The COVID outbreak at the Tanami gold mine in July exposed mining’s vulnerability, write E/Professor Odwyn Jones and C/Professor Bill Musk.
COVID-19 has, and is, shutting down national and regional economies and mining and other industries are not unaffected.
Labour-intensive industries are particularly vulnerable, and every effort must be made to avoid the rampant spread of the virus in the close confines of underground mines as witnessed at the Tanami gold mine in Northern Territory.
Indeed, the infected aerosols, if released by an infected miner, will be transported to other miners at downstream locations due to the nature of mine ventilation.
The International Labour Organisation (ILO) has developed its own COVID-19 and mining prevention and control checklist (V1, May 2020), and here are a few of the issues raised:
- Has mine management developed and shared a statement of its commitment to prevent and reduce the risk of exposure to the virus and transmission at the mine-site in consultation with workers and their representatives?
- Have risk assessments specific to COVID-19 been carried out jointly with workers or their representatives and are the identified risks being addressed in the preparedness and response plan?
- Has mine management, workers and their representatives been informed and trained in adopting measures to prevent risks of exposure to the virus and how to act in case of infection?
- Does the training include the correct use, maintenance and disposal of effective personal protective equipment (PPE)?
- Has a high-risk group or “vulnerable persons register” been established?
- Are frequently used facilities and equipment regularly disinfected?
- Is “unnecessary site access” kept to a minimum?
- Is mine management proactively seeking undertakings from suppliers and contractors regarding their health and hygiene practices and controls?
There are many other useful information sources including WA’s Department of Mines, Industry Regulations and Safety’s COVID-19 information pamphlet and Safety Plan. WorkSafe Tasmania’ has a useful COVID Safe set of guidelines. It is also noteworthy that there has been a requirement for several years now that mines in WA develop an Infectious Diseases Management Plan.
Despite the ever-changing COVID-19 scenario within Australia, its mining industry continues to operate at more-or-less full capacity, and the sector is considered by governments to be an essential service. Nevertheless, fly-in fly-out work arrangements pose serious challenges to infection control where in large operations, several hundred workers are routinely having to share working and living facilities where physical distancing is difficult to achieve.
Indeed, Mount Isa’s mayor is angry, stating that “while the government is telling us not to go out to cafes and to work from home if we can, we are still flying in workers by the planeload – it just seems ludicrous.”
Underground aerosol transmission
In an article published in The Lancet (April 15, 2021), the authors concluded “there is consistent, strong evidence that SARS-CoV-2 spreads by airborne transmission. Although other routes can contribute, we believe that the airborne route is likely to be dominant. The public health community should act accordingly and without further delay.”
The ventilating air stream in underground mines is normally fully turbulent, with random eddies continuously being formed. Such chaotic airflows are ideal to keep infected aerosols airborne.
These exhaled aerosols can, apparently, coalesce with water droplets or solid or liquid pollution particulates (e.g. smoke, smog or diesel fumes). Indeed, the SARS-CoV-2 aerosols have been observed on airborne particulates and there is mounting evidence for associating COVID-19 outbreaks with high levels of particulate pollution in the size range 0.2-10 microns (Jarvis M.C., Nov. 2020)
Consequently, COVID-19 aerosol particles could move with the underground ventilation airflow whilst remaining infective for an hour or more, which means they could potentially travel great distances. Little research has been directed at this phenomenon and there is a gap in our knowledge on how the effectiveness of dispersal depends on environmental conditions, particularly turbulence.
An infected cloud of infected aerosols could in more gentle airflows remain reasonably compact (e.g. in laminar airflows or in the gentler regions in turbulent tunnel flows near the roof or sides of mine airways). Even if such a cloud becomes dispersed within the turbulent airflow, the aerosols will still remain infective for quite some time.
Unfortunately, most worksites in hard-rock underground mines are located at the face of development headings or stopes where diesel-powered heavy equipment is operating, and where secondary ventilation is required. Consequently, even in the best of situations the effectiveness of secondary ventilation is limited, which can result in the local build-up of pollutants.
These conditions could equally result in the build-up of virus-loading making inter-person transmission to nearby colleagues more likely.
In the open air, winds will also carry and disperse aerosols and its turbulence can keep particles airborne, so that downwind infection could also become a serious hazard.
These fine particulates (<100nm) can also be emitted from a range of anthropogenic sources, such as indoor cooking or diesel engine exhaust fumes in underground mines and can possibly harbour and assist in transporting airborne pathogens.
It is also noteworthy that the activated carbon in diesel engine exhaust has strong adsorptive properties and is acknowledged as a versatile adsorbent of organic, inorganic and pathogenic contaminants. Many recent studies have found strong positive correlations between atmospheric particulate levels and levels of COVID 19 infections. The influence of atmospheric pollutants in connection of SARS-CoV-2 transmission needs further attention and research.
Of all the occupations, underground hard-rock mining provides one of the greatest challenges to employers in carrying out their duty of care for employees during the pandemic. In order to provide safe working conditions for underground miners employers need to have in place (ILO checklist):
- A well-designed Covid-19 risk assessment protocol, drawn up in close consultation with workers and/or their representatives.
- Medical facilities with appropriate equipment for COVID-19 treatment and care, or arrangements for safe transfer to hospital.
- Employers need to ensure employees, as well as contractors, are well-informed and trained to cope with the unique risks relating to varying occupations and tasks.
- A high-risk list of vulnerable workers: i.e. those over 65 years of age and those with underlying medical conditions.
- Adequate hygiene and cleaning facilities and services as well as safe accommodation, dining and leisure facilities based on safe physical distancing.
- Provision of appropriate PPE for all employees who require their use for personal safety.
- Safe travel and transport facilities for employees to and from work sites.
- Employers should aim to maximise vaccination of their workforces update.
However, the most important message is that underground mines have great potential to become locations for superspreading events. Hence mining operations need to manage the potential for the spread of infection in accordance with the many well-documented risk-management and COVID 19-Safe industry guidelines available.
However, there is still much we need to know and this is an area of much needed further research.
References on request