Harmful cyanobacteria blooms are potential public health threats in nearly every state in the U.S. due to their presence in drinking and recreational waters.  The extent of this threat is not well known.  Exposure to these toxins can cause an array of adverse health effects ranging from rashes and allergies to devastating liver damage in susceptible populations.  The public health threat is potentially intensified when standard water treatment technologies do not effectively remove these toxins.  In some cases, water treatment can exacerbate the problem rather than alleviate it.  For example, the use of copper sulfate as an agent to control a bloom may, in fact, disrupt cells and release toxins into the water.  However, it is not known how often toxin-producing blooms occur in drinking water sources and publicly accessible ponds, or if most standard drinking water treatments reduce toxin concentrations sufficiently to protect public health.  It is also unclear whether the public is being routinely exposed to very low levels of these toxins in drinking or recreational waters or what the long-term impact of these exposures might be.  For these reasons and because cyanobacterial toxins are extremely potent, the U.S. Environmental Protection Agency (EPA) has included cyanobacteria and cyanobacterial toxins on their Contaminant Candidates List.  This requires data solicitation to assess the occurrence of these toxins in drinking water sources and treated drinking water, the health effects associated with these exposures, and analytical methods for detecting these toxins in water.


Lyngbya is a toxic marine cyanobacterium (blue-green algae) which forms clumps or mats of fine strands that attach to seaweed and rocks. Through the accumulation of gas bubbles mats can rise to the surface to form large floating mats, which can wash up on beaches often mixed with seagrass.

Exposure to Lyngbya can cause skin, eye, and respiratory irritation. People who have come into contact with Lyngbya may complain of a stinging, burning or itching sensation within minutes to hours after exposure. Affected areas may appear red and swollen, and small blisters may form. In severe cases, affected skin may peel off.  Reddening and swelling of the conjunctiva of the eye and the mucous membrane of the nose may also occur if those parts of the body have direct contact with Lyngbya.

Because of the potential for severe irritation, boaters should avoid swimming or wading in areas where Lyngbya is growing or floating in the water and should not have direct contact with material washed onto the beach.

Additional Information

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Contaminant Candidates List

Last updated: July 31, 2012