The aftermath of asbestos prohibition in industry and its association with malignant mesothelioma in the south of Iran: An enduring predicament yet to be resolved

Our plain-English summary of The aftermath of asbestos prohibition in industry and its association with malignant mesothelioma in the south of Iran: An enduring predicament yet to be resolved, by A. Rezvani, R. Shahriarirad, S. Jahanshahi, et al (Health Science Reports, 2024).

The study

• Authors: A. Rezvani, R. Shahriarirad, S. Jahanshahi, D. Fouladi, M. Tavallali, B. Ziaian, M.J. Fallahi
• Journal: Health Science Reports
• Published: 2024;7(10):e70117
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Purpose: Malignant Mesothelioma (MM) is a rare malignancy of the serosa membranes with a high mortality rate and long latent period. The relationship between a group of mineral fibers known as asbestos and mesothelioma is now well accepted in which people can be exposed to these fibers by various means during their lifetime and has been its usage has banned in many countries, such as Iran, which announced its gradual elimination from 1999 over a period of 7 years by using safe substitutes. However, the mineral particles are able to sustain itself in the environment, air, water, and soil and on the other hand, symptoms may take up to half a century to develop in exposed individuals. Also, there remains a shortage of comprehensive investigation on the effects of asbestos exposure within the familial context (household or domestic exposure) or on individuals residing in proximity to asbestos mines or factories (environmental exposure). Based on the high number of MM cases in Iran, and also our hypothesis that residuals of asbestos in the environment and petroleum products may be the etiological factor for MM, we conducted this study to evaluate the clinic epidemiological features of MM in the south of Iran its relation to possible asbestos exposure.

Methods: In this study, we analyzed the demographic features and occupations of confirmed cases of MM in Shiraz, southern Iran along with the follow-up of the patients' disease from 2008 to 2018, while also comparing the features of our patients with a control group compromising of 105 non-MM patients.

Results: Among the 35 confirmed cases of MM, with an average age of 61 years, 9 (25.7%) were female, and 26 (74.3%) were male. During our assessment, 12 patients had already died, with a mean time of 11.26 months post-diagnosis. Our findings revealed a higher prevalence of MM among housekeepers and employees of oil companies. In comparison to the control group, individuals with occupational exposure and those residing near refinery locations were at a heightened risk of developing MM. However, based on regression analysis, only occupations associated with refineries exhibited a significant correlation with MM (p = 0.028; OR: 14.602; 95% CI: 1.328-160.499).

Conclusion: Both occupational and para-occupational exposure demonstrated a significant correlation with MM, whereas our regression analysis did not affirm geographical and environmental factors as contributors to MM. Despite the industry's prohibition of direct asbestos usage, the persistent existence of asbestos particles in the environment for decades, coupled with the long latency period of MM, warrants further investigation. Health authorities and policymakers should recognize this potential hazard, prompting an enhancement of early detection within at-risk groups.

© 2024 The Authors. Health Science Reports published by Wiley Periodicals LLC.

In plain English

This retrospective study at Namazi Hospital in Shiraz, southern Iran, compared 35 malignant mesothelioma patients diagnosed 2008 to 2018 with 105 controls of similar age and sex, mostly trauma or orthopedic patients. Of 47 patients found in hospital records, 12 could not be contacted. The study did not measure asbestos or identify the fiber types involved in participants' exposures. Of the patients, 26 were men and 9 were women, and median survival was 12 months (95% CI 11.42 to 12.57); the text says 12 had died, but Table 1 lists 23 deaths. Six patients (17.1%) and 1 control (1%) had worked for oil companies, which the authors counted as occupational exposure (odds ratio 21.51, 95% CI 2.49 to 185.95). Living near a refinery applied to 13 of 35 patients and 14 of 105 controls (odds ratio 3.84, 95% CI 1.58 to 9.33). When factors were analysed together, only occupational exposure remained significant (odds ratio 14.60, 95% CI 1.33 to 160.50). The authors concluded that occupational and household exposure correlated with mesothelioma, while their analysis did not confirm environmental factors.

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: Retrospective study of hospital records with a comparison (control) group, analysed with chi-square or Fisher's exact tests, odds ratios and logistic regression
• Who was studied: 35 patients with malignant mesothelioma confirmed by immunohistochemistry at Namazi Hospital, Shiraz, southern Iran, diagnosed 2008 to 2018. Of 47 identified, 12 were excluded because they had no contact information or did not respond. The 105 controls came from other departments and hospitals, were mainly trauma and orthopedic patients, and had a comparable age and sex distribution. Data came from phone calls to patients or, for patients who had died, close relatives. Follow-up ran to the end of 2022.
• Exposure: The study did not measure asbestos or identify the fiber types involved in participants' exposures. Exposures were inferred from previous occupation (ISCO-08 classification), with oil company employment treated as occupational exposure, and from living near a refinery. Living near a refinery was defined as living in houses located in the factories or in organizational and institutional housing of refinery and petrochemical companies, at most five kilometers away. Smoking and family history were also recorded.
• Main results:
  • Of the 35 mesothelioma patients, 9 (25.7%) were female and 26 (74.3%) were male. The mean age was 61.05 years.
  • The text says that among the mesothelioma patients, 12 (34%) had died and 23 (66%) were alive at the time of the study. Table 1 contradicts this: its mortality row lists 23 (65.7%) patients as positive and 12 (34.3%) as negative.
  • Median survival among the mesothelioma patients was 12 months (IQR 16; 95% CI 11.42 to 12.57).
  • 6 of 35 patients (17.1%) and 1 of 105 controls (1%) had worked for an oil company. The association was significant: OR 21.51 (95% CI 2.49 to 185.95), p = 0.001.
  • Living near a refinery applied to 13 patients (37.1% of patients) and 14 controls (13.3% of controls). Of the 27 people living near a refinery, 13 (48.1%) were patients. OR 3.84 (95% CI 1.58 to 9.33), p = 0.005.
  • In logistic regression including age, gender, smoking, living location relative to a refinery and occupation, occupational exposure versus nonoccupational exposure was significantly associated with mesothelioma: OR 14.60 (95% CI 1.33 to 160.50), p = 0.03. According to the authors, the regression did not confirm living location as a risk factor.
  • Smoking (active or passive) was reported by 16 patients and 40 controls. It was not significantly associated with mesothelioma (p = 0.433).
  • Housekeeper was the most frequent occupation among patients: 8 of 35 patients (22.9%) and 19 of 105 controls (18.1%).
  • No patient had a family history of mesothelioma.
• The authors' conclusion: The authors concluded that occupational and household exposure showed a significant correlation with mesothelioma, while their regression analysis did not confirm geographical and environmental factors as contributors. They wrote that environmental and domestic exposure risk remains a matter of debate needing further investigation.
• Limitations the authors state:
  • There was no detailed environmental assessment of asbestos particles, and the geographical radius influenced by refineries was not specified.
  • Clinical features, long-term survival, changes in latency period and duration of exposure were not documented, because they were not the focus of the study.

Topics

Medical terms in this study, explained in our Lexicon: Malignant Mesothelioma, Mineral Fiber, Mesothelioma, Asbestos Exposure, Environmental Exposure, Occupational Exposure, Take-home Exposure, Latency.

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