Early morning swimmers at Walden Pond. Photo by Andrew Peddar

Health advisory: Walden Pond fish found high in PFAS

March 6, 2023

If you fish in Walden Pond, think twice about eating what you catch.

The Massachusetts Department of Public Health has sent out a fish consumption advisory warning that recent testing of fish at the pond Henry David Thoreau immortalized found elevated levels of per- and polyfluoroalkyl substances (PFAS) above recommended levels for regular consumption.

Walden Pond was included on a list that included 12 other waterbodies at state parks operated by the Department of Conservation and Recreation. Other affected fishing areas included:

  • Ashland Reservoir in Ashland
  • Chicopee Reservoir in Chicopee
  • Lake Cochituate in Natick
  • Dennison Lake in Winchendon
  • Dunn Pond in Gardner
  • Fearing Pond in Plymouth
  • Houghtons Pond in Milton
  • Pearce Lake in Saugus
  • Pequot Pond in Westfield
  • Lake Quinsigamond in Worcester
  • Walden Pond in Concord
  • Wallum Lake in Douglas
  • Watsons Pond in Taunton

DPH also sampled surface water at these locations, and PFAS was not found at levels that would be unsafe for swimming or any other recreational activities at these locations.

PFAS are a group of man-made chemicals manufactured and used in a variety of consumer products and industries worldwide. Based on studies of laboratory animals and people, exposure to certain PFAS has been associated with changes in liver and kidney function, changes in thyroid hormone and cholesterol levels, and immune system effects. In addition, PFAS exposure has been shown to cause developmental effects to fetuses during pregnancy. Some studies also suggest an increased risk of developing cancer following long-term exposures to elevated levels of some PFAS.

DPH prioritized the testing of fish and surface water at these waterbodies because they are popular locations for swimming and fishing. They are also located in communities in or near Environmental Justice Populations, where the existing burden of disease and exposure to sources of pollution are greatest. 

Surface water testing at seven marine beaches, including Carson, Constitution, Savin Hill, and Tenean beaches in Boston Harbor; Revere Beach in Broad Sound; Kings Beach in Nahant Bay; and Wollaston Beach in Quincy Bay showed that these beaches are safe for swimming.

Because the new fish consumption advisories are different for each waterbody, recommendations range from consuming two meals per week to no fish consumption. DPH fish consumption advice applies to the consumption of all native game fish, but do not apply to stocked trout at a waterbody. Stocked fish are raised in fish hatcheries and then released. Therefore, they are unlikely to spend enough time in a lake or pond to become contaminated.