Occupational cancer in Britain

The agents that the International Agency for Research on Cancer (IARC) has classified as either causing (Group 1 agents) or possibly causing (Group 2A agents) mesothelioma, and lung and laryngeal cancer, and for which estimation has been carried out, are summarised in Table 1 . Up to the end of 2008, there were 32 occupational carcinogens or circumstances for lung cancer classified by IARC as Group 1 and 2A agents. In the present study, burden estimation has been carried out for 21 of these agents/exposures. Welding fumes are classified as a Group 2B carcinogen; however, welders could potentially be exposed to several carcinogens, for which separate estimates have been made, including nickel, chromium, lead, polycyclic aromatic hydrocarbons (PAHs) and asbestos. It is not possible to identify and exclude welders specifically from the industry categories used by CAREX for these exposure estimates, and evidence suggests that other unidentified carcinogenic agents in welding fume may also be contributing to the observed lung cancer risk, or that synergism between the known risk agents may be operating to raise the risk in welders to above that observed in workers exposed to the agents separately (see below). For this reason, a separate estimate for welders as an occupation has been carried out. In addition, tin miners in Cornwall have been included because of exposure to radon. As very few workers have been exposed to mustard gas, no estimation has been carried out for laryngeal or lung cancer. For the same reason, no estimation has been carried out for lung cancer for bis(chloromethyl)ether, haematite mining and α -chlorinated toluenes. Also excluded for lung cancer are: coal tars and pitches, soots, coal gasification, coke production, aluminium production (all included with the estimation for PAHs); hairdressers and barbers (included with environmental tobacco smoke (ETS)); isopropyl alcohol manufacture (included with strong acids and very small numbers exposed), art glass (included with arsenic); non-arsenical insecticides (included with 2,3,7,8-tetrachlorodibenzo-para-dioxin (dioxins)); talc containing asbestiform fibres (included with asbestos); epichlorohydrin (unknown number exposed) and work in the rubber industry (the British study shows no increased risk). A detailed review of occupational risk factor studies identified for these three cancers is provided in the relevant Health and Safety Executive (HSE) technical reports, including those carcinogens for which no estimation has been carried out ( HSE, 2012a , 2012b , 2012c ). All forms of asbestos, serpentine (chrysotile) and amphiboles (crocidolite, amosite, tremolite) are carcinogenic to humans, although the potency of chrysotile might be lower than that of other types ( IARC, 1987 ; IPCS, 1998 ). Numerous studies and reviews have been published on workers exposed to asbestos. In Britain, heavy asbestos exposure in the past occurred in shipbuilding, railway engineering, asbestos product manufacture and construction. Workers with the highest risks today are likely to be those subject to incidental exposures during the course of their work; for example, building maintenance workers. The role of asbestos and laryngeal cancer remains controversial ( Siemiatycki et al, 2004 ). Recent reviews ( Browne and Gee, 2000 ; Griffiths and Molony, 2003 ; Wight et al, 2003 ) concluded that the evidence is weak and that increases in risk may be because of insufficient adjustment for alcohol and tobacco consumption. In a review by Goodman et al (1999) of 69 cohorts, the overall meta-standardised mortality ratio (SMR) for laryngeal cancer, without taking into account latency and confounding factors (tobacco and alcohol), was 1.33 (95% confidence interval (CI)=1.14–1.55), with a very high degree of homogeneity. In addition, a proxy of dosage exposure (using deaths from mesothelioma) showed no exposure–response in laryngeal cancer. A weak association between laryngeal cancer and asbestos was concluded. However, many of the industries included in this meta-analysis are no longer those where exposure to asbestos occurs in Britain. A meta-analysis was therefore carried out by the study group on nine case–control studies (eight population-based and one industry-based study from Europe and the United States) that included adjustments for tobacco and alcohol consumption. The overall meta-standardised incidence ratio (SIR) of 1.38 (95% CI=1.17–1.63) has been used to estimate the attributable fraction (AF) for the high exposure level. The relative risk for low exposure was based on a harmonic mean of the high/low ratios across all other cancer–exposure pairs in the overall project for which data were available. As this was <1, the relative risk (RR) for low exposure has been set to 1. The most comprehensive source of information on mesothelioma in Great Britain is the British Mesothelioma