Miners act on unacceptable dust exposures

While the focus for many has been on the reduction of dust exposure limits across Australia, experts from Australia’s leading professional association for occupational hygienists challenge the mining sector to shift its attention to the effectiveness of dust controls implemented in the workplace.

Improvements to mine dust control have continued to roll in as state governments and institutions put a spotlight on dust exposure.

Respirable coal and silica dust regulatory limits in Queensland and New South Wales are now set at 1.5 milligrams per cubic metre and 0.05 milligrams per cubic metre, respectively.

Western Australia is set to cap its respirable coal dust exposure to 1.5 milligrams per cubic metre starting October 2021, and has halved the respirable silica dust exposure standard to 0.05 milligrams per cubic metre.

New South Wales, a state with sprawling coalfields, will be the first mining jurisdiction in Australia to apply a diesel particulate matter exposure standard of 0.1 milligrams per cubic metre in February 2021.

Further reduction of the respirable silica workplace exposure standard (WES) to a lower value on paper does not mean that more miners will be protected, Australian Institute of Occupational Hygienists (AIOH) secretary Sharann Johnson says.

“Miners are protected when companies implement and maintain effective controls to comply with the current standard,” she tells Safe to Work.

“If companies are not complying with the current standard how do we expect them to comply with a lower standard?

“Controls that are being implemented such as improved ventilation, dust suppression, positive pressure cabins to isolate workers, cleaner air-conditioned cabins on trucks and mobile equipment, have made significant improvements to comply with the current WES standard.”

Queensland

Changing the focus to the effectiveness of dust controls in mine sites means that increasing technology advancement becomes important to help drive action and give confidence that controls are working.

AIOH member Dustin Bennett, who provides consulting services on occupational hygiene to Queensland mines, says companies must continue to monitor dust levels, but ensuring the effectiveness of controls is an area the industry needs to invest more energy on.

“Verifying the effectiveness of controls is what’s going to ensure workers are safe. The challenge is, how can you tell whether this control works better than that one, and what is the benefit?” he says.

“Control solutions have not reached a point of stability where one could objectively say whether they work or not. This may create confusion and hesitation at a site level.

“One would ask, ‘What’s the reduction afforded by the control?’ ‘Will it work with my different dust conditions on site?’ ‘Is it guaranteed?’ Dust control is seldom as simple as turning on a solution and it will work.”

Bennett says real-time dust monitoring technology has been gaining momentum in helping to verify controls by instantaneously measuring dust levels, particularly in the last three years.

However, it is still in a phase of immaturity globally. One of the technology challenges is reliably getting measurements that mimic the airborne dust that make their way into the respiratory system.

With the absence of regulatory guidance on real-time dust monitoring, the international mining sector is coming together to find best-use cases for real-time monitoring.

Even so, Bennett has observed that the mining sector’s attitude towards dust exposure over the past 10 years has moved beyond legislative obligations.

He says the sector has moved from taking a fairly immature and non-integrated approach to dust control, to a fully integrated approach over the span of his career in mining.

“When I started in mining two decades ago, dust was not a large part of daily conversation. I wouldn’t have a conversation about dust exposure with a general manager on site,” Bennett says.

“Today, dust is spoken about by all levels of workforce, from the site-based personnel all the way to the executive level, almost on a daily basis, which is a good outcome of a tough situation since the re-emergence of dust lung diseases in Queensland and New South Wales.

“That has sent shockwaves through all the industry and really improved dust conditions in all mine sites.”

Western Australia

Despite the improvement that the mining sector has delivered across Australia, some things can fall through the cracks.

AIOH member Laurie Glossop, who specialises in occupational hygiene in relation to hard rock mining in Western Australia, agrees that dust control is a significant issue in the sector.

 

“Maintenance is very important and that’s where sometimes that’s not happening in mine sites. The dusty nature of the mining process means that operators will always need to be controlling it. Without maintenance, control mechanisms can quickly become ineffective,” Glossop, who has been an occupational hygienist since 1980, says.

