Is McIntyre Powder to blame for neurological diseases in miners?

Headway being made on research, workers' compensation

Is McIntyre Powder to blame for neurological diseases in miners?


Ray Mills worked at four of the five Rio Alco mines in Elliot Lake, Ont. for 29 years. At the start of his shift, he was required to walk through a room where black aluminum dust was sprayed through compressed air. 

“Everybody had to walk through it,” says Mills, who is 77 years old and lives in London, Ont. “If you happened to be there when they turned the air on, it was a big black cloud of it… The canister was about the size of a soup can. He might put two cans out before each shift.”

The dust was McIntyre Powder and it was used as a method to prevent miners from developing silicosis at many mines in northern Ontario between 1943 and 1979. The province’s records reveal 27,500 miners were exposed to aluminum dust. The dust was also used in mines in Quebec, British Columbia, Manitoba, Saskatchewan and the Northwest Territories as well as the United States and around the world.

Additionally, some workers who were exposed to silica dust in pottery manufacturing, foundries, silica brick manufacturing and refractories were also subject to the McIntyre Powder treatment.  

Developed by the McIntyre Research Foundation — which was made up of executives from McIntyre Porcupine Mines in Schumacher, Ont. — the belief was that coating the miners’ lungs with aluminum dust would protect them from contracting silicosis.

Mills says the method wasn’t questioned at the time among the miners. 

“It was there. You never talked about it. You just carried on,” he says.

In 2015, Mills was diagnosed with Parkinson’s disease — and now he has some questions. He says McIntyre Powder is “very high on the suspect list” in terms of what led to his diagnosis.

The practice of inhaling McIntyre Powder has garnered much media, industry and political attention in recent years, as exposed miners have developed health conditions in staggering numbers. 

Out of 452 miners (both living and dead) on the McIntyre Powder Project list, two-thirds have respiratory disorders and one-third have neurological disorders. The most common neurological disease is Parkinson’s with 43 miners out of 452 being diagnosed with the condition. Alzheimer’s is also common, with 27 miners being diagnosed, followed by dementia in 16 miners.

There are 97 cancer diagnoses on the list, 47 of which are for lung cancer. There are also some relatively obscure conditions such as Lewy body dementia, progressive supranuclear palsy and amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig’s disease. According to ALS Canada, the lifetime risk of developing ALS is 1 in 1,000 — but there are 14 known cases of ALS among the miners.

Many miners have multiple health issues and others have symptoms of a disorder but do not have a diagnosis yet.

The McIntyre Powder Project is a voluntary registry to document health issues (particularly neurological) in miners and other workers who were exposed to McIntyre Powder aluminum dust in their workplaces. The project was started by Janice Martell whose father, Jim Hobbs, worked in nickel and uranium mines in Ontario and breathed in McIntyre Powder everyday.  

In 2014, Martell began investigating the practice after she suspected a possible connection between the powder and her father’s Parkinson’s disease diagnosis. Hobbs succumbed to the disease and passed away last May. 



Beginning in 1932, researchers from McIntyre Porcupine Mines tested McIntyre Powder with 50 guinea pigs and 13 rabbits. These studies showed that while silicosis was produced in five months in the control animals that inhaled silica dust, the addition of aluminum powder to the silica dust completely prevented the occurrence of silicosis, even after exposure for up to 22 months. 

In 1941, the McIntyre Porcupine Mines began testing aluminum dust inhalation as a treatment for miners who had silicosis. The camp had 350 miners with silicosis, but after reviewing X-rays and eliminating those who were “foreigners” or “of the non-cooperative type” just 20 were selected to receive treatment, according to an archival document from the powder’s co-creator, W.D. Robson.

The treatment consisted of a five-minute inhalation of aluminum powder daily, with sessions increasing by five minutes every few days until one month had passed. After one month, the patient began receiving 30-minute inhalation sessions daily. The treatments continued for six days per week until 200 treatments had been administered.

The first 10 miners that were treated had shown “remarkable results,” Robson said. However, two cases did not respond to the treatment. In both cases, when the disease was examined by X-ray, it presented as clear-cut nodulation. Those that responded well to the treatment had a snowflake appearance when examined by X-ray. 