Register, set up in the late 1960s in response to reports associating the disease with asbestos exposure ( McElvenny et al, 2005 ). A recent population-based case–control study of mesothelioma cases in Britain suggests that nearly half of currently occurring deaths in men are attributable to exposures in construction, such as those arising during the installation of asbestos building materials for fire protection purposes ( Rake et al, 2009 ). The authors also concluded that a substantial proportion of cases that were not attributable to identifiable sources of asbestos exposure (14% of male and 62% of female cases) were nevertheless caused by asbestos, and that the source was likely to be an increase in ambient asbestos exposure that coincided with the widespread occupational exposures of the 1960s and 1970s; 16% of female cases overall were attributable to domestic exposures. The AF for mesothelioma was derived directly from this study and several other UK mesothelioma studies. We have included the total proportion due to asbestos exposure (including the proportion of cases unattributed as such), as the distinction between paraoccupational and environmental exposures is somewhat blurred in the case of a carcinogen that has been so widely used as a building product. On this basis, between 96% and 98% of male mesothelioma cases are due to asbestos exposure ( Howel et al, 1997 ; Yates et al, 1997 ; Rake et al, 2009 ). Combining the results from Rake et al (2009) with those from two studies in which results were reported separately for women ( Spirtas et al, 1994 ; Goldberg et al, 2006 ) gave estimates of 75–90% for women. The ratio of asbestos-related lung cancer to mesothelioma deaths has been estimated in a number of studies and is likely to vary depending on particular exposure circumstances ( Albin et al, 1999 ). An analysis based on the overall British population estimated the ratio to be between two-thirds and one ( Darnton et al, 2006 ). In the light of an earlier analysis based on the West of Scotland population that estimated the ratio to be somewhat higher ( Irvine et al, 1993 ), we judged an overall ratio of 1 : 1 to be a and used this than into account the that past of exposure to asbestos are on the incidence by the to mesothelioma deaths that are lung cancer in is because of the in A number of studies increased lung cancer in workers. et al on studies with estimate of and derived a of (95% The review by Goodman et al (1999) a of (95% although there was a between studies. An increased risk of lung and laryngeal cancer has been in workers exposed to strong for example, in a number of including production of and manufacture and production, as as manufacture of and ( IARC, ). et al a population-based case–control study for laryngeal cancer in in which work was from which of exposure to was carried out. The estimates reported were for alcohol and tobacco consumption. A strong association was overall for laryngeal cancer with exposure to ratio An exposure–response was and these have been used for the AF estimation high (95% low (95% In a study of male workers in in the industry ( and ), the for lung cancer for the was (95% and has been used in the AF estimation for lung cancer for the workers. et al an of for lung cancer in a study of and workers exposed to an of has been used for the other studies of the between containing and lung cancer have not for other occupational one review to that the evidence of a was weak ( et al, 1997 ). and fumes may exposure to many including and and and and ( IARC, 1987 ). and cancer in workers in the rubber industry have been in the United two ( et al, ; and 2000 ; et al, ). ( et al, ) up male rubber workers from during a weak mortality from laryngeal cancer on the of observed The of workers work rubber in the mortality from laryngeal cancer was for men for the ( and 2000 ) a lower estimate in an from to 2004 ( et al, ). As the for the reported by et al was for the burden estimation risk exposure as the during which exposure occurred that was relevant to the of cancer in the an of was used for AF estimation for laryngeal cancer. A was not provided for this and therefore we used the in and to As this study a for mortality and cancer incidence for lung cancer, no AF estimation was carried out for this cancer. the UK were included in a meta-analysis by et al that included studies of the rubber industry from many several and A of (95% for to that of et al , and an of (95% for was estimated for laryngeal cancer. for lung cancer were as (95% for mortality and (95% for The with substantial exposure of and and ( IARC, 1987 ; 1997 ). is a substantial of exposure to and lung cancer. The studies have been carried out in the United and workers exposed to in and in a study of workers estimated an of for that has been used in the AF estimation for the For exposures above this the was (95% and this was used for the exposure