• Merete Drevvatne Bugge, Kristina Kjærheim, Solveig Føreland, Wijnand Eduard, and Helge Kjuus.
• National Institute of Occupational Health, Pb. 8149 Dep, Oslo N-0033, Norway. mdb@stami.no
• Occup Environ Med. 2012 Aug 1; 69 (8): 527-33.

ObjectivesAn increased lung cancer risk associated with total dust exposure in the silicon carbide (SiC) industry has previously been reported. The aim of the present study was to examine the relative importance of specific exposure factors by using a comprehensive, historic job exposure matrix based on about 8000 measurements.MethodsCumulative exposure to total and respirable dust, respirable quartz, cristobalite, and SiC particles and SiC fibres was assessed for 1687 long-term workers employed during 1913-2003 in the Norwegian SiC industry. Standardised incidence ratios for lung cancer, with follow-up during 1953-2008, were calculated stratified by cumulative exposure categories. Poisson regression analyses were performed using both categorised and log-transformed cumulative exposure variables.ResultsThe lung cancer incidence was about twofold increased at the highest level of exposure to each of the exposure factors (standardised incidence ratios 1.9-2.3 for all agents). Internal analyses showed associations between exposure level and lung cancer incidence for all investigated factors, but a significant trend only for total dust and cristobalite. In multivariate analyses, cristobalite showed the most consistent associations, followed by SiC fibres.ConclusionsThe results indicated that crystalline silica in the form of cristobalite was the most important occupational exposure factor responsible for lung cancer excess in the Norwegian SiC industry. SiC fibres seemed to have an additional effect.

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