Cancer

Introduction

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.

Attributable proportions and numbers of work-related cancers

Work is underway to produce up-to-date estimates of the current burden of occupational cancer in Great Britain due to past exposures to carcinogens, and estimates of the future burden due to more recent and current exposures. HSE previously estimated the current burden of occupational cancer in Great Britain from the estimate put forward by Doll and Peto in 1981¹ that 4% of cancer in the US was attributable occupational causes.

Initial findings from the first phase of this work, which includes estimates for six cancer sites, have now been published². Full estimates of the current burden of occupational cancer from a consideration of all 24 cancer sites for which the International Agency for Research on Cancer (IARC) has classified as definite or probable human carcinogens are due to be published during late 2009 and early 2010. Some refinements to the methodology have been made since the publication of the results for the first six cancers. The full results will therefore incorporate updated estimates for these cancer sites.

Emerging findings from the full consideration of all 24 cancer sites suggest that the overall burden of occupation cancer in Great Britain is currently around 8000 deaths and 14,000 cancer registrations per year.

Occupational cases of cancer for the first six cancer sites considered make up a substantial proportion of the total occupational burden. The initial results for these cancer sites 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 a more detailed results, a full description of the research methodology is set in the research reports. The proceedings of two methodological workshops associated with this project are also available: November 2004 workshop³ and June 2006 workshop⁴.

Other statistical information on work-related cancers

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:

• Leukaemia (other than chronic lymphatic leukaemia) or cancer of the bone, female breast, testis or thyroid due to exposure to electromagnetic radiation or ionising particles (disease number A1)
• Acute non-lymphatic leukaemia due to exposure to benzene (C7).
• Skin cancer due to exposure to arsenic, arsenic compounds, tar, pitch, bitumen, mineral oil (including paraffin) or soot (C21).
• Sinonasal cancer due to exposure to nickel compounds (C22a) or due to exposure to wood, leather and fibre board dust (D6).
• Lung cancer due to exposure to nickel compounds (C22b) or due to work as a tin miner, exposure to bis(chloromethyl) ether, or to zinc, calcium or strontium chromates (D10) or due to silica exposure (D11).
• Bladder cancer due to exposure various compounds during chemical manufacturing or processing, including 1-naphthylamine, 2-naphthylamine, benzidine, auramine, magenta, 4-aminobiphenyl, MbOCA, orthotoluidine, 4-chloro-2-methylaniline, and coal tar pitch volatiles produced in aluminium smelting (C23).
• Angiosarcoma of the Liver due to exposure to vinyl chloride monomer (C24).
• Mesothelioma (D3).
• Asbestos related lung cancer (lung cancer with asbestosis (D8) or lung cancer and evidence of at least 5-years asbestos exposure before 1975 in certain jobs (D8A))

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 fewer 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 115 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 550 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.

References

1. Doll R, Peto R. The causes of cancer: quantitative estimates of avoidable risks of cancer in the United States today. Oxford University Press 1981 ISBN 0 19 261359 6.
2. Rushton L, Hutchings S, Brown T. The burden of occupational cancer in Great Britain: Results for bladder cancer, leukaemia, cancer of the lung,mesothelioma, non-melanoma skin cancer and sinonasal cancer. RR595, HSE Books 2007.
3. Evans G, McElvenny D. Burden of occupational cancer in Great Britain. Summary of workshop held on 22 and 23 November 2004 in Manchester. Coggon D, Kriebel D, editors. HSL/2005/54 Health and Safety Laboratory 2005.
4. McElvenny D, Wegerdt J, Rushton L. Burden of occupational cancer in Great Britain. Summary reportof cancer epidemiology workshop held on 27 and 28 June 2006, Shrigley Hall, Macclesfield. Evans G, editor. HEX/07/01 Health and Safety Laboratory 2007.