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Research Article

Intervening to Reduce the Future Burden of OccupationalCancer in Britain: What Could Work?

Sally Hutchings1, John W. Cherrie2, Martie Van Tongeren2, and Lesley Rushton1

AbstractIn Britain, 14 carcinogenic agents and occupational circumstances currently account for 86%of estimated

occupation attributable cancer. The future burden associatedwith these carcinogens has been forecast, using

attributable fractions for forecast scenarios representing patterns of past and predicted future exposure, and

exposure levels representing the introduction of new occupational exposure limits, increased levels of

compliance with these limits and other reductions in worker exposure. Without intervention, occupational

attributable cancers are forecast to remain at more than 10,000 by 2060. With modest intervention over

2,600, or with stricter interventionsmore than 8,200 cancers could be avoided by 2060 although because of

long latency no impact will be seen until at least 10 years after intervention. Effective interventions assessed

in this study include reducing workplace exposure limits and improving compliance with these limits.

Cancers associated with asbestos, diesel engine exhaust, polycyclic aromatic hydrocarbons, work as a

painter, radon, and solar radiation are forecast to continue, with construction remaining the prime industry

of concern. Although exposure levels to the established carcinogens are falling, workers are remaining

exposed at low levels at which there is still a cancer risk, although the aging population also contributes to

rising cancer numbers, These forecasts can be used to assess the relative costs to society of different

occupational carcinogenic agents, and the relative merits and savings associated with alternative interven-

tion strategies. The methods are adaptable for different data circumstances, other types of interventions

and could be extended to environmental carcinogens and other chronic diseases. Cancer Prev Res; 5(10);

1213–22. �2012 AACR.

IntroductionWehave estimated that 8%of cancers inmen and 2.3% in

women are caused by work, giving more than 8,000 deathsand 13,600 cancer registrations in Great Britain (1) for alloccupational carcinogens and occupational circumstancesclassified by the International Agency for Research onCancer (IARC) as Group I (established) or IIA (probable)carcinogens that had either "strong" or "suggestive" evi-dence of carcinogenicity in humans (2).The methodology has been extended to estimate the

future burden of occupational cancer and to forecast theimpact of alternative policy decisions affecting future work-place exposure levels (3). This article presents estimates ofthe future burden of occupational cancer under a series of

scenarios of change for 14 occupational carcinogens andcircumstances in Great Britain that each contribute at least100 occupation attributable registrations to current burdenand account for 86.3% of the total burden (Table 1).

Materials and MethodsA full description of the methodology for estimating the

current (4) and future burden (3) of occupational cancercan be found elsewhere. For our current burden estimation,Levin’s formula was used to estimate the attributable frac-tion (AF), that is, the proportion of cases caused by occu-pational exposure [(5, AF¼ p(E)� (RR-1)/{1þ p(E)� (RR-1)} in its simplest form]. This requires an estimate of the riskof disease, generally as relative risk (RR) which we obtainedfrom published literature, and the proportion of the pop-ulation exposed [p(E)], which we derived from nationaldata sources, accounting for employment turnover and lifeexpectancy, and adjusted for employment trends. Toaccount for cancer latency a risk exposure period (REP)was defined for each carcinogen as the exposure periodrelevant to a cancer appearing in a specific target year(10–50 years for solid tumors, 0–20 years for lymphohae-matopoetic tumors). As exposure-response risk estimatesand proportions exposed at different levels are not generallyavailable, risk estimates and proportions exposed wereobtained wherever possible for "high," "medium," and

Authors' Affiliations: 1Department of Epidemiology and Biostatistics,Imperial College London, London; and 2Institute of OccupationalMedicine,Edinburgh, United Kingdom

Note:Supplementary data for this article are available atCancer PreventionResearch Online (http://cancerprevres.aacrjournals.org/).

Corresponding Author: Sally Hutchings, Imperial College London,Department of Epidemiology and Biostatistics, Faculty of Medicine, StMary's Campus, Norfolk Place, London W23PG, UK. Phone: 44-160-089-0340; Fax: 44-207-594-3196; E-mail: [email protected]

doi: 10.1158/1940-6207.CAPR-12-0070

�2012 American Association for Cancer Research.

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"low" exposure levels with a "background" level, whereappropriate, assumed to have 0 excess risk [these categorieshave been expanded from "high" and "low" only whichwere used to estimate current burden (1)]. Estimated AFswere applied to total British deaths (for 2005) and registra-tions (for 2004) to give attributable cancer numbers.

