Mortality from asbestosis and mesothelioma in Britain by birth cohort.

BACKGROUND Analysis of occupational mortality in England and Wales during 1991-2000 showed no decline in work-attributable deaths from asbestosis. AIMS To explore why there was no decline in mortality from asbestosis despite stricter controls on asbestos exposure over recent decades. METHODS Using data from registers of all deaths in Great Britain with mention of mesothelioma or asbestosis on the death certificate, we plotted death rates by 5 year age group within 5 year birth cohorts for(a) mesothelioma and (b) asbestosis without mention of mesothelioma. RESULTS Analysis was based on a total of 33,751 deaths from mesothelioma and 5396 deaths from asbestosis. For both diseases, mortality showed a clear cohort effect; within birth cohorts, death rates increased progressively with age through to 85 years and older. However, highest mortality from mesothelioma was in men born during 1939-43, whereas, mortality from asbestosis peaked in men born during 1924-38. CONCLUSIONS Our findings suggest that mortality, in Britain, from asbestosis has been determined mainly by cumulative exposure to asbestos before 45 years of age and that the effect of such exposure continues through to old age. That mortality from asbestosis peaked in earlier birth cohorts than mortality from mesothelioma may reflect a difference in exposure-response relationships for the two diseases. The discrepancy could be explained if risk of asbestosis increased more steeply than that of mesothelioma at higher levels of exposure to asbestos and if the highest prevalence of heavy exposure occurred in earlier birth cohorts than the highest prevalence of less intense exposures.