In a meeting between Robson and American doctors who were visiting the silicosis clinic, it was concluded that X-ray films of each individual case should be carefully studied to determine if they would respond well to the aluminum therapy or not. They agreed the clinic should continue with rigid selection of cases for treatment because “if one went bad, whether it was due to aluminum treatment or not, the method would be discredited.”

Ultimately, the men said it was only a matter of time before “the treatment of silicotics by the inhalation of aluminum powder would be accepted without question.” In the end, 100 miners were treated as part of this initial research. 

But there are a slew of issues with this research, namely the fact that a control group was never used nor was the random selection process — the researchers picked and chose the men they wanted to participate in the treatment. 

During that meeting in 1941, Anthony Lanza from the Metropolitan Life insurance company in the United States pointed out that the industry would make its greatest savings in compensation from the prophylactic (prevention) end than from the treatment of already established and compensated cases, and the industry should be granted the right to use preventative measures as soon as possible.

It’s important to note, however, there had never been any scientific evidence of McIntyre Powder’s preventative effects against silicosis. Most of the miners receiving treatment had already been diagnosed with the disease, although some were considered “borderline cases” and did not have an official diagnosis.

Shortly after, miners breathing in aluminum dust before their shift became commonplace. Robson and his co-creator, J.J. Denny, the chief metallurgist for McIntyre Porcupine Mine, patented the powder and mining companies had to purchase a license for use from the McIntyre Research Foundation.

At most mines, the powder was blown into the dry where the miners would change their clothes, but some had a specially built tunnel or room just for the inhalation of McIntyre Powder.

“It was a gas chamber, basically. They were locked in from outside, so they were forcibly confined and forced to inhale this neurotoxin without informed consent,” Martell says.

The recommended exposure was an aluminum dust concentration of 20,000 to 34,000 parts per millilitre air in the miners’ changing rooms before each underground shift for 10 minutes. However, the actual amount dispensed varied widely and archival documents from the McIntyre Research Foundation show they don’t actually know how much aluminum dust these miners received, according to Martell’s research.  

Of note, McIntyre Powder was a controlled substance under federal regulation and it was supposed to be administered through a prescription.

“Anyone who goes to a doctor for any kind of medicine, the doc has to go through a whole checklist: Do they have these symptoms? Is it contraindicated with other medication? They did none of that,” Martell says. “They were part of a giant public health experiment.”

Another major concern of the practice was the fact that ventilation was turned off when the powder was being administered, says Martell. But there was a breakdown of communication somewhere along the line. After their initial tests on lab animals, the McIntyre researchers released their report in 1937 that stated: “It is imperative that the use of aluminum for the prevention of silicosis should in no way interfere with the standard practice of ventilation, as large quantities of even inert dust will damage the lung structure.”

In the 1960s, the unions started to push back on the practice. They had argued adequate ventilation and respirators could prevent silicosis. In 1965, the United Steelworkers’ Local 4608 in Val D’Or, Que., was successful in stopping the McIntyre Powder process in its East Sullivan Mine. In its petition against the practice, the union noted several experts, including the American Medical Association, had said “aluminum has nothing to do with silicosis in humans” and that “aluminum dust can itself cause grave illnesses.”

In 1979, after CBC reporters broke the news of the practice on the Fifth Estate, the Ontario Ministry of Labour investigated. Although it found a decrease in mortality rates from silicosis during the term of the program and that McIntyre Powder did not produce any apparent adverse effects, it concluded there was insufficient evidence of the effectiveness of the powder, thus stopping the practice later that year. 



Workers’ exposed to McIntyre Powder who have developed neurological problems have not been able to get workers’ compensation due to a Workplace Safety and Insurance Board (WSIB) policy on the matter. The policy states: “Dementia, Alzheimer’s disease and conditions with neurologic effects are not occupational diseases or injuries by accident under the Workplace Safety and lnsurance Act when they are alleged to result from occupational aluminum exposure.”

This is the only policy in the compensation board’s 100-plus year history that states a particular exposure does not cause a particular disease. Normally, workers are able to apply with evidence and make their own case linking workplace exposure to their health issues but this policy automatically denies the related claims.