To estimate future burden AFs were estimated for a seriesof forecast target years (FTY), that is, 2010, 2020, . . ., 2060(3). A REP projected forward in time was defined for eachFTY with the contribution of past exposure to future cancerrisk decreasing for each FTY (see Supplementary Fig. S1).Adjustment factors were applied to newly recruited workers(assumed to be aged 15–24 years) in separate 10-yearestimation intervals to adjust for changing numbers usedin broad industry sectors, for example, an increase in theservice industry sector and a decrease in manufacturingindustry [based on Labour Force Survey data (6), Supple-mentary Fig. S2].Where data were available adjustment wasalsomade for declining exposure levels [see SupplementaryTable S2 for estimated data on exposure levels and futureannual declines in levels required for these adjustments to

be made, plus Workplace Exposure Limits and currentcompliance levels to these limits. Full details of the methodof adjustment can be found elsewhere (3)]. Where suitableexposure data were not available, RRs could be adjusted torepresent reduced risk scenarios, for example, excess riskwas reduced successively by 25% per decade for painters, orworkers could be shifted arbitrarily from higher to lowerrisk categories, for example, shift workers at risk of breastcancer were moved from longer to shorter duration ofexposure.

For the current burden estimate for mesotheliomauniquely associated with asbestos exposure we used num-bers directly from the UK register of mesotheliomas for2005, aswebelieve this captures practically all cases inGreatBritain and is, therefore, more appropriate for use as a basisfor burden estimation for this disease than our standardmethods, which greatly underestimate current mesothelio-ma incidence. Asbestos related lung cancer was also esti-mated for current burden frommesothelioma register num-bers using an assumption of a 1:1 ratio (1). We excludedonly a small number (30–70 men and women a year in the

Table 1. Agents for which future burden has been estimateda

Exposure

Total current burdenattributable registrations(% of total attributableregistrations) Cancer sites WEL/OEL

Our estimatedcurrentcompliance(%)

Exposure defined by agent; no appropriate exposure measurements available to use in standard settingETS 284 (2.1) Lung —

PAH as coal tars andpitches (men only)

475 (3.5) NMSC —

Radon 209 (1.5) Lung —

Solar radiation 1,541 (11.3) NMSC —

Occupational circumstancePainters 437 (3.2) Bladder, lung, stomach —

Shift work (women only) 1,957 (14.4) Breast —

Welders 175 (1.3) Lung —

Carcinogenic agents for which exposure standards can be setArsenic 129 (0.9) Lung WEL ¼ 0.1 mg/m3 99.6Asbestos 4,216 (31.0) Larynx, lung,

mesothelioma, stomachControl limit ¼ 0.1 fibers/mL 91.3

DEE 801 (5.9) Bladder, lung None. Austrian OEL ¼0.1 mg/m3

99.2

RCS 907 (6.7) Lung WEL ¼ 0.1 mg/m3 33.0Strong inorganicacid mists

122 (0.9) Larynx, lung No current WEL(was 0.3 mg/m3)b

96.3

TCDD (dioxins) 316 (2.3) Lung, NHL, STS —

Tetrachloroethylene 164 (1.2) Cervix, NHL, esophagus WEL ¼ 345 mg/m3,SCOEL ¼ 138 mg/m3c

100

Total 11,732 (86.3)

aMineral oils which account for a further 12.7% of attributable cancer registrations have been excluded as, because of the changes inthe constituents ofmineral oils that have occurred in the last few years, it was thought that the future cancer burdenwould already havebeen greatly reduced (9).bThisWELwascurrent in 2007 (10), but is currently under review (11). The estimatedcompliance indicated is to theWELcurrent in 2007.cProposed new standard being considered by Scientific Committee on Occupational Exposure Limits (SCOEL).

Hutchings et al.

Cancer Prev Res; 5(10) October 2012 Cancer Prevention Research1214




UK) of background cases (spontaneous or from naturallyoccurring asbestos) from the register numbers. For futureburden, we have allocated the current attributable meso-theliomas to 3 exposure levels, high and medium foroccupational exposure and a low category for domesticexposure and environmental exposure believed to havebeen experienced by the post 1940s birth cohort andadditional to the background rate (see footnotes to Sup-plementary Table S1 for the details of the methodology).Total AFs for cancer sites associated with multiple expo-

sures have been estimated using the product equation[AFSi ¼ 1 � Pi(1�AFi)] for independent multiplicativeestimates (7). To estimate attributable cancer numbers theforecast AFs were applied to an estimate of total cancers forthat site based on current age-specific rates applied to GreatBritain population projections (Supplementary Table S3).For mesothelioma however associated only with asbestosexposure recent projections based on past mortality rateswere used (8).

