Cyanotoxins are toxic substances produced by certain types of cyanobacteria, commonly known as blue-green algae. Cyanobacteria can form harmful blooms in water bodies, which are often referred to as harmful algal blooms, or cyanoHABs. Cyanotoxins can contaminate drinking water sources and pose serious health risks to both humans and animals, ranging from mild gastrointestinal symptoms to severe liver or neurological damage.
In addition to health concerns, cyanoHABs can cause operational challenges for drinking water systems. They can affect water taste and odor, alter pH levels, and form algal mats that physically block water system intakes. When intakes are blocked, it becomes difficult for public water systems to access and treat water, possibly disrupting supply and increasing operation and maintenance costs.
Causes of cyanoHABs
Factors affecting cyanoHAB formation and continuation include sunlight, warm water temperatures, still waters, nutrient availability (nitrogen and phosphorus), pH, and water column stability. Climate change is expected to increase both the frequency and severity of cyanoHABs due to rising temperatures, more intense sunlight, and stormwater runoff carrying additional nutrients and pollutants into lakes and streams. See DEQ's Harmful Algal Bloom Strategy for more information.
Regulations and monitoring in Oregon
Oregon Health Authority's Drinking Water Services program requires public water systems that use surface water sources and are susceptible to cyanoHABs to regularly test for cyanotoxins. Those systems must also notify the public of drinking water detections and issue drinking water advisories when testing results exceed health advisory levels for cyanotoxins. Visit OHA's Cyanotoxin Resources for Drinking Water web page for more information on rules and resources for public water systems.
DEQ partners with OHA to analyze public drinking water system samples at no cost to affected water suppliers. DEQ is also responsible for identifying pollution sources, investigating causes of cyanoHABs, and developing pollution reduction plans. Limited statewide monitoring exists, and some water bodies are sampled by DEQ and local agencies. Satellite data also provide estimates of cyanobacteria levels in Oregon's large lakes and reservoirs. Visit DEQ's Harmful Algal Blooms web page for resources, including:
- Causes, response, actions and prevention strategies for cyanoHABs
- DEQ's Freshwater Cyanobacteria HABs strategy
- Satellite estimates of cyanobacteria in Oregon lakes and reservoirs
CyanoHABs prevention and management strategies
Reducing nutrient pollution and addressing water temperature impairments are key to preventing cyanoHABs. Excess nutrients typically originate from agricultural, industrial and urban runoff sources, as well as atmospheric deposition - where airborne pollutants are carried through the atmosphere and settle onto land or water through rain, snow or dry particles. The specific strategies needed depend on watershed characteristics, type of cyanoHABs present and local regulations.
Examples of strategies for reducing and preventing cyanoHABs include:
- Implementing agricultural practices to reduce fertilizer runoff (e.g., cover crops, proper manure management, etc.)
- Improving stormwater management to prevent excess nutrients from entering water bodies
- Ensuring healthy riparian buffers to shade streams and reduce erosion
- Educating the public on responsible fertilizer use and septic system maintenance
DEQ is developing a statewide nutrient reduction strategy to prevent nutrient pollution from human activities. Water systems and communities are encouraged to provide input on this effort. For more information, go to DEQ's Nutrient Reduction Strategy web page.
Contact DEQ's Drinking Water Source Protection Program for assistance with identifying partners, tools and resources that can help with HABs prevention.