Martell learned this first hand when she submitted a claim on behalf of her father in September 2011 for Parkinson’s related to McIntyre Powder exposure. Her claim was denied and she appealed the decision. She was preparing to take the case to the Workplace Safety and Insurance Appeals Tribunal, but after finding the “negative” policy, she withdrew the claim.

“I quickly realized you can’t win a case on an individual basis because they have this policy that shuts it down,” she says. 

The policy was established in 1993, after a report on occupational aluminum exposure and health by Ontario’s Industrial Disease Standards Panel. The report noted there was some evidence to suggest high levels of occupational aluminum exposure might lead to cognitive and neurological effects, but there was an insufficient number of studies to establish consistent results.

However, the panel said it recognized a lack of evidence does not mean that a relationship does not exist. 

“lt only means that medical science cannot yet answer these questions. Clearly, further research is needed in order to resolve the significant uncertainties about aluminum and to answer the important concerns of workers,” the panel said.

In 2016, after mounting public pressure spurred by Martell’s work, the WSIB commissioned a report to look into the effects of McIntyre Powder. Intrinsik, a Mississauga, Ont.-based regulatory consulting firm, prepared a systematic review of studies that assessed workplace aluminum exposure and negative health conditions, including nervous system and respiratory disorders, cancers, cardiovascular disease, mortality and immunological response. The report noted there were only three studies that specifically assessed McIntyre Powder inhalation. Ultimately, the report said, “Although these findings cannot conclusively state whether or not aluminum exposure leads to the development of negative health conditions, the evidence considered in total has not supported a link.”

A systematic review of the literature on McIntyre Powder by a WorkSafeBC practice group echoed Intrinsik’s conclusion. Its report said the available evidence did not support any potential (causal) association between occupational exposure to McIntyre Powder and the development of neurological disorders, such as Parkinson’s or Alzheimer’s. 

But one of the studies that both agencies reviewed resonated with Martell. It showed a positive association between the powder and decreased performance on cognitive tests, but no increase in diagnosed nervous system disorders. This 1990 study by Sandra Rifat of the University of Toronto is 408 pages in its entirety. Rifat compared more than 600 miners who had been exposed to McIntyre Powder at gold and uranium mines with a control group who worked in nickel and copper mines where the powder was not used. 

The participants completed standard cognitive tests and 13 per cent of the miners exposed to McIntyre Powder showed signs of cognitive impairment, compared with five per cent of the control group. In men exposed for more than 20 years, the effect was more pronounced, with 20 per cent showing impairment. The study found a clear dose-response effect, meaning the longer the men were exposed, the worse their cognitive functioning. 

“That was the first scientific indication that there could be harm done by inhaling aluminum,” says Martell.

The WSIB officially revoked its policy in June. At press time, there were 76 claims registered for a number of conditions related to McIntyre Powder: 15 have been allowed (all for non-neurological issues); 29 remain pending; and 32 were denied. Of the approved claims, the most common condition is chronic obstructive pulmonary disease (COPD), says Aaron Lazarus, vice-president of communications and intergovernmental affairs at WSIB.

Very, very few miners who have neurological disorders have filed a claim with WSIB because they have been playing the waiting game, says Martell. They were waiting for the “negative policy” to be revoked and now that it has, they are waiting for the results of the various studies so they can use that evidence to support their claim.

In August, the WSIB commissioned researchers from the Occupational Cancer Research Centre in Toronto to conduct a new independent study on the relationship between McIntyre Powder and the development of neurological health outcomes in former miners.

“They are going to look at the Mining Master File that we have, compare that to Ontario Health data to really look at the people who have had specific exposure to McIntyre Powder and their health outcomes to determine, hopefully, with some conclusive scientific evidence whether or not there is a connection, so we can move forward and make some decisions based on that,” says Lazarus. 

The results of the study are expected back in late 2019. If a scientific link is found between McIntyre Powder and neurological diseases, the WSIB would go back and do a review of those cases — not just the ones that are pending but those that have been closed as well, says Lazarus. The agency believes “people should receive the compensation they deserve” and it has a track record of re-opening cases when new evidence comes to light, he says. An example of this is the GE plant in Peterborough, Ont., where workers had been exposed to a number of chemicals dating back to 2004. Science has evolved over the years and WSIB is going through 250 previously unapproved claims and reviewing its decisions. At press time, nearly two-thirds of these reviews had been completed, with 45 claims being approved. 

