Pooled exposure–response analyses and risk assessment for lung cancer in 10 cohorts of silica-exposed workers: an IARC multicentre study
- 631 Downloads
Objectives: Silica is one of the most common occupational exposures worldwide. In 1997 the International Agency for Research on Cancer (IARC) classified inhaled crystalline silica as a human carcinogen (group 1), but acknowledged limitations in the epidemiologic data, including inconsistencies across studies and the lack of extensive exposure–response data. We have conducted a pooled exposure–response analysis of 10 silica-exposed cohorts to investigate lung cancer.
Methods: The pooled cohort included 65,980 workers (44,160 miners, 21,820 nominees), and 1072 lung cancer deaths (663 miners, 409 nonminers). Follow-up has been extended for five of these cohorts beyond published data. Quantitative exposure estimates by job and calendar time were adopted, modified, or developed to permit common analyses by respirable silica (mg/m3) across cohorts.
Results: The log of cumulative exposure, with a 15-year lag, was a strong predictor of lung cancer (p = 0.0001), with consistency across studies (test for heterogeneity, p = 0.34). Results for the log of cumulative exposure were consistent between underground mines and other facilities. Categorical analyses by quintile of cumulative exposure resulted in a monotonic trend with odds ratios of 1.0, 1.0, 1.3, 1.5, 1.6. Analyses using a spline curve also showed a monotonic increase in risk with increasing exposure. The estimated excess lifetime risk (through age 75) of lung cancer for a worker exposed from age 20 to 65 at 0.1 mg/m3 respirable crystalline silica (the permissible level in many countries) was 1.1–1.7%, above background risks of 3–6%.
Conclusions: Our results support the decision by the IARC to classify inhaled silica in occupational settings as a carcinogen, and suggest that the current exposure limits in many countries may be inadequate. These data represent the first quantitative exposure–response analysis and risk assessment for silica using data from multiple studies.
Unable to display preview. Download preview PDF.
- 1.International Agency for Research on Cancer (IARC) (1997) Monographs on the Evaluation of Carcinogenic Risks to Humans, vol. 68: Silica, Some Silicates, Coal Dust and Para-Aramid Fibrils. Lyon: International Agency for Research on Cancer.Google Scholar
- 6.Reid P, Sluis-Cremer G (1996) Mortality of white South African gold miners. Occup Environ Med 49: 459–464.Google Scholar
- 8.Harrison J, Brower P, Attfield M, et al. (1997) Surface composition of respirable silica particles in a set of US anthracite and bituminous coal mine dusts. J Aerosol Sci 28: 689–696.Google Scholar
- 10.Miller B, Buchanan D, Hurley J, et al. (1997) The effects of exposure to diesel fumes, low-level radiation, respirable dust and quartz, on cancer mortality in coalminers. Institute of Occupational Medicine Report TM/97/04, Edinburgh.Google Scholar
- 16.Costello J, Graham W (1988) Vermont granite workers' mortality study. Am J Indust Med 13: 483–497.Google Scholar
- 20.Hnizdo E, Sluis-Cremer G (1991) Silica exposure, silicosis, and lung cancer: a mortality study of South African gold miners. Br J Indust Med 48: 53–60.Google Scholar
- 27.Banks D, Morring K, Boehlecke B (1981) Silicosis in the 1980s. J Am Indust Hyg Assoc 42: 77–79.Google Scholar
- 29.Sanderson W, Steenland K, Deddens J (2000) Historical respirable quartz exposures of industrial sand workers: 1947–1996. Am J Indust Med 38: 1–10.Google Scholar
- 30.Hewson G (1993) Estimates of silica exposure among metalliferous miners in Western Australia (1925–1993). Department of Minerals and Energy of Western Australia, Perth.Google Scholar
- 31.Davis L, Wegman D, Monson R, Froines J (1983) Mortality experience of Vermont granite workers. Am J Indust Med 4: 704–723.Google Scholar
- 32.Eisen A, Smith T, Wegman D, Louis T, Froines J (1984) Estimation of long term dust exposures in the Vermont granite sheds. J Am Indust Hyg Assoc 45: 89–94.Google Scholar
- 34.Dosemcci M, Chen J, Hearl F, et al. (1993) Estimating historical silica exposure among mine and pottery workers in the People's Republic of China. Am J Indust Med 24: 55–66.Google Scholar
- 35.McLaughlin J, Chen J-Q, Dosemeci M, et al. (1992) A nested case-control study of lung cancer among silica exposed workers in China. Br J Indust Med 49: 167–171.Google Scholar
- 36.Zhuang Z, Hearl F, Chen W, et al. (2001) Estimating historical respirable crystalline silica exposure for Chinese pottery workers, iron/copper, tin, and tungsten miners. An Occup Hyg (in press).Google Scholar
- 37.Koskela R (1995) Association of silica dust exposure with lung cancer and other disease. Dissertation, University of Tampere, Tampere, Finland.Google Scholar
- 38.Steenland K, Spaeth S, Cassinelli R, et al. (1998) NIOSH life table program for personal computers. Am J Indust Med 34: 517–518.Google Scholar
- 39.Ferlay J, Parkin D, Pisani P (1998) Globocan I: Cancer Incidence and Mortality Worldwide. Lyon: IARC Press.Google Scholar
- 40.SAS (1991) SAS User's Guide: Statistics (Version 6.07). Cary, NC: SAS Institute.Google Scholar
- 44.Stayner L, Smith R, Thun M, Schnorr T, Lemen R (1992) A dose-response analysis and quantitative assessment of lung cancer risk and occupational cadmium exposure. Anns Epidemiol 2: 177–194.Google Scholar
- 46.Steenland K, Deddens J, Stayner L (1998) Diesel exhaust and lung cancer in the trucking industry exposure-response analysis and risk assessment. Am J Indust Med 34: 220–228.Google Scholar
- 50.Checkoway H, Franzblau A (2000) Is silicosis required for silica-associated lung cancer? Am J Indust Med 37: 252–259.Google Scholar
- 54.Deddens J, Hornung R (1995) Quantitative examples of continuous exposure measurement errors that bias risk estimates away from the null. In: Smith C, Christiani D, Kelsey K, eds. Chemical Risk Assessment of Occupational Health. London: Auburn, pp. 77–85.Google Scholar
- 55.Gibb H, Lees P, Pinsky P, Rooney B (2000) Lung cancer among workers in chromium chemical production. Am J Indust Med 38: 115–116.Google Scholar
- 56.Enterline P, Henderson V, Marsh G (1987) Exposure to arsenic and respiratory cancer. Am J Epidemiol 25: 929–938.Google Scholar
- 57.ICNCM (International Committee on Nickel Carcinogenesis in Man) (1990) Report of the International Committee on Nickel Carcinogenesis in Man. Scand J Work Environ Health 16: 1–84.Google Scholar