Lung cancer incidence among Norwegian silicon carbide industry workers: associations with particulate exposure factors
- 1National Institute of Occupational Health, Oslo, Norway
- 2Cancer Registry of Norway, Oslo, Norway
- 3Department of Public Health and General Practice, Norwegian University of Science and Technology, Trondheim, Norway
- Correspondence to Dr Merete Drevvatne Bugge, National Institute of Occupational Health, Pb. 8149 Dep, Oslo N-0033, Norway;
Contributors MDB updated the Norwegian silicon carbide industry cohort with employment periods and new employees in the period 1997–2003. She contributed to the development of the job coding system. She performed all the statistical analyses and wrote the paper. KK was cosupervisor on the project, with expertise on register studies of cancer and mortality. She read and commented on the manuscript. SF collected all the historical exposure data and performed new measurements of exposure. She contributed to the development of the job coding system. She constructed the job exposure matrix used in the epidemiological analyses. She read and commented on the manuscript. WE was cosupervisor on the project, with expertise on exposure related epidemiological analyses. He supervised the analyses, read and commented on the manuscript. HK was the main supervisor on the project. He supervised the epidemiological analyses, and read and commented on the manuscript.
- Accepted 18 April 2012
- Published Online First 18 May 2012
Objectives An 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.
Methods Cumulative 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.
Results The 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.
Conclusions The 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.
- job exposure matrix
- inorganic fibres
- mortality studies
- hygiene/occupational hygiene
- exposure monitoring
- exposure assessment
- organic dusts
- retrospective exposure assessment
- longitudinal studies
Funding The research has been supported with the aid of EXTRA funds from the Norwegian Foundation for Health and Rehabilitation, and with grants from the Norwegian Ministry of Labour.
Competing interests None declared.
Ethics approval The ethics approval was provided by Regional Committee for Medical Research Ethics South-East Norway, Oslo.
Provenance and peer review Not commissioned; externally peer reviewed.
This is an open-access article distributed under the terms of the Creative Commons Attribution Non-commercial License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited, the use is non commercial and is otherwise in compliance with the license. See: http://creativecommons.org/licenses/by-nc/2.0/ and http://creativecommons.org/licenses/by-nc/2.0/legalcode.