Document Jv7DNa0VboDm9YEen0Mm4brzr

Pergamon PH; SOOd3-487(^)OOJ^9 COCtMT7V97 (17,00 + 0.00 MM t'trtkia Vttl MESOTHELIOMA MORTALITY IN BRITAIN: PATTERNS BY BIRTH COHORT AND OCCUPATION J. T. Hodgson,* J. Peto,f j. R. Jones* and F, E, Matthewst Epkteanofc' and Medical Statistic* Umt, Health and Safety Executive, Room 241, Magdalen House, Stanley Pretmct, Bootle, Merseyside L203QZ, U ,K.-, aod tSection ofEpidemiology, Institute of Canter Research, 15 CotswokS Road, Beltnotit, Surrey SM2 5NG, U .K. OBJECTIVES To assess the impact of asbestos exposure on successive cohorts of the British population and on different occupational groups. METHODS Data were taken from the HSE's mesothelioma register, which has records of all death certificates in Great Britain since 1968 on which mesothelioma was recorded. Death rates by age and birth cohort were modelled by Poisson regression. Occupational effects were assessed by calculating proportional mortality ratios, based on the occupations recorded on death certificates. The main cohort and occupational analyses reported here are based on data up to 1991. The data for 1992-1994 have recently been released and the final set of figures compares the observed data for these three years with expected values based on projections of the age-cohort model fitted to the date up to 1991. COHORT ANALYSIS Male mesothelioma death rates show a dear pattern by age and cohort (see Fig. 1 for clarity, only alternate 5 year cohorts are shown and the youngest observation point for each cohort, which has zero deaths for most cohorts, has also been omitted). Rates increased steeply with age mid with a similar age-specific pattern for each cohort. At all ages for which adirect comparison can be made, rates increase from cohort to cohort up to the 1940s, The multiplicative model: rtc * A,Ct, where rK is the rate for age group a in cohort c, {A,} are age factors common across cohorts and (Cc) are cohort factors common across ages provides a very close statistical fit to the observed rates. The details of the fitting process have been described elsewhere (Peto el al., 1995). The estimated lifetime risk of mesothelioma implied by this model for each cohort rises over 20-fold from the cohort bom around 1900 to that bom around 1945, for which the lifetime risk is [Page 2 af 7) 130 J. T. Hodgson et at Kg. 1. about 1.3%. Rates then fell and the 1950 and 1955 cohorts had risks 30 and 50% tower, respectively, than those for the 1945 cohort. The pattern for females was similar, though the age and cohort slopes were less steep. OCCUPATIONAL ANALYSIS The occupations with the highest PMRs arc shown in Table 1. AU have dearly rased potential for asbestos exposure, and building workers, especially plumbers and gas fitters, carpenters and electricians are the largest high risk group. The groups with risks clearly raised above the average only account for about half the recorded deaths. In order to display PMRs across the whole range of occupations without the picture being confused by the imprecisely determined PMRs of small job groups. Fig. 2 shows the PMRs for 27 major job groups. These job groups were selected initially by choosing each job group which accounted for more than 1% of total (all cause) male deaths. There were 28 such job group. Two of these groups (sales representatives and sales managers nec) had very similar PMRs and have been combined into a single category. Two job groups which fell below the 1% of total deaths boundary but which had natural links with job groups above that boundary were combined with their larger partner and treated as a single group: face trained coal miners with other coal miners and teachers in higher education with teachers nec. The final result b a set of 27 job groups which together account for 63% of all deaths. - The PMRs for these 27 groups show a wide spread from 0.25 for fanners up to 4.45 for plumbers and gas fitters, an 18-fold difference. As one moves up the spectrum of risk three broad groupings can be distinguished. Between the lowest two or three jobs and the highest dozen or so jobs the PMRs are very closely bunched between 0.5 and 0.9. Coal miners and farmers have PMRs which fall dearly below this range and motor mechanics (although they have a wide confidence limit) are doser to these two lowest risk groups than to the next highest group. The 11 job groups with PMRs above 0.9 (they are in fact all above 1) show a Table I. Jobgr Meat! Velde ' Plural C*rp< Elect ' ttphe Coon . ' BoQe Elm . Chen ' Sheet , Staff. Prat Proft ; Platt. | Wtfc Mao; Dod Elect Ted) . Bmk Labe. Thai Mad Pam steady these The makir nance (Page 3 of 7) Mesothelioma mortality m Britton - ]jj Table 1, Proportional mortality ratios (PMRi) of men aged 16-74 from mesothelioma la England and Waits 1979-80,1982-90 Job group PMR (all men = 1) Number Percent Cumulative percent Mttil Plate Worker* Vefcxie Body Bsflden Plumbers rad Gas Fitters Carpenters Electririms Upholsterers Cosatrottion Workers BoOer Operators Electrical Plant Operators Chemical Engineers rad Scientist! Sheet Metal Workers ScaSoidcit Production Fitters Professional Enpneers nec Plasterer* Welders Managers in Construction Dockers rad Goods Porters Electrical Engineers (so described) Technicians occ . Braiders tod Handymen : Laboratory Tec&adatu Draughtsmen 1 Machine Tool Operators Painlm and Decorators ntc > - 7 6.19 4.43 3.66 2.91 Z83 Z56 2.54 2-54 2.4$ 2.33 2.26 2.16 2.11 Z03 2.03 ' 1.97 1-95 1.S7 1.72 1.64 1.64 1.61 03 1.31 110 35 201 258 161 19 1ST 39 18 18 . 