Health and Safety
Executive / Commission
Statistics
Cancer is caused by a complex interplay of factors and as such it is difficult to assess the role of occupational exposures in its causation. Furthermore, many solid tumours present themselves many years (usually at least 10 but in some cases over 25 years) after the relevant exposures took place, making the association of disease with such exposures particularly difficult to establish. This means that national records of cancer registrations or deaths, or data sources such as the THOR network or Industrial Injuries Disablement Benefit (IIDB) scheme, do not allow an accurate assessment of the overall number of work-related cancers to be made.
However, it is possible to estimate the number, or proportion, of cases of cancer that would not have occurred in the absence of workplace causes (the attributable number or attributable proportion - sometimes referred to as the attributable fraction). Doing so requires there to be available information about the risk of cancer from workplace hazards relative to the general risk, information on the numbers exposed to those risks and information on the total numbers of cases of cancers of interest.
HSE has previously estimated the number of cancers attributable to occupational causes in Great Britain by applying estimates of the attributable proportion, as put forward by Doll and Peto in 1981 1, to British death and cancer registration data. Doll and Peto considered cancer on a site-by-site basis and estimated the possible contribution of occupation to cancer mortality for each. This led them to estimate that 4% of cancer overall was attributable to occupational causes, with about two-fold uncertainty.
There are a number of problems in using Doll and Peto’s estimates – including the fact that they were based on the US, and that being made in 1981 they now severely underestimate the number of asbestos related cancers, which has increased dramatically since then (More information). Work is therefore in hand to produce estimates of the current occupational cancer burden in Britain to take account of more recent research and historical exposures to workplace carcinogens in Britain. Initial findings from the first phase of this work, which includes estimates for six cancer sites, have now been published 2. The proceedings of two methodological workshops associated with this project are also available: November 2004 workshop [PDF 238KB]
3 and June 2006 workshop [PDF 5.08MB] 4
Since only six cancer sites have so far been considered, the new research does not yet provide an updated estimate for the overall proportion of cancers attributable to occupational causes in Britain. However, occupational cases of these six cancer sites are likely to make up a substantial proportion of the total occupational burden. The initial results are reproduced in Table CAN01. The estimates vary according to whether they include estimated numbers of cancers due to only “established” carcinogens, or whether estimates for “uncertain” carcinogens are also included. If the latter are included, then the number of deaths in total from these six kinds of cancer which are attributable to occupational causes is estimated to be around 7,300 in 2004 (of which 14% were among women). This is equivalent to 4.9% of all cancer deaths – slightly higher than the 4% estimated by Doll and Peto for all cancer sites. The number of cancer registrations in total from these six kinds of cancer which are attributable to occupational causes is estimated to be around 13,300 in 2003 (15% among women).
Asbestos related cancers (all of the mesotheliomas and about 40% of the lung cancer deaths shown in Table CAN01) make up a substantial proportion of the occupational cancer deaths. Of the non-asbestos related cancers, other lung cancers caused by silica, diesel engine exhaust or work as a painter, and bladder cancers caused by mineral oils make substantial contributions. Non-melanoma skin cancers also make an important contribution to occupational cancer registrations.
As well as the more detailed results, a full description of the research methodology is set in the research reports. Since the publication of the initial results, some refinements to the methodology have been made following a further workshop in June 2008, and updated estimates (and methodology) will be published in autumn 2008. Estimates for cancer sites so far not considered, as well as for the overall current occupational cancer burden and the future burden due to current exposures to carcinogens, will be published in autumn 2009.
The specific forms of occupational cancer which are currently compensable under the Department for Work and Pensions Industrial Injuries and Disablement Benefit (IIDB) scheme are listed below:
The total number of people of compensated for non-asbestos related cancers (that is, excluding mesothelioma and asbestos-related lung cancer) has typically been around 50 per year or less during the last ten years (Tables IIDB01, IIDB03, IIDB05), and thus constitutes only a small proportion of the total number of occupational cancers occurring. Of the asbestos related cancers, many mesothelioma cases are now compensated, but only a minority of asbestos related lung cancers are compensated despite recent changes to the eligibility criteria. (Table IIDB05)
Reports from the SWORD/OPRA surveillance scheme provide data on the number of cases of occupational Lung Cancer reported to chest physicians and occupational physicians, as shown in Table THORR01. The estimated number of the lung cancers has fluctuated somewhat erratically since 1998 with an average of about 120 cases per year. Table THORS01 shows the number of cases of occupational skin cancer reported to occupational physicians and dermatologists in the EPIDERM/OPRA scheme. The estimated number of skin cancers has also varied considerably, but with generally higher numbers of estimated annual cases in recent years (an average of about 600 estimated cases were reported each year over the last four years). However, statistical modelling of the EPIDERM/OPRA data by the University of Manchester to allow for various factors that affect reporting levels (including the number and type of participating specialist and occupational physicians, their reporting habits, and seasonal effects associated with the time of year they report) in fact suggests an overall downward trend in incidence.