Whatcom County Health and Community Services issued a water quality advisory on Monday, July 28, for residents who draw drinking water directly from Lake Samish through private home water systems. A surface water test on the east shore of the lake detected elevated levels of microcystin, a cyanotoxin produced by blue-green algae blooms, also known as Harmful Algae Blooms or HABs.
The test results show microcystin at levels that remain safe for healthy adults and children over six years old. However, the levels exceed the limits considered safe for vulnerable groups. Residents in those categories are being asked to take immediate precautions for as long as the bloom is present.
Who Is Most at Risk
The advisory specifically identifies the following groups as being at highest risk from exposure to even small amounts of microcystin in drinking water: infants and young children, pregnant or nursing women, people with weakened immune systems, elderly persons, and anyone who already has liver disease. For those individuals, the county is recommending that water drawn from Lake Samish not be used for drinking, cooking, boiling, or brushing teeth. It also should not be used to prepare infant formula.
Alternative water sources, including bottled water, should be used for drinking and cooking by vulnerable household members until the bloom has passed and water quality has been confirmed safe. At current measured levels, bathing and handwashing are considered safe for all groups. Pets and livestock should be kept away from bloom-affected water.
Lake Samish sits in a valley south of Bellingham along the I-5 corridor, and a number of lakeshore properties use the lake as a private drinking water source through home filtration systems. The county is sending direct notices to residents who live along the lake and may use it as a domestic water source. Not all home filtration systems are confirmed to remove cyanotoxins, which is a key part of the advisory.
What the County Is Doing
Whatcom County Health and Community Services collected the water sample in response to a report of a visible harmful algae bloom at the lake. The test results confirmed microcystin is present. The county does not yet know how far the cyanotoxin has spread from the east shore testing location, nor how long the bloom will persist. Additional monitoring is ongoing.
Current microcystin levels remain safe for swimming and other recreational water activities, according to the county, because safety guidelines for recreation allow for higher toxin exposure thresholds than drinking water guidelines. People swallow significantly less water during swimming than when drinking.
Harmful algae blooms can often be identified visually. They may look like spilled paint on the water surface and can appear blue-green, brown, or reddish-green. If a bloom is visible at or near a water intake, the county advises not drinking the water until the bloom is gone and never drinking untreated lake water, as standard filters and purifiers do not remove algae toxins.
Symptoms and When to Seek Care
Cyanotoxins can enter the body through swallowing water, skin contact, or inhaling mist. Swallowing microcystins primarily causes gastrointestinal symptoms including nausea, vomiting, diarrhea, stomach pain, and in rare cases signs of serious liver damage. Symptoms can appear within hours to a few days after exposure.
Breathing in mist or spray from contaminated water can cause cough, sore throat, and shortness of breath. Direct skin or eye contact can cause irritation. Some types of cyanobacteria also produce anatoxins and saxitoxins, which affect the brain and nervous system and can cause tingling, muscle twitching, headaches, dizziness, and in severe cases seizures. Anyone experiencing symptoms after contact with lake water or bloom-adjacent drinking water should seek medical care promptly.
For pets showing symptoms after contact with the lake, veterinary care is also recommended immediately.
How to Report a Bloom and Get Updates
Residents who observe a bloom at Lake Samish or elsewhere in Whatcom County can report it by calling 360-778-6000 or emailing Whatcom County Health and Community Services. Additional information about algae blooms and current data for lakes across Whatcom County is available at nwtoxicalgae.org, a regional resource tracking harmful algae conditions.
Residents can also sign up for email and text alerts about drinking water quality advisories, including future harmful algae bloom notifications, through the county health department website. For anyone concerned about a recreational water illness, an online complaint form is available through the county.
Lake Samish has a history of summertime algae bloom activity, and this advisory follows a broader county-level alert about blue-green algae issued earlier this month across multiple Whatcom County lakes. The county government continues to monitor water quality at recreational and residential water bodies throughout the summer season as warm temperatures and drought conditions increase bloom risk.
