December 2019

A gateway to healthier environments in WA’s hard-rock underground mines

  • By Emeritus Professor Odwyn Jones AO FAusIMM, Clinical Professor Bill Musk AM, Chris Davis FAusIMM, Martin Ralph

A recent health and environmental study of existing conditions in a hard-rock operational underground mine could greatly benefit the wider industry

Recent applied research work carried out at one of Western Australia’s (WA) underground gold mines has produced some very interesting and informative data. If acted upon, this health and environmental study of existing conditions in a hard-rock operational underground mine could greatly benefit the wider industry.

The program consisted of two research projects which were presented to a public forum held on 29 July 2019. The research projects comprised a field study of the atmospheric conditions at worksites and other stationary monitoring stations sponsored by both the Minerals Research Institute of Western Australia (MRIWA) and the WA Department of Mines, Industry Regulation and Safety (DMIRS) (MRIWA Research Report 495, 2019); and a health impact study sponsored by the DMIRS, the first component of which has been published by Mengran Du et al (2019).

Review of health impact study findings

  • Exposure to Diesel Exhaust Emissions (DEE), whilst reducing due to improved ventilation practices and technological advances in engine design and aftertreatment devices, is still a major threat to the long-term health of underground miners in hard-rock mines.
  • The study indicated that the 80 participating underground miners were exposed to significantly greater levels of elemental carbon (EC), volatile organic compounds (VOCs), nitrogen dioxide (NO2), lung-deposited surface area (LDSA) and nanoparticles than the control group of 20 surface personnel.
  • Underground miners demonstrated a decline in lung function during working shifts caused by exposure to DEE, and whilst these changes of themselves are too small to cause symptoms, repeated small changes can accumulate to cause irreversible damage (as with cigarette smoking).
  • Pre- and post-shift urinary biomarkers increased during the shift for underground miners, which provided a measure of the body’s uptake of polycyclic aromatic hydrocarbons (PAHs), a carcinogenic toxin stored in the kidneys, liver and fat.
  • A statistically significant increase in systolic blood pressure of underground miners occurred across the shift. Although the increase was within the bounds of error of the measurement technique, if the increase is repeated each shift, it has the potential to increase the risk for cardiovascular events.
  • Numerous CpG sites (regions of DNA) were identified in blood samples of underground miners; some of which can induce biochemical alteration to DNA. Of the 29 methylated CpG sites, 12 were known to be associated with chronic diseases including cancer and cardiovascular diseases. Further details and the full study can be found in the published paper.

Health surveillance measures and procedures

The requirements for a health surveillance system are clearly defined in the ‘DMIRS Safety Guidance about risk-based approach to health surveillance.’ It states that:

  • employers need such a system to ‘identify changes in the health of workers’ exposed to hazardous substances
  • ‘risk-based health assessment or biological monitoring is required where workers are exposed to hazardous agents – chemical or other substances that can lead to ill health or disease’
  • such systems ‘should also ensure that control measures in the workplace are effective and provide… safe work practices’ (DMIRS, 2019).

Furthermore, it lists the following common examples of the elements of health surveillance systems:

  • recording occupational and medical history
  • providing health advice
  • facilitating physical examination
  • maintaining records of exposure
  • providing and recording respiratory (lung) function tests
  • carrying out biological monitoring to ascertain the extent to which chemicals have entered the human body following exposure (DMIRS, 2019).

Reference is also made to the fact that the approved person (who could be a medical practitioner) responsible for the surveillance system may require workers to undertake additional surveillance. Both the worker and employer must be notified of the results and need for remedial action (DMIRS, 2019).

Based on decades of concern regarding the health hazard to underground mineworkers exposed on a regular basis to diesel engine exhaust fumes, confirmed more recently by research evidence of its specific health impacts, there is every reason to recommend that such a health assessment and surveillance system and associated procedures be established in WA for underground mineworkers exposed to diesel engine exhaust fumes.

Ideally, such a health assessment and surveillance system should be managed and operated by an autonomous body. The information collected should be integrated with existing X-ray surveillance for pneumoconiosis and retained indefinitely in order to allow follow-up of the workers for the occurrence of cancers and deaths.

Digital all-electric mines

As Andreas Nordbrandt, Atlas Copco’s President of Underground Rock Excavation Division stated two years ago, ‘our customers’ future is electric.’ He emphasised that it’s becoming realistic to visualise ‘zero-emission electric equipment’ replacing diesel-powered mobile equipment sooner rather than later (Mining Journal, 2017).

At the same time he stated that ‘the company’s immediate plans are to expand its portfolio of electric powered equipment including loaders, drill-rigs and haul trucks’ and while admitting to higher upfront costs, he emphasised the advantages of lower mining costs and potentially considerable savings in ventilating and cooling in the deeper mines.

A report in the Guardian newspaper (2017) stated that ‘legal claims over exposure to diesel fumes at work are growing as unions warn toxic air in the workplace is a ticking time bomb on par with asbestos,’ with the UK’s largest trade union (Unite) establishing a diesel emissions register for employees to record their exposure.

Surely now is the time for the WA mining industry and its regulators to develop its own ‘Clean Air Plan’ for underground mines, including guidelines for the replacement of diesel-powered mobile equipment with electric-powered equivalents as soon as practicable.

Currently the Canadian market is leading the charge, starting with Kirkland Lake Gold’s Macassa operation, where battery-electric machines were installed in 2013 (Tollinsky, 2013). These machines have continued to maintain high performance levels and currently the Macassa mine accounts for more than 80 per cent of Kirkland Lake Gold’s production (Goodbody, 2019).

