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RIDOH and DEM End Blue-Green Algae Monitoring Season

The Rhode Island Department of Health (RIDOH) and the Rhode Island Department of Environmental Management (DEM) have completed their final 2020 monitoring and evaluation of blue-green algae conditions in affected freshwater sites. Blue-green algae, also known as cyanobacteria, can produce toxins that can harm humans and animals.

A visual survey conducted over the last week of December 2020 found that cyanobacteria blooms had largely dissipated at most sites. Blue-green algae are generally less active in the lower light and temperature conditions of winter. However, the possibility of blooms below the surface and/or toxin persisting after the bloom is gone represent, even in iced-over conditions, a potential risk. With limited resources, efforts focus on seasons when recreational use is high, and when blooms are prevalent. The monitoring program is expected to resume in June 2021, dependent upon resources.

Regardless of season, the public is reminded to avoid contact with any body of water that is bright green or has a dense, floating algal mat on the water's surface. Blue-green algae blooms may look like green paint or thick pea soup.

Contact with water containing blue-green algae toxins can cause irritation of the skin, nose, eyes, and/or throat. Ingestion of untreated water containing blue-green algal toxins can cause stomach ache, diarrhea, vomiting, and nausea. Other health effects, which are rarer, include dizziness, headache, fever, liver damage, and nervous system damage. Young children and pets are at greater risk than adults, due to their size and because they are more likely to drink contaminated water.

People who experience the symptoms associated with blue-green algae exposure and who have been swimming or fishing in water or drinking untreated water from a waterbody with a confirmed or suspected cyanobacteria bloom, should contact their healthcare providers. People who come into contact with potentially affected waters should rinse their skin and wash their clothes with clean water as soon as possible. People observing pets exhibiting adverse health symptoms after contact with potentially affected waters should contact their veterinarians. Pets who encounter potentially affected waters should not be allowed to lick water off their fur and should be rinsed with clean water as soon as possible.

For more information and a list of historical advisories, visit Send reports of suspected blue-green algae blooms, along with photographs if possible, to

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