As toxin advisory continues at Detroit Lake, North Santiam River, here's what to know

The Oregon Health Authority declared a health advisory for Detroit Lake, Big Cliff Reservoir and the North Santiam River on July 16 due to toxic blue-green algae at the trio of recreation destinations east of Salem.

Subsequent tests have continued to show high levels of a cyanotoxin called microcystin, a toxin that can cause sickness in adults but is particularly dangerous for small children and dogs, health officials said.

The health advisory isn’t a new phenomenon — Detroit Lake frequently had toxic algae blooms in the past, but this is the first one since 2018 and the first to include the North Santiam River.

Part of the reason is better testing. In 2018, after cyanotoxins entered the drinking water of Salem, a major effort was put in place to detect high toxin levels in the Santiam.

The Statesman Journal talked to David Farrer, public health toxicologist for OHA, for a look at what the advisory means for those heading to the Santiam Canyon.

Is drinking water safe for towns that pull drinking water from the Santiam?

Yes. Treated drinking water in cities such as Salem, Stayton, Gates and Jefferson all have toxin levels that are either non-existent or below safety thresholds. All treated city water is safe to drink.

The toxins are showing up in the “raw” water from the North Santiam that is tested before it is treated. That’s why this is an advisory for recreational activities.

What’s the concern about water in Detroit Lake, Big Cliff and the North Santiam?

The biggest danger is swallowing or inhaling the water. That can come from swimming or an activity like water skiing or even whitewater rafting or kayaking if the spray is hitting you in the face.

Why is it dangerous?

The algae bloom at Detroit Lake tested positive for a toxin called microcystin. Not all algae blooms are toxic, but this one is, and it’s at a high enough concentration that the toxins are staying potent enough as they’re released downstream into the North Santiam to stay above levels that we consider safe.

Symptoms of sickness would be similar to stomach flu or food poisoning, 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.

Have we seen any sickness since the advisory has been issued?

We’ve had one confirmed sickness and the death of a dog at Turner Lake (a separate health advisory) . On social media, there was (a report of) another likely sickness to a dog. But the illness is notoriously underreported because the symptoms are very similar to food poisoning, and that’s what it gets attributed to. It’s very helpful for us if people report an illness or suspected illness .

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.

The main thing is that, if you see scum on the surface, or green floating globs suspended in the water, those are areas you definitely want to stay away from.

What is the threshold for the health advisory?

The level where a recreational advisory is issued is 8 micrograms per liter in the water. The drinking water level is much lower, at 0.3 micrograms per liter.

Where have tests shown high levels of toxins?

Not every testing location in the three bodies of water have toxins above 8 micrograms per liter in the water. At Detroit Lake, for example, the area near the log boom has frequently tested above safe levels, but the Santiam Flats area hasn’t. Big Cliff Reservoir has frequently tested above safe levels. The North Santiam has been a mixed bag, with some tests above safe levels and others below.

Toxin levels are not uniform across the lake or river. OHA issues advisories for the whole lake or river when any part of it is over the advisory threshold because blooms can move over the course of a day or week, and the agency isn't nimble enough to respond that quickly to lift or issue advisories for parts of the lake that may or may not have a bloom at any given moment.

Given that, is it safe to 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 or river.

What about fishing?

We are not sure. We don’t have much data on toxin levels in fish when a bloom is on. If you do 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 the advisory enforceable? Is it against the law to go swimming at Detroit Lake or tubing in the North Santiam?

It's not a closure and not enforceable, and we don't want it to be. 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.

How many tests below 8 micrograms are required to lift the advisory?

When testing has been frequent (as in this case) such that we can observe trends over time, we only need one round of sampling results in which all of the locations sampled in the lake are below the advisory threshold. We will likely consider Detroit Lake separately from Big Cliff and from the Santiam River when it comes to lifting the advisory.

What causes this toxic algae blooms?

Two main nutrients are nitrogen and phosphorus. Those nutrients can come from agricultural runoff or the leaking septic system from cabins around the lake. It can even come from invasive species.

We’ve had one of the hottest months of July on record . Could that have made a difference?

Yes. It got hot pretty early this year. The heat definitely has the potential to accelerate toxic algae growth because as the water temperature rises, it increases the favorable conditions for bacteria growth.

Zach Urness has been an outdoors reporter in Oregon for 16 years and is host of the Explore Oregon Podcast . Urness is the author of “ Best Hikes with Kids: Oregon ” and “ Hiking Southern Oregon .” He can be reached at zurness@StatesmanJournal.com or (503) 399-6801. Find him on X at @ZachsORoutdoors.

This article originally appeared on Salem Statesman Journal: As toxin advisory continues at Detroit Lake, North Santiam River, here's what to know