Carcinogens and occupational circumstances includedin the estimatesTable 1 gives the carcinogens and occupational circum-

stances from the current burden estimation forwhich futurecancer burden was estimated, and the cancer sites thatwere affected. The carcinogens have been categorized as:(i) those for which no appropriate exposure measurementswere available to use in standard setting; (ii) exposuresdefined by occupational circumstance; and (iii) carcino-genic agents for which standards exist or can be set.

Choosing scenariosSupplementary Table S4 gives the scenarios tested for

each carcinogen and occupational circumstance. Unlessotherwise stated 2 baseline scenarios have been evaluated:baseline scenario 1 historic employment and exposure leveltrends until 2010, no change thereafter, and baseline trendscenario 2historic andpredicted employment and exposuretrends included up to 2030, constant thereafter. Interven-tion scenarios have been compared with baseline 1.For those agents where standards can be set the scenarios

test the introduction of or reductions in current occupa-tional exposure limits (OEL) and improved compliance tothese standards. For arsenic and tetrachloroethylene theexisting workplace exposure limits (WEL), and for stronginorganic acidmists an earlierWEL, weremuch greater thanestimated current average exposure levels (SupplementaryTable S2). For these and also for TCDD, the estimatedboundary level between the 2 lowest exposure categorieswas used as a starting point for a possible exposure standard(Supplementary Table S1). For TCDD the low/backgroundboundary was used, representing a threshold below whichexcess risk for the agent was 0 (background exposed). Nosuch threshold is generally recognized for genotoxic carci-nogens, so the high/low- or medium/low-boundary levelwas chosen for the other 3 substances.For asbestos and diesel engine exhaust (DEE), no indus-

tries were categorized as background exposed with zero

excess risk, so an estimate of the threshold level for back-ground exposure was obtained from independent data. ForDEE, 0.001 mg/m3 as elemental carbon was chosen toreflect exposure levels in daily life, based on backgroundurban and suburban exposure measurements in Britain(12). For asbestos an upper boundary of 0.00001 f/mL wasassumed for background exposure, based on urban expo-sure levels fromwhichmesothelioma cases considered to becaused by "background" exposure may arise (13).

For occupational circumstances such as painters andwelders, where no specified carcinogen has been identified,only a single RR was available. A decline in exposure levelhas therefore been assumed to translate linearly to a fall inexcess risk. This approach was also adopted for dermalexposure to polycyclic aromatic hydrocarbon (PAH) in coaltars and pitches for which no exposure level RRs wereavailable. For shift work, limits on the total time spent onnight shifts over a lifetime were used as the intervention.

Where levels of exposure were not amenable to WELsetting, proportions of the exposed workers were movedto lower exposure categories (e.g., solar radiation) or areduction in total numbers exposed (e.g., radon) was usedin the forecasting. For environmental tobacco smoke (ETS),the effects of different levels of compliance to the currentindoor smoking bans were tested.

ResultsTable 2 gives for all the carcinogens and occupational

circumstances tested the attributable numbers of cancerregistrations for 2010 and 2060 together with the numbersof cancer registrations avoided in 2060 for each of thescenarios in Supplementary Table S4. Attributable cancerregistrations are shown per year for each target year. Sup-plementary Table S5 also gives AFs and combined results bycancer site across the 14 carcinogens or occupational cir-cumstances. Full results can be found elsewhere (14).

As historic and forecast exposure levels decline, the AFsgenerally decline for baseline scenarios 1 and 2 to about1.5% of all cancer by 2060 (Table 2, and for example Figs.1A(i) and A(ii) for DEE and lung cancer). However, forbreast cancer associated with shift work, rising employmentin service sector industries (Supplementary Fig. S2) leads torising occupational AFs [Fig. 1B(i)].

Predictions of total Great Britain cancers taking accountof only demographic changes leads to increasing attribut-able occupational cancer numbers because of the aging andincreasing population [Figs. 1A(ii) and B(ii)]. Between9,900 (scenario 2) and 10,500 (scenario 1) occupationalcancers can be expected per year by 2060 from the baselinescenarios, not much lower than the numbers attributed tooccupation in 2010. Breast cancer and nonmelanoma skincancer (NMSC) from sun exposure account for 60%–70%of these (Table 2).

