New Research Confirms Hazards of Asbestos-Cement
The paper: Cancer Incidence Among Workers in the Asbestos-Cement Producing Industry in Norway by B Ulvestad, K Kjaerheim et al1 reports high levels of asbestos-related disease amongst former employees of an asbestos-cement factory. Between 1942-1968, the majority of asbestos (92%) used at this plant was chrysotile, most of which was imported from Canada; the remainder was amphiboles (anthophyllite, amosite or crocidolite).
This paper is of particular interest as research on this cohort has not been published previously. As would be expected, the longer the employment, the higher the risk of malignant mesothelioma and lung cancer.
“Among the workers employed 5 years or more, the risk of malignant mesothelioma was elevated. The standardized incidence ratio was highest for the workers employed 15 years or more. Lung cancer was elevated for workers employed 1-4 years and for those with 15 or more years of employment. Lung cancer was observed for three never smokers and one ex-smoker.”
It is interesting to note that the “ratio of mesothelioma to lung cancer cases was 1:2 in the total cohort.” The authors seem surprised that even after the dry milling and manual handling of asbestos was stopped in 1952, the risk to workers continued. While the standardized incidence ratio (SIR) for malignant mesothelioma was 99.0 for workers employed before 1952, the SIR for the 1952-1959 cohort was 35.3.
“This study of asbestos-cement workers demonstrated an elevated risk of cancer at all sites, mainly due to excess risks of malignant mesothelioma, lung cancer, oral cancer, colorectal cancer, and bladder cancer.”
The scientists appear uneasy about concluding that the use of chrysotile was implicated in the disease-formation citing many papers which rely on the “Amphibole Hypothesis.” Reluctantly, however, they state:
“Excess mortality from lung cancer and mesothelioma has also been reported from other studies, in which the exposure to chrysotile fibers has dominated. In our study we could not rule out the possibility that chrysotile contributed to the excess cancer risk.”
March 16, 2003
1 This paper appeared in the Scandinavian Journal of Work Environment and Health 2002, vol. 28, no 6, pages 411-417