John T. Hodgson

Continuing increase in mesothelioma mortality in Britain.

Mesothelioma is closely related to exposure to asbestos, and mesothelioma mortality can be taken as an index of past exposure to asbestos in the population. We analysed mesothelioma mortality since 1968 to assess the current state of the mesothelioma epidemic, and to predict its future course. We found that rates of mesothelioma in men formed a clear pattern defined by age and date of birth. Rates rose steeply with age showing a very similar pattern in all five-year birth cohorts. By date of birth, rates increased from mid-1893 to mid-1948, and then fell. Relative to the 1943-48 cohort, the risk for the 1948-53 cohort is 0.79 and for the 1953-58 cohort 0.48. Despite these falls, if the age profile of rates for these cohorts follows the pattern of past cohorts, their predicted lifetime mesothelioma risks will be 1.3%, 1.0%, and 0.6%. Combining projections for all cohorts results in a peak of annual male mesothelioma deaths in about the year 2020 of between 2700 and 3300 deaths. If diagnostic trend is responsible for a 20% growth in recorded cases every 5 years--an extreme but arguable case--and if this trend has now ceased, the peak of annual male deaths will be reduced to 1300, reached around the year 2010. Analysis of occupations recorded on death certificates indicate that building workers, especially plumbers and gas fitters, carpenters and electricians are the largest high-risk group. These data indicate that mesothelioma deaths will continue to increase for at least 15 and more likely 25 years. For the worst affected cohorts--men born in the 1940s--mesothelioma may account for around 1% of all deaths. Asbestos exposure at work in construction and building maintenance will account for a large proportion of these deaths, and it is important that such workers should be aware of the risks and take appropriate precautions.

Occupational, domestic and environmental mesothelioma risks in the British population: a case-control study

We obtained lifetime occupational and residential histories by telephone interview with 622 mesothelioma patients (512 men, 110 women) and 1420 population controls. Odds ratios (ORs) were converted to lifetime risk (LR) estimates for Britons born in the 1940s. Male ORs (95% confidence interval (CI)) relative to low-risk occupations for >10 years of exposure before the age of 30 years were 50.0 (25.8–96.8) for carpenters (LR 1 in 17), 17.1 (10.3–28.3) for plumbers, electricians and painters, 7.0 (3.2–15.2) for other construction workers, 15.3 (9.0–26.2) for other recognised high-risk occupations and 5.2 (3.1–8.5) in other industries where asbestos may be encountered. The LR was similar in apparently unexposed men and women (∼1 in 1000), and this was approximately doubled in exposed workers’ relatives (OR 2.0, 95% CI 1.3–3.2). No other environmental hazards were identified. In all, 14% of male and 62% of female cases were not attributable to occupational or domestic asbestos exposure. Approximately half of the male cases were construction workers, and only four had worked for more than 5 years in asbestos product manufacture.

Projection of mesothelioma mortality in Britain using Bayesian methods.

Background:Mesothelioma mortality has increased more than ten-fold over the past 40 years in Great Britain, with >1700 male deaths recorded in the British mesothelioma register in 2006. Annual mesothelioma deaths now account for >1% of all cancer deaths. A Poisson regression model based on a previous work by Hodgson et al has been fitted, which has allowed informed statistical inferences about model parameters and predictions of future mesothelioma mortality to be made.Methods:In the Poisson regression model, the mesothelioma risk of an individual depends on the average collective asbestos dose for the individual in a given year and an age-specific exposure potential. The model has been fitted to the data within a Bayesian framework using the Metropolis–Hastings algorithm, a Markov Chain Monte Carlo technique, providing credible intervals for model parameters as well as prediction intervals for the number of future cases of mortality.Results:Males were most likely to have been exposed to asbestos between the ages of 30 and 49 years, with the peak year of asbestos exposure estimated to be 1963. The estimated number of background cases was 1.08 cases per million population.Conclusion:Mortality among males is predicted to peak at approximately 2040 deaths in the year 2016, with a rapid decline thereafter. Approximately 91 000 deaths are predicted to occur from 1968 to 2050 with around 61 000 of these occurring from 2007 onwards.

