Warm, sunny days can lead to growth of algae in local lakes, called an "algae bloom." Blue-green algae grows 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. Blue-green algae blooms can be so thick that you cannot see into the water or can cause a scum that can be several inches thick, especially near the shoreline.
If you visit a lake and notice a bright green, blue-green, white or brownish color, cloudiness or thick scum along the shore, stay out of the water. Some blue-green algae produces toxins, which can cause illness in humans and kill pets, fish, waterfowl, and other animals. Children and pets are most vulnerable.
Whether a particular bloom is actually toxic cannot be determined without special testing. Moreover, testing only provides information on that single sample at a particular moment in time. Even the 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, so if the water at your beach looks bad, don’t swim in it, don’t drink from it and don’t allow people, pets, or livestock in it.
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When an algae bloom is occurring in a lake, take these simple precautions:
• If the water at a lake looks bad, don’t swim. Find another place to go.
• If your drinking water supply is lake water, use an alternate supply. Boiling and algicides (chemicals that kill algae) are not effective treatments, and may 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 drink the water and then lick the scum off their fur or paws. Dogs can fall ill almost immediately after swallowing waters affected by toxic algae. Children are vulnerable because they have less body weight and may accidentally swallow more water than adults.
• Blue-green algae can produce nerve toxins and liver toxins. Signs of neurotoxin poisoning usually appear within 15-20 minutes after exposure. In animals, signs include weakness, staggering, difficulty breathing, convulsions and death. In people, signs may include numbness of the lips, tingling in fingers and toes, dizziness, and paralysis. Algae can also cause skin rashes.
It may be hours or days before signs of liver poisoning appear. Liver toxins can cause abdominal pain, jaundice, diarrhea and vomiting in humans, and death in animals. Get proper medical or veterinary attention right away if you, your children, pets, or livestock have signs of poisoning.
Some activities are OK in lakes with algae blooms. Boating and fishing are OK, but avoid areas where algae are visible. Rinse boats and trailers before going to another lake. While eating freshly caught and cleaned fish may be OK, it is not recommended.
Wash your hands after contact with fish or algae-contaminated water.
For more information or to report an algae bloom or other swimming-related illness, call Thurston County Public Health and Social Services Department at 360-867-2643; also see www.co.thurston.wa.us/health/ehadm/swimming/swimming_index.html. The TDD line is 360-867-2603.
Dr. Diana T. Yu is the Health Officer for Thurston and Mason counties. She can be reached at 360-867-2501 or firstname.lastname@example.org.