Chris McNamara has been drinking the water at his home in Mississippi Mills, Ont., for more than 20 years without a second thought, but recent tests show toxic chemicals found in firefighting foams were also coming from the taps in his and other homes neighbouring a National Research Council fire safety testing facility.

The NRC has been delivering bottled water to some homes and is paying for charcoal water filtration systems in others, but McNamara said that can't erase what he and his wife — along with the residents of 50 neighbouring homes — may have already ingested.

"There was no taste. Nothing changed in our water," he told CBC News."How long has this been going on?"

The NRC has operated the National Fire Laboratory on Ramsay Concession Road 8 in Mississippi Mills since 1981. Houses are constructed inside the large warehouse-like building and set on fire to test firefighting chemicals.

Image | National Fire Laboratory

Caption: The National Fire Laboratory is located on Ramsay Concession Road 8. (CBC)

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The fire centre was one of 150 federal properties singled out for environmental assessment, which began in 2013.

Perfluoroalkylated substances, or PFAS, were discovered in the groundwater from drill sites close to the facility's border.

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.

So far about 40 homes have been tested, said NRC spokesperson Charles Drouin, and one shows PFAS levels slightly above what Health Canada deems to potentially cause health risks.

More than half showed no PFAS at all, and the remaining homes showed very slight levels of PFAS that aren't cause for human health concern, according to Health Canada's water screening values.

PFAS are used in a wide variety of industrial and consumer products, including adhesives, cosmetics, cleaning products and firefighting foams, "as well as water-, stain-, and oil-repellent coatings for fabrics and paper," according to a Health Canada drinking water fact sheet.

The cause of the PFAS in the groundwater hasn't yet been determined, Drouin said. Their presence in firefighting foams was the reason for the environmental assessment in the first place, but the assessment isn't complete and is "looking at a variety of potential explanations," he said.

More residences need to be tested, Drouin said.

McNamara said he received a call to inform him that his water was being tested in January, and found out that his neighbours has also received calls.

"Everybody started getting together and asking questions. 'What's up? What are they testing for? What's all this about? Does anybody know anything?' And nobody had a clue," he said.

When the results came back, McNamara said he was still unsure what it all meant.

"Everything was stamped confidential. To addressee only," McNamara said. "I had to phone someone to say, 'Okay, what do the test results mean? Because it doesn't make sense.' I didn't know how to read it. It was all foreign."

He said he decided to take the NRC up on its offer of free filtered water because he didn't know if what was coming out of his tap was safe.

Residents in the affected area are holding an informal public meeting on March 16.