Article Text
Abstract
Objectives Increased mortality from asthma, chronic bronchitis and emphysema has previously been reported among workers in the silicon carbide (SiC) industry. The objective of the present study was to evaluate the influence of specific exposure factors on mortality from obstructive lung diseases (OLD), using a newly revised job-exposure matrix.
Materials and methods 1687 long-term workers employed in 1913–2003 in the Norwegian SiC industry were characterised with respect to cumulative exposure to quartz, cristobalite, SiC particles and SiC fibres. Standardised mortality ratios (SMRs) for underlying causes of death, 1951–2007, were calculated stratified by category of cumulative exposure, and Poisson regression analyses of OLD were performed using cumulative exposure variables.
Results An increased total mortality (SMR 1.1, 95% CI 1.0 to 1.2) and increased mortality from cancer, non-malignant respiratory diseases and external factors, were observed. The SMR of OLD was increased at the highest level of cumulative exposure to all investigated exposure factors. In the internal analyses, a twofold increased risk of OLD was observed with increasing levels of cumulative exposure to SiC particles. In a multivariate model, SiC particles showed the most stable increased risk estimate when controlled for other exposure factors, among workers with less than 15 years of employment. Among workers with more than 15 years of employment, crystalline silica, primarily cristobalite, seemed to be the most important exposure factor.
Conclusion Exposure to SiC and crystalline silica may contribute to OLD development among SiC industry workers in different time windows, and possibly through different mechanisms.
- Epidemiology
- respiratory
- mortality studies
- inorganic dusts
- inorganic fibres
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Footnotes
Funding The project has been financed with the aid of EXTRA funds from the Norwegian Foundation for Health and Rehabilitation, and with support from the Ministry of Labour and Social Inclusion.
Competing interests None.
Ethics approval This study was conducted with the approval of the Regional Committee for Medical Research Ethics South-East Norway, Oslo University, Norway.
Provenance and peer review Not commissioned; externally peer reviewed.