Mortality among British asbestos workers undergoing regular medical examinations (1971-2005)

Our plain-English summary of Mortality among British asbestos workers undergoing regular medical examinations (1971-2005), by A.H. Harding, A. Darnton, J. Wegerdt, et al (Occupational and Environmental Medicine, 2009).

The study

• Authors: A.H. Harding, A. Darnton, J. Wegerdt, D. McElvenny
• Journal: Occupational and Environmental Medicine
• Published: 2009;66(7):487-95
• Cited by: 49 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: The Great Britain Asbestos Survey was established to monitor mortality among workers covered by regulations to control occupational exposure to asbestos. This study updates the estimated burden of asbestos-related mortality in the cohort, and identifies risk factors associated with mortality.

Methods: From 1971, workers were recruited during initially voluntary and later statutory medical examinations. A brief questionnaire was completed during the medical, and participants were flagged for death registrations. Standardised mortality ratios (SMRs) and proportional mortality ratios (PMRs) were calculated for deaths occurring before 2006. Poisson regression analyses were undertaken for diseases with significant excess mortality.

Results: There were 15 496 deaths among 98 117 workers followed-up for 1 779 580 person-years. The SMR for all cause mortality was 141 (95% CI 139 to 143) and for all malignant neoplasms 163 (95% CI 159 to 167). The SMRs for cancers of the stomach (166), lung (187), peritoneum (3730) and pleura (968), mesothelioma (513), cerebrovascular disease (164) and asbestosis (5594) were statistically significantly elevated, as were the corresponding PMRs. In age and sex adjusted analysis, birth cohort, age at first exposure, year of first exposure, duration of exposure, latency and job type were associated with the relative risk of lung, pleural and peritoneal cancers, asbestosis and mesothelioma mortality.

Conclusions: Known associations between asbestos exposure and mortality from lung, peritoneal and pleural cancers, mesothelioma and asbestosis were confirmed, and evidence of associations with stroke and stomach cancer mortality was observed. Limited evidence suggested that asbestos-related disease risk may be lower among those first exposed in more recent times.

