Trends in Airborne Chrysotile Asbestos Fibre Concentrations in Asbestos Cement Manufacturing Factories in Zimbabwe from 1996 to 2016

Our plain-English summary of Trends in Airborne Chrysotile Asbestos Fibre Concentrations in Asbestos Cement Manufacturing Factories in Zimbabwe from 1996 to 2016, by B. Mutetwa, D. Moyo, D. Brouwer (International Journal of Environmental Research and Public Health, 2021).

The study

• Authors: B. Mutetwa, D. Moyo, D. Brouwer
• Journal: International Journal of Environmental Research and Public Health
• Published: 2021;18(20)
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Zimbabwe has two major factories that have been manufacturing chrysotile asbestos cement products since the 1940s. Exposure monitoring of airborne fibres has been ongoing since the early 1990s. This study examines trends in personal exposure chrysotile asbestos fibre concentrations for the period 1996-2016. Close to 3000 historical personal exposure measurements extracted from paper records in the two factories were analysed for trends in exposure. Exposure over time was characterised according to three time periods and calendar years. Mean personal exposure chrysotile asbestos fibre concentrations generally showed a downward trend over the years in both factories. Exposure data showed that over the observed period 57% and 50% of mean personal exposure chrysotile asbestos fibre concentrations in the Harare and Bulawayo factories, respectively, were above the OEL, with overexposure being exhibited before 2008. Overall, personal exposure asbestos fibre concentrations in the factories dropped from 0.15 f/mL in 1996 to 0.05-0.06 f/mL in 2016-a decrease of 60-67%. These results can be used in future epidemiological studies, and in predicting the occurrence of asbestos-related diseases in Zimbabwe.

In plain English

This study analysed historical air-monitoring records from Zimbabwe's two chrysotile asbestos cement factories, in Harare and Bulawayo, covering 1996 to 2016. The authors used 2890 personal air samples, taken on workers by company staff and extracted from paper records, which were combined into 1663 monthly averages by task. Of these monthly averaged values, 60.3% of the 1063 in the Harare factory and 58.6% of the 600 in the Bulawayo factory exceeded the recommended limit of 0.1 fibres per millilitre (f/mL). The overall mean was 0.11 f/mL. Fettling table work had the highest share above the limit (Harare 76.2%, Bulawayo 84.3%), along with Bulawayo multi-cutter work (81.3%). Concentrations fell over time. In Harare they fell 14.3% from 1996–2000 to 2001–2008 and 50% from 2001–2008 to 2009–2016. In Bulawayo the falls were 21.4% and 45.5%. The authors concluded that exposure trended downward, with high concentrations in or before 2008, and that the Harare factory showed more overexposure. They noted gaps in yearly data and that the factories had no production figures available.

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: Secondary analysis of historical workplace exposure-monitoring records (descriptive trend analysis)
• Who was studied: Personal air samples from operational areas of two chrysotile asbestos cement factories in Harare and Bulawayo, Zimbabwe, 1996 to 2016. There were 2890 personal samples, analysed as 1663 monthly averaged concentrations (1063 Harare, 600 Bulawayo).
• Exposure: Airborne chrysotile asbestos fibres in tasks such as cutting saws, fettling table, kollergang (loading raw fibre), moulded goods, ground hard waste, laundry room, lathe machining of pipes and multi-cutter operations. Fibres were measured by personal sampling and counted by phase-contrast microscopy (detection limit 0.02 f/mL). Results were compared with a recommended occupational exposure limit of 0.1 f/mL.
• Main results:
  • Across 1996 to 2016, 60.3% of values in the Harare factory (N 1063) and 58.6% in the Bulawayo factory (N 600) exceeded the 0.1 f/mL limit. These N values sum to the 1663 monthly averages, and the methods state that monthly averaged levels were used for analysis.
  • Analysis was based on monthly averaged personal exposure levels
  • The overall mean personal exposure concentration in the Zimbabwe factories was 0.11 f/mL
  • Fettling table operations (Harare 76.2%, Bulawayo 84.3%) and Bulawayo multi-cutter operations (81.3%) had the highest proportions of concentrations above the limit
  • Harare factory: overall exposure declined 14.3% from 1996–2000 to 2001–2008, and 50% from 2001–2008 to 2009–2016
  • Bulawayo factory: overall exposure declined 21.4% from 1996–2000 to 2001–2008, and 45.5% from 2001–2008 to 2009–2016
  • Bulawayo factory concentrations ranged from 0.09–0.22 f/mL in 1996–2000, compared with 0.03–0.10 f/mL in 2009–2016
  • Concentrations below the limit began after 2008, except for fettling table operations in Harare and multi-cutter operations in Bulawayo
• The authors' conclusion: The authors concluded that personal chrysotile exposure in both factories showed a downward trend, with high concentrations in or before 2008. They also concluded that the Harare factory showed more overexposure than the Bulawayo factory, and stated that the results could aid future epidemiological studies.
• Limitations the authors state:
  • Measurements were missing for some operational areas in some years, creating data gaps that affected the patterns over time
  • Production rates, which might have helped explain the exposure patterns, were not available from the factories

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile.

Medical terms in this study, explained in our Lexicon: Chrysotile, Asbestos-Cement.

Related studies

• Prediction of Asbestos-Related Diseases (ARDs) and Chrysotile Asbestos Exposure Concentrations in Asbestos-Cement (AC) Manufacturing Factories in Zimbabwe — B. Mutetwa, D. Moyo, et al. (2022)
• Job Exposure Matrix for Chrysotile Asbestos Fibre in the Asbestos Cement Manufacturing (ACM) Industry in Zimbabwe — B. Mutetwa, D. Moyo, et al. (2022)
• A comparison of parallel dust and fibre measurements of airborne chrysotile asbestos in a large mine and processing factories in the Russian Federation — E. Feletto, S.J. Schonfeld, et al. (2017)
• Comparison of direct and indirect methods of measuring airborne chrysotile fibre concentration — C. Eypert-Blaison, S. Veissiere, et al. (2010)
• Asbestos fibre burden in the lungs of patients with mesothelioma who lived near asbestos-cement factories — P.G. Barbieri, D. Mirabelli, et al. (2012)
• Chrysotile asbestos and health in Zimbabwe: I. Analysis of miners and millers compensated for asbestos-related diseases since independence (1980) — M.R. Cullen, R.S. Baloyi (1991)

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