Without new intervention strategies, the numbers ofcancers from low-level exposure will continue to increaseeven though exposure levels are forecast to decline (scenario2). Figs. 2A and B illustrate this for lung cancer and DEE,

Forecasts of the Future Burden of Occupational Cancer

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where, although exposure levels are falling by an estimat-ed 7.4% a year, substantial proportions of the populationremain exposed at low levels of exposure which still carrya small excess risk (RR ¼ 1.1). Introducing an exposurestandard of 0.1 mg/m3 and assuming even 99% compli-ance does not improve on this (Figs. 2C and D, scenario6a in Supplementary Table S4). In contrast if an exposurestandard could be introduced for DEE at the estimatedlevel below which excess risk was 0, that is, 0.001 mg/m3

as elemental carbon [scenario 6, Figs. 2E and F], lungcancers induced by DEE would nearly disappear by 2060[Fig. 1A(ii)]. For this level of reduction, however, tech-nology driven intervention may be the only realisticsolution.

Low-level exposures will also continue to give high fore-cast numbers of asbestos related mesotheliomas for bothbaseline scenarios (63 in men and 208 in women forbaseline trend 2) because of the increasing proportionexposed at low levels, even though a 13% annual reductionin average exposure levels has been assumed, and themesothelioma projections used to estimate our forecastnumbers have also taken falling exposure levels intoaccount (8). However, this is not the case for lung and the

other asbestos-related cancers as, in the absence of a suitablerisk estimate, zero excess risk has been assumed other thanfor mesothelioma at this low (nonoccupational) level.[Supplementary Figs. S3A–F and G–L show results for lungcancer and mesothelioma]. Even if exposures could bereduced to the levels indicated by the strictest scenario(6) tested, that is, to below 1/100th of the existing standard,some mesotheliomas remain in 2060 (61 men and 182women), because of continued exposure at the level ofadditional background risk estimated for the 1940s birthcohort, above the low threshold at which it is believedexcess risk will be zero (13). However, these forecasts donot take account of any change to the background riskamong later birth cohorts. Our forecast mesotheliomaestimates for women are higher than for men because ofthe higher RRs for medium and low exposure used in theircalculation (Supplementary Table S1); they are given sep-arately as we have less confidence in the results for womenbecause of the small number of cases on which the riskestimates were based.

For solid tumor cancers for which long latencies areassumed, no difference is seen between any of the inter-ventions and the baseline scenarios before 2030. The

Table 2. Total forecast cancers attributable to leading occupational carcinogens, 2060

Attributable numbers of cancer registrations

Attributable numbers ofcancer registrationsavoided a by 2060

Scenariob: All (1) (2) (3) (4) (5) (6) (3) (4) (5) (6)

Exposure Cancer site 2010 2060 2060

Exposure defined by agent; no appropriate exposure measurements available to use in standard settingETS Lung 1,470 0 0 68 158 �68 �158PAHs—coal tars NMSC 489 805 883 606 479 437 405 200 327 368 401Radon Lung 218 379 411 341 318 310 190 38 61 69 189Solar radiation NMSC 1,751 3,096 3,307 2,574 2,048 1517 165 522 1,048 1,580 2,931Occupational circumstancePainters Bladder, lung, stomach 455 639 645 480 380 347 321 159 259 292 318Shift work Breast 1,660 3,111 3,904 2,169 1,198 197 0 942 1,913 2,914 3,111Welders Lung 190 141 64 106 84 77 71 35 57 64 71Carcinogenic agents for which exposure standards can be setArsenic Lung 128 93 47 91 89 88 88 1 4 5 5Asbestos Larynx, lung, mesothelioma,

stomach3,841 268 271 264 264 262 243 4 4 6 24

DEEc Bladder, lung 380 409 402 454 415 377 35 (410) 0 0 32 374 (0)Silica Lung 837 799 446 102 50 22 10 697 750 778 789Strong acids Larynx, lung 122 39 7 18 12 10 10 21 27 29 29TCDD Lung, NHL, STS 283 8 0 4 4 4 4 4 4 4 4Tetrachloroethylene Cervix, NHL, oesophagus 139 136 120 124 120 118 118 12 16 18 18Total 11,663 10,472 9,880 7,379 5,601 3,755 1,657 2,616 4,446 6,125 8,223

aRelative to baseline scenario (1). Except for ETS, negative results, where the intervention has increased forecast cancer numbers [e.g.for DEE scenario (3) 90%compliance is lower than the current estimated compliance to the proposed standard], have been set to zero.All negative results are excluded from the total estimates.bScenarios are as described in Supplementary Table S4.cResults in brackets for DEE are for the additional intervention scenario 6a.

