Exposure-response relationship between chrysotile exposure and mortality from lung cancer and asbestosis

Our plain-English summary of Exposure-response relationship between chrysotile exposure and mortality from lung cancer and asbestosis, by Q. Deng, X. Wang, M. Wang, et al (Occupational and Environmental Medicine, 2012).

The study

• Authors: Q. Deng, X. Wang, M. Wang, Y. Lan
• Journal: Occupational and Environmental Medicine
• Published: 2012;69(2):81-6
• Cited by: 26 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: To describe mortality in workers exposed to chrysotile asbestos, and determine exposure-response relationships between asbestos exposure and mortality from lung cancer and asbestosis by fitting and comparing different models.

Methods: A prospective cohort consisting of 586 workers in an asbestos textile factory was followed from 1 January 1972 to 31 December 2006. A structured questionnaire was administered to collect personal information and exposure data. Paired concentration samples measured in the workshops were used to convert dust concentrations to fibre concentrations. Individual cumulative asbestos exposure was estimated as the product of fibre concentrations and duration of employment in each job and expressed as fibre-years/ml. The vital status of cohort members was followed annually. Poisson regression analysis was applied to fit log-linear, log-quadratic, power, additive relative risk and categorical models to estimate exposure-response relationships between cumulative fibre exposure and mortality from lung cancer and asbestosis.

Results: Of the 226 deaths (14.6 per 1000 person-years) over the 35-year follow-up, 51 were from lung cancer (3.29 per 1000 person-years) and 37 from asbestosis (2.39 per 1000 person-years). A significant exposure-response relationships with either lung cancer or asbestosis (p<0.001) was observed in the final model. The power model with lagged 10 years was found to be the best model of those evaluated for both lung cancer (β coefficient=0.53) and asbestosis (β coefficient=0.63).

Conclusions: The study confirmed strong associations between exposure to chrysotile asbestos and lung cancer and asbestosis, in which clear exposure-response relationships were observed.

In plain English

The authors followed 586 male workers at an asbestos plant in Chongqing, China, that used chrysotile asbestos to make textiles, rubber (friction) plate and asbestos cement. The men had worked there at least a year before 1972 and were followed from 1972 to 2006. Each worker's cumulative exposure was estimated partly by converting old dust measurements to fibre concentrations. The average was 126.1 fibre-years/ml. There were 226 deaths: 51 from lung cancer and 37 from asbestosis (including its complications). There were also two mesothelioma cases, one pleural and one peritoneal. Of the statistical models compared, a 'power' model counting exposure with a 10-year lag fit best for both lung cancer and asbestosis, with risk rising as cumulative exposure rose. No statistically significant smoking-asbestos interaction was found for lung cancer. The authors said the study may have been too small to detect one. The authors concluded that chrysotile exposure was strongly associated with lung cancer and asbestosis deaths. They noted that exposure estimates came from workplace rather than personal air samples and from converted dust data.

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: Prospective cohort study (mortality follow-up) with Poisson regression modelling of exposure-response
• Who was studied: 586 male workers registered before 1 January 1972 who had worked at least 1 year at an asbestos plant in Chongqing, China. They were followed until 31 December 2006, contributing 15 487.7 person-years.
• Exposure: Chrysotile asbestos used to make asbestos textile, rubber (friction) plate and asbestos cement. Samples showed very low tremolite contamination. Estimated average cumulative exposure was 126.1 fibre-years/ml (SD 181.1).
• Main results:
  • In the whole cohort there were 226 deaths over the 35-year follow-up (14.6 per 1000 person-years). Of these, 51 were from lung cancer (3.29 per 1000 person-years) and 37 from asbestosis (2.39 per 1000 person-years).
  • Asbestosis deaths included deaths from asbestosis complications such as cor pulmonale.
  • Two mesothelioma cases were observed in the cohort, one pleural and one peritoneal.
  • Of the models evaluated, the power model with a 10-year lag was chosen as the best fitting model for both lung cancer and asbestosis mortality.
  • For lung cancer mortality, the final power model gave parameters a = 5 and β = 0.53 (p less than 0.001), indicating that risk increased with cumulative exposure.
  • For asbestosis mortality, the final power model gave a = 1 and β = 0.63 (p less than 0.001). The authors gave a relative risk of 10.4 as an example for 40 years of exposure to 1 f/ml.
  • No significant interaction between smoking and cumulative asbestos exposure was observed for lung cancer.
• The authors' conclusion: The authors concluded that the study confirmed strong associations between chrysotile exposure and lung cancer and asbestosis, with clear exposure-response relationships.
• Limitations the authors state:
  • Exposure estimates were based on periodic workplace air sampling rather than personal sampling.
  • Earlier dust measurements were converted to fibre concentrations using later paired samples, which might have caused exposure misclassification.
  • Under the Chinese diagnostic criteria used, radiograph category 1/0 was not classed as pneumoconiosis, which might have led to underestimating asbestosis.
  • The study may have had too little power to detect a smoking-asbestos interaction, because very few workers were non-smokers. Detailed smoking-level data were also lacking.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis, Chrysotile, Lung cancer.

Medical terms in this study, explained in our Lexicon: Chrysotile, Lung Cancer, Asbestos Exposure, Relative Risk.

Related studies

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• Lung cancer mortality in North Carolina and South Carolina chrysotile asbestos textile workers — L. Elliott, D. Loomis, et al. (2012)
• The 1891-1920 birth cohort of Quebec chrysotile miners and millers: development from 1904 and mortality to 1992 — F.D. Liddell, A.D. McDonald, et al. (1997)
• Exposure to chrysotile mining dust and digestive cancer mortality in a Chinese miner/miller cohort — S. Lin, X. Wang, et al. (2014)
• Exposure-response estimate for lung cancer and asbestosis in a predominantly chrysotile-exposed Chinese factory cohort — M.N. Courtice, X. Wang, et al. (2016)
• Mortality in a Chinese chrysotile miner cohort — X. Wang, S. Lin, et al. (2012)

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