48 . 11 . . 304 105 ' 27 70 40 69 39 24 . 98 27 28 ' 179 100 2.5 0.8 . 4-5 5,8 3.6 0.4 4.2 0.9 0.4 0.4 U 0.2 6.8 2.3 0.6 1.6 0.9 1,5 0.9 0.5 2.2 0.6 0.6 4 2.2 2.5 3.2 7.7 13.5 17,1 17.5 21.7 22.5 22.9' 23.3 24.4 24.7 31.4 33.8 34,4 35.9 36.8 38.4 . 39.2 39,8 42 42.6 43.2 47.2 49.4 steady and quite steep gradient of increasing risk with no obvious break points. AU these jobs have a dear potential for above-average asbestos exposure. There are no indications in the PMR Values of the central group of jobs for making any sub-grouping; however, with two exceptions (production and mainte nance managers and lorry drivers) the manual occupations within this group lie at Kg. 2. * Tabic, 2, Observed male mesothelioma deaths up to 1994 by age group and birth cohort, and (in brackets) difference from numbers predicted on the basis of ,' projections based on data up to 1991 . . Cohort: men bom in period . 39-34 35-39 - Age group 40-44 45-49 ' 50-54 55-59 Total obaervedprojected difference ' for cohort luty 1938-Jane 1943 July 1943-dune 1948 My 1948-Jane 1933 July 1933-Juae 1958 5 7 4 4 (+ 0.9) 18 .33 23 (+ 2,4) 7{- 1.8) 63 90 (+ 10) 39 C- 3.6) 2 {+ 0.7) 178 (+ 16) 135 (- 13) 1 (- 4.9) -- 282(4-24) 20 (+. 5 )' 21 (- 3) -- 37 -2 -6.1 -02 . J. T. Hodgson L y <* < w 32H ' fWt X wSl^E'S1 tig%% si fir (P a g e Mesothelioma mortality in Britain m the higher risk cud and the non-manual occupations at the lower risk end. If the high and low .ends of this middle group, are aggregated in this way the average PMRs for the two sub-groups are significantly different: 0.8 (95% Cl, 0.72, 0.89) for the higher (mainly manual) group; and 0.57 (95% 1,0.52,0.62) for the lower (mainly non-manual) group. If the lowest three Job groups are conabbed, their PMP, is significantly lower again, 0.28 (95% Cl, 0.23, 0.35). These groups are shown on Fig. 2 as Groups A, B and C (labelled in order of decreasing nsk). Of course, the boundaries between these groups are to some extent arbitrary. However, this grouping does capture the main features of the data in terms of the distribution of PMRs and (apart from, group C) shows a good degree of coherence in the kinds of occupation within the groups. It is worth noting that none of the 167 smaller job groups in the full occupational classification (data not shown here) has a PMR significantly lower than that of group C, so this group can reasonably be taken to define the lowest risk group for mesothelioma (in the period of observation). In relation to this group, group B has about twice the mesothelioma risk and group A about three times the risk. * The relative risks between these groups have been fairly stable over time and overall death rates for the three higher risk groups have increased about 6-fold between 1968-73 and 1987-91, The low risk group's rate has increased Mold over the same period. COHORT PATTERNS W THE LATEST DATA The results described above are all based on data up to 1991. After a delay while the national mortality statistics system was being computerised, the mesothelioma data for the three years 1992-1994 have now been released. It is of bterest to examine whether the new data are consistent with the date up to 1991 and in particular whether the age-specific rates for the more recently bom cohorts (for whom asbestos exposure has almost certainly fallen, as controls have been more strictly applied, and usage has fallen) continue to rise in fine with the pattern seen in earlier cohorts. The comparisons are shown in Table 2. These data show that the observed numbers in the most recent 3 years have been slightly higher than projected for the earliest of the four cohorts shown, close to tits projected values for the 1943-48 cohort and below the projected values for the two later cohorts. CONCLUSIONS Asbestos exposure sufficient to cause mesothelioma has been widespread in the male population. Building workers have been at high risk and should continue to be alert to the dangers of working on asbestos materials. . REFERENCE . Pete, 1., Hodgson, J. T., Matthews, F. E. and Jones, I, R. (1995) Continuing increase in mesothelioma mortality in Britain. Lanctt 345,535-39. INHALED PARTICLES ' VIII proceedings of an International Symposium x on Mialed Particles organised by the . British Occupational Hygiene Society 26-30 August 1996 Editors N. CHERRY T. OGDEN Supplement to the Annals of Occupational Hygiene o -Av PERGAMON (Page 7 of 7) ORIGINAL