Nova Scotia has suspended the use of all hair-strand drug and alcohol testing in child protection cases, following a CBC News investigation.
At least three provinces have now ordered child welfare agencies to stop using the tests.
Questions about the science of hair testing began after serious shortcomings were found at the Motherisk Lab at Toronto's Hospital for Sick Children, which now admits its hair test results could be inaccurate.
As many as 380 people from Nova Scotia received a positive hair-strand drug or alcohol test at Motherisk between 1997 and 2015, results that are now unreliable.
The hospital can't say how those tests were used or exactly how many people are affected.
It closed the Motherisk hair-testing lab in April 2015. But Nova Scotia has continued to order hair-strand testing from Toronto-based Dynacare to use in child protection cases.
Testing 'not an exact science'
That practice will stop effective immediately.
The government decided to suspend the testing after months of reviewing practices across the country.
Officials discovered that hair testing is "not an exact science," said Wendy Bungay, director of child protection for Nova Scotia's Department of Community Services.
"The information that we're getting is that there are some potential biases that need to be acknowledged from the get-go," Bungay said in an interview with CBC News.
"We originally thought it would give you very specific information about [drug or alcohol] usage for a specific date and time. That's not the case."
Some existing hair tests may be used in court. But Bungay said officials will be careful about how the tests are weighed when deciding whether parents lose their children.
She said the tests have always been one of several tools used to determine the future of families.
In March, Dynacare defended its practices through an emailed statement, describing its test results as "robust."
"Dynacare provides a robust, high-quality analytical toxicology service for analysis of drugs-of-abuse in hair," a statement sent by Dynacare spokeswoman Andrea Price says.
Price declined to comment Tuesday about Nova Scotia's decision to suspend the use of hair testing.
Bungay said she doesn't think Dynacare's lab has the same shortcomings that were discovered at Motherisk.
The testing is supposed to determine the amount of drugs or alcohol a person has consumed.
But Albert Fraser, a retired forensic toxicologist, has warned against using hair tests from any lab in child protection cases, describing it as a "developing science."
"It's an emerging discipline," Fraser told CBC News in March. "But it's not a mature scientific discipline."
He said there are unanswered questions about hair testing, including whether the results have a "colour bias."
Ontario placed a moratorium on hair testing more than a year ago, directing children's aid societies to stop using the tests "out of an abundance of caution."
New Brunswick followed suit on March 1, admitting there are "concerns about the overall reliability of this type of testing."
Nova Scotia waited to act because government didn't have all the information it needed, Bungay said.
"We wanted to make sure that if we were going to take that position, that we had done due diligence and done the research required to come to a conclusion that was fair and balanced."
No full review
The Nova Scotia government is working with a forensic toxicologist and Sick Kids to figure out exactly how many people in the province had their hair tested at Motherisk.
When the lab closed last year, the province estimated 49 open child protection cases involved Motherisk testing.
The open cases are being reviewed. But the province hasn't committed to looking into closed cases, something Ontario and New Brunswick are doing.
Bungay said government will only look into a closed case if a parent involved in the case asks for a review.