NORTH ATTLEBORO — Officials are warning women of child-bearing age and children to not eat large mouth bass caught in portions of Falls Pond, and others to limit their consumption of the fish to twice a month.
Meanwhile in an unrelated development, the town conservation commission has issued a notice saying the pond was recently treated for invasive, non-native vegetation.
The fish warning extends to women who are pregnant, could become pregnant, or are nursing. It also applies to children under age 12.
The state Department of Public Health says tests on the fish in the North Basin of Falls Pond have found elevated levels of mercury, just over the state limit.
The fish had a .53 parts per million concentration of mercury while the state guideline level is .50.
Falls Pond was one of 15 fresh water bodies added last week to a list of 181 in Massachusetts with fish on the warning list.
“It is relatively common for ponds to have mercury in their water and sediment, largely due to airborne emissions which can travel hundreds of miles before settling into the sediment of affected water bodies,” the state Department of Public Health said in a statement.
“When this happens, the mercury cycles through the environment where it is eventually ingested by small fish, which are in turn eaten by larger fish, so that the mercury accumulates as it gets passed up the food chain. As a result of bioaccumulation, the mercury levels in fish can be exponentially higher than the water they inhabit.”
Town Conservation Agent Shannon Palmer said the section of the pond in question, North Basin, is the larger, northern end of the pond where the beach is. It’s where swimmers and fishing enthusiasts tend to go, she said.
Signs have gone up at the pond notifying people of the fish and vegetation situations, Palmer said, adding it is a coincidence that they happened at the same time.
The mercury problem was discovered by the state, which informed the town.
“The mercury levels in the fish tested from Falls Pond, North Basin were compared to the DPH guideline level of 0.5 parts per million (ppm). The mercury levels detected in large mouth bass were above the DPH guideline value and thus the regular consumption of these fish may pose a potential health concern,” a letter from the state to the town health department states.
Anne Marie Fleming, the town’s public health nurse, said fish are tested routinely and the warnings are fairly common statewide.
According to the World Health Organization, mercury can be harmful to small children and fetuses by impeding growth in their brains and neurological systems.
The agency also says on its website that mercury “occurs naturally in the earth’s crust. It is released into the environment from volcanic activity, weathering of rocks and as a result of human activity.
“Human activity is the main cause of mercury releases, particularly coal-fired power stations, residential coal burning for heating and cooking, industrial processes, waste incinerators and as a result of mining for mercury, gold and other metals.”