Modeling mesothelioma risk associated with environmental asbestos exposure

Our plain-English summary of Modeling mesothelioma risk associated with environmental asbestos exposure, by M.M. Maule, C. Magnani, P. Dalmasso, et al (Environmental Health Perspectives, 2007).

The study

• Authors: M.M. Maule, C. Magnani, P. Dalmasso, D. Mirabelli, F. Merletti, A. Biggeri
• Journal: Environmental Health Perspectives
• Published: 2007;115(7):1066-71
• Cited by: 83 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Environmental asbestos pollution can cause malignant mesothelioma, but few studies have involved dose-response analyses with detailed information on occupational, domestic, and environmental exposures.

Objectives: In the present study, we examined the spatial variation of mesothelioma risk in an area with high levels of asbestos pollution from an industrial plant, adjusting for occupational and domestic exposures.

Methods: This population-based case-control study included 103 incident cases of mesothelioma and 272 controls in 1987-1993 in the area around Casale Monferrato, Italy, where an important asbestos cement plant had been active for decades. Information collected included lifelong occupational and residential histories. Mesothelioma risk was estimated through logistic regression and a mixed additive-multiplicative model in which an additive scale was assumed for the risk associated with both residential distance from the plant and occupational exposures. The adjusted excess risk gradient by residential distance was modeled as an exponential decay with a threshold.

Results: Residents at the location of the asbestos cement factory had a relative risk for mesothelioma of 10.5 [95% confidence interval (CI), 3.8-50.1), adjusted for occupational and domestic exposures. Risk decreased rapidly with increasing distance from the factory, but at 10-km the risk was still 60% of its value at the source. The relative risk for occupational exposure was 6.0 (95% CI, 2.9-13.0), but this increased to 27.5 (95% CI, 7.8-153.4) when adjusted for residential distance.

Conclusions: This study provides strong evidence that asbestos pollution from an industrial source greatly increases mesothelioma risk. Furthermore, relative risks from occupational exposure were underestimated and were markedly increased when adjusted for residential distance.

In plain English

This population-based case-control study looked at pleural malignant mesothelioma around Casale Monferrato, Italy. An asbestos cement plant there, using chrysotile and crocidolite, operated from 1907 to 1985. The study included 103 cases diagnosed from 1987 to 1993 and 272 controls, with lifelong work and residence histories. For the 97 cases and 250 controls whose homes could be mapped, distance from the longest-held home (excluding the last 20 years) to the plant stood in for environmental exposure. The authors estimated a relative risk of 10.5 (95% CI 3.8 to 50.1) for hypothetical residents at the plant site, adjusted for work and household exposures. This fell to 4.2 at 10 km. Work in the asbestos cement industry had a relative risk of 6.0 (95% CI 2.9 to 13.0), rising to 27.5 (95% CI 7.8 to 153.4) after adjusting for residential distance. The authors said this showed occupational risk had been underestimated. Cases were also spatially clustered. The authors concluded the study gave strong evidence of increased mesothelioma risk from industrial asbestos pollution. They noted the small number of subjects, and that air was never measured in the 1950s and 1960s.

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: Population-based case-control study of pleural malignant mesothelioma
• Who was studied: 103 of 116 eligible cases and 272 of 330 eligible controls were interviewed. They were residents of Casale Monferrato, Italy, and the surrounding area (roughly 52 towns, over 100,000 inhabitants), with pleural mesothelioma diagnosed 1 January 1987 to 30 June 1993.
• Exposure: Environmental exposure came from an asbestos cement plant active 1907 to 1985. The authors inferred that its airborne emissions included chrysotile and crocidolite. Exposure was measured as distance from the longest-held residence (excluding the last 20 years) to the plant. Also studied: work in the asbestos cement industry, household (domestic) asbestos materials, and relatives' work in the asbestos cement industry.
• Main results:
  • Geographic coordinates of the longest-held residence were available for 97 cases (94%) and 250 controls (92%).
  • From the distance model, hypothetical residents living at the asbestos cement plant (zero distance) had a relative risk of 10.5 (95% CI, 3.8 to 50.1), adjusted for occupational and domestic exposures.
  • At 10 km from the plant, the estimated relative risk had fallen from 10.5 to 4.2.
  • In distance bands, risk decreased with increasing distance from the plant, with a spatial trend of p less than 0.0001.
  • The 3 to 5 km band had 16 cases (16.5%) and 13 controls (5.2%). Compared with residence more than 15 km away, its odds ratio was 14.3 (95% CI 4.7 to 43.6) adjusted for age and sex, and 12.1 (95% CI 3.9 to 37.9) fully adjusted.
  • Restricting the distance analysis to people without occupational exposure did not significantly change the risk estimates.
  • 28 cases and 14 controls had worked in the asbestos cement industry. In the logistic model, this gave an odds ratio of 7.1 (95% CI, 3.5 to 14.3).
  • In the mixed model, the relative risk for asbestos cement occupation was 6.0 (95% CI, 2.9 to 13.0) without distance adjustment. With adjustment for residential distance it was 27.5 (95% CI, 7.8 to 153.4).
  • The authors interpreted this increase as showing that the relative risk from occupational exposure had been underestimated.
  • Domestic exposure was reported by 51 cases (49.5%) and 98 controls (36.2%). Its odds ratio was 1.7 (95% CI 1.1 to 2.7) adjusted for age and sex, and 1.5 (95% CI 0.9 to 2.4) after also adjusting for asbestos cement occupation.
  • Relatives' asbestos cement occupation was reported by 24 cases (23.3%) and 22 controls (8.1%). Its odds ratio was 3.4 (95% CI 1.8 to 6.5) adjusted for age and sex, and 2.4 (95% CI 1.2 to 4.8) after also adjusting for asbestos cement occupation.
  • Cases were spatially clustered, with aggregations of average size about 300 m (Diggle's D-test p = 0.016).
• The authors' conclusion: The authors concluded that the study provides strong evidence of increased mesothelioma risk from environmental asbestos pollution from an industrial source.
• Limitations the authors state:
  • The study was small (few subjects).
  • Environmental asbestos was never measured in the 1950s and 1960s, when the plant was fully active and the most relevant exposures presumably occurred.
  • Using asbestos cement work as the proxy for all occupational exposure favored specificity over sensitivity.
  • The distance model left residual variability unexplained.

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelioma, Asbestos Exposure, Malignant Mesothelioma, Dose-response relationship, Environmental Exposure, Case-Control Study, Casale Monferrato, Asbestos-Cement.

Related studies

• An air quality data analysis system for interrelating effects, standards, and needed source reductions: Part 13--Applying the EPA Proposed Guidelines for Carcinogen Risk Assessment to a set of asbestos lung cancer mortality data — R.I. Larsen (2003)
• Increased risk of malignant mesothelioma of the pleura after residential or domestic exposure to asbestos: a case-control study in Casale Monferrato, Italy — C. Magnani, P. Dalmasso, et al. (2001)
• Risk-based indicators of Canadians' exposures to environmental carcinogens — E. Setton, P. Hystad, et al. (2013)
• Mineral-fluid interaction in the lungs: insights from reaction-path modeling — S.A. Wood, A.E. Taunton, et al. (2006)
• Pleural mesothelioma and occupational and non-occupational asbestos exposure: a case-control study with quantitative risk assessment — D. Ferrante, D. Mirabelli, et al. (2016)
• Environmental exposure to asbestos and risk of pleural mesothelioma: review and meta-analysis — V. Bourdès, P. Boffetta, et al. (2000)

Browse more research in Environmental Health Perspectives, or return to medical research.