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Figure 1. Results for baseline andintervention scenarios for (A) lungcancer attributable to DEE exposure(men plus women) and (B) breastcancer attributable to night shiftwork (women only), in terms of (i)attributable fractions and (ii) cancerregistrations.






intervention scenarios were developed to be progressivelymore effective leading to progressive reductions in AFs andattributable cancers. Together the minimum interventionsproposed in scenario 3 (the first and least restrictive sce-nario) would avoid over 2,600 cancers a year by 2060,although only about 38 of these are for the chemicals(arsenic, acid mists, TCDD, and tetrachloroethylene). Thecurrent (0.1 f/mL) standard for asbestos or a proposed (0.1mg/m3) standard for DEE do not result in any "avoided"cancers by 2060 (current compliance to these standards,shown in Table 1, exceeds 90%). For respirable crystallinesilica (RCS) an improvement in compliance to the 0.1 mg/m3 8 hour time weighted average OEL from 33% to 90%could lead to nearly 700 fewer lung cancers annually by2060 (Table 2). The number of cancers avoided increases

as standards are tightened or exposure is progressivelyreduced (scenarios 4 and 5, Table 2).

The scenarios with the most extreme intervention (sce-nario 5 for most of the chemical agents; scenario 6 forasbestos and DEE, shift work and solar radiation, and forradon, painters, welders, and coal tars and pitches) showhow close to zero the attributable cancer numbers mightrealistically be expected to fall (Table 2). Numbers fall to 0only if an intervention results in all workers moving toexposure categories with zero excess risk, for example,achieving full compliance to no smoking in workplaces.Comparing the results for scenario 5, where excess risk hasbeen reduced by 25% in successive decades for painters,welders, and coal tars and pitches, and (6) where a halvingof risk is achieved in the first decade, indicates the

Figure 2. Proportions exposed toDEE and occupation attributableregistrations for lung cancerassuming (A and B) linearemployment trends and 7.4%annual exposure level decline to2021–30, (C and D) introducing anexposure standard of 0.1 mg/m3

from 2010 with 99% compliance,and (E and F) introducing a muchstricter exposure standard of 0.001mg/m3 from 2010 with 90%compliance, by achieved exposurelevel in the forecast target year,men and women together.

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importance of early versus delayed intervention. Halvingthe proportions exposed in workplaces to radon in 2010(scenario 6), for example by introducing appropriate tech-nology, is far more effective than the gradual reductionshown in the other interventions. Similarly, achieving areduction in risk from solar radiation to that associatedwithmixed indoor and outdoor exposure (RR ¼ 1.01, Supple-mentary Table S1), for example, using appropriate skinprotection measures, removes most of the large numbersof predicted NMSCs. Restricting women to amaximumof 5years on night shift work, for which the epidemiologicalevidence suggests excess risk is 0, would eliminate breastcancers attributable to this exposure [Fig. 1B(ii)].Our testing scenarios assume that compliance to expo-

sure standards is less than 100%. Our results indicate that alarge reduction in number of cancers can be achieved with90% compliance to a current or proposed standard (sce-nario 3), and that 99% compliance (arsenic, RCS, strongacids, TCDD, tetrachloroethylene, scenario 6, and DEE

scenario 6a) only avoids an additional 109 cancers by2060 (including 92 lung cancers from RCS exposure).

Forecasts for industry sectors with a current estimate(2004; ref. 15) of more than 80 attributable cancers aregiven in Table 3 and Supplementary Table S6. The rankingof the predicted cancers by industry sector in 2060 (scenario2) remains similar to that in 2010 with constructionremaining the most important industry sector for potentialrisk reduction targeting (21% in 2060), followed by 3service industry sectors, and with breast cancer associatedwith night-shift work across all industry sectors also aleading contributor. By 2060, large numbers of workers arestill projected to be exposed at low levels to the relevantcarcinogens (DEE and asbestos, plus tetrachloroethylene indry cleaners) in personal and household services and landtransport. In land transport more than two-thirds, and indefense (armed forces) nearly all attributable cancers areforecast to be NMSCs because of high level (outdoor) sunexposure (Supplementary Table S6).

