Arlington Board of Health Warns of Toxic Algae in Spy Pond, August 2009

Natasha Thorne, Health Compliance Officer of the Arlington Board of Health has notified us of a safety issue at Spy Pond.  Dogs and humans should stay out of the water until the toxic algae situation has resolved.  Consult the Board of Health for further information.

Ms. Thorne’s letter, and the Public Health Advisory she sent us, are reprinted below:


The Arlington Health Department is requesting your help to notify dog owners of the risks associated with allowing their dogs to swim in Spy Pond. High levels of microcystis algae continue to be detected in water samples from Spy Pond. This type of algae can be toxic to both humans and animals. It can be especially toxic if it is ingested in high doses as well as cause skin irritation and a rash after wading or swimming.

Although signs have been posted at Spy Pond and a Public Health Advisory has been released via the Town Alert system, it seems that more outreach is needed, therefore I am hoping you would be willing to post something to your website or direct me to another source to get this information out.

Please find the Public Health Advisory attached

Thank you,

Natasha Thorne
Health Compliance Officer
Arlington Board of Health



Town of Arlington

27 Maple Street
Arlington, Massachusetts 02476
Christine Connolly Sharkey, MPH, CHO                            Tel: 781 316-3170
Director of Health and Human Services                            Fax: 781 316-3175

August 17, 2009

High levels of microcystis algae continue to be detected in water samples from Spy Pond. This type of algae can be toxic to humans and animals. Water samples are being collected and monitored on a weekly basis by the Massachusetts Department of Public Health and the Mystic Watershed Association. This Public Health Advisory will remain in effect until cell counts drop to safe levels for two consecutive weeks. This type of algae can be toxic if ingested in high doses and can cause skin irritation and a rash after wading or swimming .The Arlington Board of Health strongly advises residents not to swim or stand in the water and especially urges residents to keep pets away from the water.

Microcystis is a cyanobacteria algae that grows naturally beneath or on the surface of many waterbodies.  Under certain conditions (such as warm weather and an abundance of nutrients in the water) the algae may undergo an explosive type of growth that results in dense, floating mats of algae.  This is commonly referred to as an “algae bloom.”

Contact with high levels of the cyanobacteria algae has been found to contribute to eye, ear, and skin irritation.  Microcystis is different from most other types of algae because it contains and can secrete a toxin into the water.  During an algae bloom, the amount of algae and toxin in the water can become elevated and exposure can be potentially harmful to people and animals.

Health concerns vary depending on the concentrations of microcystis and its toxin, microcystin.  Ingestion of elevated concentrations of the algae and its toxin can lead to more serious health effects (e.g. muscle cramps, twitching, and liver damage)

Since algae benefit from warm, sunny weather, as the days get shorter and cooler, the algae are likely to dissipate.  Any toxins that are in the water will decline over time as the algae die off.  In addition, any rainfall will help to circulate the water and break-up the bloom.

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