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

Sustainable management of hazardous asbestos-containing materials: Containment, stabilization and inertization

Asbestos is a group of six major silicate minerals that belong to the serpentine and amphibole families, and include chrysotile, amosite, crocidolite, anthophyllite, tremolite and actinolite. Weathering and human disturbance of asbestos-containing materials (ACMs) can lead to the emission of asbestos dust, and the inhalation of respirable asbestos fibrous dust can lead to 'mesothelioma' cancer and other diseases, including the progressive lung disease called 'asbestosis'. There is a considerable legacy of in-situ ACMs in the built environment, and it is not practically or economically possible to safely remove ACMs from the built environment. The aim of the review is to examine the three approaches used for the sustainable management of hazardous ACMs in the built environment: containment, stabilization, and inertization or destruction. Most of the asbestos remaining in the built environment can be contained in a physically secured form so that it does not present a significant health risk of emitting toxic airborne fibres. In settings where safe removal is not practically feasible, stabilization and encapsulation can provide a promising solution, especially in areas where ACMs are exposed to weathering or disturbance. Complete destruction and inertization of asbestos can be achieved by thermal decomposition using plasma and microwave radiation. Bioremediation and chemical treatment (e.g., ultrasound with oxalic acid) have been found to be effective in the inertization of ACMs. Technologies that achieve complete destruction of ACMs are found to be attractive because the treated products can be recycled or safely disposed of in landfills.

Asbestos dust concentrations and health conditions of workers at asbestos-cement corrugated sheet production manufacturers in Vietnam: a nationwide assessment

This study examined contemporary concentrations of asbestos dust during production and the health conditions of workers at asbestos-cement corrugated sheet production manufacturers in Vietnam. A nationwide survey was conducted on 28 factories (with 206 air samples) and 2459 workers. Asbestos fiber dust and the health status of workers were assessed. Results showed that 108/206 (52.4%) samples had asbestos fiber dust. The average concentration of asbestos fibers was 0.19 ± 0.14 fibers/ml. The percentage of workers with thickened pleural lesions/pleural calcification nodules was low. More studies are needed to evaluate the effectiveness of biomarkers in preventing the onset of lung cancer and mesothelioma in workers.

Prediction of Asbestos-Related Diseases (ARDs) and Chrysotile Asbestos Exposure Concentrations in Asbestos-Cement (AC) Manufacturing Factories in Zimbabwe

The use of historical asbestos measurement data in occupational exposure assessment is essential as it allows more quantitative analysis of possible exposure response relationships in asbestos-related disease (ARD) occurrence. The aim of this study was to predict possible ARDs, namely lung cancer, mesothelioma, gastrointestinal cancer, and asbestosis, in two chrysotile asbestos cement (AC) manufacturing factories. Prediction of ARDs was done using a specific designed job-exposure matrix for airborne chrysotile asbestos fibre concentrations obtained from the Harare and Bulawayo AC factories and through application of OSHA's linear dose effect model in which ARDs were estimated through extrapolation at 1, 10, 20, and 25 years of exposure. The results show that more cancer and asbestosis cases are likely to be experienced among those exposed before 2008 as exposure levels and subsequently cumulative exposure were generally much higher than those experienced after 2008. After a possible exposure period of 25 years, overall cancer cases predicted in the Harare factory were 325 cases per 100,000 workers, while for the Bulawayo factory, 347 cancer cases per 100,000 workers exposed may be experienced. Possible high numbers of ARDs are likely to be associated with specific tasks/job titles, e.g., saw cutting, kollergang, fettling table, ground hard waste, and possibly pipe-making operations, as cumulative exposures, though lower than reported in other studies, may present higher risk of health impairment. The study gives insights into possible ARDs, namely lung cancer, mesothelioma, gastrointestinal cancer, and asbestosis, that may be anticipated at various cumulative exposures over 1, 10, 20, and 25 years of exposure in AC manufacturing factories in Zimbabwe. Additionally, results from the study can also form a basis for more in-depth assessment of asbestos cancer morbidity studies in the AC manufacturing industries.

Job Exposure Matrix for Chrysotile Asbestos Fibre in the Asbestos Cement Manufacturing (ACM) Industry in Zimbabwe

Occupational chrysotile asbestos exposure data in Zimbabwe is limited. The aim of this study was therefore to develop a job exposure matrix (JEM) specific to the chrysotile asbestos cement manufacturing industry using the available personal exposure concentration data. Quantitative personal exposure chrysotile fibre concentration data collected by the two factories from 1996 to 2020 were used to construct the JEM. Exposure groups from which data was extracted were classified based on the Zimbabwe Standard Classification of Occupations (ZSCO), 2009-2019. Analysis of amphiboles in raw chrysotile was done by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Descriptive statistics, namely mean, standard deviation and range were computed for the main variable, job/occupation. All jobs/occupations in both factories had annual mean personal exposure concentrations exceeding the OEL of 0.1 f/mL, except for the period from 2009 to 2016 in the Harare factory and the period from 2009 to 2020 in the Bulawayo factory. Despite the Harare factory having no AC manufacturing activity since 2017, personal exposure concentrations showed elevated levels for the period 2018-2020. Amphiboles were detected in almost all bulk samples of chrysotile asbestos analysed. The established JEM, which has been generated from actual local quantitative exposure measurements, can be used in evaluating historical exposure to chrysotile asbestos fibre, to better understand and predict occurrence of ARDs in future.