Table 3. Forecast cancersa attributable to leading occupational carcinogens, by industry currentlyestimated with over 80 attributable registrations, ordered by baseline scenario (2) forecasts for 2060

Attributable numbers of cancer registrations

Scenariob: All (1) (2) (3) (4) (5) (6)

Industry/occupation 2010 2060

Construction 4,680 2,450 2,200 1,550 1,260 940 130Painters and decorators (construction) 340 560 610 420 330 300 280Roofers, road surfacers, Roadmen, Paviors (Construction) 480 800 880 600 480 430 400Shift work (across all industries/occupations)c 1,650 3,090 3,880 2,160 1,190 200 0Land transport 420 560 660 520 440 370 30Public administration and defence 340 580 660 490 400 300 30Personal and household services 400 230 240 230 230 200 140Sanitary and similar services 90 160 200 140 110 90 10Recreational and cultural servicesd 100 130 160 110 100 70 10Wholesale and retail trade and restaurants and hotels 660 130 150 150 180 110 70Farming 320 170 120 120 70 10 10Financing, insurance, real estate and business servicesd 190 70 80 60 60 60 40Welders 190 140 60 110 80 80 70Painters (not construction) 110 80 30 60 50 50 40Mining 130 40 20 40 30 20 10Non-ferrous metal basic industries 80 40 10 30 30 30 30Manufacture of transport equipment 190 20 0 10 10 10 10Manufacture of industrial chemicals 100 10 0 10 10 10 0Manufacture of other chemical products 100 10 0 10 0 0 0

aTotals may differ from main tables as agents are summed (product sums) separately by industry and other subgroups.bScenarios are as described in Supplementary Table S4.cShift workers may be employed in all industries/occupations, but the cancer site involved (breast) does not overlap with cancer sites.associated with other carcinogenic agents or occupations to which these workers may also have been exposed.dThese industry sectors had less than 80 attributable registrations in the current burden estimates (2004), but are included as at least 80are forecast for 2010. Iron andsteel basic industries,manufactureof instruments, photographic andoptical goodsandof non- electricalmachinery, metal workers and printing, publishing and allied industries had at least 80 current burden attributable registrations, but areexcluded as these were predominantly due to exposure to mineral oils.






DiscussionOur results have shown the potential for considerable

eventual reduction in future occupationally related cancersthrough a range of interventions, although the long legacyof past exposures will continue for up to 50 years. Evenwiththe most stringent scenario tested, cancers are forecast tocontinue because of exposure to asbestos, PAHs as coal tarsand pitches, work as a painter, and exposure to radon andsolar radiation, with construction remaining the primeindustry of concern. Expected increases in cancer in generalas the population ages contribute to the continuing highlevels of someoccupational cancers, andpredicted increasesin numbers working particularly in service sector industriesalso makes a contribution, for example to forecasts for shiftwork breast cancers, exposure to solar radiation, DEE andasbestos. In estimating the future burden of occupationalcancer, wehave included the top 14 carcinogenic agents andoccupational circumstances, which account for 86% of theestimated current burden of occupational cancer in Britain.Forecasts for agents currently contributing a further 1,800cancer registrations, including mineral oils, chromium VI,cobalt, aromatic amines and inorganic lead, nonarsenicalinsecticides, work as a hairdresser or barber, soots andwooddust exposure, and other agents currently responsible forfewer cancers in Great Britain but classified by IARC asGroup I carcinogens [including benzene, benzo(a)pyrene(PAH), beryllium, cadmium, formaldehyde, occupationalexposure during iron and steel founding, leather dust,nickel compounds, and rubber manufacturing] have notbeen included in the projection, but are equally importantfor cancer prevention. If these had been included, 14%more occupational attributable cancers (an additional1,600 a year) might be forecast (proportionately) by2060without intervention, with about 500of these avoidedwith some minimum intervention as described for theestimated agents.

The contribution to the future total burden of largenumbers of workers exposed at low levels within severalservice industries is highlighted, rather than the currentmore highly exposedmanufacturing industry sectors, whereinterventions appear to be more effective in transferringworkers from high to low exposed groups. For asbestos andDEE in particular, although exposure levels have beendeclining cancers still occur because of the low thresholdsbelow which it is thought that excess risk disappears.

If numbers exposed from CAREX had been used toestimate cancer caused by asbestos exposure, lung cancerwould have been underestimated possibly 12-fold andmesothelioma 2-fold for men and women compared withobserved UK mesotheliomas (14). This suggests thatnumbers exposed to asbestos are underestimated byCAREX; our forecasts based on observed mesotheliomacases take this into account. CAREX-based estimates ofnumbers occupationally exposed, 2.6% of men and 1.5%of women, contrast with estimates of 65% of men and23% of women based on the population controls in theUK study from which we have drawn risk estimates formesothelioma (16).

