Assessment of cancer risks due to environmental exposure to asbestos

Our plain-English summary of Assessment of cancer risks due to environmental exposure to asbestos, by H.A. Driece, S. Siesling, P.H. Swuste, et al (Journal of Exposure Science & Environmental Epidemiology, 2010).

The study

• Authors: H.A. Driece, S. Siesling, P.H. Swuste, A. Burdorf
• Journal: Journal of Exposure Science & Environmental Epidemiology
• Published: 2010;20(5):478-85
• Cited by: 24 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

In a rural area widespread pollution of friable and non-friable waste products was present, used to harden dirt tracks, yards, and driveways during 1935-1974. Exposure to environmental asbestos was assessed by a site approach, based on number of polluted sites within postal code areas, and by a household approach, based on number of households in the close vicinity to polluted sites within postal code areas. Based on asbestos soil investigations, 293 sites were identified with asbestos waste material at the surface, of which 77% contained crocidolite fibres as well as chrysotile fibres. The 293 sites-at-risk varied from 5 m(2) to 2722 m(2) and were surrounded by 347 households within 100 m of these sites. Distance to the plant was associated with the number of sites (r=0.36), and with the number of households (r=0.52). However, categorization of postal code areas into low, intermediate or high likelihood of exposure to asbestos showed a modest agreement between the site and household approach. In the site approach a total of 2.3 million person-years at risk were estimated with an average exposure of 1674 fibres/m(3) and an expected 1.8 cases of malignant mesothelioma each year. The household approach resulted in estimates of 1.2 million person-years at risk, and 0.9 cases of malignant mesothelioma per year, respectively. This study illustrates that asbestos waste on the surface of roads and yards in an area with over 130,000 inhabitants may result in long-term exposure to asbestos that will cause several cases of malignant mesothelioma each year. Although distance to plant, number of polluted sites and number of exposed household were associated, the modest agreement among these measures of exposure indicate that the exposure assessment strategy chosen in a particular study may result in considerable misclassification. Without detailed information on individual behaviour within the polluted area, it is difficult to show that a more individually oriented approach will perform better than an ecological approach.

In plain English

This study estimated, rather than counted, mesothelioma risk from asbestos waste in the rural Dutch municipality of Hof van Twente. An asbestos cement plant gave residents waste containing chrysotile, crocidolite and amosite to harden dirt tracks, yards and driveways from 1935 to 1974. Of 416 polluted sites investigated, 293 had asbestos waste at the surface. At these sites, 77% of samples contained crocidolite as well as chrysotile. The 293 sites ranged from 5 to 2722 m2 and had 347 households within 100 m. The authors compared two ways of estimating exposure by postal code area: counting polluted sites, or counting nearby households. The two agreed only modestly (weighted kappa 0.37). The site approach gave 2.3 million person-years at risk, at average exposure below 1674 fibres/m3, and an estimated 1.8 extra cases of malignant mesothelioma per year (maximum 9.6). The household approach gave 1.2 million person-years and 0.9 cases per year (maximum 5.2). The authors concluded that such waste may cause a couple of cases each year. They also concluded that the choice of exposure method may cause considerable misclassification. They judged underestimation of exposure more likely than overestimation.

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: Exposure assessment and modelled risk assessment by postal code area, comparing a site-based approach with a household-based approach; expected mesothelioma cases were calculated from a published risk model, not observed
• Who was studied: Residents of the rural municipality Hof van Twente (largest village Goor) and surrounding postal code areas, where 416 asbestos-polluted sites were investigated during 2003–2007; a dynamic cohort of residents for 1960–2007 was modelled for a region of about 130,000 inhabitants
• Exposure: Environmental exposure to friable and non-friable asbestos waste (chrysotile, crocidolite and amosite) from an asbestos cement plant, given to residents to harden dirt tracks, yards and driveways during 1935–1974
• Main results:
  • Of 416 polluted sites, 293 had asbestos waste at the surface; 67% of these 293 sites were dirt roads or yards used daily by inhabitants
  • At the surface sites, 77% of asbestos samples contained crocidolite as well as chrysotile, and 22% contained only chrysotile
  • The 293 sites ranged from 5 m2 to 2722 m2 and had 347 households within 100 m
  • Across postal code areas, distance to the plant was associated with the number of polluted sites (r = 0.36, P-value 0.06) and with the number of exposed households (r = 0.52, P-value 0.005)
  • Agreement between the site and household approaches in sorting postal code areas into low, intermediate and high exposure categories: Cohen's weighted kappa 0.37
  • The authors interpreted the modest agreement among exposure measures as meaning that the exposure assessment strategy chosen may result in considerable misclassification
  • Site approach: 2.3 million person-years at risk at average exposure below 1674 fibres/m3, giving an estimated additional 1.8 cases of malignant mesothelioma per year (maximum estimate 9.6 per year)
  • Household approach: 1.2 million person-years at risk
  • Household approach: an estimated 0.9 cases of malignant mesothelioma per year (maximum estimate 5.2 per year)
  • High exposure category, site approach: an estimated additional 78 cases of malignant mesothelioma (maximum 431) over the 48-year period of contamination
  • High exposure category, household approach: an estimated 42 cases (maximum 231) over the same period
• The authors' conclusion: The authors concluded that asbestos waste on the surface of roads and yards may result in long-term exposure of approximately 2000 fibres/m3, and that these concentrations will result in a couple of cases of malignant mesothelioma each year
• Limitations the authors state:
  • Asbestos emissions from the factory itself during its producing period could not be taken into account
  • Privately owned polluted sites were found only through voluntary notification by owners, so it is unknown how many sites were missed
  • The demographic make-up of the village of Goor was applied to all postal code areas
  • It is unknown whether exposure measured in the mid-1980s reflects conditions from 1960 onwards
  • The air concentration measured 5 m from a polluted road was used as a worst-case value for everyone within 100 m
  • Without information on residents' movement patterns, it could not be verified whether the household approach has less misclassification than the site approach
  • The authors considered it more likely that individual exposure was underestimated than overestimated

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile, Crocidolite, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Environmental Exposure, Friable, Crocidolite, Chrysotile, Malignant Mesothelioma.

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