lake swimming area Saturday, while a jet skier raced along a shoreline to the east.
The family from McPherson County hadn’t seen signs placed on a hill between a parking lot and the beach, warning them to stay out of the water because of a toxic blue-green algae bloom.
“We wondered why there weren’t any other people here,” one of them said.
County residents have become accustomed to blue-green algae watches and warnings at Marion Reservoir and Marion County Lake. Many are familiar with the list of skin, respiratory, and gastrointestinal symptoms caused by algae toxins.
A lesser-known hazard of blue-green algae toxin exposure provides another reason to stay out of the water, a Kansas State University toxicology professor said.
Deon van der Merwe is head of the Veterinary Diagnostic Laboratory toxicology section and specializes in blue-green algae research.
“Microcystin, which is the most commonly produced toxin, is a human carcinogen,” van der Merwe said.
He compared the risk of microcystine exposure to increased cancer risk among long-term smokers.
“Even if you don’t have symptoms, if you have repeated exposure over a period of time it can contribute to your risk of developing cancer,” he said. “The problem here is that every time you get an exposure it adds a little risk, a little more likelihood, and they build up over time.”
Microcystine can cause cell mutations, van der Merwe said. It takes many mutations before cancer forms.
“It really is a risk, but the question is how big is the risk,” he said. “How acceptable a level of risk is is going to be different for different communities and different individuals.”
When coupled with more immediate health risks, van der Merwe believes there is sufficient reason to avoid contact with water during watches and warnings.
“I would not allow my children to go in there,” he said.
Two things are measured when water is tested — the amount of algae and the amount of toxins. High levels of either one can justify a watch or a warning, but only toxins cause health problems.
Kansas Department of Health and Environment issues weekly watches and warnings, but doesn’t publicize whether they are due to algae cell counts or toxin levels.
However, a chart distributed weekly by KDHE to government officials indicates watches and warnings for the county this summer, including those last week, have been triggered by high algae cell counts and not by toxin levels.
Van der Merwe reviewed test data for samples used for last week’s status updates and reached a different conclusion.
He said toxin levels at the reservoir were high.
“In all three test sites, both the cell counts and microcystin concentration are enough to trigger a warning,” he said.
A week earlier, two of the three reservoir samples had toxin concentrations high enough to trigger a watch or warning, van der Merwe said, but KDHE’s chart listed algae cell counts as the cause.
Algae cell counts were high and toxins low for last Thursday’s warning for the county lake.
Van der Merwe said issuing watches and warnings without high toxin levels was prudent.
“It’s conservative, but it’s the safe way to do it,” he said. “If you have the cell counts, you really should stay away because there’s a delay between when the sample gets analyzed and when you might want to access the lake. They can start producing toxins from one day to the next.”
KDHE draws water samples from both lakes on Mondays. Lake status updates are issued Thursdays.
Variations in sampling procedures and changing lake and weather conditions complicate assessing threats, van der Merwe said. KDHE draws samples from the same places each week, which makes it easier to establish consistency and comparisons.
“It certainly is possible to influence a result by the way you take a sample,” he said. “If you take just one sample there’s typically a lot of variation in the lake. You have to keep in mind it is not a complete picture. The density of algae can vary significantly over distance and time.”