Epidemiology of Environmental Exposure and Malignant Mesothelioma

Our plain-English summary of Epidemiology of Environmental Exposure and Malignant Mesothelioma, by B. Liu, M. van Gerwen, S. Bonassi, et al (Journal of Thoracic Oncology, 2017).

The study

• Authors: B. Liu, M. van Gerwen, S. Bonassi, E. Taioli, International Association for the Study of Lung Cancer Mesothelioma Task Force
• Journal: Journal of Thoracic Oncology
• Published: 2017;12(7):1031-1045
• Type of article: Review
• Cited by: 77 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Although the association between exposure to asbestos and malignant mesothelioma (particularly malignant pleural mesothelioma) has been well established, the health impact of environmental exposure (EE) to asbestos has been less studied. This review summarizes the most recent studies on the association between malignant mesothelioma and EE with asbestos to identify features associated with EE and quantify the association with malignant mesothelioma. There were 44 studies from 18 countries that met our selection criteria, with a considerable amount of heterogeneity in their study design, measures of exposure, and health outcomes. The male-to-female ratio was close to or less than 1 and generally lower than the ratio reported when both occupational and environmental exposures were considered. Although recent studies have continued to improve our understanding of environmental exposure to asbestos, challenges remain. We have highlighted a few new research directions, such as a need for reliable matrices to identify common and less recognized types of EE, asbestos biomarker studies specifically focusing on EE, and research on populations and geographic areas that have not been previously studied.

Copyright © 2017 International Association for the Study of Lung Cancer. Published by Elsevier Inc. All rights reserved.

In plain English

This was a review of published research, not a new study. In December 2016 the authors searched PubMed for English-language studies from the previous five years on malignant mesothelioma and environmental (non-occupational) asbestos exposure, and kept 44 studies from 18 countries. They grouped environmental exposure into four kinds: naturally occurring asbestos, living near asbestos industry or mines, household exposure through workers' families, and other non-work exposures such as home renovation. Because the studies differed greatly, they did not combine results in a meta-analysis. Sixteen studies scored below average on a quality checklist. Across the studies, the male-to-female ratio among cases with environmental exposure was often close to or below 1. In the national registries cited, environmental exposure accounted for about 4% of cases in Japan, 8% in Italy and 9% in France. Studies of neighborhood exposure reported lower risk with greater distance from the source. Many cases, mostly women, had no identifiable asbestos source. The authors concluded that challenges remain. They called for better exposure assessment, biomarker studies focused on environmental exposure, and research in understudied populations and countries.

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 studies identified through a PubMed search, with a quality assessment of each study but no meta-analysis
• Who was studied: 44 published studies (from an initial 1960 records, 340 of them from the past 5 years in English) conducted in 18 countries, including Italy, Turkey, Australia, France and its territories, Egypt, Japan, Mexico, the UK, the Netherlands, Korea, Greece, China, South Africa, Spain, Canada, Denmark and the US
• Exposure: Environmental (all non-occupational) asbestos exposure, grouped into four categories: naturally occurring asbestos (NOA) in areas without asbestos industry; neighborhood exposure near industrial or mining sources; household exposure of family members of asbestos workers; and other non-occupational exposure such as hobbies, do-it-yourself home maintenance and renovation, or living in urban or polluted areas. Fiber types reported in the reviewed studies included crocidolite, chrysotile, amosite, tremolite, erionite, fluoro-edenite and others.
• Main results:
  • Across the reviewed studies, the male-to-female ratio among mesothelioma cases with environmental exposure was often close to or less than 1. It was generally lower than ratios reported when all exposure types were considered.
  • In the large national registries cited, the share of mesothelioma cases with environmental exposure was approximately 4% in Japan, 8% in Italy and 9% in France.
  • Studies of neighborhood exposure reported that greater distance from the source and shorter exposure duration were associated with lower mesothelioma risk. In one reviewed study (Tarrés et al., Barcelona, Spain), the mesothelioma incidence rate ratio was 12.92 (95% CI 10.77-15.33) for people living less than 500 m from an asbestos cement plant. It fell to 0.70 and 0.23 for those living 500-2000 m and more than 2000 to 10000 m away.
  • In one reviewed case-control study (Ferrante et al.), the odds ratios for pleural mesothelioma, compared with background exposure (below 0.1 fiber/ml-years), were:
• 3.8 (95% CI 1.3-11.1) for 0.1 to under 1 fiber/ml-years
• 14.8 (95% CI 5.7-38.6) for 1 to under 10 fiber/ml-years
• 23.3 (95% CI 2.9-186.9) for 10 or more fiber/ml-years
  • A considerable share of cases in the reviewed studies had no identifiable source of asbestos exposure, and these were mostly women. For example, in a British case-control study (Rake et al.), 14% of male and 62% of female cases could not be attributed to occupational or domestic asbestos exposure.
  • Few biomarker studies focused specifically on environmental exposure. The reviewed ones were from Turkey and looked at markers such as osteopontin, mesothelin, SMRP and TRX.
• The authors' conclusion: The authors concluded that recent studies have improved understanding of mesothelioma linked to environmental asbestos exposure, but challenges remain. They called for:
• reliable exposure matrices that use indicators such as latency and age at first exposure and at diagnosis
• biomarker studies focused on environmental exposure
• research on less recognized exposure sources and on understudied populations and countries
• Limitations the authors state:
  • The reviewed studies differed so much in design, exposure measures and health outcomes that no quantitative meta-analysis was done.
  • Study quality varied: quality scores ranged from -2.7 to 1.4, and 16 studies scored below average.
  • The fiber type that residents were exposed to was often inferred from the minerals known in the area rather than measured.
  • Traditional exposure questionnaires, which focus on work exposure, may not capture all sources of environmental exposure.

Topics

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

Medical terms in this study, explained in our Lexicon: Epidemiology, Environmental Exposure, Malignant Mesothelioma, Pleural Mesothelioma, Biomarker.

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