It is also possible that the asbestos-related lung cancer tomesothelioma ratio is higher than the 1:1we have assumed.By estimating AFs on proportions exposed from the UKstudy and lung cancer RRs, Supplementary Table S1, therewould be 5,194 attributable lung cancers rather than 1,768in 2010 falling to 13 (not 5) in 2060 for baseline scenario 1.This would represent a current lung:mesothelioma ratio ofabout 3:1 in men and 6:1 in women. Similar ratios havebeen observed in asbestos exposed cohorts elsewhere (17).However, using an alternative, lower estimate of the pro-portions exposed to asbestos (still higher however than theCAREX estimates), based on themesothelioma attributablefractions derived from CAREX data and the RRs in Supple-mentary Table S1 but that have then been uprated tomesothelioma register numbers, gives more modest esti-mates, of 1984 attributable lung cancers in 2010 fallingto 5 in 2060 for baseline scenario 1. This would representa current lung:mesothelioma ratio of 1.2:1 in men and0.3:1 in women.

Pragmatic approaches have been developed to takeaccount of limitations in the data available for Britain.Alternative exposure levels or employment trends and dif-ferent risk estimates could be used for other countries andsituations and variations in existing standards can readily beexplored.

Only limited intervention options were tested in thisstudy, for example, reducing workplace limits and improv-ing compliance with these limits. Many other potentiallyeffective interventions have not been assessed, such asimproving technology, increasing awareness, and changingattitudes and behaviors that are important in exposurecontrol and risk reduction. Translating these interventionsinto testable scenarios is problematic; our solution has beento show the impact of the results that might be achieved,such as reduction in excess risk or shifts to lower exposurecategories. We have shown that intervening to reduce expo-sure to workplace carcinogens could lead to the avoidanceof more than 8,200 cancers per year by 2060. In compar-ison, with nearly 20% of all cancers (excluding NMSC)currently attributed to smoking (18), about an 8% imme-diate reduction in smoking levels would be required toavoid the same number of tobacco-related cancers. Theremoval of a workplace carcinogen entirely is of course themost effective possible intervention, by replacement with aless toxic or nonchemical means of fulfilling the samefunction, for example, for tetrachloroethylene. In this case,only the legacy of past exposures will remain.

The level of compliance to future OELs, that is the pro-portion of worker-exposures remaining above these limits,has also been tested. Full (100%) compliance cannot inpracticebeusedwith the lognormaldistributionassumptionand testing compliances approaching 100% gives unrealis-tically low results; as compliance approaches 100%, eventhough the standard may be well above the zero riskthreshold, the distribution mean and proportions exposedabove any zero risk threshold approach zero. In general,90% compliance has been assumed to represent a realisti-cally achievable target. Testing the timings of the

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introduction of standards and also the effect of differentcompliance levels in different industry sectors or sizes ofindustry has been explored. For RCS in Britain, it has beenshown that improvement in compliance in small companiesand among the self-employed is more effective at reducinglung cancer than reducing the current standard (3).Where the current standardwas found to exceed themean

of current exposures by up to 2 orders of magnitude, testingvalues at a half or even a quarter of the standard does notreally inform risk reduction strategies, as the estimatedproportions exposed at high levels under the test scenariowill unrealistically exceed the proportions exposed in themid 1970s at those levels, leading to increased AFs andnegative estimates of cancers "avoided." Although this canbe addressed by assuming compliance levels stricter thancurrently achieved estimates, we have tested standards thatare less than the current estimated mean levels of exposureand therefore of more interest, although these may bedifficult to achieve in practice.If there are several risk factors contributing to the burden

of a disease, a change in attribution for one factor will resultin a change in the attribution of the others. For example, iffuture smoking–related lung cancer falls giving a reducednonoccupational AF, the relative importance of occupationas a risk factor could increase leading to a rise in theoccupational AF, although this AF would now be appliedto lower projected lung cancer numbers. Attributable num-bers rather than AFs, therefore, represent a more usefulestimate of the future cancer burden caused by occupation.In addition, it is for this reason that estimated futureoccupational AFs have been applied to estimates of futurecancer numbers based on current cancer rates applied toprojected population estimates, ignoring future changes inother lifestyle or environmental risk factors. Cancer num-bers attributable to occupation are then comparable by rankorder between agents and industries. However the actual

estimates may be considered to be inflated either (i) as thepopulation is aging and numbers are increasing whenemployment levels and, therefore, exposed numbers aredeclining or (ii) as other causal factors decline so thatoccupational agents operating synergistically with an envi-ronmental or lifestyle factor (e.g., asbestos and smoking forlung cancer) produce fewer cancers. The effect is illustratedin Fig. 3 for forecast lung cancers attributable to the expo-sures contributing at least 100 cancers (Table 1), estimatedusing cancer projections based on no change from 2005,demographic change only and increase to 2030 based on anage-period-cohort modeling approach (19).