occurs in mining and and in the manufacture of and the of studies carried out in the United The overall of (95% from a study by et al of male workers from in and has been used for the group be that were two of the of the of the risk estimate for low exposure was based on a harmonic mean of the high/low ratios across all other cancer–exposure pairs in the overall project where data were available. As this was <1, the for low exposure has been set to 1. is used in in that as for as in in and in ( and ; IARC, 1993 ). by The results of studies the of occupational exposure of are and has not been in studies. the results evidence of an increased risk of lung cancer exposure to ( ). et al occupational United two one United one to workers. these the were and the of (95% was estimated by the for the AF estimation for the workers. The review also summarised the exposure–response and et al the to be or for that are exposed to between and of A of 1 has therefore been used for the exposure occurs in production and the production of other and welding ( IARC, ). exposure to in production, production and as as has been with an increased risk of lung cancer. A comprehensive review and meta-analysis by and of of industries an overall of (95% In studies that for the was (95% and has been used for the group in the AF However, has been that the is weak because of the to to the ( 2000 ). et al also concluded that is a weak that the risk of lung cancer mortality with of occupational exposure to 1 was is of the exposure 1 that was with an increased lung cancer to an of which has been used for the exposure to occurs during of in the production of and in the manufacture and maintenance of and the of ( IARC, 2006 ). have been in A case–control study in a industry a increased risk of lung cancer with exposure to and ( et al, 1998 ). The increased with exposure and with of and adjustment for not the increased risk was in a study of the production to those exposed to ( et al, 2000 ). For the AF the of from et al has been used for the For the their overall for lung cancer of (95% was to occurs in the and and mining and construction. risk for lung cancer has not been in all circumstances and may on of the or on factors or of ( IARC, 1997 ). have been a number of reviews of the association between lung cancer and exposure to and these have been summarised in the relevant technical ( HSE, 2012b ). et al estimated a of 1.33 (95% for lung cancer from studies. An of (95% was for lung cancer in a exposure–response analysis ( et al, ). analysis of exposure in a with The for the of exposure and was (95% A meta-analysis by and estimated an overall of (95% for lung cancer, with an of in the of (95% and an of in the of (95% A review by et al estimated a for studies of (95% from case–control studies the was (95% and for mortality ratio studies was (95% for studies where was known and were to those by and . For the AF and overall estimate was for has been used for the the group is to have an of the study of et al . is a of by an The and is the of that to be as the lung have been two reviews the association between exposure and lung cancer risk ( et al, 1998 ; and 1999 ). and (1999) studies risk for and showed evidence of a of (95% has been used for the group in the AF For the we have used a of (95% from a United study ( et al, ). these studies have been published with the an risk and are summarised in the relevant technical studies and reviews have that is a of disease in and ( 1998 , 2004 ). exposure has been in the and and and and et al carried out a comprehensive meta-analysis of case–control and studies estimates of the association between lung cancer and exposure to The risk estimates used for the AF estimation from this study were for exposed to (95% for women and (95% for results are to a analysis of two case–control studies ( et al, 2004 ) and meta-analysis ( ). of the of the risk estimate for low exposure was based on a harmonic mean of the high/low ratios across all other cancer–exposure pairs in the overall project where data were available. As this was <1, the for low exposure has been set to 1. is a of cancer has been with lung cancer. The relative risks for occupational exposure to were from , of relative risk of (see HSE, 2012b for this an estimate of for men and for women exposed to an estimated of was However, several studies have not an increased risk of lung in the British ( et al, ( et al, 2006 industry workers ( et al, 1994 ; et al, 1999 the for Workers ( et al, 1999 and analysis of and studies ( et al, ). all of the information exposure and cancer is derived from studies of and workers and exposure to reviews have been published on this ( et al, 2000 ; et al, 2000 ; and 2000 ). have been an increased risk ( and ; and 2000 ). The most recent industry of and and an of (95% one study with the highest where confounding with was to have occurred gave a of (95% this has been