Spontaneous abortion in the british semiconductor industry : An HSE investigation

BACKGROUND The UK Health and Safety Executive (HSE) conducted a study to examine the risk of spontaneous abortion (SAB) in British female semiconductor industry workers, following reports from the USA which suggested an association between risk of SAB and work in fabrication rooms and/or exposure to ethylene glycol ethers. METHODS A nested case-control study based on 2,207 women who had worked at eight manufacturing sites during a 5-year retrospective time frame was established; 36 cases were matched with 80 controls. RESULTS The overall SAB rate in the industry was 10.0%. (65 SABs/651 pregnancies) The crude odds ratio (OR) for fabrication work was 0.65 (95% CI 0.30-1.40). This was essentially unchanged after adjustment for a range of potential confounding factors in the first 3 months of pregnancy and was reduced to 0.58 (95% CI 0.26-1.30) after adjustment for smoking in the previous 12 months. There were no statistically significantly elevated ORs for any work group or any specific chemical or physical exposure in the industry. CONCLUSIONS There is no evidence of an increased risk of SAB in the British semiconductor industry. Am. J. Ind. Med. 36:557-572, 1999. Published 1999 Wiley-Liss, Inc.

Pleural mesothelioma and lung cancer risks in relation to occupational history and asbestos lung burden

Background We have conducted a population-based study of pleural mesothelioma patients with occupational histories and measured asbestos lung burdens in occupationally exposed workers and in the general population. The relationship between lung burden and risk, particularly at environmental exposure levels, will enable future mesothelioma rates in people born after 1965 who never installed asbestos to be predicted from their asbestos lung burdens. Methods Following personal interview asbestos fibres longer than 5 µm were counted by transmission electron microscopy in lung samples obtained from 133 patients with mesothelioma and 262 patients with lung cancer. ORs for mesothelioma were converted to lifetime risks. Results Lifetime mesothelioma risk is approximately 0.02% per 1000 amphibole fibres per gram of dry lung tissue over a more than 100-fold range, from 1 to 4 in the most heavily exposed building workers to less than 1 in 500 in most of the population. The asbestos fibres counted were amosite (75%), crocidolite (18%), other amphiboles (5%) and chrysotile (2%). Conclusions The approximate linearity of the dose–response together with lung burden measurements in younger people will provide reasonably reliable predictions of future mesothelioma rates in those born since 1965 whose risks cannot yet be seen in national rates. Burdens in those born more recently will indicate the continuing occupational and environmental hazards under current asbestos control regulations. Our results confirm the major contribution of amosite to UK mesothelioma incidence and the substantial contribution of non-occupational exposure, particularly in women.

Mesothelioma risk from chrysotile

We welcome the appearance of the new analysis of asbestos related mortality by Loomis et al ( Occup Environ Med 2009;66:535–42) which constitutes an important addition to the available evidence. We note that the lung cancer risk from these data highlighted by the authors and based on their internal analyses is identical to that suggested as the “best estimate” in our earlier meta-analysis1: a relative risk of 1.102 per 100 f/ml.yr translates almost exactly to an excess over expected of 0.1% per f/ml.yr. The risk of mesothelioma derived from these new data is higher by a factor of 10 than that which emerged from our meta-analysis. The following …

Time trends in the incidence of work-related mental ill-health and musculoskeletal disorders in the UK.

