A health advisory has been issued for Detroit Lake due to the presence of toxic blue-green algae, the Oregon Health Authority said on Friday.
Water testing at the reservoir east of Salem confirmed toxin levels that can be harmful to humans and animals, the agency said.
Visitors should avoid swallowing water while swimming, water skiing or power boating in areas where blooms are identified, OHA said.
The toxic bloom was located in the Heater Creek arm of the reservoir when testing was conducted on May 31. However, the advisory applies to the entire reservoir because the bloom often moves across the reservoir to different areas, said David Farrer, public health toxicologist for the OHA.
"It can move pretty fast," Farrer said. "It gets blown around by the wind and can sink and come back up somewhere else. There are lots of clear areas in the reservoir, but because it can end up just about anywhere, we issue the advisory for the entire lake."
Exposure to toxins can produce a variety of symptoms including numbness, tingling and dizziness that can lead to difficulty breathing or heart problems, and require immediate medical attention, OHA said in a news release.
"Symptoms of skin irritation, weakness, diarrhea, nausea, cramps and fainting should receive medical attention if they persist or worsen," OHA said.
The toxin the algae bloom tested positive for is called cylindrospermopsin, Farrer said. It was tested at a level of 70 parts per billion. OHA issues a health advisory for anything above 20 parts per billion.
The last time cylindrospermopsin sparked a health advistory at Detroit Lake was 2015.
Children and pets are at increased risk for exposure because of their size and level of activity. People who bring their pets to Detroit Lake for recreation activities should take special precautions to keep them from drinking from or swimming in the lake, OHA said.
Toxic algae blooms are more common later in the summer, but it's not unusual to have one at the beginning of June, Farrer said.
"You'll often have a bloom when there's rain after an extended period of dryness," he said. "The run-off can carry excess nutrients into the lake. But for any bloom, it's hard to tell exactly what causes it."
The health advisory will be lifted when tests confirm toxin levels that are no longer dangerous.
In-depth on toxic algae
Below is a question and answer with Farrer on exactly what the health advisory means for those planning to head to Detroit Lake.
Is it dangerous to go motorboating, water skiing or swimming at Detroit Lake?
Yes. Water skiing is the most dangerous because the combination of basically swimming in the water, and the spray that gets kicked up, makes it easy to inhale droplets of the water. The biggest danger is swallowing or inhaling the water.
Why is it dangerous?
The algae bloom at Detroit Lake tested positive for a toxin called cylindrospermopsin. Not all algae blooms are toxic, but this one is.
The danger is that this toxin can cause kidney and liver damage. Symptoms would be similar to stomach flu, including vomiting, stomach pain and diarrhea. If you're going to be impacted, it's usually going to be within 24 hours of exposure. Every year we see some illness, but so far it hasn't been fatal for humans in Oregon or the United States.
Whom are you most worried about in these situations?
Young children and dogs are the most at risk. With young children, it's the fact that they're more likely to swallow water when they're swimming.
Dogs are by far the biggest risk. They drink a lot more water than a human would, and they'll also drink in areas where there is a higher concentration of the toxic algae. Humans normally avoid those scummy floating algae blooms that you can see on the surface of the water, but anecdotally, we think dogs might actually like the flavor of the scum and will eat it, which brings a much more concentrated dose. With dogs, it can often end in death.
What about fishing?
It is safe to eat the fish. We recommend cleaning the fish and not eating the internal organs. Fishing itself is a low-risk activity because people don’t usually get much water in their mouths while out fishing.”
Is it safe swim or boat in areas where you don't see the floating algae blooms?
We apply the advisory to the entire reservoir. You can't predict where the blooms will be, and you can't always see them very well. The greatest risk is the scum itself, but we advise people to stay out of bodily contact with the water in the entire reservoir.
Will the toxic algae be around all summer?
I think there is a good chance this advisory will be lifted at some point. To try to predict when is pretty difficult. Very often lakes will have a bloom early in the season, and then it goes away so we can lift the advisory, and then it comes back later in the season.
Your department issued an advisory. Is that enforceable — meaning, is it against the law to go swimming at Detroit Lake right now?
It's not a closure, so no. It's not something that's enforceable, and we don't want to enforce a rule like that. We're just giving people the chance to make informed decisions, to understand what the risks are. You're free to choose what you do with that information.
Plenty of activities remain safe, though, even being on the water?
It's healthy for people to be outside and there are a lot of things you can still do at Detroit Lake. Boating is safe as long as there isn't a lot of spray. Canoeing on the lake is safe. You can hike on the shoreline and camp. It's just swimming and water skiing, mainly, that we don't recommend.