Characterization of hard metal dusts from sintering and detonation coating processes and comparative hydroxyl radical production.
Dust samples from sintering and detonation coating hard-metal processes were characterized, compared, and contrasted for morphology, composition, and generation of hydroxyl radicals. Inhalation of respirable hard-metal (sintered carbide) dusts from hard-metal processes is known to cause fibrotic and asthmatic lung disease. Scanning electron microscopy/energy-dispersive X-ray analysis was used for morphology, composition, and elemental distribution. An electron spin resonance (ESR) spin trapping technique was used to detect hydroxyl radical generation. Samples were incubated with air-saturated buffer solutions containing a spin trap and analyzed by ESR for the presence of *OH in solution. Postdetonation coating samples often had surface contamination of Co on the WC particles, as shown by elemental mapping of individual particles; this was not evident in predetonation samples or unsintered materials in this study. ESR measurements show that both detonation-gun materials were capable of generating *OH , while the WC, cobalt, and presintered mixture did not produce detectable amounts of *OH radicals. The DMPO/*OH adduct formation was apparently facilitated by Fe-mediated reactions for predetonation dusts, and by Fe-mediated site-specific reactions for postdetonation dusts. The overspray materials from the detonation-gun process produced 9-fold more *OH radicals than the predetonation coating mixture. Overall, this study indicates there are substantial differences between postdetonation materials and both predetonation and unsintered hard-metal process materials with respect to morphology, elemental distribution, and *OH radical generation reactions and that these differences may be important in the toxic potential of those materials.
Keane
Michael J
MJ
Health Effects Laboratory Division, National Institute for Occupational Safety and Health, 1095 Willowdale Road, Morgantown, WV 26505, USA.
Hornsby-Myers
Jennifer L
JL
Stephens
James W
JW
Harrison
Joel C
JC
Myers
John R
JR
Wallace
William E
WE
D000395:Air Pollutants, Occupational / Q000032:analysis; D004391:Dust / Q000032:analysis*; D004577:Electron Probe Microanalysis; D017665:Hydroxyl Radical / Q000737:chemistry*; D008670:Metals / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D016273:Occupational Exposure / Q000032:analysis; D019097:Spin Trapping
D000395:Air Pollutants, Occupational; D004391:Dust; D008670:Metals; D017665:Hydroxyl Radical