McIntyre Powder (MP) is a finely ground aluminium 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 aluminium and metal impurities than the light grey MP (p?0.001). X-ray diffractometry shows that while aluminium hydroxide dominates the aluminium speciation in both variations, the higher total aluminium content in the black MP is attributable to a greater proportion of elemental aluminium. Physical characterisation (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 characterisation will provide crucial data to help inform future toxicological, epidemiological, and biological studies of any long-term effects related to the inhalation of aluminium dust and nanomaterials.
Authors: Zarnke A, Rasmussen PE, David MO, Eidi H, Kennedy K, Hedges K, Irick T, Thome C, Pirkkanen J, Boreham D.
; Full Source: Journal of Occupational & Environmental Hygiene. 2019 Sep 18:1-12. doi: 10.1080/15459624.2019.1657581. [Epub ahead of print]