Environmental exposure to asbestos and risk of pleural mesothelioma: review and meta-analysis

Our plain-English summary of Environmental exposure to asbestos and risk of pleural mesothelioma: review and meta-analysis, by V. Bourdès, P. Boffetta, P. Pisani (European Journal of Epidemiology, 2000).

The study

• Authors: V. Bourdès, P. Boffetta, P. Pisani
• Journal: European Journal of Epidemiology
• Published: 2000;16(5):411-7
• Type of article: Review
• Cited by: 128 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

A number of epidemiological studies have addressed the risk of pleural mesothelioma from environmental (household and neighborhood) exposure to asbestos, but no overall risk estimate is available. We reviewed the epidemiological studies on risk of pleural mesothelioma and household or neighborhood exposure to asbestos. We identified eight relevant studies; most were conducted in populations with relatively high exposure levels. We combined the risk estimates in a meta-analysis based on the random-effects model. The relative risks (RRs) of pleural mesothelioma for household exposure ranged between 4.0 and 23.7, and the summary risk estimate was 8.1 (95% confidence interval [CI]: 5.3-12). For neighborhood exposure, RRs ranged between 5.1 and 9.3 (with a single RR of 0.2) and the summary estimate was 7.0 (95% CI: 4.7-11). This review suggests a substantial increase in risk of pleural mesothelioma following high environmental exposure to asbestos; however, the available data are insufficient to estimate the magnitude of the excess risk at the levels of environmental exposure commonly encountered by the general population in industrial countries.

In plain English

This article was a review and meta-analysis. The authors pooled results from published studies of pleural mesothelioma in people exposed to asbestos outside work. The exposure was either at home (such as dust brought home on a worker's clothes) or from living near mines, asbestos factories or natural sources. They found eight eligible studies, from South Africa, Canada, the USA, Italy, the UK and Turkey. Across five studies of household exposure, the combined relative risk was 8.1 (95% confidence interval 5.3 to 12). Across six studies of neighborhood exposure, it was 7.0 (95% confidence interval 4.7 to 11). Risk appeared higher with amphibole than with chrysotile exposure, but the authors said this difference was not statistically significant. The authors concluded that high environmental exposure was linked to a several-fold increase in risk. They said the data were insufficient to estimate risk at the lower levels most people in industrial countries encounter. Because the studies involved relatively high exposures, the authors said the results likely overestimate risk for people without a specific exposure source.

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: Review of published epidemiological studies with a quantitative meta-analysis (random-effects model). The authors focused on results for women where available.
• Who was studied: Eight studies giving results on pleural mesothelioma: two from the USA or Canada, two from the UK, two from Italy, one from South Africa and one from Turkey. Four were ecological studies, one was a cohort study and three were case-control studies.
• Exposure: Non-occupational asbestos exposure, either household (for example dust brought home on workers' clothes, or tremolite-contaminated whitewash) or neighborhood (living near mines, asbestos cement plants or industrial sources). Two studies involved mainly amphibole exposure, two mainly chrysotile, and four had no clear predominant fiber type.
• Main results:
  • Household exposure (five studies): the combined relative risk of pleural mesothelioma was 8.1 (95% CI 5.3 to 12).
  • Household exposure: relative risks in the individual studies ranged from 4.0 to 23.7.
  • Neighborhood exposure (six studies): relative risks in the individual studies ranged from 5.1 to 9.3, with one study at 0.2. The combined relative risk was 7.0 (95% CI 4.7 to 11).
  • Mainly chrysotile studies: the combined relative risk was 1.5 (95% CI 0.04 to 53) for neighborhood exposure (two studies) and 4.0 (95% CI 0.8 to 20) for household exposure (one study). The authors described the increase for neighborhood chrysotile exposure as not significant.
  • Mainly amphibole studies: the combined relative risk was 8.7 (95% CI 6.7 to 11) for neighborhood exposure (one study) and 21 (95% CI 2.8 to 157) for household exposure (one study).
  • The authors said the higher risk with amphiboles than with chrysotile may also hold for environmentally exposed populations, but the difference was not statistically significant and should be interpreted with caution.
  • For neighborhood exposure, the combined estimate did not seem to depend on study design. Results also did not change by mortality versus incidence or by gender (details not shown).
  • Only two studies reported on peritoneal mesothelioma after environmental exposure. These were not part of the meta-analysis.
• The authors' conclusion: The authors concluded that their meta-analysis showed a several-fold increase in mesothelioma risk among people with high environmental asbestos exposure. They said the available data were insufficient to estimate the risk at the environmental exposure levels most people in industrial countries encounter. They considered it plausible that such low levels cause a sizable number of cases, but said a precise estimate cannot rest on this meta-analysis alone.
• Limitations the authors state:
  • The included studies involved relatively high exposures, so the results likely overestimate risk for residents of industrialized countries without a specific exposure source.
  • No epidemiological studies were available on more common situations, such as exposure in buildings, in schools or in the general urban environment.
  • The studies looked at different sources of environmental exposure, which makes the results harder to interpret.
  • Possible publication bias. The authors reported that their plot of study results did not suggest that small negative studies were missing.
  • Possible confounding by unrecognized occupational asbestos exposure, particularly where exposure information came from proxies.
  • Possible misclassification of the diagnosis, especially when it was based on death certificates.
  • Information on cumulative exposure was not available from most studies.
  • Ecological studies lack individual information on asbestos exposure and on potential confounders.
  • For household exposure, analysis by fiber type was limited because all but one study were in areas with predominant or concomitant amphibole exposure.

Topics

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

Medical terms in this study, explained in our Lexicon: Environmental Exposure, Pleural Mesothelioma, Meta-Analysis, Relative Risk, confidence interval.

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