HOLLISTON, Mass. (AP) — Allegra Denehy was at a neighborhood get-together when she discovered an unsettling coincidence.

Several months pregnant with daughter Tessa, Denehy told neighbors about her doctor's recent discovery that Tessa would be born with only one kidney. Another mom, living a stone's throw from Denehy's house, spoke up.

Her son had just been born with one kidney.

"The more people I talked to, the more people we found who had weird or unexplained medical (issues)," Denehy said, "especially kids."

By the time Tessa had been diagnosed with autism and epilepsy, Denehy found a group of mothers whose children had chromosome 18 disorders. The mothers reached out to the state, and the Department of Public Health studied Holliston and four surrounding communities for evidence of a cluster but ultimately recommended no further action.

"We just kind of wanted answers, and didn't know where to turn to," said Holliston mom Nichole Cordon, whose daughter had open-heart surgery at two weeks old. "We just started thinking 'could there be something here?'"

Nearly a decade after that backyard party, researchers at Boston University and Clark University think something might be there.

A study published earlier this month claimed Holliston's shallow aquifer — where the town's drinking water comes from — is vulnerable to contamination. Three Holliston residents — including Denehy and Cordon — are listed as contributors, and have been working with researchers for years.

"Shallow aquifers are always of great interest in terms of public health," Boston University researcher Birgit Claus Henn said. "Very shallow ones, like the one in Holliston, are of particular concern."

They often have high levels of contaminants to start with, she pointed out. High demand for water overworks the system and wells pull on more concentrated levels of contaminants.

"We're concerned particularly about drinking water," Clark University researcher Timothy J. Downs said. "That's used for consumption, also cooking and bathing as well."

The study looked at publicly available data spanning decades, and focused primarily on well water that had not yet been through Holliston's treatment plants. Researchers did not independently collect and test water samples.

Though researchers highlighted about 20 contaminants of concern, one in particular is a visible problem for many Holliston residents.

Manganese.

"We don't drink the water," Holliston resident Lindsay Bacchiocchi Mullett said. "I don't even like to cook with it."

Mullett joined about a dozen customers who responded to a Daily News reporter's Facebook request by posting photos or stories of regular brown water.

After the study broke, residents packed a water rate hearing held during the selectmen's meeting on Monday to share more stories.

"I can't drink the water. I never know when it's going to come out brown," Holliston resident Martha Pellegrino said at the hearing. "What people are posting on Facebook is very real to us."

The Boston University and Clark University joint study also included photos by Holliston residents of brown water. One photo, of running water, looked like blood pouring out of the tap.

"I have been frustrated with this issue for over nine years," Holliston resident Bess Batt wrote in an email to the Daily News, accompanied by a photo of cloudy water running into a bathtub. "Spent, probably, thousands in bottled water for my kids and I. I won't let them drink it."

Discolored water is a regular problem in Holliston, Department of Public Works Director Sean Reese said. His department even has a solvent to get rid of brown staining when residents wash their laundry in the discolored water.

Though this month's study focuses on Holliston, manganese is a problem across New England, especially in shallow aquifers that are overworked.

"It's a chronic problem in New England," Bellingham Department of Public Works Director Donald DiMartino said. "We have actually been removing manganese since 1991."

Manganese, unlike most of the contaminants listed in the Boston University-Clark University study, is labeled a secondary contaminant by the state and federal government. That means the government says too much of is an aesthetics issue and is not considered a health concern.

In other words, cities and towns don't have to focus on filtering it out. Many do, but it's not required.

"We meet the standards, but nobody is going to drink a glass of orange water," Holiliston Director of Public Works Sean Reese said.

With studies like the one focused on Holliston, the government classification could change.

"I think it will be the next regulated contaminant," Reese said. "It's going to happen. ... When, I don't know."

Henn and Downs said they question the state and federal standards.

"We're not questioning compliance here. We're concerned that the regulation may not be protective enough or adequate," Henn said. "There's only a secondary MCL for manganese. I would question that."

Many cities and towns in MetroWest - including Holliston and Bellingham - are already filtering out manganese.

"In my mind, I've already flipped the switch," said John Schreiber, the primary operator at Hopedale's treatment plant.

In Holliston, Reese said the town's two treatment plants filter out manganese, but a third plant is needed. The town tries to keep on top of the brown water by flushing, but that's just a Band-Aid.

"I can only advocate so loud," Reese told a packed water rate hearing Monday night, after people started talking about the water study. "You need to go to Town Meeting. You need to support the initiatives of the water department."

Reese has been advocating for the third treatment plant, which - at a cost of more than $8 million - will appear on the May Town Meeting warrant.

The Boston University-Clark University researchers are careful. The study is an early step, they point out. It only shows that exposure to contaminants was possible, not that exposure to humans actually happened.

"Let me just say I think it's possible," Downs said on whether the water could have caused birth defects. "We know certainly a lot more than we did when we initiated this study."

The group is now working on a pilot study, collecting baby teeth from children who were in utero in Holliston. Researchers will look for contaminants in the teeth, and gather data on health issues in the families in question.

On a sunny Friday afternoon, 9-year-old Tessa sang to herself and drew across her coloring book while her mom explained that the family doesn't even make coffee or ice cubes from tap water.

A water cooler, stationed at the end of Denehy's kitchen counter and re-filled monthly, is a quiet statement on her struggle to understand what - if anything - is causing health problems.

"Nothing's a problem until it's a problem," Denehy said. People used to cover their walls in lead paint, she said. "I just wonder if it will be the same thing with manganese."

She doesn't know if manganese caused her daughter's autism, epilepsy, and missing kidney. She doesn't even know if the health issues and birth defects she's noticed locally throughout the years have anything to do with the drinking water.

But she's not alone in feeling something is wrong, and this group of local parents and nearby researchers will keep trying to find an answer.

"Our children already have their developmental issues, delays," Cordon said. "Our thing is for the future of this town."

Knowledge is power, Cordon pointed out.

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Online: http://bit.ly/2CPZThN

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Information from: MetroWest Daily News (Framingham, Mass.), http://www.metrowestdailynews.com