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196 ESTIMATION OF THE BURDEN OF CANCER IN GREAT BRITAIN DUE TO OCCUPATION: GENERAL METHODOLOGY
Objectives:
The aim of this project is to update the 1981 Doll and Peto estimates of attributable burden of cancer due to occupation for Great Britain. Estimates of the relative contributions of different occupational exposures are also required.
Methods:
The primary measure of burden used in the project is the attributable fraction (AF) which combines the relative risk associated with exposure (RR) with the proportion exposed (Pr(E)). For each cancer/exposure pairing, a “best epidemiological study” is identified for the RR estimate, and depending on the source of the estimate (industry- or population-based studies, meta-analysis or review), either Levin’s equation, which requires an independent estimate of Pr(E), or Miettinen’s equation, which uses an internal (study-based) estimate of the proportion of the cases exposed (Pr(E|D)), is used. Where possible, RRs by specific exposure level are used, but in general exposed numbers are split between high and low exposure levels that match the “best study” exposure scenarios. For Levin’s equation, an estimate of the numbers ever exposed over the relevant exposure period (REP), (which depends on the cancer latency) is required. CAREX data are the main source, or where these are not available, estimates are obtained from national surveys (the Labour Force Survey and Census of Employment). An employee turnover factor is used to estimate numbers ever exposed, and national estimates of the population of working age during the REP are used for the proportion denominator.
Results:
In practice, RRs from meta-analyses and reviews and UK industry-based cohorts have nearly always been used, therefore requiring Levin’s equation for the AF. Estimates by defined exposure level could rarely be used, as matching estimates of numbers exposed were not generally available. Limited data on cancer latency is also a weakness.
Conclusion:
A robust and transparent method of estimating occupation attributable fraction has been developed for Great Britain. Future work …