Important Note! This page discusses cyanotoxins in drinking water. For information on cyanotoxins in recreational waters (like Clackamette Cove), please visit our Clackamette Cove Water Quality Page. 

What are cyanotoxins & how do they get in the water?

Cyanobacteria, also known as blue-green algae, naturally occur in surface waters. Under certain conditions, such as in warm water containing a lot of nutrients, they can rapidly form harmful algal blooms (HABs). Some of these blooms are capable of producing toxins known as cyanotoxins that can harm humans and animals.

Oregon City’s drinking water treatment plant can generally remove most cyanobacterial cells and low concentrations of toxins. However, during a severe bloom event when drinking water sources contain high levels of cyanobacteria and cyanotoxins, the treatment plant may not be able to remove all toxins.

In the past, an increase in toxin-producing blooms has been linked to two major factors: increased nutrient concentrations from runoff (primarily nitrogen and phosphorus) and increasing water temperatures. Reducing nutrient pollution, such as nitrogen and phosphorus, in drinking water sources is important for the long-term management of HABs and the risk they pose to public health and water quality. Oregon City is committed to protecting its drinking water source. You can view our latest Drinking Water Protection Plan (2021) in the documents section below.

Are cyanotoxins harmful?

Cyanotoxins are capable of harming humans. Cyanotoxins can cause nausea, vomiting, and diarrhea. They can also damage the liver and kidneys. The Oregon Health Authority (OHA) has found no evidence that these toxins are carcinogenic or that they may cause other long term health effects

Given the potential health risks they pose, national Drinking Water Health Advisories were developed by the U.S. Environmental Protection Agency for two cyanotoxins: microcystins and cylindrospermopsin. These national Drinking Water Health Advisory levels were then adopted by Oregon Health Authority. These are currently the only two regulated cyanotoxins in drinking water.

Below are the current health advisory levels for drinking water.

Vulnerable people means infants, children under the age of six, pregnant women, nursing mothers, those with pre-existing liver conditions, and those receiving dialysis treatment.

How will I know if Cyanotoxins are in my drinking water?

The drinking water treatment plant collects raw water samples every other week between May and October for cyanotoxin analysis. Cyanobacteria blooms are most likely to occur during these months. If cyanotoxins are detected in raw water, treated water samples are collected. In the event cyanotoxins are detected in treated water at concentrations above the health advisory levels a public notice will be issued to all customers. If there is an active public alert for cyanotoxins in drinking water, it will appear at the top of this page. You can also use our public alerts look up tool to search for your address to see if there are any drinking water alerts for your home or business.

Additional Watershed Monitoring

Oregon City, as a member of the Clackamas River Water Providers, has been working with Portland General Electric (PGE) since 2006 to monitor harmful algal blooms in the Clackamas River. Through these efforts, PGE conducts weekly monitoring for blooms at North Fork Reservoir (which is upstream of Oregon City’s drinking water intake) from May to October each year. If an algae bloom is identified by PGE, samples are collected and tested for cyanotoxins. This work can help serve as a potential early warning system for us. If cyanotoxins are detected upstream in the North Fork Reservoir, we may be able to increase sampling frequency at our drinking water intake and/or better prepare for the possibility of cyanotoxins to travel downstream. We will continue to work closely with PGE to monitor for blooms throughout the summer months. To date, no cyanotoxins have ever been detected in Oregon City’s drinking water.