All results presented here are subject to the biases towhich our estimates of the current burden of occupation-al cancer are subject, described elsewhere (4). The mostimportant of these are data-based, particularly relating tothe matching of RRs to our allocation of industries toexposure level categories, and the reliability of the datacontributing to estimates of numbers ever exposed. Somereallocation of industries between exposure categories hasoccurred between the estimation of current and futureburden where additional categories have been intro-duced. In particular moving large numbers in construc-tion and land transport from "high" to a new "medium"exposed category for DEE has resulted in much lowernumbers of lung cancers attributable to DEE than esti-mated for current burden, as a reduced RR has been usedfor the medium exposed. For bladder cancer, the currentburden "high" exposed RR was retained for this largegroup and a more specifically targeted higher RR has beenused for the new and smaller high exposed group ofminers and services allied to transport. Also, introducinga low "nonoccupational" category for asbestos exposuredoes reduce the forecast estimates for the asbestos-relatedcancers other than mesothelioma; as no risk estimateswere available for this group, zero excess risk was assumed

Figure 3. Lung cancers in mencaused by occupational exposures,various cancer projections.






for the workers moving out of the higher occupationalrisk categories with our estimated annual fall in work-place exposure levels.

In summary, comparison of a range of interventions forthe most important current occupational carcinogens hasshown the potential for future reduction of occupationallyrelated cancer. Interventions to reduce exposure to carcino-gens may often also lead to reductions in other healthrelated conditions in the working and living environment,e.g. reduction of silica exposure will not only reduce lungcancer but will affect respiratory function and other non-malignant respiratory diseases. Our methods can beadapted for different data circumstances, to investigateother types of interventions and could be extended toenvironmental carcinogens and other chronic diseases.Although the forecasts presented here are for Britain, themethods have been used to test the impact of introducingalternative exposure standards in the countries of the Euro-peanUnion for 25 chemical occupational carcinogens (20),and are readily transferable to other national and occupa-tional settings.

Disclosure of Potential Conflicts of InterestNo potential conflicts of interest were disclosed.

Authors' ContributionsConception and design: S.J. Hutchings, J.W. Cherrie, M.V. Tongeren, L.RushtonDevelopment of methodology: S.J. Hutchings, J.W. Cherrie, M.V.Tongeren,Acquisitionofdata (provided animals, acquired andmanagedpatients,provided facilities, etc.): J.W. Cherrie, M.V. Tongeren, L. RushtonAnalysis and interpretation of data (e.g., statistical analysis, biosta-tistics, computational analysis): S.J. Hutchings, M.V. Tongeren, L.RushtonWriting, review, and/or revision of the manuscript: S.J. Hutchings, M.V.Tongeren, L. RushtonStudy supervision: L. Rushton

AcknowledgmentsThe authors thank the participants of the future burden methodology

workshop, particularly Drs. John Hodgson, David Kriebel, Hans Kromhout,DamienMcElvenny, Kyle Steenland, Kurt Straif, and organizer Gareth Evans.The contributions and advice from the Health and Safety Executive and therest of the project team is gratefully acknowledged, in particular AndyDarnton for his advice on the issues surrounding asbestos.

Grant SupportThe work was supported by the UK Health and Safety Executive (grant

number JN 3117).The costs of publication of this article were defrayed in part by the pay-

ment of page charges. This article must therefore be hereby marked adver-tisement in accordancewith 18U.S.C. Section 1734 solely to indicate this fact.

Received May 8, 2012; revised July 11, 2012; accepted July 31, 2012;published OnlineFirst September 7, 2012.

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Hutchings et al.





2012;5:1213-1222. Published OnlineFirst September 7, 2012.Cancer Prev Res Sally Hutchings, John W. Cherrie, Martie Van Tongeren, et al. Britain: What Could Work?Intervening to Reduce the Future Burden of Occupational Cancer in

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