Hard metal dusts, typically WC/Co, but not pure WC or Co particles, cause the so-called'hard metal lung disease'when inhaled over long periods of time at the workplace.
In order to investigate the chemical nature of the dust which originates the disease, the surface behaviour of pure cobalt, pure tungsten carbide, an industrial hard metal dust and a mechanical mixture of cobalt and tungsten carbide have been compared.
Electron microscopy reveals an intimate contact between metal and carbide in the mixed dusts.
The mixed dust is more active than the single components in the adsorption of water vapour in both adsorbed amount and interaction energy (111 kJ mol-1 for the mixture, 95 kJ mol-1 for pure cobalt and 84 kJ mol-1 for pure WC).
Both industrial and mechanical mixtures are more active than pure components in the catalytic decomposition of hydrogen peroxide.
Incubation of the mixed dusts in phosphate buffered solutions causes a progressive release of cobalt (it) ions in solution and the appearance of round smooth aggregates (diameter ca. 300-400 mum) at the expense of smaller particles.
The mixed dusts, but not the pure components, promote the homolytic rupture of carbon-hydrogen bond in aqueous suspension, as revealed by the formation of carboxylate radicals from formate ions.
This is evidenced by the use of DMPO as a spin trap, which yields the DMPO-CO2-adduct whose EPR spectrum intensity measures the amount of radicals generated. (...)
Mots-clés Pascal : Cobalt, Tungstène carbure, Particule métallique, Interaction, Surface, Propriété surface, Mélange, Etude comparative, Radical libre, Libération, Interception spin, Absorption eau, Toxicité, Inhalation, Activité catalytique, Solution aqueuse, Etude expérimentale, In vitro, Pneumopathie, Atmosphère industrielle, Exposition professionnelle, Appareil respiratoire pathologie, Pollution air, Médecine travail
Mots-clés Pascal anglais : Cobalt, Tungsten carbide, Metal particle, Interaction, Surface, Surface properties, Mixture, Comparative study, Free radical, Release, Spin trapping, Water absorption, Toxicity, Inhalation, Catalyst activity, Aqueous solution, Experimental study, In vitro, Pneumopathy, Industrial atmosphere, Occupational exposure, Respiratory disease, Air pollution, Occupational medicine
Notice produite par :
Inist-CNRS - Institut de l'Information Scientifique et Technique
Cote : 97-0491758
Code Inist : 002B03L05. Création : 03/02/1998.