Government officials have confirmed the National Fire Laboratory is the source of chemicals that contaminated the drinking water in Mississippi Mills, Ont.

Homeowners living near the facility found out in December 2015 that perfluoroalkylated substances, or PFAS, were discovered in their tap water. It's the same chemical often found in firefighting foams.

They admitted they were essentially ground zero of the problem. - Mississippi Mills Mayor Shaun McLaughlin

In an emailed statement to CBC News, the National Research Council confirmed Thursday that "ongoing environmental assessments have indicated that PFAS found in the nearby residential wells originated from the National Fire Laboratory site.

"Since identifying PFAS at the National Research Council's National Fire Laboratory, our focus has been on carrying out an effective and thorough environmental assessment and on the continued safeguarding of the health and safety of residents and employees," the statement said.

"They admitted they were essentially ground zero of the problem," said the municipality's mayor, Shaun McLaughlin. "This is the first time they've actually owned that piece of the mystery."

Back in 2013, the NRC knew contaminants were found in the groundwater from drill sites close to the facility.

J.D. Heffern, his wife and three daughters learned their drinking water may be contaminated in December 2015. (Submitted Photo) Two years later, the government department started delivering bottled water to some neighbouring homes and paying for charcoal water filtration systems.

Residents pushing for answers

Ever since, residents in more than 70 homes in the community of Ramsay Meadows have been pushing for answers. The NRC says it's been carrying out environmental assessments.

"Results to date indicate low to no detection of PFAS in residential water..." said the NRC in a statement to CBC News. "According to Health Canada, there are no expected health impacts over a lifetime of exposure, if levels of PFAS in drinking water fall below the applicable Health Canada screening values."

A working group representing the Ramsay Meadows homeowners says they appreciate the NRC being honest about the results. The department's acting president, Maria Aubrey, met with two of the residents at the end of June.

"We are kind of taken aback a little bit," said chairperson J.D. Heffern. "They've come back and said here's the evidence. We've done testing to the west of the facility, we've done testing in various places and our conclusion is the National Fire Lab is in fact the source of the contaminants in a plume-like formation coming towards Ramsey Meadows."

Lingering concerns over health

Residents who live near the fire lab don't know how long they were exposed to the chemicals and what the impact could be.

We don't know about the long-term effects. - J.D. Heffern , chairperson of residents' working group

Scientific information is limited on PFAS, Health Canada says.

But in studies done on animals, "high levels of PFAS have been linked with negative health effects ... including liver damage and impacts on neurological development," the agency's fact sheet says.

In humans, short-term exposure to PFAS at levels slightly above the safety threshold isn't expected to have health effects, according to Health Canada, but the agency does not define what constitutes short- or long-term exposure.

"We don't know about the long-term effects," said Heffern.