Avoid water contact in lakes with algae blooms

Contributing writerNovember 5, 2011 

Recently, advisories have warned about algae blooms in local lakes. Blue-green algae reproduce rapidly in fresh water when the amount of sunlight, temperature and nutrients are adequate.

Within a few days, a “clear” lake, pond or ditch can become cloudy with algae growth. This is an algae bloom. Blue-green algae blooms usually float to the surface and can be several inches thick near the shoreline.

If you visit a lake and notice a bright green color or thick scum along the shore, stay out of the water. Avoid areas where there are obvious algae blooms. Some blue-green algae produce toxins, which can cause illness in humans and kill pets, fish, waterfowl and other animals.

When an algae bloom is in a lake, take these simple precautions:

 • If the water at a lake looks bad, don’t swim or contact the water.

 • If your water supply is lake water, use an alternate supply. Boiling and algicides are not effective treatments, and might release any potential toxins into the water.

 • Keep children, pets, and livestock away from the water. Poisoning is more severe the smaller the person or animal and the larger the amount of toxin ingested. Pets are the most susceptible because they tend to both drink water and then lick the scum off their fur or paws. Children are also vulnerable because they have less body weight and might accidentally swallow more water than adults.

Get proper medical or veterinary attention right away if you, your children, pets or livestock have signs of poisoning.

 • Blue-green algae can produce nerve toxins and liver toxins. Signs of neurotoxin poisoning usually appear within 15-20 minutes after ingestion. In animals, signs include weakness, staggering, difficulty in breathing, convulsions and death. In people, signs might include numbness of the lips, tingling in fingers and toes and dizziness. Algae also can cause skin rashes.

 • It might be hours or days before signs of liver poisoning appear. Liver toxins can cause abdominal pain, diarrhea and vomiting in humans and death in animals.

Some activities are OK in lakes with algae blooms. Boating is fine, but avoid areas where algae are visible. Rinse boats and trailers before going to another lake. Fishing is OK, but fish should be cleaned as soon as possible and all internal organs should be immediately discarded. Remember to wash your hands after cleaning fish.

Whether a particular bloom is toxic can’t be determined without special testing. Moreover, testing provides information only on that single sample, at a particular moment of time. Even scientific experts have not yet solved the mystery of why, when and how algae turns toxic.

In other words, there is no way to predict when, or if, an algae bloom will be toxic. If the water at your beach looks bad, stay out.

For more information, including a list of lakes with algae advisories, contact Thurston County Public Health and Social Services Department at co.thurston.wa.us/health/ehadm/swimming/blue_green_algae.html or 360-867-2626, (TDD line 360-867-2603).

Dr. Diana T. Yu is the health officer for Thurston and Mason counties. Reach her at 360-867-2501 or email yud@co.thurston.wa.us.

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