WINCHESTER – For most people who live near it or travel a distance to enjoy its deep waters and scenic beauty, Upper Mystic Lake conjures up happy thoughts.
For generations, the lake has been a popular spot, especially on summer weekends, when parents bring their youngsters to frolic in the shallows off the public Sandy Beach or build sand castles, anglers wait for fish to bite, and families gather to picnic by the water.
Nobody worries about the chemicals under the lake’s surface – at least none of the beachgoers interviewed on a recent Sunday. But that’s probably because few people know what several scientists who have studied the lake in recent years know – that it contains as much as 10 tons of arsenic and undetermined amounts of lead and chromium.
The scientists say that even though most of the contaminants are buried in the sediment on the bottom of the lake, trace levels of arsenic have been detected in the water. And while the researchers have different opinions about the risk of being in the water, all say they believe people at the lake have a right to know about the contamination.
But there are no warning signs at the beach or elsewhere around the lake.
“I guess if I were a person that lived on the lake or used the lake, I would want to know,” said Dartmouth College biology professor Celia Chen, who studied arsenic and lead in fish pulled from the Upper Mystic. “I think that kind of information is something the public should know about.”
John Durant, a professor of civil and environmental engineering at Tufts University who also has conducted research on the lake, said he also would “seriously consider putting a sign” up if he worked for environmental authorities.
The arsenic is a remnant of the sulfuric acid manufacturing industry that operated in the region from the end of the 19th century through the 1930s, according to researchers. The manufacturers used arsenic-rich iron pyrates, which were imported from Spain, to make the acid, and the arsenic leaked or was dumped into the Aberjona River, which flows into Upper Mystic Lake. Lead, which was used in pesticides and had been a gasoline additive, and chromium, used in dyes by the leather tanning industry from the turn of the century, also collected on the bottom of the lake.
Various scientific studies have documented arsenic in the lake since the early 1990s. But no cautionary sign has gone up because the contamination levels were not considered dangerous to human health, according to the state Department of Conservation and Recreation, which operates the beach.
“Unless you’re going to eat the sediment at the bottom of the lake, it’s not really going to pose a danger to human health. We don’t think people are eating the sediment at the bottom of the lake,” said department spokeswoman Wendy Fox. “There is no requirement to post it because it is not considered dangerous.”
The department last tested the lake for arsenic in 1991 and in 1992, Fox said, and found levels that were well below the state’s maximum standard for drinking water. In response to inquiries from the Globe, however, the department stated that it would once again test the lake for arsenic before next summer’s swimming season in the interest of public safety. Houghton’s Pond in Milton and Pierce Lake at Breakheart Reservation in Saugus, where traces of arsenic were detected in the water in the early ’90s, also will be tested, Fox said.
Scientific opinions on the risks from the submerged arsenic differ.
Harold Hemond, a professor of civil and environmental engineering at the Massachusetts Institute of Technology who has done extensive work documenting chemical pollution in the lake, said he swims in the lake, and noted that the levels of arsenic in the water are actually below federal drinking-water standards. The highest concentrations that were detected in the lake’s surface waters are about 5 grams of arsenic per billion grams of water, while the US Environmental Protection Agency’s drinking water standard is 10 grams of arsenic per billion, he said.
Although concentrations significantly higher than the drinking-water standard – as high as 1 gram of arsenic per 1,000 grams of sediment – have been detected in the lake-bottom sediments, Hemond said, recreational users of the Upper Mystic should not worry because most of the arsenic is buried under a couple of feet of sediment in the deepest part of the lake, which is under almost 80 feet of water.
“The arsenic is likely to remain there in the absence of major physical or chemical changes to the lake,” Hemond stated in an e-mail. “Our current studies do not show evidence of any major chemical changes in the lake that would affect this situation.”
Durant also said that the only real water-quality concerns in Upper Mystic Lake are sewage bacteria, not toxic chemicals. “People recreate in the Upper Mystic Lake every day, and there are no reports of any problems,” he said.
But Chen said she is not sure it is completely safe for people to swim in the lake or eat fish taken from its depths.
“I don’t think people know how much arsenic is absorbed through the skin. In that regard, I don’t think it would be a good idea to swim in the lake. Arsenic exposure is associated with skin cancer and bladder cancer,” she said, adding that accidental swallowing of water is another concern.
“When people swim, they drink a certain amount of water – certainly kids do,” she said.
A Dartmouth study that Chen coauthored found that arsenic levels were up to 10 times higher in Upper Mystic Lake plankton compared with plankton from 20 uncontaminated lakes in the Northeast. Arsenic levels in fish, however, were found to be within range of levels in fish from uncontaminated water bodies. But Chen said she cannot say Upper Mystic Lake fish are safe to eat because her team did not have the resources to test the larger and older fish, which might have accumulated higher levels of arsenic with longer exposure to the contaminant.
“The smaller fish we looked at – under 6 inches – were not the fish people eat,” she said. “I think they should go and test the larger fish.”
Organisms that live on the lake bottom – such as worms, snails, and freshwater clams – also were not tested, she said.
Robert Breault, a scientist with the US Geological Survey who coauthored the most recent study of the Mystic River watershed, also said that a detailed health-risk assessment should be conducted. The study, published in 2005, found that arsenic levels in the Lower Mystic Lake were higher than in the Charles River. Upper Mystic Lake, which has more arsenic than Lower Mystic Lake, according to Durant, was not included in that study.
“When people swim, contaminated sediment can go in your nose, your mouth; it can go in your eyes,” Breault said, explaining that exposure through the skin is not the only concern. “Little kids like to eat dirt. That’s why I’m saying a detailed health-risk assessment should be done.”
Fox said the Department of Conservation and Recreation has no plans to do a detailed health-risk assessment or to test the larger fish for arsenic. But, she said, the department will speak with scientists and determine whether a further risk-assessment study is necessary.
On Sandy Beach, several beachgoers said they would have wanted to be told about the arsenic.
“I think that’s really unfair because I had no idea about that and we’ve been coming here for years,” said Medford resident Kathlene Crowley, 46. “I think the city should definitely post that because there are so many little kids in there. . . . They’re like fish; they swallow the water.”
Tufts students Allison Palomaki, 21; Emma Shields, 21; and Maia Leppo, 22, also said they would have wanted to know.
“At least to be more careful when you get your head under water,” Shields said.
But Arlington resident Mary Bond, 75, who has been swimming in the lake every summer since she was a child, said that knowing about the arsenic would not have affected her. “It hasn’t bothered me yet.