In plain English

This study followed 98,117 workers in the Great Britain Asbestos Survey, which recruited workers covered by asbestos regulations at medical examinations from 1971. Ninety-five percent were men. By the end of 2005 there had been 15,496 deaths. The authors compared deaths with national rates and looked for risk factors within the group. There were 41% more deaths from all causes than expected (SMR 141, 95% CI 139 to 143). Deaths were significantly raised for cancers of the lung, pleura, peritoneum and stomach, for mesothelioma (counted for 2001 to 2005 only), and for stroke and asbestosis. Insulation workers had the highest asbestosis risk compared with manufacturing workers. Removal and insulation workers had higher mesothelioma risks than manufacturing workers. Smoking was strongly linked to lung cancer. The authors concluded that the study confirmed known links between asbestos and asbestosis, lung, pleural and peritoneal cancers and mesothelioma, and gave evidence of links with stroke and stomach cancer. They found some evidence that risk may be lower for workers first exposed more recently, but said longer follow-up is needed. Direct information on fiber type and exposure intensity was not available for all workers, though job type gave some insight.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Cohort mortality study comparing deaths with national rates (standardised and proportional mortality ratios), plus internal Poisson regression analysis of risk factors
• Who was studied: 98,117 workers (93,622 men and 4,495 women) in the Great Britain Asbestos Survey, recruited at medical examinations from 1971 to 2005. They were followed for 1,779,580 person-years, with 15,496 deaths.
• Exposure: Occupational asbestos exposure, assumed from participation in the survey. Jobs were grouped as manufacturing, stripping/removal, other exposed, and insulation work. Direct information on asbestos type, intensity and length of exposure was not available for all workers, although job type gave some insight. Limited, job-specific information on current exposure and control practices, without quantitative estimates, was recorded for workers recruited under the 1987 regulations. The authors suggested insulation work likely involved substantial amphibole exposure.
• Main results:
  • Whole cohort: deaths from all causes were significantly above national rates (SMR 141; 95% CI 139 to 143).
  • Whole cohort: SMRs were significantly elevated for stomach cancer (166), lung cancer (187), peritoneal cancer (3730), pleural cancer (968), mesothelioma (513, deaths 2001 to 2005 only), cerebrovascular disease (164) and asbestosis (5594). The corresponding PMRs were also elevated.
  • Some smoking-related causes of death had raised SMRs but not raised PMRs. These were cancers of the oesophagus, colon, rectum, liver, larynx, kidney and bladder, and circulatory disease overall. The authors suggested these excesses might be due to confounding such as smoking rather than asbestos.
  • Asbestosis risk compared with manufacturing workers: insulation workers RR 5.98 (95% CI 3.84 to 9.31); removal workers RR 2.21 (95% CI 1.24 to 3.93).
  • Lung cancer risk compared with manufacturing workers: insulation workers RR 1.84 (95% CI 1.60 to 2.10); removal workers RR 1.30 (95% CI 1.12 to 1.50).
  • Lung cancer risk compared with never smokers: current smokers RR 14.3 (95% CI 10.2 to 20.1); former smokers RR 4.55 (95% CI 3.20 to 6.46).
  • Workers with at least 40 years of exposure, compared with less than 10 years: pleural cancer RR 4.35 (95% CI 2.18 to 8.68); peritoneal cancer RR 14.9 (95% CI 5.80 to 38.5).
  • Mesothelioma risk compared with manufacturing workers: removal workers RR 3.19 (95% CI 2.16 to 4.72); insulation workers RR 2.65 (95% CI 1.64 to 4.30). Mesothelioma risk rose with time since first exposure, peaking 50 to 59 years after first exposure (RR 28.1, 95% CI 12.2 to 64.6, compared with less than 20 years).
  • Relative risks of asbestosis and of lung, pleural and peritoneal cancers were lower for workers born after 1939 and for workers first exposed after 1959. The authors said this may reflect stricter laws, but may also reflect the long latency of these diseases.
  • The authors reported that smoking was a risk factor for asbestosis and lung cancer but not for the mesotheliomas.
• The authors' conclusion: The authors concluded that the analysis confirmed known associations between asbestos exposure and mortality from asbestosis, lung, pleural and peritoneal cancers and mesothelioma, and gave evidence of associations with stroke and stomach cancer. They found some evidence that risk may be lower among those first exposed more recently, but said further follow-up is needed to confirm this.
• Limitations the authors state:
  • The SMRs were likely to be confounded by other risk factors, particularly smoking.
  • The PMR analysis cannot be considered a formal adjustment for confounding.
  • Only the underlying cause of death on death certificates was used, so the true burden of some asbestos-related diseases may have been underestimated.
  • Results for peritoneal cancer cannot be taken to describe peritoneal mesothelioma alone.
  • The new ICD code for mesothelioma may have produced spurious time trends.
  • Direct information on asbestos type, exposure intensity and length of exposure was not available for all workers, although job type gave some insight into exposures.
  • No information was collected on other risk factors such as diet and physical activity, and only limited information on asbestos exposure.
  • Most removal workers had less than 20 years of follow-up, too short to show the full extent of long-latency diseases.

Topics

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Proportional mortality, Neoplasm, Peritoneum, Pleura, Mesothelioma, Latency, Relative Risk.

Related studies

• Cardiovascular disease mortality among British asbestos workers (1971-2005) — A.H. Harding, A. Darnton, et al. (2012)
• Asbestosis and mesothelioma among British asbestos workers (1971-2005) — A.H. Harding, A.J. Darnton (2010)
• Cohort mortality study of pulp and paper mill workers in British Columbia, Canada — P.R. Band, N.D. Le, et al. (1997)
• Mortality in a cohort of asbestos-exposed workers undergoing health surveillance — F. Barbiero, T. Zanin, et al. (2018)
• The effect of smoking on the risk of lung cancer mortality for asbestos workers in Great Britain (1971-2005) — G. Frost, A. Darnton, et al. (2011)
• Medical examination for asbestos-related disease — S.M. Levin, P.E. Kann, et al. (2000)

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