Objectives Studies of workers in two US cohorts of asbestos textile workers exposed to chrysotile (North Carolina (NC) and South Carolina (SC)) found increasing risk of lung cancer mortality with cumulative fibre exposure. However, the risk appeared to increase more steeply in SC, possibly due to differences in study methods. The authors conducted pooled analyses of the cohorts and investigated the exposure-disease relationship using uniform cohort inclusion criteria and statistical methods.
Methods Workers were included after 30 days of employment in a production job during qualifying years, and vital status ascertained through 2003 (2001 for SC). Poisson regression was used to estimate the exposure-response relationship between asbestos and lung cancer, using both exponential and linear relative rate models adjusted for age, sex, race, birth cohort and decade of follow-up.
Results The cohort included 6136 workers, contributing 218 631 person-years of observation and 3356 deaths. Cumulative exposures at the four study facilities varied considerably. The pooled relative rate for lung cancer, comparing 100 f-yr/ml to 0 f-yr/ml, was 1.11 (95% CI 1.06 to 1.16) for the combined cohort, with different effects in the NC cohort (RR=1.10, 95% CI 1.03 to 1.16) and the SC cohort (RR=1.67, 95% CI 1.44 to 1.93).
Conclusions Increased rates of lung cancer were significantly associated with cumulative fibre exposure overall and in both the Carolina asbestos-textile cohorts. Previously reported differences in exposure-response between the cohorts do not appear to be related to inclusion criteria or analytical methods.
- lung neoplasms
- cohort study
- public health
- hygiene/occupational hygiene
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Disclaimer The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health.
Funding Funding was provided by grant R01-OH007803 from the National Institute for Occupational Safety and Health, USA. The funding agency had no involvement in the study design; in the collection, analysis and interpretation of data; in the writing of the report; or in the decision to submit the paper for publication.
Competing interests None.
Ethics approval The study was approved by the institutional review boards of the University of North Carolina, Chapel Hill.
Provenance and peer review Not commissioned; externally peer reviewed.
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