Cobalt Exposure and Lung Disease in Tungsten Carbide Production: A Cross-sectional Study of Current Workers

Abstract

A cross-sectional study of 1,039 tungsten carbide (TC) production workers was carried out. The purposes were (1) to evaluate the prevalence of interstitial lung disease (ILD) and work-related wheezing, (2) to assess correlations between cobalt exposure and pulmonary disease, (3) to compare lung disease in grinders of hard carbide versus nongrinders, and (4) to evaluate the effects of new and previous threshold limit values for cobalt of 50 and 100 micrograms/m3. We obtained medical and occupational histories, flow-volume loops, single breath carbon monoxide diffusing capacity (DLCO), and chest radiographs. Time-weighted average cobalt levels were determined at every step in the production process. Work-related wheeze occurred in 113 participants (10.9%). Profusion greater than or equal to 1/0 occurred in 26 (2.6%) and interstitial lung disease (defined as profusion greater than or equal to 1M, FVC or DLCO less than or equal to 70%, and FEV1/FVC% greater than or equal to 75) in 7 (0.7%). The relative odds of work-related wheeze was 2.1 times for present cobalt exposures exceeding 50 micrograms/m3 compared with exposures less than or equal to 50 micrograms/m3. The relative odds of profusion greater than or equal to 1/0 was 5.1 times for average lifetime cobalt exposures exceeding 100 micrograms/m3 compared with exposures less than or equal to 100 micrograms/m3 in those with latency exceeding 10 yr. ILD was found in three workers with very low average lifetime exposures (less than 8 micrograms/m3) and shorter latencies. Grinders of hard carbide had lower mean DLCO than nongrinders, even though their cobalt exposures were lower.(ABSTRACT TRUNCATED AT 250 WORDS)

Characteristics of Dusts Encountered during the Production of Cemented Tungsten Carbides

“…If Co particles in the presence of WC particles cause HMD via generation of ROS [4][5][6] , then our characterization of airborne particles may help to explain the inconsistent findings of epidemiological studies, e.g., between Meyer-Bisch et al 1) and Sprince et al 2) ; only Sprince et al 2) showed a higher risk in the later stages of the CTC manufacturing process. We observed that airborne particles potentially available for inhalation in spray drying and all subsequent work areas were a mixture of elemental tungsten and elemental Co particles and/or multi-constituent W/Co particles (ostensibly WC/Co particles, but the relative carbon contribution of the collection substrate and metal carbides is unknown).…”

Characterization of exposures among cemented tungsten carbide workers. Part I: Size-fractionated exposures to airborne cobalt and tungsten particles

“…If occupational asthma is caused by exposure to particles with aerodynamic sizes capable of depositing in the tracheobronchial, bronchial, and alveolar regions of the lung and with chemical composition that contains cobalt (alone or in the presence of tungsten carbide), then our air-monitoring results in conjunction with in vitro dissolution test results may help to explain why cases of occupational asthma are observed among workers who handle pre-sintered hard metal powders and grind and manipulate sintered CTC parts (Davison et al, 1983;Sprince et al 1988;Meyer-Bisch et al, 1989;Shirakawa et al, 1989;Kusaka et al, 1996) and among diamond polishers whose only exposure is to cobalt (Gheysens et al, 1985). Consistent with these studies, we observed exposures to cobalt in all work areas spanning powder production to handling finished product parts.…”

“…If HMD and lung cancer are caused by alveolar deposition of respirable-size particles that contain cobalt associated with tungsten, then our air monitoring exposure data may help to understand lung cancer and explain why HMD is observed among workers exposed to pre-sintered material alone (Meyer-Bisch et al, 1989), post-sintered CTC material alone (Sprince et al, 1988), and both pre-and post-sintered materials (Bech et al, 1962;Coates and Watson, 1971;Sjo¨gren et al, 1980;Davison et al, 1983;Sprince et al, 1984;Cugell et al, 1990;Figueroa et al, 1992;Fischbein et al, 1992). Consistent with these studies, we observed that workers were co-exposed to respirable cobalt-and tungstencontaining particles in all work areas (see Tables 4 and 5) spanning powder production (pre-sintered materials) through handling final product parts (post-sintered materials).…”

“…Workplace studies have identified cases of occupational asthma among CTC workers exposed to both cobalt and tungsten (Davison et al, 1983;Sprince et al 1988;Meyer-Bisch et al, 1989;Shirakawa et al, 1989;Kusaka et al, 1996) and diamond polishers exposed to cobalt alone (Gheysens et al, 1985). Cases of HMD have been reported among workers in all phases of CTC production (Bech et al, 1962;Coates and Watson, 1971;Sjo¨gren et al, 1980;Davison et al, 1983;Sprince et al, 1984Sprince et al, , 1988Meyer-Bisch et al, 1989;Cugell et al, 1990;Figueroa et al, 1992;Fischbein et al, 1992), which may be due to exposures to tungsten carbide particles in association with cobalt particles (Lasfargues et al, 1992(Lasfargues et al, , 1995Lison and Lauwerys, 1990, 1994, 1995Lison et al, , 1996. In humans, excess lung cancer has been observed among hard metal workers exposed to CTC dusts (Lasfargues et al, 1994;Moulin et al, 1998;Wild et al, 2000;Lison et al, 2001), but not among cobalt production workers exposed to cobalt alone (Moulin et al, 1993).…”

“…Historically, exposure assessments and epidemiological studies of hard-metal-induced adverse health effects have focused on measurements of total airborne cobalt aerosol mass concentration using 37-mm cassette samplers or other sampling heads without regard to particle size (Fairhall et al, 1947;Bech et al, 1962;Sprince et al, 1984Sprince et al, , 1988MeyerBisch et al, 1989;Sesana et al, 1994;Teschke et al, 1995;Kumagai et al, 1996). A few historical studies have investigated combined airborne exposures to cobalt and tungsten among CTC workers (Lichtenstein et al, 1975;Koponen et al, 1981Koponen et al, , 1982Kraus et al, 2001); however, these studies also used total mass concentration exposure estimates.…”