Physical and chemical characterization of McIntyre Powder: An aluminum dust inhaled by miners to combat silicosis
- DOI
- Language of the publication
- English
- Date
- 2019-09-18
- Type
- Article
- Author(s)
- Zarnke, Andrew
- Rasmussen, Pat E
- David, Marie-Odile
- Eidi, Housam
- Kennedy, Konnor
- Publisher
- Taylor & Francis
Abstract
McIntyre Powder (MP) is a finely ground aluminum powder that was used between 1943 and 1979 as a prophylaxis for silicosis. Silicosis is a chronic lung disease caused by the inhalation of crystalline silica dust and was prevalent in the Canadian mining industry during this time period. The McIntyre Research Foundation developed, patented, and produced the MP and distributed it to licensees in Canada, the United States, Mexico, Chile, Belgian Congo, and Western Australia. In the province of Ontario, Canada it is estimated that at least 27,500 miners between 1943 and 1979 were exposed to MP. The present study was undertaken to examine the chemical and physical characteristics of two variations of MP (light grey and black). Chemical analyses (using X-ray Fluorescence and Inductively Coupled Plasma approaches) indicate that the black MP contains significantly higher concentrations of aluminum and metal impurities than the light grey MP (p < 0.001). X-ray diffractometry shows that while aluminum hydroxide dominates the aluminum speciation in both variations, the higher total aluminum content in the black MP is attributable to a greater proportion of elemental aluminum. Physical characterization (using electron microscopy, light microscopy, and dynamic light scattering) indicates that the light grey MP consists of particles ranging from 5 nm to 5 µm in diameter. Atomic Force Microscopy shows that the light grey MP particles in the nanoparticle range (<100 nm) have a mode between 5 and 10 nm. Consequently, it is possible that inhaled smaller MP nanoparticles may be transported via blood and lymph fluid circulation to many different organs including the brain. It is also possible for inhaled larger MP particles to deposit onto lung tissue and for potential health effects to arise from inflammatory responses through immune activation. This MP characterization will provide crucial data to help inform future toxicological, epidemiological, and biological studies of any long-term effects related to the inhalation of aluminum dust and nanomaterials.
Plain language summary
Health Canada is responsible for evaluating risks associated with inhaling airborne particles, which requires knowledge of their physical and chemical properties. This study was undertaken by Laurentian University in collaboration with Health Canada, the Occupational Health Clinics for Ontario Workers, and other academic partners to characterize a finely ground aluminum dust called “McIntyre Powder”. In the middle of the 20th century, it was thought that McIntyre Powder could be used as a preventative treatment to combat silicosis. Silicosis is a chronic lung disease which was prevalent in the Canadian mining industry at that time, caused by the inhalation of crystalline silica dust. In the province of Ontario, Canada it is estimated that at least 27,500 miners were exposed to McIntyre Powder treatments between 1949 and 1979. Two variations of McIntyre Powder were obtained for this study: a black powder and a light grey powder. Chemical analyses indicated that the black powder contains significantly higher concentrations of aluminum and metal impurities than the light grey powder. X-ray Diffractometry showed that, while aluminum hydroxide is the dominant form of aluminum in both variations, the black powder has a greater proportion of elemental aluminum. Physical characterization (using electron, light, and atomic force microscopy and dynamic light scattering) showed that the light grey powder consists of particles ranging from 5 nm to 5 µm in diameter, with a significant proportion in the nanoparticle range (<100 nm). This McIntyre Powder characterization study will provide information to help inform future toxicological and epidemiological investigations of potential long term effects related to the inhalation of aluminum dust and nanoparticles. In addition, the methodologies used in this study will assist in future characterization of particles to which Canadians are exposed through the inhalation pathway, and will contribute to human health risk assessments conducted under the Chemicals Management Plan.
Subject
- Health,
- Health and safety