used for the workers in the AF of the of the risk estimate for low exposure was based on a harmonic mean of the high/low ratios across all other cancer–exposure pairs in the overall project where data were available. As this was <1, the for low exposure has been set to 1. are used in a of occupational and and those in which exposure occurs and and The evidence for an increased risk of lung cancer in exposed workers is not for example, studies of have results ( et al, 1998 ; 1998 ), increases have been observed in the of studies of workers in the industry ( 1997 ). the studies of workers in a review by an estimate (95% for lung cancer was by the and has been used for the AF estimation for a across the case–control and population-based studies from review studies of the and industry gave an overall risk for lung cancer of (95% which has been used for industry with high exposure to of the of the risk estimate for low exposure was based on a harmonic mean of the high/low ratios across all other cancer–exposure pairs in the overall project where data were available. As this was <1, the for low exposure has been set to 1. to and occurs in the production and welding of and in and the manufacture of as as in mining and ( IARC, ). and studies of workers in the production and of The most evidence of an increased risk for lung cancer occurred in those with high exposures in the past because In all other including mining and and production and welding exposures were with low risks of lung although studies of these industries an increase in lung cancer, these were to other exposures including and asbestos. In Britain, the most recent by and of the gave an for lung cancer of (95% this has been used for the AF estimation and to the population and the lung cancer risk in to The of (95% was used for all exposed workers from the with low or exposure have been to have no risk of lung cancer to occurs in a number of industries and including the of coke coal production, aluminium occupation as a in and reviews have concluded that an increased risk for lung cancer to exposure is present in many industries and ( et al, 1997 ; et al, 2004 ; et al, ). The risk estimate used in the AF estimation is an of the relative risk estimate for all the from the et al for A exposed is and the is by to the of ( where is the mean example, in for the a mean of (95% et al , of the of in a of from to , with of the , and . For the present study, the above was used to an estimate the of of these exposure The low exposed were to have an of to occupational exposure to occurs in in there are estimated to be numbers of workers exposed in in of occurring high by the on Health of to of ( 1998 ), is estimated that 2000 deaths are attributable to exposure to ( 2000 ). of the 2000 deaths are estimated to from exposure in the The AF to men and women to exposure to was estimated directly from the and lower estimates of these attributable numbers by by the total lung cancer deaths in and above in 2005 gave a for the overall AF of for men and which was used to the of to the overall lung cancer attributable deaths and were between industries in proportion to numbers exposed in the with industry based on attributable may be during the used by and and as a in the of such as Workers in the manufacture of may be exposed to and these studies have been in the relevant ( HSE, 2012b ). et al (2009) have carried out a meta-analysis of a number of studies of from the and estimated a of (95% has been used for the AF estimation for of Workers in may be exposed to low of in the of by and and and and of used for and of A risk estimate from et al for from an analysis of a of workers exposed to and has been used for the AF estimation of workers in and For workers in an overall risk estimate for lung cancer of (95% from an study of workers in has been used ( et al, 2006 ). et al and and identified a number of work in the United where occupational exposure to could The with possibly the highest than in production, included production, coal and workers on The overall risk estimate of (95% from the IARC of workers study ( et al, 1997 ) has been used for these and the industry where exposure may studies from the United and including and have an lung cancer risk in the industry ( ; et al, ; et al, ; et al, 2003 ). However, has been concluded that the increases observed in most studies could be by the high of the industry and exposure to with risks from to has been and in Britain tin miners in are known to be a high risk of exposure to radon. In a study of these miners up from to the for lung cancer shows a with of from for workers to for workers with exposure ( and ). An overall for lung cancer for workers of (95% was estimated for the of the study, based on lung cancer However, lung cancer deaths were between and 1999 in this of which occurred from to risk to the study as by the population lung cancer to estimate the number