Occupational and environmental exposures and cancers in developing countries

Our plain-English summary of Occupational and environmental exposures and cancers in developing countries, by D. Hashim, P. Boffetta (Annals of Global Health, 2014).

The study

• Authors: D. Hashim, P. Boffetta
• Journal: Annals of Global Health
• Published: 2014;80(5):393-411
• Type of article: Review
• Cited by: 95 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Over the past few decades, there has been a decline in cancers attributable to environmental and occupational carcinogens of asbestos, arsenic, and indoor and outdoor air pollution in high-income countries. For low- to middle-income countries (LMICs), however, these exposures are likely to increase as industrialization expands and populations grow.

Objective: The aim of this study was to review the evidence on the cancer risks and burdens of selected environmental and occupational exposures in less-developed economies.

Findings: A causal association has been established between asbestos exposure and mesothelioma and lung cancer. For arsenic exposure, there is strong evidence of bladder, skin, lung, liver, and kidney cancer effects. Women are at the highest risk for lung cancer due to indoor air pollution exposure; however, the carcinogenic effect on the risk for cancer in children has not been studied in these countries. Cancer risks associated with ambient air pollution remain the least studied in LMICs, although reported exposures are higher than World Health Organization, European, and US standards. Although some associations between lung cancer and ambient air pollutants have been reported, studies in LMICs are weak or subject to exposure misclassification. For pulmonary cancers, tobacco smoking and respiratory diseases have a positive synergistic effect on cancer risks.

Conclusions: A precise quantification of the burden of human cancer attributable to environmental and occupational exposures in LMICs is uncertain. Although the prevalence of carcinogenic exposures has been reported to be high in many such countries, the effects of the exposures have not been studied due to varying country-specific limitations, some of which include lack of resources and government support.

Copyright © 2014 Icahn School of Medicine at Mount Sinai. Published by Elsevier Inc. All rights reserved.

In plain English

This article was a review, not a new study. The authors gathered published research on cancer from four exposures in low- and middle-income countries: asbestos, arsenic, indoor air pollution and outdoor air pollution. They emphasized large epidemiological studies and recent global burden estimates. On asbestos, the review stated that chrysotile accounts for more than 95% of the asbestos used worldwide. In one cited Chinese study, asbestos factory workers had a risk of lung cancer death more than three times that of control workers (HR 3.31; 95% CI 1.60-6.87). Other studies covered Chinese chrysotile miners, Taiwanese shipbreaking workers, and a Turkish study linking birth closer to asbestos-bearing rock (ophiolites) with malignant mesothelioma. Using data from 56 countries, one study estimated 213,200 mesothelioma cases as 15-year cumulative mortality for 1994-2008, an annual average of about 14,200. The review said underreporting likely makes it conservative. The authors concluded that asbestos's health consequences are being underestimated in these countries and that banning asbestos mining, manufacture and general use is imperative. They called their review not exhaustive and noted remaining knowledge gaps.

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 (described as a state-of-the-art review); no new data collected
• Who was studied: Published studies from developing (low- to middle-income) countries, with emphasis on large epidemiological studies and global burden assessments; regions included the former Soviet Union, Eastern Mediterranean, Western Pacific, South Asia, Africa and Latin America
• Exposure: Asbestos (occupational and environmental, including chrysotile and naturally occurring asbestos), arsenic, indoor air pollution and ambient (outdoor) air pollution
• Main results:
  • A cited Chinese prospective cohort study (577 asbestos-manufacturing factory workers and 435 control workers, followed 1972-2008) found that the asbestos workers' risk of lung cancer death was more than threefold that of the controls (HR 3.31; 95% CI 1.60-6.87)
  • A cited study of 1539 Chinese chrysotile asbestos miners compared lung cancer mortality with that for less than 10 years of asbestos work. It reported an SMR of 4.92 (95% CI 2.88-8.43) for 10 years or more and an SMR of 7.46 (95% CI 5.41-10.28) for at least 20 years.
  • A cited study of 4155 male shipbreaking workers in Taiwan found raised oral cavity cancer incidence compared with the general population of Taiwan (83 cases; SIR 1.99; 95% CI 1.58-2.46); mesothelioma cases were found in flame cutters
  • A cited case-control study in Turkey reported malignant mesothelioma odds ratios of 1.68 (95% CI 1.39-2.04) for men and 2.15 (95% CI 1.69-2.74) for women for every 5 km decrease in distance of birthplace to ophiolites (asbestos-bearing rock)
  • A cited ecological study in New Caledonia (109 mesothelioma cases, 1984-2008) identified serpentinite-type asbestos on roads as the greatest environmental risk factor
  • In Brazil, mesothelioma mortality rates rose from 0.56 to 1.01 deaths per 1 million inhabitants over 1980-2003, according to a cited report
  • A cited global study used data from 56 countries on mesothelioma rates and asbestos use. It estimated 213,200 mesothelioma cases as a 15-year cumulative mortality for 1994-2008, an annual average of about 14,200 cases. The review said these estimates are likely conservative.
• The authors' conclusion: The authors concluded that the health consequences of asbestos exposure in high-consumption developing countries are being underestimated and that a ban on the mining, manufacture and general use of asbestos is imperative. More broadly, they concluded that a gap in knowledge of cancer risks from these exposures remains in low- and middle-income countries, particularly for indoor and outdoor air pollutants.
• Limitations the authors state:
  • The review did not assess all carcinogenic exposures or all countries and is not exhaustive
  • Given the long latency of mesothelioma and continued asbestos use, available mortality data cannot show the full cancer consequences
  • Underreporting in developing countries means global mesothelioma estimates are likely conservative

Topics

Medical terms in this study, explained in our Lexicon: Environmental Exposure, Occupational Exposure, Asbestos Exposure, Mesothelioma, Lung Cancer, Carcinogenic, Synergistic Effect.

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• Interstitial Lung Diseases in Developing Countries — P. Rivera-Ortega, M. Molina-Molina (2019)
• Asbestos-related hazards in developing countries — B.S. Levy, A. Seplow (1992)
• High Time for Complete Ban on Asbestos Use in Developing Countries — T. Chen, X.M. Sun, et al. (2019)
• An estimate of cancers attributable to occupational exposures in France — P. Boffetta, P. Autier, et al. (2010)
• Transfer of occupational health problems from a developed to a developing country: lessons from the Japan-South Korea experience — J. Park, N. Hisanaga, et al. (2009)

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