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The original item was published from 7/7/2021 2:47:47 PM to 7/14/2021 5:00:05 PM.

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Posted on: July 7, 2021

[ARCHIVED] White Pond No Swimming Water Use Advisory


Based on a recommendation from the Massachusetts Department of Public Health (MDPH), a No Swimming water use advisory has been issued for all of White Pond due to a bloom of cyanobacteria (blue-green algae).  These blooms may produce toxins that can make pets and people sick.


The Concord Board of Health strongly advises:

  • Do not swim anywhere in White Pond
  • Do not allow your pet to swim in or drink the water.
  • Rinse pets and children off immediately if they come into contact with an algae bloom.           
  • Avoid contact with areas of algae concentration along the shore.        


Issuance of a Public Health No Swimming Advisory

MDPH recommends issuing a public health advisory to avoid all contact (including swimming) with recreational freshwater when at least one of the following criteria is met:

1.  A visible cyanobacteria scum or mat is evident;

2.  Total cell count of cyanobacteria exceeds 70,000 cells/mL;

3.  Concentration of the toxin microcystins exceeds 8 μg/L; or

4.  Concentration of the toxin cylindrospermopsin exceeds 15 μg/L

These guideline values are based on US Environmental Protection Agency (US EPA)1 and World Health Organization (WHO)2,3 recommendations.

The No Swimming Advisory at White Pond has been issued due to a persistent cyanobacteria (blue-green algae) scum which has been visible at various locations around the pond for the past several weeks and which shows no sign of dissipating.  The current bloom in White Pond appears as areas of blue, green, bright green or yellowish floating scum along the shoreline and in the water column, see pictures below.   The no swimming advisory will remain in effect until no visible scum is present at the pond.  


When will this advisory be lifted?

Algae blooms may last for weeks in the summer, or may disappear quite quickly.   Town staff will regularly observe White Pond for the presence of a visible algae bloom over the coming weeks.    

Once the bloom has subsided and is no longer visible, water sampling will occur. MDPH recommends that the water advisory not be lifted until two consecutive weekly samples show algal cell counts below the safe limit of 70,000 cells/milliliter of water.


What are Cyanobacteria (Blue-Green Algae) Blooms?

Cyanobacteria can form harmful blooms in lakes, ponds, and rivers that make the water murky, and can sometimes make the water look like pea soup or paint. 

Blue-green blooms can produce toxins that can make pets and people sick.   Toxins may be present within the cyanobacteria cells or in the water.  

Health concerns associated with cyanobacteria blooms vary depending on the type of cyanobacteria, the route of exposure, and the amount of cyanotoxins present. Ingestion is the primary concern since ingesting small amounts of cyanobacteria or cyanotoxin can cause gastrointestinal symptoms while larger amounts may cause liver or neurological damage. Contact with cyanobacteria can cause skin or eye irritation. Inhaling water spray containing cyanobacteria can cause asthma-like symptoms. Small children and pets are more susceptible to the effects of cyanotoxins than adults.

PETS--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 fairly soon after exposure. Animals of most concern are dogs, which have been known to eat the scum that washes ashore and/or lick scum out of their fur. In Massachusetts and in many other states, canine fatalities have been observed due to the ingestion of harmful algae.

For more information, call the Concord Board of Health at 978 318 3275

MDPH, US Centers for Disease Control and Prevention (CDC)  and US EPA websites provide further information on cyanobacteria blooms:

Blue Green Algae 7/7/2021

Blue Green Algae 7/7/2021 Blue Green Algae 7/7/2021


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