McIntyre Powder Study


The goal of this study was to use the Mining Master File to study the risk of neurological disease among Ontario miners who were exposed to McIntyre Powder.

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McIntyre Powder is an aluminum and aluminum oxide powder that was administered to miners in Ontario between 1943 and 1979. It was thought to prevent silicosis among miners, but later was found to have no protective effect. Now, there is concern that it may have resulted in increased risk of neurological diseases among exposed miners. While a few previous studies examined the risks of neurological diseases due to McIntyre Powder, the results have been inconclusive.

The Mining Master File is an electronic database that contains medical exam records and work histories for approximately 90,000 Ontario miners. It also contains information on exposure to McIntyre Powder. This project used the Mining Master File along with other historical records and health databases to examine the risk of neurological disease in Ontario miners.


The Mining Master File was assessed for completeness and enhanced with additional data on McIntyre Powder using historical records. It was then linked to health databases to identify miners who were diagnosed with chronic neurological diseases, including Alzheimer’s disease, parkinsonism, Parkinson’s disease and motor neuron disease. The risk of neurological disease among miners who were exposed to McIntyre powder was compared to both the general Ontario population and to other Ontario miners who were not exposed to McIntyre Powder.


This study found evidence of an association between McIntyre Powder exposure and increased risk of Parkinson’s disease. While no association was observed between McIntyre Powder exposure and Alzheimer’s disease or motor neuron disease, miners overall had a higher risk compared to the general population.


This was the largest study on the neurological effects of McIntyre Powder to date. The findings provide evidence that Ontario miners, especially those historically exposed to McIntyre Powder, are at increased risk of neurological disease. These findings could have implications for workers’ compensation.


This study was funded by the Workplace Safety and Insurance Board.

  • OCRC Report: Investigation of McIntyre Powder Exposure and Neurological Outcomes in the Mining Master File Cohort

Research Team
Paul Demers
Victoria Arrandale
OCRC and University of Toronto
Nathan DeBono
Colin Berriault
Jill MacLeod
Xiaoke Zeng
OCRC and University of Toronto
Anne Harris
Ryerson University