of lung cancer deaths up to an overall of (95% for lung cancer, which was the used for the burden exposures in the and industry and nickel, and studies have identified from to studies risks from to higher risks were observed in case–control studies ( IARC, , 1987 ). and have been as exposures with an increased risk in and are in ( et al, 1997 ). A UK study of workers an of (95% for lung cancer ( et al, 1994 ). data were not the for other cancers were not is to the results of other studies ( 1997 ; et al, 2000 ; et al, 2003 ) and has been used for the AF are used in such as and are exposed by to and other of and is during ( IARC, ). of an of lung cancer of ( IARC, ), and the evidence that the be by A meta-analysis of studies of workers exposed to a by and was used to the risk The overall for lung cancer was (95% and the for lung cancer from occupational studies was (95% although the confounding of and alcohol could not be estimate has been used for the AF to lung cancer and as a Workers exposed to non-arsenical insecticides in manufacture and in also potentially be exposed to and therefore the burden estimate for non-arsenical insecticides has been included in the estimate for However, are also potentially exposed to non-arsenical A review of the on cancer incidence and mortality and that the for lung cancer from to with an of (95% ( 2005 ). However, an of 1 in an AF of and therefore an estimate was not for are exposed to a of fumes and containing a of and of and other An meta-analysis and welders observed an increased lung cancer risk all types of workers ( 1997 ). et al this study and an overall for of (95% this has been used for the AF The data industry and for estimation of numbers exposed the are in Table 1 . was as high for the carcinogens and industry manufacture of and and in industries and construction. all industry and and manufacture of and and as as in the and manufacture of and and manufacture of other and and and in and and and and manufacture of other and and in industries and construction. manufacture of other coal and other and as as in and and and construction. construction, and to and and all and and and and and and manufacture of and and in and and as as in construction. manufacture of and and in and and manufacture of and other and and in and and all known to exposure to and and workers. the operating in the United by and were used to identify the relevant occupational three sources of data were used to numbers exposed in numbers exposed from the of in industries ( HSE, 1998 the for and male and information from the British and for female the number of tin miners was from the study of and . of cancer latency and cancers in and above in could be attributable to A latency of and up to has been for all Table 1 the carcinogens and occupational circumstances for which separate estimates were carried out. Table the numbers and of those exposed the separately for women and The attributable numbers of deaths and attributable numbers of are in Table for women and The AF for all exposures for laryngeal cancer was (95% which to (95% attributable deaths and (95% attributable The estimated total and AF for all exposures for lung cancer was (95% which to (95% attributable deaths and (95% attributable The estimated total and for mesothelioma to occupational exposure was (95% which to (95% attributable deaths and (95% attributable 1 the attributable for lung cancer for the 21 carcinogens for which estimation was carried out for men and women. exposure by the number of lung cancer and was for all the mesothelioma ( Table ). A total of men and women were estimated to have been exposed to asbestos in the ( Table ). The of cases occurred in workers in the however, the studies of asbestos were in other such as asbestos manufacture and of attributable lung cancer in 2004 for men and women by carcinogen or occupational 1 and Table that and were also for numbers of cancer and A total of men and women were estimated to have been exposed to during the ( Table ). In of cases were in the in women cases occurred in the manufacture of other and and exposure occurred men and women the For the of cases occurred in to and for women cases occurred in A number of men and women were estimated to have been exposed to the as exposure was estimated to have occurred men and women the The numbers occurred for and other workers with also high for aluminium manufacture of and manufacture of and exposure occurred women than men the The of these occurred in and and and An estimated men and women were exposed to occurring their during their in of the with known high of A total of men and women were estimated to have been exposed to in the industries were the industries in which most cases occupational work as a and work as a were by IARC without to particular exposures these also cancer ( Table , 1 ). An estimated men and women were as a the the of men as and and women in and