More recently, both Goldcorp’s Borden gold project and Glencore’s Onaping Depth nickel-copper project are being developed as fully electric operations due mainly to high ambient rock temperatures and the increasing costs of ventilation to cope with the health hazards of diesel-engine exhaust fumes (Leonida, 2017).

The Global Mining Guidelines Group (GMG) published ‘Recommended Practices for Battery Electric Vehicles (BEVs) in Underground Mines’ in 2017. These guidelines highlight the issues needing careful consideration prior to embarking on replacing diesel-powered mobile equipment at existing mines with fully electric systems or planning the development of new fully electric mines.

As we move further into the digital age, electric equipment will become the key to new, more efficient and energy-saving ways of extracting ores from the deep and ultra-deep underground mines. The deeper the mine, the more attractive fully electric systems become, by overcoming many of the challenges of coping with high in situ rock temperatures and the extra heat, humidity and toxic diesel engine exhaust fumes.

Support for all-electric mines is coming from many quarters with the International Council on Mining and Metals planning to minimise the impact of underground diesel engine exhaust by 2025 (ICMM, 2018). Further evidence of the extent and speed at which electric vehicles are reaching global markets is provided by Epiroc, Sweden’s mining equipment manufacturer, which aims to electrify all its underground machines within five years.

‘As we move further into the digital age, electric equipment will become the key to new, more efficient and energy-saving ways of extracting ores.’

However, at present battery-powered vehicles cost about twice as much as their diesel counterparts, making the switch to electric vehicles prohibitive. Epiroc’s willingness to lease batteries for its new vehicles largely overcomes this problem by reducing the initial outlay to little more than that of an equivalent diesel machine.

Recommendations

  • A health assessment and surveillance system and associated procedures should be established in WA for all underground mineworkers exposed on a regular basis to diesel engine exhaust fumes. While the elements of such a system have already been mentioned, it is important to emphasise the need for regularly monitoring elemental carbon (EC) and, if at all possible, nanoparticle concentration and distribution, as well as lung deposited surface area (LDSA) and airborne concentrations of the gases produced by diesel-powered vehicles.
  • Standards and guidelines for EC for longer working shifts and rosters need to be made much clearer.
  • More attention needs to be given to the design of ventilation of development headings in order to improve the volume of the ventilating airflow reaching the face and its effectiveness in removing and diluting the toxic and noxious products produced by diesel engines.
  • Bearing in mind the toxic mixture of chemical compounds in diesel engine exhaust, the likelihood of mineworkers developing ‘Multiple Chemical Sensitivity Disorder’ should also be explored, since it is an emerging disabling illness characterised by chronic adverse effects from exposure to low levels of chemicals (Martini et al, 2013). Consequently, much more attention must be paid to preventing such poisoning, including ensuring the exhaust cleaning devices are in good repair and that an effective ventilation system is in place.
  • More detailed and extensive study of the correlation between EC and nanoparticle concentration, and ageing of diesel particulate matter (DPM) as it travels through the ventilation circuit is required.
  • When working in hazardous environments the role of education and training for all relevant personnel cannot be over-emphasised. This entails instruction in hazard recognition and control measures, safe work practices, monitoring systems and preventative measures, etc. Such training for management, mineworkers, regulators and researchers ensures there is a common language for effective communication.
  • Increased use of SF6 tracer gas studies is justified based on the assumption it represents, in large measure, the movement of ultra-fine particles.
  • Continuing use of computational fluid dynamic (CFD) modelling is also justified since it appears to give good agreement with SF6 tracer gas studies and assists in improving and optimising key areas in the ventilation circuit.
  • As stated earlier, the medium to longer-term future lies with digital all–electric mines and, consequently, it is timely for the industry and its regulators to develop guidelines for the future development of new all-electric mines and/or the replacement of existing diesel-powered fleets with their BEV equivalents.

Closing comment

Strong claims are being made for the benefits of ‘new technology diesel engine’ (NTDE) technology with catalysed diesel particulate filters in greatly reducing particulates and toxic emissions. But its penetration into the off-road diesel engine market will inevitably take many years (Vermuelen, 2017). However, using such technology may be confounded by the increase of NO2 emission and release of reactive ultra-fine particles (Karthikeynan et al, 2013).

This confounding challenge of increased NO2/NO ratios which occur with oxidation catalysts, causing deteriorating air quality, is a matter of considerable concern for those responsible for diesel-powered mobile equipment in underground mines. As stated by Cauda et al in 2012, ‘in mine environments with inadequate ventilation where local “dead spots” exist in work areas, it would be possible for NO2 levels to rise to problematic levels faster with the use of a DOC than without.’

‘When working in hazardous environments the role of education and training for all relevant personnel cannot be over-emphasised.’

Consequently, until the final removal of diesel-powered equipment from underground mines, there is no alternative but to establish a well organised and managed health surveillance and monitoring system whereby employers can adequately exercise their duty of care for the continued health and wellbeing of mineworkers.

References

Black S and Mullins B, 2019. Minerals Research Institute of Western Australia – Research Report M495.
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ICMM (International Council on Mining and Metals), 2018. Industry and vehicle manufacturers join forces to develop cleaner, safer vehicles [online]. Available from: https://www.icmm.com/en-gb/news/2018/icsv_pr
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