Abstract:
The objective of this cross-sectional study was to characterize the degree to which employees in Washington state are exposed to hard metal particulates (cobalt, chromium), and to identify engineering or environmental determinants of exposure. Ninety-nine subjects were recruited from 11 different shops. These shops represented several classes of hard metal (HM) using companies such as saw mills, saw manufacturers, and saw repair shops. Approximately two full shift TWA air samples were collected from each subject. Several bulk samples of metal working fluids were collected from each company and analyzed for cobalt and chromium. A work activity log was completed for each subject to identify the locations and activities of sampled workers throughout the sampling day.
A total of 162 full shift inhalable particulate samples were obtained and analyzed for cobalt, chromium, and particulate mass. The mean cobalt levels of HM exposed workers in the study was 20.2 ug/m3 (range:0.7-279.0 ug/m3), the mean chromium exposure was 4.6ug/m3 (range: 0.0-169.0 ug/m3), and the mean inhalable particulate exposure was 1.98 mg/m3 (range: 0.08-29.8 mg/m3). Saw manufacturing shops had the highest cobalt exposures, followed by saw reconditioning shops, and sawmills respectively. Linear regression models were developed for cobalt and total inhalable particulate to determine characteristics of the workplace that were associated with higher exposures, and to estimate average exposures to each individual in the study. One of two models developed for cobalt indicated that cobalt exposure levels were significantly associated with the cobalt concentration in metal working fluid, wet or dry grinding of tungsten carbide, brazing or welding of tungsten carbide, brazing or welding of stellite, and job title. The results of the study provide a better understanding of the extent of worker exposure to HM in Washington state tool industries, and offer a focus for implementing effective exposure controls.