How People and Animals Are Exposed to HABs and Their Toxins
How People Are Exposed to HAB Species and Toxins
The most common exposures to freshwater HAB species and toxins are those that occur during swimming or other recreational activities in and on the water. These exposures include:
- Oral exposure from accidental or deliberate ingestion of contaminated water; and
- Dermal exposure by direct contact of exposed parts of the body to water containing cyanobacteria cells. Also, cyanobacteria cells containing toxins can accumulate in bathing suits, particularly diving suits, and break open, exposing skin to toxins.
Other major routes of human exposure to freshwater HABs are through ingestion of toxin-contaminated drinking water, inhalation while showering, eating foods contaminated with HAB toxins (e.g., fish and shellfish) and algal dietary supplements, and exposure from water used in medical treatments (e.g., medical dialysis).
Wind-driven currents may cause blooms to amass on shorelines. These accumulations are much larger than blooms in open waters, thus presenting a greater risk to human and animal health. When in doubt, stay out! If you see signs of a bloom, stay out of the water and keep your pets out of the water. You cannot tell if a bloom is harmful by looking at it, so it is best to use caution and stay away. Do not fish, swim, boat, or play water sports in areas where there are possible harmful algae or cyanobacteria.
- Algal Blooms Can Harm Your Health (video)
- Look Out for Harmful Algal Blooms (pdf) (infographic)
For marine HABs, the primary exposure pathway is by eating contaminated seafood, especially shellfish. Marine toxins first accumulate in grazing organisms or filter-feeding shellfish that acquire them from the algae and the toxins may then accumulate higher in the food web (e.g., in predators). People are then exposed when they eat seafood containing the marine HAB toxins. There is one marine HAB, the red tide forming Karenia brevis, that can be aerosolized through wave action and has been implicated in respiratory illness from exposure through breathing the aerosols.
Learn more from the U.S. Centers for Disease Control and Prevention about human health HAB exposure, illness and how to protect yourself, including information for healthcare providers:
How Animals Are Exposed to HAB Species and Toxins
Pets and other animals can be exposed to HAB toxins through drinking toxin-contaminated water, swimming in waters with a HAB, eating HAB mats, eating contaminated animals (e.g., fish or shellfish), or by licking toxins off their fur or hair.
If you suspect a freshwater or marine HAB is present, don't let your pet drink the water, play or eat scum mats, or swim in the water body. Also, don't let your pet lick their fur after swimming in contaminated water. If your pet has come into contact with water that may contain a HAB, rinse them with tap water as soon as possible. Seek veterinary care immediately if your pet has consumed or licked scum on its fur after swimming or playing in water that may have a HAB. Symptoms of exposure to HABs in pets can include excessive salivation, fatigue, difficulty breathing, vomiting, diarrhea, and seizures. Death can occur within hours to days of exposure.