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Researchers delve deep into the fine details of McIntyre Powder

Nanoparticles found in aluminum dust inhaled by miners as advocates build compensation case

Researchers are hopeful that newly discovered details about the composition of McIntyre Powder will prompt a look into the biological impact of the aluminum dust on the former miners who inhaled it.

The findings are included in a new report led by researcher Andrew Zarnke, a PhD candidate at Laurentian University in Sudbury, entitled “Physical and chemical characterization of McIntyre Powder: An aluminum dust inhaled by miners to combat silicosis.”

The report was published in mid-September in the Journal of Occupational Environmental Hygiene and is now available online as a free download.

It was already widely known that McIntyre Powder was largely comprised of ground-up aluminum. But learning the size of the particles in it, along with its chemical makeup, helps form a baseline for future experiments that may explain how the powder impacted miners’ long-term health.

“If we see a response (in the body), we need to understand what about the powder might be causing the response,” Zarnke said during a Sept. 23 presentation of his findings in Elliot Lake.

“So it was essential to understand what was in McIntyre Powder and as much detail about it as possible.”

Zarnke spoke alongside Janice Martell, an advocate for miners who were impacted by McIntyre Powder, and Dr. Christine Oliver, a physician and consultant lending her expertise in lung function.

All three are doing work for the Occupational Health Clinics for Ontario Workers (OHCOW) in building a database of former miners, their work histories and their health records.

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McIntyre Power was created by mining executives as a way to prevent silicosis in underground miners who were developing the lung disease after inhaling silica dust. The substance was blown into the mine dry before a shift, and workers were only released after they had inhaled the dust for about 10 minutes.

It was later revealed that the powder had no benefit to miners’ health, yet the practice persisted for nearly 40 years, impacting 27,500 miners in Ontario alone.

Today, many of those miners are living with a range of illnesses – cardiovascular, respiratory, and neurodegenerative, along with a range of cancers – that they believe McIntyre Powder could have caused.

Zarnke’s research builds on a 1940s analysis conducted by the McIntyre Research Foundation, the organization comprised of mining executives that was responsible for developing the powder.

That initial research found that about 24 per cent of the particles measured smaller than 200 nanometres (a nanometre is one-billionth of a metre.) With the technology at the time, that was the smallest particle that could be detected.

Using modern-day methods, Zarnke was able to enhance the resolution of the particles, and found some of the smallest were five nanometres in size. The smaller the particle, he said, the further in the body it can travel.

“So you can see that it might not be that hard for these particles to actually get inside of the cell,” Zarnke said. “It’s not just on the outside of the cell that they’re having the effects.”

Zarnke said the volume of the particles inhaled is also significant.

The recommended dose for McIntyre Powder was roughly 0.7 milligrams per cubic metre of air distributed over an eight-hour period.

Miners, prior to going underground, were typically exposed to a dose of 35 milligrams in 10 minutes 

“It's a dose rate,” Zarnke said. “The way that your body responds to a super-high level of dust in a short period of time is much different than the way your body responds to a low level of dust over a longer period of time.

In fact, the amount of exposure miners received is seven times the acceptable amount, according to particulate guidelines set out in the current Occupational Health and Safety Act, he added.

When the body’s system for expelling foreign particles becomes overwhelmed, it doesn’t work properly, Zarnke said, and that’s when “lung overload” conditions can occur.

“It's been shown in the literature that smaller particles can induce lung overload conditions at much lower concentrations because such a higher proportion of particles are getting into the lower part of the lung,” he said. “It's this one mechanism being relied on and it can overwhelm that system much more easily.”

Studies unrelated to McIntyre Powder found that very small particles can also easily pass through lung tissue into the bloodstream or lymph nodes, and from there, can move all around the body.

When researchers looked at the preserved tissues of people in highly populated areas where there are high levels of particulate, they’ve found nanoparticles in the brain, placental tissue, fetuses, and heart tissue.

“So these small particles can be transported around the body very easily, and that’s why, I think, we’re seeing such a wide array of conditions (in the miners),” Zarnke said.

Miners were exposed to McIntyre Powder just before they went underground, reducing their bodies’ ability to expel the particulate, and then after descending, they were further exposed to silica, diesel exhaust, radon gas and other particulate common underground, Zarnke said.

“So you're inhibiting the natural protection mechanisms before you even go down,” he added.

The next phase of Zarnke's research involves looking at the cellular response to aluminum nanoparticles and McIntyre Powder.

Dr. Oliver, who has spent the last few decades specializing in occupational lung disease, is examining individual claims to determine whether miners have a case for compensation. She’s also helping to prepare disease reports that miners can use to bolster their cases with the Workplace Safety & Insurance Board (WSIB).

Oliver noted that illnesses like chronic obstructive pulmonary disease (COPD) and asthma are often overlooked as occupational disease, especially when the patient is also a smoker.

But vapours, gases, dust and fumes (VGDF) are estimated to account for at least 15 per cent of cases of COPD, for example, and when they interact with underground exposures, the result is cumulative, Oliver said.

“There have been several studies done that show that if you have exposure to VGDF, underground diesel exhaust, general dust, silica, and you smoke, then the interactive effect between the two is greater than additive,” Oliver said.

“Not only does cigarette smoking not negate the contribution of underground mine exposures, but it actually enhances the carcinogenicity and toxicity with regard to COPD and these underground exposures.”

Add in McIntyre Powder, and it’s a “triple whammy” to the body, she added.

Janice Martell, who has spent the last five years compiling information on McIntyre Powder, calls the practice of dousing miners with aluminum dust “a giant public health experiment,” for which miners should be compensated.

As part of her work, she’s helping miners to file claims with the WSIB with the hope that they’ll receive some compensation.

But navigating the bureaucratic red tape has been a slow, laborious process, and many of the miners are dying of their illnesses before seeing any reparation.

Her father, Jim Hobbs, was one of them. After retiring from a 30-year mining career, Hobbs was diagnosed with Parkinson’s disease in 2001. He died of the illness in 2017 at the age of 76.

It’s Martell’s belief that occupational disease should receive as much attention as workplace fatalities.

Statistics show that 1,000 workers a year in Canada are killed on the job. But occupational disease kills between six and 10 times that number of workers, she noted.

“It makes front-page headlines when there’s a sudden death at a mine,” Martell said. “You don’t get that with occupational disease.

“It’s really important that we show a face to these. These are not just statistics.”