Protecting workers from respirable dust in machinery cabins and control rooms

Respirable dust is a common sight at the nation's mine.

Dust particles may be small, but they can cause big problems for the health and safety of workers at mines, quarries, landfills, ports, and in construction and demolition. Engineering controls and education are needed to make sure workers stay safe.

Exposure to dust at mineral processing and industrial work sites is a cause for concern, leading to potentially serious respiratory problems and diseases if not kept in check.

The current workplace exposure standards set out by Safe Work Australia state that exposure to respirable crystalline silica (RCS) should not exceed 0.1 milligram per cubic metre over an eight-hour time-weighted average.

A 2016 study by Oxford Academic found that 6.6 per cent of Australian workers faced exposure to RCS, with earthmoving works or excavation works, and construction workers the most likely to be affected.

RCS, or silica dust, is extremely small (around 100 times smaller than the average grain of sand), so it is generally imperceptible when inhaled. It is often the product of natural rocks and quartz, as well as construction materials such as bricks, cement, tiles and some plastics.

The everyday minerals processing works common to materials processing causes hazardous dust to rise into the air in significant quantities, so it is important that protection is in place to ensure workers stay safe.

Coal workers’ pneumoconiosis (CWP), a disease caused by respirable coal dust and colloquially known as black lung, has also received increased public awareness in Australia due to a spate of recent cases in Queensland.

The control cabin of a D10 dozer.

 

In the United States too, black lung is a problem — a study by the American Journal of Public Health revealed last year that in the coal-rich Appalachian states of Kentucky, Virginia and West Virginia, a shocking one in five coal miners with over 25 years’ experience had contracted the disease.

Respirable dust exposure is usually broken down into three stages. Inhalable dust (or the inhalable fraction) is the airborne particle that is breathed through the mouth or nostrils.

This then becomes a thoracic fraction when it penetrates the airways of the lung. Following this is the respirable fraction, which represents the particulates that can breach the gas exchange tissue of the lungs. These are usually between four and 10 microns in diameter, and represent the biggest threat for industrial site workers over an extended period of time.

This dust is so small that it can be easily overlooked. Australian company BreatheSafe has adopted the European Standard EN15695-3 as the baseline for rules regarding exposure limits for cabin operators in the absence of sufficiently detailed Australian regulations.

This standard is actually designed to protect operators in tractor cabins using hazardous materials such as pesticides, but according to BreatheSafe sales and operations manager, Javier Riveros, they are equally applicable to mining cabins.

“The cabin has to be very well-sealed so that there’s no chance for particles to ingress into the cab, and there is a stipulation that the filter has to be highly efficient at levels above 99 per cent,” he tells Safe to Work.

Safe Work Queensland guidance materials released in December 2018 recommend that cabin doors and windows be closed at all times to maintain an effective seal and to maintain pressure. High efficiency particulate air (HEPA) filters should also be fitted to further isolate the operator and protect expensive components in the cabin from becoming damaged.

It is important that operators keep cabins sealed and windows closed to avoid contamination.

 

BreatheSafe offers audits on machinery cabins to make sure operators are effectively protected. The company’s goal is to work towards implementing zero harm at industrial sites, including protection from exposure to silica dust (particularly in the mining and construction industries), asbestos, sulphuric acid, hydrogen fluoride, diesel particulate matter and other inhalable and respirable substances.

BreatheSafe’s cabin audits follow similar guidance principles to Safe Work Queensland’s for managing hazardous substances recommendations, ensuring a tight seal to isolate the cabin’s air conditioning system.

The company also implements software that uses cameras that can be placed in the cabin or worn by the operator (on their helmet for example) to help identify sources of exposure to respirable dust.

“This software can be used as a real-time dust monitor to correlate visual data so you can actually pinpoint when you’ve had high exposure and what the operator was doing at the time,” explains Riveros.

“In the case of a cabin, if the operator keeps opening and closing a window for example, it can show that there are high spikes and that the operator is doing something unsafe.”

Riveros says that while it is unfeasible to keep the cabin sealed at all times — such as instances where a driver has to exit the cab to check on something — it is also quite common for workers in cabins to have their windows open in spite of the risks.

By introducing such engineering controls, it is possible to significantly reduce respirable dust, he continues.

“The whole idea is that if you’re in a pressurised cabin with high-efficiency filters you maintain the closure of doors and windows at all times, but it just depends,” he says. “Some operators may have to go out and clear tracks or debris that has threatened their view or impeded their movement and in such situations they will have to open the door to do something.

“The main thing is that when we have this audit we can actually show them that by doing that they’ve introduced dust into the cabin.”

This article also appears in the Apr-Jun 2019 edition of Safe to Work.