Characterisation of emission and exposure to diesel engine exhaust from trackless mobile machinery in underground South African Platinum Mines: Evaluating strategies to prevent and control exposure
| dc.contributor.author | Manyike-Modau, Amukelani Portia | |
| dc.contributor.supervisor | Brouwer, Derk | |
| dc.date.accessioned | 2024-12-10T08:52:12Z | |
| dc.date.available | 2024-12-10T08:52:12Z | |
| dc.date.issued | 2024 | |
| dc.description | A research report Research submitted to fulfillment for the requirements for the PHD in Public Health at the School of Public Health, Faculty of Health Sciences, School of Public Health, University of the Witwatersrand Johannesburg 2024 | |
| dc.description.abstract | Background: Mining remains one of the major economic drivers in South Africa, as is evident through continued focus on long-term investments in mining and the mechanisation of mining operations. Mechanisation uses diesel-powered machinery; such machinery offers greater versatility than electric and battery-operated vehicles due to their ability to cover greater distances and move between different working sections (1). Diesel powered machines are most preferred because of their high energy efficiency and low carbon monoxide and carbon dioxide emissions compared to gasoline equipment (2). Using diesel-powered machines in mechanised mining has introduced a new risk to mine workers working in confined spaces underground. Diesel engine exhaust (DEE) can increase significantly due to wear or breakdown of the engine components and after-treatment systems. The impact on emissions varies depending on the engine type, age, and state of wear and tear (3). Significant evidence demonstrates a correlation between DEE exposure and respiratory outcomes in mine workers. DEE is a known carcinogen. In 2012, the International Agency for Research on Cancer (IARC) classified DEE as being carcinogenic to humans (class I) when inhaled, based on sufficient evidence that exposure is associated with an increased risk for lung cancer (4). There has been an incredible drive to manage diesel Particulate matter (DPM) in the South African mining industry (SAMI). The approach, however, has been focused on monitoring personal exposure to DPM rather than a multifaceted approach that includes eliminating or reducing the pollutant at the source. Efforts should be made to ensure that management plans for engineered solutions and risk-based approaches are in place when monitoring DPM (5). As a result, research in the mining domain has focused on developing integrated control strategies/solutions to prevent exposure to diesel engine exhaust. South Africa shares the same concern with other countries regarding the DPM challenges in mining operations. The South African legal framework requires the employer to conduct a risk assessment and implement measures to prevent employees from overexposure to harmful airborne pollutants (MHSA 1996). Therefore, without local guidelines and regulations, SAMI can use the available scientific knowledge to control the exposure of DPM to employees and to ensure continuous monitoring of employees while working at the mines. Currently, no specific systems guide sets standards or limits for personal or occupational exposure or tailpipe emissions of DPM (6,7). Further, even though enough knowledge is The Occupational Cancer Research Centre Report published in 2017 presented different control strategies for DPM following the hierarchy of control principles (8). These ranged from the proactive (most effective) to reactive (less effective) controls and included the following controls: elimination using alternative energy such as electric or battery-powered machines, substitution such as replacing, repowering, or engine rebuilds, and this would typically include retrofitting the engines with engine after-treatment systems; Engineering controls which may include retrofitting the engines with after-treatment technologies, improving general ventilation systems, idling technologies, installation of protective cabs; Administrative controls which may include preventative maintenance, idling policies, operator training and planned schedule for the site such as planning the number of machines required to operate in a working place; and lastly the use of personal protective equipment such as respirators. These controlscan be implemented in a multifaceted approach to reduce or prevent employees from being overly exposed (3,8,9). Diesel emission is a complex mixture and may require multiple control strategies to minimise employee exposure. In the study conducted by Bugarski et al, 2009, they highlighted different monitoring and control strategies ranging from emissions monitoring, including undiluted emissions measurements, i.e., Both ‘tailpipe output’ and ‘engine out’ (upstream of after- treatment systems), and the installation of after-treatment strategies and higher tier standard engine emissions. The control strategies can help identify and distinguish between engine maintenance issues and emission control device failures and assist in estimating ventilation requirements (10). In addition, in a study by Hines in 2019, significant improvements were achieved in reducing tailpipe emissions (reduction at source) by implementing an emission- based maintenance (EBM) program. This has resulted in a reduction of Carbon Monoxide (CO) by more than 80% and DPM by more than 47% on personal exposure, showing the direct impact the EBM has on reducing exposure of DPM to employees working underground. The study successfully reduced tailpipe emissions by introducing the EBM program at the mines. Further, fuel usage was also reduced by 7-20%, showing that when machines are well maintained, there are improvements in efficiencies and even utilisation and availability of machines for production (11). Objective: The overarching aim of the research project was to determine the characteristics of diesel engine exhaust emissions at the source (aerodynamic size fractions) and evaluate how maintenance, maintenance plus installation of diesel particulate filters (DPF), and ventilation will impact the levels of DEE at the source and in the workplace. Methods: A quantitative, quasi-experimental study, designed with an intervention component, was conducted in two Platinum underground mines in South Africa. DEE was measured at the source, and DPM was personally exposed to employees. DPM dispersion modelling was conducted underground, and different control strategies were evaluated to determine their role in reducing the pollutant underground. Results: The concentration of median particles significantly decreased post the interventions, achieving an efficacy of 90-96% and 20-40% (p-value=0.001) for the machines that underwent maintenance plus installation of the DPF and machines that underwent maintenance only, respectively. Most particles emitted were in the ultrafine aerodynamic range, with a diameter between ≥0.01<0.1μm and an aerodynamic fine size of ≥0.1<1μm. Conclusion: A combination of control strategies (maintenance, retrofitting of machines with DPF, and ventilation) has shown great potential to reduce DEE in underground mines. Therefore, focused effort is required to implement integrated strategies to prevent or minimise exposure to DEE. Future studies to link dispersion models with real-time monitors are recommended to improve DEE's risk-based management | |
| dc.description.submitter | MM2024 | |
| dc.faculty | Faculty of Health Sciences | |
| dc.identifier | https://orcid.org/ 0009-0004-4941-4703 | |
| dc.identifier.citation | Manyike-Modau, Amukelani Portia. (2024). Characterisation of emission and exposure to diesel engine exhaust from trackless mobile machinery in underground South African Platinum Mines: Evaluating strategies to prevent and control exposure [PhD thesis, University of the Witwatersrand, Johannesburg]. WireDSpace.https://hdl.handle.net/10539/43234 | |
| dc.identifier.uri | https://hdl.handle.net/10539/43234 | |
| dc.language.iso | en | |
| dc.publisher | University of the Witwatersrand, Johannesburg | |
| dc.rights | © 2024 University of the Witwatersrand, Johannesburg. All rights reserved. The copyright in this work vests in the University of the Witwatersrand, Johannesburg. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of University of the Witwatersrand, Johannesburg. | |
| dc.rights.holder | University of the Witwatersrand, Johannesburg | |
| dc.school | School of Public Health | |
| dc.subject | VENTILATION | |
| dc.subject | DIESEL ENGINE EXHAUST | |
| dc.subject | DIESEL PARTICULATE MATTER | |
| dc.subject.other | SDG-7: Affordable and clean energy | |
| dc.title | Characterisation of emission and exposure to diesel engine exhaust from trackless mobile machinery in underground South African Platinum Mines: Evaluating strategies to prevent and control exposure | |
| dc.type | Thesis |