Protecting Workers from Respirable Dust Hazards in Open Pit Mining

By Henry Skjerven
Last updated: December 30, 2021
Key Takeaways

Open pit mining creates incredible amounts of dusts. WIthout proper respiratory protection, your workers are at risk of serious health complications.

An open pit mining operation is one that extracts minerals by digging through the surface. The excavation can run deep, but unlike underground mining, the activities take place in the open air.


That eliminates or reduces some of the risks involved in mining. But working in the open air doesn't mean that workers can breathe easily. Open pit mining produces large quantities of dust, which is a significant hazard in and of itself.

The scope of open-pit mining is huge. My personal experience with them covers a few different types:

  • Limestone quarrying
  • Open pit iron mines
  • Open pit tar sands
  • Open pit coal mining

All of these types of operations produce a tremendous amount of dusts. And every safety professional knows that respirable dusts can cause irreversible damage to the respiratory system, damage that can ultimately be fatal.

On top of that, some of these operations have their own additional hazards. Limestone quarrying, for example, due to the strong alkaline nature of that mineral.

(Learn about The Dangers of Silica to Your Respiratory System)

Complicating things is the fact that these hazards are microscopic. We're talking respirable dusts of 10 microns or even smaller. It's wrapped into the very definition of a respirable dust:

Particles that will penetrate into the gas exchange region of the lungs. A hazardous particulate size less than 5 microns. Particle sizes of 2.5 micron (PM2.5) are often used in USA.


At that size, these dusts can go straight to the alveoli (where your lungs and your circulatory system interact) and can stay there, impeding the functioning of your lungs.

Dust Control in Open Pit Mining

There are different types of open pit mining. But at a basic level, they have one thing in common: producing dust by mechanical means. That includes:

  • Drilling
  • Explosives
  • Digging
  • Transporting material (wheel-generated dusts on haul roads)
  • Primary and secondary crushing
  • Screening
  • Handling, sorting, and piling finished materials
  • Running conveyor systems
  • Creating spoil piles
  • Loading and transporting product

Last I checked, all of these operations still require workers to be present in the immediate area, in the area where dusts are produced and dispersed.

Just like all of these operations produce dusts in similar ways, these dusts can also be controlled in the same manner. I've seen the use of water, fog cannons, and even a mixture of water and calcium chloride applied on haul roads.

All of these are effective. However, it's important to also have controls at the personal level. That means respiratory PPE and basic personal hygiene measures.

Hazard Identification and Respiratory PPE

Unfortunately, the PPE used by miners hasn't always been adequate.

As the operator of a primary crusher in a limestone quarry, I spent ten-hour shifts in a literal cloud of dusts. My PPE at the time was a dry rag tied over my mouth and nose. At the end of a shift, I would be covered in dust and that dust made its way into my truck, my home, and even my bed.

I wish I had known then what I understood now – that these risks weren't worth taking and that respirators can quite literally save your health and your life. I'm old enough, though, that there was still no legislation in place requiring them. So, it was a rag over the nose for me.

(Learn about The Basic Types of Respirators – And How to Select the Right One for Your Workplace)

That's not nearly adequate enough. But what is?

Before we figure that out, we need to know about the levels of exposure. If you don't have a dust sampling program in place, it's time to get one.

The open pit iron mines in northern Labrador and Quebec, for example, had full-time industrial hygienists on staff who ran daily monitoring and inspection programs. They kept years of data, including annual pulmonary function tests on all staff.

However, while hazard recognition is important, it's not the same as hazard control.

After hazard recognition comes hazard identification. Then testing and monitoring, which are two critical components of your control system.

PPE is also going to be essential. Every open pit operation must have a respiratory protection program, covering all the bases with regard to due diligence, and policies and procedures that ensure personal respiratory protection is in use every single day.

Look into continuous personal dust monitoring (CPDM) certification, which is required in the coal mining industry. It puts the use of PPE squarely with the worker (though it's still the employer's responsibility to put that PPE into the hands of their employees).

But even something as simple as a disposable N95 mask can be effective for limiting exposure to respirable dusts, so long as it is used properly.

Your hazard assessment will determine exactly what kind of protection is needed. And remember that you have tremendous amounts of resources at your disposal. The Mine Safety and Health Administration (MSHA) under the US Department of Labour is your go-to link and source. NIOSH, OSHA, and ANSI all speak to the subject as well. Respiratory PPE manufacturers will also be happy to help you assess your PPE needs.

(Learn about the Key Components You Need to Have in Your Respiratory Protection Program)

Take Steps to Reduce Exposure to Dusts

If you're in charge of safety for an open pit mining operation, be sure to familiarize yourself with the problems caused by respirable dusts, as well as the dust controls that can significantly reduce the risks of exposure.

Take the time to acquire a working knowledge of the primary outcome of these dust exposures: pneumoconiosis. Study up on asbestosis and silicosis. Look at the statistics on illnesses and deaths from dust exposure. Coal mining and black lung may have received huge media attention for decades, but there are extreme hazards in other types of mining as well.

I didn't recognize these risks when I worked in those pits and I certainly didn't do enough to protect my lungs from the dusts that surrounded me.

When I fill prescriptions for asthma and COPD medications, I can't help but wonder if there's a direct connection between all the dusts I breathed in and what my lungs go through now.

I'll never know for sure. But I do know that no one should be exposed to dusts the way I was, and that includes your workers. So, make sure your respiratory program is comprehensive and that every worker has the protection they need.

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Written by Henry Skjerven

Henry Skjerven

Mr. Skjerven has consulted professionally for over 27 years, with extensive Canadian experience, literally from coast to coast but with a home base in Western Canada. His experience ranges from marketing, adult education, and heavy transportation (rail) to municipal public works, fleet and transportation, oil and gas construction in the tar sands, emergency response (Fire and Ambulance), Public Works, Parks and Recreation, Security, as well as human resources and software systems, including enterprise style projects.

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