High risk of malignant mesothelioma and pleural plaques in subjects born close to ophiolites

Our plain-English summary of High risk of malignant mesothelioma and pleural plaques in subjects born close to ophiolites, by M. Bayram, I. Dongel, N.D. Bakan, et al (Chest, 2013).

The study

• Authors: M. Bayram, I. Dongel, N.D. Bakan, H. Yalççn, R. Cevit, P. Dumortier, B. Nemery
• Journal: Chest
• Published: 2013;143(1):164-171
• Cited by: 31 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Ophiolites, a special sequence of geologic rock units, are known sources of naturally occurring asbestos. The aim of this study was to test whether the occurrence of malignant mesothelioma (MM) or pleural plaques (PPs) in the province of Sivas, Turkey, is determined by the proximity of the patient's birthplace to ophiolites and, if so, to establish the magnitude of the risk.

Methods: The birthplaces of patients with MM or PPs (cases) and patients with prostate or breast cancer (control subjects), diagnosed between 2000 and 2010 and identified through a mandatory cancer registry or from hospital records (PPs), were located on a geologic map, and the nearest distance to ophiolites was measured. The relation of MM or PPs with distance to ophiolites was analyzed by logistic regression. Samples of soil and house plaster were determined by x-ray diffraction.

Results: Patients with MM (n = 100) or PPs (n = 133) were born significantly nearer to ophiolites (median distance, 4.5 km for men, 0 km for women) than were patients with prostate cancer (n = 161) or breast cancer (n = 139) (median distance, 20 km for both). ORs were 1.6 (men) ( P < .001) and 2.0 (women) ( P < .001) for every 5-km decrease in the distance of birthplace to ophiolites for MM, compared with prostate and breast cancer, respectively.

Conclusion: In this area without substantial industrial asbestos use, there is an association between the occurrence of mesothelioma (and of PPs) and the proximity of the subject's birthplace to ophiolites.

In plain English

This case-control study tested whether people diagnosed between 2000 and 2010 in Sivas province, Turkey, with malignant mesothelioma or pleural plaques had been born closer to ophiolites, rock formations that are natural sources of asbestos, than people with prostate or breast cancer. The authors measured the distance from each birthplace to the nearest ophiolite for 100 mesothelioma, 133 pleural plaque, 161 prostate cancer and 139 breast cancer patients. The median distance was 0 km for women and 4.5 km for men with mesothelioma or plaques, against 20 km for the cancer patients. For each 5 km closer to ophiolites, the odds ratio for mesothelioma was 1.68 in men (95% confidence interval 1.39 to 2.04, compared with prostate cancer) and 2.15 in women (1.69 to 2.74, compared with breast cancer). Results were similar when only people born in rural areas were analyzed. Soil and wall plaster samples contained chrysotile-type serpentine minerals. The authors concluded there is an association with birthplace proximity. They noted that one study cannot show cause and that exposure duration and occupational exposure could not be assessed.

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: Case-control study using cancer registry and hospital records, with mapping of birthplaces and logistic regression; soil and plaster samples analyzed by x-ray diffraction
• Who was studied: Patients in Sivas province, Turkey, diagnosed 2000 to 2010 whose birthplace could be found. Cases were 100 with malignant mesothelioma (55 men) and 133 with pleural plaques (80 men). Controls were 161 with prostate cancer (men) and 139 with breast cancer (women). Mesothelioma and cancer patients came from the provincial cancer registry, and pleural plaque patients from two hospital databases.
• Exposure: Naturally occurring asbestos from ophiolites, measured as the straight-line distance from birthplace to the nearest ophiolite area (0 km if born inside one), in 5-km units. The authors describe the fibers as chrysotile and tremolite, and identify locally made wall plaster as the probable main route of exposure.
• Main results:
  • Median distance from birthplace to ophiolites was 0 km for women with mesothelioma or pleural plaques and 4.5 km for men with these conditions. It was 20 km for patients with prostate or breast cancer.
  • Odds ratios were calculated for each 5 km closer to ophiolites. For men compared with prostate cancer patients: mesothelioma 1.68 (95% CI 1.39-2.04) and pleural plaques 1.69 (1.43-2.06). For women compared with breast cancer patients: mesothelioma 2.15 (1.69-2.74) and pleural plaques 1.93 (1.58-2.37). For all patients: mesothelioma 1.88 (1.63-2.16) and pleural plaques 1.79 (1.59-2.03). All had p less than 0.001.
  • In a reanalysis limited to people born in rural areas (excluding Sivas city), odds ratios for mesothelioma were 1.41 (1.1-1.81) for men and 1.97 (1.37-2.83) for women. For pleural plaques they were 1.28 (1.05-1.56) for men and 1.46 (1.14-1.88) for women.
  • Patients with mesothelioma were not born closer to or farther from ophiolites than patients with pleural plaques.
  • When the analysis was repeated using only the 79 mesothelioma patients with a detailed pathology report, the odds ratios were slightly lower in both sexes but remained statistically significant.
  • X-ray diffraction of soil and plaster samples found chrysotile-type serpentine minerals. Plaster from the home of a man who died of malignant mesothelioma in 2008 contained 95% serpentine.
  • Median survival of the mesothelioma patients was 8.1 months.
• The authors' conclusion: The authors concluded that, in this area without substantial industrial asbestos use, mesothelioma and pleural plaques are associated with being born close to ophiolites. They added that a single epidemiologic study cannot show that such an association is causal.
• Limitations the authors state:
  • Duration of exposure and cumulative fiber exposure could not be estimated, because only place of birth was used and full residential and work histories were not reconstructed.
  • Occupational exposures could not be taken into account because the records were inadequate.
  • Patients born in rural Sivas who were diagnosed after moving out of the province would not be in the Sivas registry, which may have led to underestimation of the problem.
  • Pleural plaques were diagnosed by chest radiograph or CT scan, not confirmed by tissue examination.
  • The control groups may not have been ideal, because breast and prostate cancer rates may differ between urban and rural areas.
  • Genetic susceptibility as a contributing factor could not be excluded.
  • A single epidemiologic study cannot show that the association is causal.

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: Mesothelioma, Pleural Plaques, Ophiolite, naturally occurring asbestos (NOA), Cancer Registry, X-Ray Diffraction (XRD).

Related studies

• Is living close to ophiolites related to asbestos related diseases? Cross-sectional study — I. Döngel, M. Bayram, et al. (2013)
• Observations on environmental asbestos exposure in a high risk area — U. Sahin, O. Ozturk, et al. (2009)
• Residential proximity to naturally occurring asbestos: health risk or ecologic fallacy? — C.A. Brodkin, J.R. Balmes, et al. (2006)
• Residential proximity to naturally occurring asbestos and mesothelioma risk in California — X.L. Pan, H.W. Day, et al. (2005)
• Serum biomarkers in patients with mesothelioma and pleural plaques and healthy subjects exposed to naturally occurring asbestos — M. Bayram, I. Dongel, et al. (2014)
• Non-occupational exposure to asbestos and risk of pleural mesothelioma: review and meta-analysis — G.M. Marsh, A.S. Riordan, et al. (2017)

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