Lung Cancer Risk in Hard-Metal Workers

Abstract

An industry-wide mortality study on the association between lung cancer and occupational exposure to cobalt and tungsten carbide was carried out in the French hard-metal industry. This case-control study was nested in the historical cohort of workers ever employed in this industry's 10 facilities, most of which are located in eastern France. Workers were followed up from 1968 to 1991. Occupational exposure was assessed using a job-exposure matrix that provided semiquantitative scores for 320 job periods. These scores were significantly correlated with the levels of cobalt measured in 744 historical air samples. In this cohort, which comprised 5,777 males and 1,682 females, the death rate from lung cancer was significant (63 deaths, standardized mortality ratio=1.30, 95% confidence interval (CI) 1.00-1.66) when compared with national death rates. Sixty-one cases and 180 controls were included in the study. When the exposures during the last 10 years were ignored, a twofold lung cancer risk was observed among workers simultaneously exposed to cobalt and tungsten carbide (odds ratio (OR)=1.93, 95% CI 1.03-3.62) adjusted for other cobalt exposure (OR=2.21, 95% CI 0.99-4.90). The odds ratios increased with cumulative exposure (first quartile, OR=1.00; second quartile, OR=2.64; third quartile, OR=2.59; fourth quartile, OR=4.13) and, to a lesser degree, with duration of exposure (one decade, OR=1.00; two decades, OR=1.61; three decades, OR=2.77; four decades, OR=2.03). Adjustments for smoking and for exposures to known or suspected carcinogens did not change the results, yet the odds ratio for smoking (3.38) was lower than expected, suggesting the possibility of some misclassification. Occupational risk was highest among smokers. This study supports the hypothesis that workers who manufacture hard metals have an increased mortality from lung cancer due to simultaneous exposure to cobalt and tungsten carbide.

Lung Cancer Risk in Male Dentists: A Retrospective Cohort Study in Japan, 1964–1997

“…A TLV-TWA (Threshold Limit Value-Time Weighted Average) of 0.5 mg/mg 3 , as metal and trivalent chromium compounds, is recommended to minimize the potential risk of respiratory disorder, by ACGIH 44) . Epidemiological and experimental observations show that cobalt will be carcinogenic in the human lung 32,45) . IARC lists cobalt as Group2B (possibly carcinogenic to humans) 43) .…”

Nanotoxicity: emerging concerns regarding nanomaterial safety and occupational hard metal (WC-Co) nanoparticle exposure

“…44,[51][52][53][54][55][56][57][58][59] Diagnosis of HMLD is a challenge, as symptoms are general and often mistaken for other respiratory ailments: patients often report difficulty breathing and present with reduced lung capacity, progressive lung inflammation, and eventual fibrosis. 57,60,61 HMLD has been reported in hard metal manufacturing and oil and mining/drilling industries, where workers were exposed to WC-Co dusts or fumes on a daily basis for a number of years prior to diagnosis.…”

“…71 There is also accumulating evidence that patients with HMLD are at a twofold increased risk of developing lung cancer. 54,56 It has been argued that the generation of reactive oxygen species by WC-Co particles, which may directly cause DNA damage, along with the ability of cobalt ions to inhibit DNA repair mechanisms, may play a synergistic role in the development of lung cancer in HMLD patients. 56 However, this hypothesis is yet to be verified in vivo and the relationship between the inflammatory disease state and development of lung cancer remains unclear.…”

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

“…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). In vitro and in vivo studies indicate that the genotoxicty of cobalt in the presence of tungsten carbide is greater than either component alone (Anard et al, 1997;Van Goethem et al, 1997;Lison et al, 2001;De Boeck et al, 2003a, b;Mateuca et al, 2005).…”