Cyanobacteria Alerts

Blue-green algae, or cyanobacteria, can naturally grow into large harmful blooms in lakes, ponds, and rivers during summer and fall.  The blooms make the water murky, and can sometimes make the water look like pea soup or paint. The blooms can produce toxins that may make people and pets sick. Toxins may be present within the algae cells or in the water.

If you or your child come in contact with an affected body of water, rinse off immediately.  If you or your child experiences symptoms after contact with cyanobacteria, consult with a healthcare professional. 

The biggest concern is if you ingested blue-green algae while swimming. Second to that, there is concern if you have direct skin contact or inhale water droplets containing the algae or toxins. 

Contact may cause skin and eye irritation. Inhalation can cause respiratory irritation and exacerbate pre-existing respiratory conditions. Ingestion can cause acute gastrointestinal symptoms, such as cramping, vomiting, and diarrhea. The health effects can be more serious, especially for children due to their smaller body weights.   

These health effects can include issues with the functioning of the liver, kidneys, and/or neurological systems. In severe cases toxins produced by blue-green algae can result in death.

Call your veterinarian immediately if your pet has been around an algae bloom and shows symptoms such as vomiting, staggering, drooling, or convulsions. These symptoms present themselves soon after exposure.  

Pets have been known to eat the scum that washes ashore and lick scum out of their fur. In Massachusetts and in many other states, canine deaths have been documented due to the ingestion of harmful algae.

Avoid swimming, fishing, paddleboarding, kayaking, canoeing, and other activities in direct contact with the water. Do not allow pets to walk or swim in or drink the water or algae scum on the shore.

Email or call the Environmental and Occupational Health Division at environment@bphc.org or 617-534-5965.

The Environmental and Occupational Health Division will refer the case to the Massachusetts Department of Public Health for investigation.

Algae blooms may last for weeks in the summertime or may disappear quite quickly. 

The Massachusetts Department of Public Health (DPH) will continue to monitor cyanobacteria algae levels in a specific area. DPH will conduct sampling for laboratory analysis once the bloom has dissipated. DPH requires two rounds of samples collected a week apart that are below the threshold of 70,000 cells/milliliter of water to determine that the advisory can be lifted.