Objectives To determine UK trends (from 1996 to 2009) in incidence of work-related mental ill-health and musculoskeletal disorders, for all industry as well as for health and social care employees. Second, to investigate whether there may have been a recent shift from a physical to psychological perspective in how patients present their illness by comparing reporting trends for back pain and ‘other work stress’. Methods Multilevel models were used to investigate changes in incidence of work-related illness, as diagnosed by specialist physicians. The dependent variable comprised case reports to The Health and Occupation Research network. Comparisons were made between medical specialties, industry (health and social care vs all other employees), gender and diagnosis. Results Trends for Occupational Physicians’ (OP) reporting mental ill-health (average annual increase +3.7% (95% CI +2.2% to +5.2%)) differed significantly (p<0.001) from psychiatrists’ reporting over the same time period (−5.9% (95% CI −7.6% to −4.2%)). For OPs’ reporting, the rate of increase was greater for females and for health and social care employees. A fall in incidence of musculoskeletal disorders for OPs of −5.8% (95% CI −7.3% to −4.3%) and rheumatologists’ reporting −6.6% (95% CI −8.3% to −4.8%) was found, with little variation by gender or industry. Within health and social care, an increase in incidence of ‘other work stress’ was accompanied by a similar decrease in ‘spine/back pain’. Conclusions The evidence presented is consistent with a shift in the presentation of ill-health from a physical to psychological perspective, although changes in hazards, prevention measures and physician awareness should also be considered as explanations.

Guinea pig maximisation test for skin sensitisation: the use of fewer test animals

Current European Community (Annex V) guidelines recommend the use of 20 test animals in the guinea pig maximisation test for skin sensitisation. The suitability, for classification and labelling purposes, of reducing the number of test animals has been examined by analysing the results of 40 studies submitted to the Health and Safety Executive, and by the use of a mathematical model. Our results suggest that in most cases an experiment with ten test animals can be used to determine satisfactorily whether a substance should be labelled with the risk phrase “may cause sensitisation by skin contact”. However, serious consideration should be given to the need for additional investigation if two or three of the ten test animals show a sensitisation response. The highest nonirritant concentration of a substance should be used at challenge. Clearer guidance in Annex V on evaluating challenge responses would be beneficial.

Mortality from asbestosis and mesothelioma in Britain by birth cohort

BACKGROUND Analysis of occupational mortality in England and Wales during 1991-2000 showed no decline in work-attributable deaths from asbestosis. AIMS To explore why there was no decline in mortality from asbestosis despite stricter controls on asbestos exposure over recent decades. METHODS Using data from registers of all deaths in Great Britain with mention of mesothelioma or asbestosis on the death certificate, we plotted death rates by 5 year age group within 5 year birth cohorts for(a) mesothelioma and (b) asbestosis without mention of mesothelioma. RESULTS Analysis was based on a total of 33,751 deaths from mesothelioma and 5396 deaths from asbestosis. For both diseases, mortality showed a clear cohort effect; within birth cohorts, death rates increased progressively with age through to 85 years and older. However, highest mortality from mesothelioma was in men born during 1939-43, whereas, mortality from asbestosis peaked in men born during 1924-38. CONCLUSIONS Our findings suggest that mortality, in Britain, from asbestosis has been determined mainly by cumulative exposure to asbestos before 45 years of age and that the effect of such exposure continues through to old age. That mortality from asbestosis peaked in earlier birth cohorts than mortality from mesothelioma may reflect a difference in exposure-response relationships for the two diseases. The discrepancy could be explained if risk of asbestosis increased more steeply than that of mesothelioma at higher levels of exposure to asbestos and if the highest prevalence of heavy exposure occurred in earlier birth cohorts than the highest prevalence of less intense exposures.

Authors' reply to letters from Egilman et al and Oliver et al

Dr Egilman and colleagues claim our report1 implies that chrysotile does not cause mesothelioma. So did the International Chrysotile Association, the website of which highlighted our paper with the misleading headline ‘reliable scientific data confirms negligible role of chrysotile in UK patients with asbestos-related lung disease’.2 Our results are consistent with the strong evidence that chrysotile did not cause a large proportion of UK mesotheliomas, but they certainly do not show that the risk is negligible. We said ‘the rapid clearance of chrysotile from the lung with a half-life of a few months explains its virtual absence in our samples, and implies that we cannot estimate its effects except by noting that amphibole lung burdens account very well …