Environmental asbestos exposure and clustering of malignant mesothelioma in community: a spatial analysis in a population-based case-control study

Our plain-English summary of Environmental asbestos exposure and clustering of malignant mesothelioma in community: a spatial analysis in a population-based case-control study, by C. Airoldi, C. Magnani, F. Lazzarato, et al (Environmental Health, 2021).

The study

• Authors: C. Airoldi, C. Magnani, F. Lazzarato, D. Mirabelli, S. Tunesi, D. Ferrante
• Journal: Environmental Health
• Published: 2021;20(1):103
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Neighborhood exposure to asbestos increases the risk of developing malignant mesothelioma (MM) in residents who live near asbestos mines and asbestos product plants. The area of Casale Monferrato (Northwest Italy) was impacted by several sources of asbestos environmental pollution, due to the presence of the largest Italian asbestos cement (AC) plant. In the present study, we examined the spatial variation of MM risk in an area with high levels of asbestos pollution and secondly, and we explored the pattern of clustering.

Methods: A population-based case-control study conducted between 2001 and 2006 included 200 cases and 348 controls. Demographic and occupational data along with residential information were recorded. Bivariate Kernel density estimation was used to map spatial variation in disease risk while an adjusted logistic model was applied to estimate the impact of residential distance from the AC plant. Kulldorf test and Cuzick Edward test were then performed.

Results: One hundred ninety-six cases and 322 controls were included in the analyses. The contour plot of the cases to controls ratio showed a well-defined peak of MM incidence near the AC factory, and the risk decreased monotonically in all directions when large bandwidths were used. However, considering narrower smoothing parameters, several peaks of increased risk were reported. A constant trend of decreasing OR with increasing distance was observed, with estimates of 10.9 (95% CI 5.32-22.38) and 10.48 (95%CI 4.54-24.2) for 0-5 km and 5-10 km, respectively (reference > 15 km). Finally, a significant (p < 0.0001) excess of cases near the pollution source was identified and cases are spatially clustered relative to the controls until 13 nearest neighbors.

Conclusions: In this study, we found an increasing pattern of mesothelioma risk in the area around a big AC factory and we detected secondary clusters of cases due to local exposure points, possibly associated to the use of asbestos materials.

© 2021. The Author(s).

In plain English

This population-based case-control study used 2001 to 2006 data from Casale Monferrato, Italy. It examined whether pleural mesothelioma risk varied with home distance from the Eternit asbestos-cement plant, and whether cases clustered. Main analyses included 196 cases and 322 controls. Each person's location was their longest-held home within the health authority area, excluding the 20 years before diagnosis. Compared with people living beyond 15 km, and adjusted for age, sex and interview type, odds ratios were 10.91 (95% CI 5.32 to 22.38) at 0 to 5 km and 10.48 (4.54 to 24.2) at 5 to 10 km. Among people without occupational exposure, the 0 to 5 km odds ratio was 13.73 (4.57 to 41.32). A scan test found a cluster around the town with 168 cases and 146 controls. Finer mapping showed smaller peaks, but this result was not statistically significant (p = 0.656). The authors concluded that the factory had a large impact on mesothelioma incidence in the area, with secondary clusters possibly associated with asbestos materials. They noted lower control response may have caused selection bias, but re-estimated associations were unchanged, suggesting no bias occurred.

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 with spatial (mapping and clustering) analysis of residential locations
• Who was studied: Residents of the Casale Monferrato Local Health Authority area (60 towns and villages, northwest Italy). The study identified 223 eligible pleural mesothelioma cases and 552 controls matched on age and sex. Of these, 200 cases and 348 controls were interviewed. The main analysis (20-year lag) included 196 cases and 322 controls.
• Exposure: The exposure was distance from the Eternit asbestos-cement plant (active 1907 to 1986), measured from each person's longest-held residence within the Local Health Authority area. The 20 years before diagnosis were excluded. The article's background states that in 1981 the company reported using 15,000 tons of asbestos (10% crocidolite). Models were also adjusted for expert-estimated occupational and domestic asbestos exposure.
• Main results:
  • All subjects, adjusted for age, sex and type of interview, with more than 15 km as reference: odds ratio 10.91 (95% CI 5.32 to 22.38) for 0 to 5 km, 10.48 (4.54 to 24.2) for 5 to 10 km, and 2.2 (0.9 to 5.33) for 10 to 15 km.
  • All subjects: 64.3% of cases had their longest-held residence within 5 km of the plant, compared with 34.5% of controls.
  • All subjects: odds ratio per 1 km increase in distance was 0.87 (95% CI 0.84 to 0.91), adjusted for age, sex and type of interview.
  • Non-occupationally exposed subjects (82 cases and 181 controls), with more than 15 km as reference: odds ratio 13.73 (95% CI 4.57 to 41.32) for 0 to 5 km and 8.5 (2.29 to 31.61) for 5 to 10 km.
  • No controls lived within 500 m of the plant, while 8 cases did (3 of them without occupational exposure).
  • The Kulldorf test identified an area with a significant excess of cases (p = 0.001). It was centered 1.71 km south of the plant, had a radius of 8.64 km, and contained 168 cases and 146 controls.
  • With wide smoothing (10 and 20 km bandwidths), risk peaked near the factory, and the global test of clustering gave p = 0.001. With narrow smoothing (2 and 4 km), the map showed several local peaks. This narrow-smoothing result was not statistically significant (p = 0.656), and most local clusters were based on few subjects.
  • The Cuzick Edward test indicated that cases clustered relative to controls up to 13 nearest neighbors.
  • A sensitivity analysis using a 10-year lag (198 cases, 331 controls) showed no relevant differences from the main analyses.
• The authors' conclusion: The authors concluded that the asbestos-cement factory had a large impact on mesothelioma incidence in the area, with clustering of cases. They also concluded that there were secondary clusters due to local exposure points, possibly associated with the use of asbestos materials.
• Limitations the authors state:
  • Non-response was higher among controls. This affected study power and may have led to selection bias. The authors re-estimated the association between asbestos exposure and mesothelioma and found it unchanged, which they say suggests that no bias actually occurred.
  • The main models adjusted only for occupational and domestic asbestos exposure, not for the environmental component. The authors report that adding the environmental component gave similar distance estimates.
  • The narrow-smoothing map result should be taken with caution, because it was not statistically significant and most local clusters were based on few subjects.
  • Changing distance thresholds and covariates gave consistent results, except for the raised incidence model.

Topics

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

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

Related studies

• The relationship between malignant mesothelioma and an asbestos cement plant environmental risk: a spatial case-control study in the city of Bari (Italy) — M. Musti, A. Pollice, et al. (2009)
• Epidemiological patterns of asbestos exposure and spatial clusters of incident cases of malignant mesothelioma from the Italian national registry — M. Corfiati, A. Scarselli, et al. (2015)
• Investigation of occupational and environmental causes of respiratory cancers (ICARE): a multicenter, population-based case-control study in France — D. Luce, I. Stücker, et al. (2011)
• Pleural mesothelioma and occupational and non-occupational asbestos exposure: a case-control study with quantitative risk assessment — D. Ferrante, D. Mirabelli, et al. (2016)
• Peritoneal mesothelioma and asbestos exposure: a population-based case-control study in Lombardy, Italy — D. Consonni, C. Calvi, et al. (2019)
• Cancer incidence in Priolo, Sicily: a spatial approach for estimation of industrial air pollution impact — L. Fazzo, M. Carere, et al. (2016)

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