Asbestos exposure and mesothelioma incidence and mortality in Bulgaria

Our plain-English summary of Asbestos exposure and mesothelioma incidence and mortality in Bulgaria, by K. Vangelova, I. Dimitrova (Reviews on Environmental Health, 2016).

The study

• Authors: K. Vangelova, I. Dimitrova
• Journal: Reviews on Environmental Health
• Published: 2016;31(2):203-9
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Bulgaria totally banned the import, production and use of asbestos in 2005, but produced and used asbestos products during the last 3-4 decades of the 20th century. The aim of this study was to follow the incidence and mortality of mesothelioma in Bulgaria in relation to past occupational exposures. A literature search between 1960 and 2014 was conducted to obtain information on asbestos consumption, occupational exposure and asbestos-related diseases (ARDs). Data on registered mesotheliomas were provided by the National Cancer Register and data for recognized occupational ARDs were provided by the National Social Security Institute. An increase in the incidence of mesothelioma from 5 to 58 from 1993 to 2013, with 666 cases in the 21-year period, was registered. Incidence, mortality rates, deaths and male-to-female ratios and were lower in comparison to industrialized countries. The increase in mesothelioma incidence is considered as a consequence of more recent production and use of asbestos and asbestos products and the high occupational exposure between 1977 and 1989, while the lower rate of mesothelioma deaths and male-to-female ratio need to be investigated further.

In plain English

This study looked at mesothelioma in Bulgaria, where asbestos use began around 1960. The authors searched the literature from 1960 to 2014 on asbestos use and workplace exposure, and analyzed national cancer register data for 1993 to 2013. Bulgaria mined anthophyllite and tremolite asbestos and imported chrysotile and crocidolite. Earlier measurements for 1977 to 1989 found average shift levels of up to 30 fibers per cubic centimeter in primary asbestos processing and up to 24 in asbestos-cement production; the legal limit was 3 fibers per cubic centimeter, lowered to 2 in 1987. The register recorded 666 mesothelioma cases from 1993 to 2013 (397 males, 269 females). Yearly cases rose from 5 in 1993 to 58 in 2013, mainly pleural cases and people over 60. Whether the cases were work-related was not studied. Survival was under 12 months in 77% of cases. From 2005 to 2012 there were 68 mesothelioma deaths (38 males, 30 females). The authors considered the rise a consequence of more recent asbestos use and high past exposure. They noted that rates remained lower than in industrialized 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: Descriptive study combining a literature search (1960 to 2014) on asbestos use, occupational exposure and asbestos-related diseases with national cancer register and occupational disease register data
• Who was studied: All types of mesothelioma (ICD-10 code C45) recorded by Bulgaria's population-based National Cancer Register, 1993 to 2013; mortality data for 2005 to 2012
• Exposure: Past occupational asbestos exposure in Bulgarian asbestos industries, taken from earlier published measurements (Table 1). The legal limit for average shift concentration was 3 f/cm3 from 1977 and 2 f/cm3 from 1987. For 1977 to 1989, the table gives ranges of 5 to 30 f/cm3 in primary asbestos material processing and 2 to 24 f/cm3 in the asbestos-cement industry.
• Main results:
  • Bulgaria imported chrysotile and crocidolite asbestos (anthophyllite and tremolite asbestos were mined in the country)
  • Anthophyllite and tremolite asbestos were mined in Bulgaria
  • Primary asbestos material processing, 1977 to 1989: average shift concentration of 5 to 30 f/cm3 (Table 1)
  • Asbestos-cement industry, 1977 to 1989: average shift concentration of 2 to 24 f/cm3 (Table 1)
  • 666 mesothelioma cases were registered in Bulgaria between 1993 and 2013
  • Of the 666 cases, 397 were in males and 269 in females (male-to-female ratio 1.48:1)
  • Registered cases per year rose from 5 in 1993 to 58 in 2013
  • The increase was mainly in pleural mesothelioma and in people over 60 years of age
  • The crude incidence rate ranged from 0.2 to 1.0 per 100,000 persons, and was higher in males
  • Among registered cases, survival was under 12 months in 77%, 1 to 2 years in 15%, and more than 2 years in 8%
  • From 2005 to 2012 there were 68 mesothelioma deaths: 30 in females and 38 in males
  • The male-to-female ratio was 1.27:1 for mesothelioma deaths and 1.49:1 for incidence
  • Age-adjusted mortality rates per 100,000 for 2005 to 2012 were below 0.11 for the total population, 0.17 for males and 0.08 for females
  • Recognized occupational asbestos-related diseases in recent years comprised 1 to 4 asbestosis cases per year; malignant asbestos-related diseases were not reported as occupational
• The authors' conclusion: The authors considered the increase in mesothelioma a consequence of more recent production and use of asbestos and of high occupational exposure from 1977 to 1989. They noted that incidence and mortality remained lower than in industrialized countries. They suggested possible reasons, including lower life expectancy, diagnostic difficulty and predominant chrysotile use. They said the low male-to-female ratios need further investigation. They suggested these ratios might relate to environmental and domestic exposure, women's work in asbestos industries, and life expectancy.
• Limitations the authors state:
  • The occupational cause of the registered mesothelioma cases was not studied
  • The extent of occupational mesothelioma in Bulgaria is unknown
  • Occupational diseases in Bulgaria are considered underreported
  • Differences in death reporting between countries may affect comparisons

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, Mesothelioma, Occupational Exposure.

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