Health Tips

Are blue-green algae toxic and a health risk to humans?

Species of blue-green algae can include both toxin-producing and non-toxin-producing strains, but there are many species of blue-green algae that do not produce toxins. Little is known about the environmental conditions that trigger toxin production, and there is no way to tell just by looking at a bloom whether or not it will produce toxins. Over time, these toxins are diluted and eventually break down and disappear.

Information regarding toxins from blue-green algae and risks to humans, fish and wildlife is very limited, but the cyanotoxins produced by the blue-green algae can be a threat to fish, pets, livestock, wild animals and humans if untreated surface water is ingested.  There is no known risk from eating fillets (muscle tissue) of healthy fish caught in bloom-affected waters.

Currently, there are no state water quality guidelines for recreational waters related to blue-green algae. However, it is recommended that people do not swim in areas experiencing intense blooms.

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How can humans be affected by blue-green algae toxins?

Blue-green algae can produce a number of toxins that can affect the liver, digestive system and nervous system, Most problems happen when water containing high levels of toxin is ingested. Abdominal cramps, nausea, diarrhea, and vomiting may occur if untreated water is swallowed.  Rashes can happen when skin is exposed to the algae when swimming.

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How can I prevent exposure to these toxins?

 Most people avoid a blue-green algae bloom because they tend to be icky-looking and smelly. It is important that people and pets do not engage in recreational water activities in blue-green algae blooms. It is especially important that individuals and pets do not consume untreated surface water from areas experiencing blooms. Boiling water does not remove or destroy these toxins.

Ways to Limit Your Contact with Blue-green Algae Toxins

• Do not drink, cook or shower with untreated water from lakes, ponds or streams, because there are many types of harmful bacteria and other pathogens in the water bodies in Florida.
• Do not allow pets or livestock to swim in or drink scummy water. People should also not swim in water with the blooms.
• If you or your animals accidentally get into a blue-green algae bloom, wash with fresh water and soap after skin contact, and avoid swallowing or inhaling water. Be sure to rinse all swimming suits and other wet clothing well as the bloom can become trapped in the material. Wash animals' fur thoroughly before they start to groom themselves.
• Avoid exposure to irrigation water drawn from untreated sources.
• Notify your local water quality officials if you notice unusual changes in the taste or smell of your tap water.

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Can blue-green algae supplements (such as Spirulina) contain toxins?

Some manufacturers collect their blue-green algae from the wild where many types (toxic and nontoxic) can grow together. A recent study found most of the products tested had low levels of blue-green algae toxin. The US FDA has received complaints from consumers about nausea; diarrhea and other symptoms after taking blue-green algae supplements but these cases have not been confirmed as being caused by the supplements.

At this time, people who choose to use these products should exercise caution. Children, pregnant women and people with impaired liver function should avoid these products until their safety has been proven.

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Are there any drinking water standards for these toxins?

There are currently no standards for blue-green algae toxin levels in drinking water in the US. Other countries and the World Health Organization have developed guidelinesfor drinking water.

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