The number of positive tests for fentanyl in samples of heroin seized by law enforcement agencies across Canada has grown from less than one per cent in 2012 to more than 60 per cent so far this year, exclusive data obtained by CBC News has revealed.

The data also showed an increase of more than 2,000 per cent over that same time period for all street drug samples tested.

The statistics are compiled by Health Canada's Drug Analysis Service (DAS), which tests approximately 120,000 samples of drugs apprehended by the Canada Border Services Agency, the Correctional Service of Canada and police forces across the country each year.

Health Canada didn't provide a detailed breakdown of results for every type of drug tested, but said heroin is an area of particular concern.

In 2012, less than one per cent of the 2,337 heroin samples tested by the DAS contained fentanyl and/or its analogues. In 2016, that number grew to 39.4 per cent of 3,658 samples. And for the first nine months of 2017, the number of heroin samples (3,337) testing positive for fentanyl jumped to 60.1 per cent.

(Natalie Holdway/CBC)

The most common drugs the service tests for include marijuana, cocaine, methamphetamine, fentanyl, heroin, hydromorphone, oxycodone, MDMA, alprazolam and GHB.

Fentanyl was not identified in any of the marijuana samples tested over the five-year period, while cocaine and methamphetamine saw increases from 0.01 per cent to 1.8 per cent and zero per cent to 1.7 per cent, respectively.

Overall, the figures are stark. In 2012, only 217 of the street drug samples tested positive for fentanyl. Just as the number of lives claimed by the deadly opioid has skyrocketed since then, so too has the number of times fentanyl has showed up in samples of illegal street drugs. As of Sept. 30, DAS found fentanyl in 4,568 samples this year – an increase of 2,005 per cent.

(Natalie Holdway/CBC)

The exponential increase of street drugs testing positive for fentanyl over the last five years doesn't surprise Dr. David Juurlink, head of clinical pharmacology and toxicology at Sunnybrook Health Sciences Centre in Toronto.

In fact, it simply mirrors what Juurlink and other health professionals dealing with Canada's opioid crisis have seen through even more sobering data — the steadily rising number of overdose deaths.

According to Health Canada, 2,816 people died of "apparent opioid-related" causes across the country in 2016. Experts believe fentanyl was involved in many of those deaths, and that it has claimed many more lives since.

"The illicit drug supply has never been more dangerous because of the profusion of fentanyl-related compounds," said Juurlink. "This is why so many people are dying. They're dying because the drugs they're using contain, you know, much more opioid than they thought."

Dr. David Juurlink, head of clinical pharmacology and toxicology at Sunnybrook Health Sciences Centre in Toronto, says the dramatic increase in fentanyl detected in samples of seized street drugs since 2012 is consistent with the rise of people dying from overdoses during that time period. (Nicole Ireland/CBC)

Fentanyl is extremely potent and relatively cheap, so dealers mix it into drugs like heroin to stretch their supplies, experts say.

"They want to save money or make higher profits," said Dr. Michael Krausz, a professor of psychiatry specializing in addiction at the University of British Columbia.

But when working with a drug as lethal as fentanyl, those dealers "are not skilled enough to keep the dose in a survivable range," Krausz said.

In 2012, the manufacturers of OxyContin, Purdue Pharmaceuticals, reformulated the drug to make it harder to crush or melt down, with the intent of discouraging abuse. At that time, many experts sounded the alarm, saying people addicted to Oxy would turn to the streets and to other opioids, including heroin.

Juurlink said several factors sparked fentanyl's rise, including an overall increase in demand for opioids as overprescription of painkillers led to addiction. The flood of prescription medication — including fentanyl patches — ended up not just in medicine cabinets, but in the hands of people selling on the streets.

"There's a lot of money to be made preying on people who need help," Juurlink said.

For Leon Alward, known as "Pops" to his friends, the data showing fentanyl's increased presence in street drugs is yet another set of numbers confirming what he already knows — that the drug is everywhere, and that it can be deadly.

But Alward, who said he refers to himself as a junkie because "I don't like to pretty it up," continues to use both heroin and fentanyl to feed his addiction.

"The thought of the [withdrawal] sickness that I know is going to come if I don't use far outweighs the risk of using," he said. "It sounds ridiculous, I know that, I understand that. But for an IV user, nobody knows what it's like."

Alward overdosed on fentanyl in a public bathroom, and would have died if he hadn't been taken to hospital by paramedics, he said.

"Every time we use we're taking our lives into our hands," he said.

Now, Alward comes to an overdose prevention site in Toronto's Moss Park​, where he also volunteers. Harm reduction workers there provide clean needles, spoons and other supplies, and keep a close watch as users take their drugs inside a tent, ready to intervene with the overdose-reversal medication naloxone, as well as oxygen, if something goes wrong.

Between the day the site opened in mid-August and the end of October, workers watched over almost 2,000 injections, and stopped or reversed about 85 overdoses, according to Nick Boyce, a harm reduction volunteer with the Toronto Overdose Prevention Society.

Nick Boyce, a harm reduction volunteer with the Toronto Overdose Prevention Society, says volunteers try to keep drug users as safe as possible by watching them for signs of overdose, and providing clean supplies, pictured here. (Evan Mitsui/CBC)

Like Juurlink, Boyce isn't surprised by the new data showing the rapid rise of fentanyl in street drugs — but said it's helpful to have the information.

"We're starting to see different kinds of reactions that we never used to in terms of how people overdose or the symptoms," he said. "Getting some better analysis would really help to understand why we're seeing what we're seeing."

For Alward, the numbers are more than just a tool to analyze the problem.

"What we're looking at is people's lives," he said. "That's me."