But Martell has some concerns, including the fact that the Ontario Health database records the researchers are using only start in 1991, she says.  

“Some of these guys are born in 1900 and they were exposed in the 1940s, so many of the ones with some of the more significant health issues are already deceased and they died before 1991. They are not going to be included,” she says.  



McIntyre Powder and its potential effect on miners has caught the attention of universities across Canada and the world. Researchers are working hard to determine how inhaling the powder would impact the brain and lead to neurological disorders.

Researchers at McMaster University in Hamilton have developed a technique where they are able to non-invasively measure the levels of aluminum in the bone of living individuals, which is a marker of long-term exposure, says Fiona McNeill, director of radiation sciences and a professor at McMaster.

“That long-term exposure we have found with many different elements when we studied it can be correlated with health effects,” she says.  

McNeill’s colleagues had recently completed a small study where they found a slightly elevated level of aluminum in the bone of Alzheimer’s patients. 

For her own research, McNeill is planning to study 15 miners with a range of exposure to McIntyre Powder and compare them to 15 aged-matched controls with no exposure. The bone aluminum would be measured for all participants.

“We may then have a technique for measuring long-term aluminum exposure as a consequence of exposure to McIntyre Powder that we could then use in a bigger study to say, ‘Does this correlate with health effects that these guys are reporting?’” McNeill said.

The study is currently in the ethics review stage, but McNeill is eager for it to get approved so she and her colleagues can start analyzing the miners.

“We have a gut feeling we probably will see something in these workers,” says McNeill. “The amounts of powder that they inhaled over the years and some of the particulate sizes, some of that particulate would have sat around in the lungs and it wouldn’t all have been coughed out… But we have no measurements yet.”

At the University of British Columbia (UBC), a brain and tissue bank is starting up to hold samples from those deceased individuals who were exposed to McIntyre Powder. Once this has been established, researchers will be able to complete cellular and molecular studies to see what has changed in these patients. 

“It’s an awful conversation to have. I had to have that conversation with my dad. But I’ve had miners asking me, ‘I can’t change what happened to me but I want to ensure that the next generation will never have to deal with this. I want to help the next guy,’” says Martell.

A second project that is in the planning stage at UBC is to expose mice to the powder in a way similar to that experienced by the miners. Exposure will either be to the powder alone or in combination with other stressors, such as radiation or other toxins linked to the neurological diseases found among the miners. A key part of this study will be to seek out gene variants that are not themselves harmful, but that can contribute to the impact of the powder.

Yet another study is working on linking aluminum compounds to nanodiamonds. Particles of McIntyre Powder would be tagged with fluorescent nanodiamonds in order see exactly where aluminum goes in the body and nervous system after inhalation by lab animals.

In October, the Ontario government announced $1 million in funding for the Occupational Health Clinics for Ontario Workers (OHCOW) to review worker exposure to McIntyre Powder. Intake clinics were set up in Timmins and Sudbury for mine workers, or their survivors, to provide information on their exposure to McIntyre Powder and their health issues. Martell quit her old job, sold her home in Elliot Lake and moved to Sudbury to work full-time for OHCOW on this project. Once all the data is captured, biostatisticians will be analyzing it to see if there are any significant associations. 

Mills understands that studies need to be conducted to prove a connection between McIntyre Powder and neurological disorders, noting they “can’t just pick something out of the sky and say this did it.” If there is a connection shown, he will be applying for compensation for his Parkinson’s disease. 

Ultimately, he hopes Martell’s work will get some answers and bring recognition for her father and all the miners who had to inhale McIntyre Powder. 

But there is one thing that Mills admittedly can’t stop “harping on” and that’s the fact that in the ‘70s, the men just did as they were told — nobody asked why and no details on the powder were given.

“It makes you wonder who today in their right mind would sit there and get something sprayed every day into their lungs?” he says. “Today, it wouldn’t be tolerated.”

This article originally appeared in the April/May 2018 issue of COS.