McIntyre Powder Used in Mining Linked to Parkinson’s Disease in Study

Inhaled McIntyre powder, which was used in the mining industry during the mid-20th century, is associated with an increased risk of Parkinson’s disease, a study has found.

Findings from the study, titled “Investigation of McIntyre Powder Exposure And Neurological Outcomes In The Mining Master File Cohort: Final Report,” may pave the way for affected miners to receive compensation.

“The study by the Occupational Cancer Research Centre and released by the Ontario Workplace Safety and Insurance Board means compensation claims that were rejected will be reviewed, hopefully resulting in justice for survivors and families,” Marty Warren, District 6 director of the United Steelworkers union, said in a press release. “This is a wonderful victory, but so many miners have died during the years it took for this conclusion to be reached.”

McIntyre powder, which contains finely ground aluminum, was administered to miners in Ontario from 1943 to 1979. Miners were required to breathe in this powder before going underground. It was purported as a way to prevent lung damage caused by silica dust; however, research later discovered the powder wasn’t effective for this purpose.

“These workers were human guinea pigs,” Warren said. “We have conducted intake clinics, where we interviewed hundreds of former miners, survivors and caregivers. Everyone came with a story about how breathing in the dust — so thick you couldn’t see — in closed rooms affected breathing, overall health and life expectancy.”

Other research has suggested the powder might increase the risk of neurological diseases, but there has been a paucity of data in humans, making it difficult to draw definitive conclusions.

To gather more information on this potential risk, researchers analyzed data from the Mining Master File, which contains medical records for Ontario miners throughout most of the 20th century. This data was combined with local health records to identify miners diagnosed with Parkinson’s or other neurological conditions after 1992, the earliest date for the local health records.

In total, data for 36,826 people were analyzed. The group was entirely male, and the median birth year was 1938.

The group was divided into those were exposed to McIntyre powder and those who weren’t. Two methods were used to determine exposure: in the first, researchers used self-reported data from the Mining Master File, finding that 9,548 (25.9%) miners were exposed. Because self-reported data can be unreliable, the researchers also used a second classification based on when and where individuals worked, estimating that 13,828 (38%) miners were exposed.

Statistical models were then constructed to compare the relative risk of Parkinson’s and other neurological diseases between those exposed and not exposed to the powder.

Based on the self-reported data, exposed miners had a 34% higher incidence rate (number of cases per person per year) of Parkinson’s, as well as a 19% higher rate of parkinsonism. There were no statistically significant associations between powder exposure and Alzheimer’s disease or motor neuron disease.

The analysis based on the second method of determining powder exposure yielded comparable results. Additionally, based on the second method, Parkinson’s risk tended to increase with the number of years the workers were exposed to McIntyre powder. This trend was not significant for self-reported exposure.

The researchers then compared rates of neurological disease among miners to those found in the general population of Ontario.

Miners had a 20% increased risk of an Alzheimer’s disease diagnosis and a 31% increased risk of motor neuron disease, but these associations were independent of powder exposure. The researchers noted that these associations warrant further investigation.

In contrast, miners overall had similar rates of Parkinson’s disease and parkinsonism as the overall population. However, miners exposed to the powder had a 27% higher risk of Parkinson’s and 14% higher risk of parkinsonism, relative to the general population. This finding was consistent for both methods of determining exposure.

“This study found an increased risk of Parkinson’s disease associated with exposure to McIntyre Powder among Ontario miners, in comparison to both unexposed miners and the general population of Ontario,” the researchers concluded.

Ken Neumann, national director of the United Steelworkers union, said this finding should now be the basis for compensation to workers in Canada, as McIntyre powder was “used extensively across Canada — in Quebec, British Columbia and in some mines in Manitoba, the Northwest Territories, Saskatchewan and the Yukon,” as well as outside Canada, in the United States, Mexico, and Australia, among other places.

“This is a national tragedy that needs to be followed up before we can ever close this shameful chapter in Canadian mining and industrial history,” Neumann said.