Between 1943 and 1979 McIntyre Powder (MP) was used in the Canadian mining industry as a prophylaxis for silicosis. Silicosis is an occupational lung disease, caused by the inhalation of crystalline silica dust. This dust is created from the cutting or breaking of many types of rocks, such as granite, sandstone, gneiss and slate and some metallic ores. McIntyre Powder was manufactured by grinding solid, aluminum pellets in a ball-mill one meter in diameter and two meters in length. It is documented that approximately 27,500 mine workers were exposed to MP in Ontario, Canada. Published studies, revealing associations between air pollution particulates and increased risk for cardiovascular disease (CVD), suggest that mine workers exposed to MP may be at a similar increase in risk for CVD. This project is aimed to advance the understanding of the potential role of occupational exposure to particulate matter, in the form of McIntyre Powder, in the development cardiovascular diseases, with a focus on a linked cohort of mine workers in Ontario, Canada. The objective of the project is to characterize the physical and chemical properties of the McIntyre Powder material to help understand how past MP-exposures may have contributed to an increased risk for developing cardiovascular disease.