This is especially relevant in Western Australia where a large part of the mining region is located in the desert.

A 50-kilometre wind, a 45-degree Celsius day and 2–3 per cent of humidity are all that is needed to make many dust suppression products evaporate in a few minutes, allowing dust to become airborne, Glossop says.

On top of the dust suppression binders and polymers that have been applied, new dust depositing on the surface will need addressing.

Further challenges include bigger and bigger haul trucks that sometimes carry more than 300 tonnes of ore at a time, as well as longer conveyor belts.

If these challenges aren’t enough for open cut mining companies, Glossop points out the dangers associated with underground longwall operations.

“Dust exposure increases with longwall technologies, along with longer conveyor belts systems inherently produce a lot of dust,” Glossop says.

Although these matters are no secrets in mining, those outside of the industry would be surprised to find out that some hard rock operations in Western Australia dig up naturally occurring asbestiform minerals, according to Glossop.

“There is the double issue of dust containing crystalline silica as well as asbestiform materials, so the need for effective control is crucial,” he says.

“Unfortunately, the hindrance to making improvements in dust control is the cost. There has not been much improvement in the reduction of airborne dust exposure in some of the mines I’ve visited over several years.”

New South Wales

Although dust control is an ongoing issue, mining companies have responded well in the lead up to and since New South Wales introduced a new exposure limit this year.

AIOH member Jennifer Hines says mining companies performed high quality investigations when an individual’s dust exposure exceeded the limit, even prior to the introduction of the new limits.

However, it has gone to another level since the limits were halved, she says.

Hines, who has been working in the mining industry for 15 years, particularly in the underground coal sector, believes mining companies have been more proactive in preventing exceedances and in re-educating their workers about respirable dust and crystalline silica, including what needs to be done to keep exposures low and what controls need to be in place and maintained.

Hines, an independent member of the Standing Committee on Airborne Contaminants and Occupational Hygiene, formerly the Standing Dust Committee, feels the challenge is now in mining companies’ ability to adapt to change.

“Mining companies have implemented many effective controls; spray systems, ventilation, appropriate procedures and good training are a few of these. They have great knowledge on what should be done when it’s business as usual. But when something happens outside of that normal scenario, at times, they may not react as quickly as they could have,” Hines says.

“Some sites have trigger action response plans (TARP) and others could do more to protect their workers by following suit and implementing them. For example, a TARP means that if the mine starts cutting more stone than they were anticipating, it should produce a ‘trigger’ to review the process and review or alter controls in response to this. These responses (or controls) are set out in the TARP, and thus a more timely reaction will be enacted.

“However, there is definitely a trend of improvement in control implementation among mining companies.”

Real-time dust monitoring is of real assistance to the coal sector. Although there is still work to be done in terms of the technology available, the use of real-time monitoring equipment can provide useful indications of dusty tasks.

It gives mining companies the ability to quickly investigate sources of exposure, and also use these as an education tool.

The dust that is the real health issue is not visible to the naked eye, and therefore it can be difficult to comprehend the hazard, according to Hines. Being able to see the reading on the screen change as different controls are trialled, including moving workers into a slightly different position on operating equipment such as a continuous miner can be a powerful education tool, she says. 

“Understanding your sources of exposure is important as you can then put the appropriate controls,” she continues.

“If people are not monitoring dust levels to understand what they’re exposed to, then controls won’t be put in place and workers are likely to be exposed.

“Monitoring itself does not fix the situation, it does, however, inform you if there is a problem.”

As for automation, the coal sector has realised the benefits of new mining technologies as they remove employees from dusty environments.

Instead of being in the face of a longwall, employees can avoid being in the area altogether.

Hines has observed a step change in the New South Wales coal mining sector that is likely to result in more positive change.

With the reduction in the state’s dust exposure limits, she expects the increasing standard to continue to force improvement.

Reduction of occupational exposure limits is only one step in the journey of protecting workers. 

However, it will be an ineffective one without improved controls and compliance by the industries involved.

This article will appear in the November-December issue of Safe to Work.