2. Occupational Hygiene Monitoring of Dust
• Types of dust in small mines & quarries
• Requirement to monitor dust
• How is monitoring conducted?
• What analysis is done on samples?
• What do the results mean?
• Free Dust Sampling Program – status
3. Occupational Hygiene Monitoring of Dust
The two main types of atmospheric dust are:
Inhalable Dust – dust particles that are inhaled and are trapped in the nose and throat region
Respirable Dust – very fine dust particles that are inhaled and find their way deep into the lungs.
What is Silica Dust?
Silica – is a mineral present in most rocks, sand, gravel, clay and shale.
When rocks materials are mechanically crushed, drilled, split or
screened fine particles of crystalline silica, or quartz, is released as
Respirable Crystalline Silica – is very fine silica dust particles that can
find their way deep into the lungs.
Breathing in crystalline silica dust over a long period of time can
lead to lung cancer and silicosis.
Silicosis – is an irreversible scarring and stiffening of the lung tissue.
4. Occupational Hygiene Monitoring of Dust
Why do we need to monitor dust?
Under the Work Health & Safety Act:
A Person Conducting a Business or Undertaking has a duty of
care to ensure people in the workplace are not exposed to health
and safety risks.
What monitoring is required?
Under the Work Health & Safety (Mines and Petroleum Sites)
Monitoring of the health hazards associated with the mining
operation is required.
Monitoring of the exposure of workers to the health hazards is
5. There are two main types of dust monitoring:
Personal Exposure Monitoring –
sample is collected from the breathing zone of the worker.
the worker wears the monitoring device while working (full shift).
results are directly comparable to the Workplace Exposure Standard’s (WES’s).
Static or Area Monitoring -
monitoring in a fixed location (not worn by worker)
monitoring duration can be short (15 minutes) or full shift
results are NOT directly comparable to the Workplace Exposure Standards.
results used to determine if dust is an issue in a certain area, or
to determine if dust control measures are effective.
There are also two main ways of measuring dust:
Active Sampling – a measured volume of air is drawn onto a filter using a
small sampling pump.
Real Time Monitoring – air passes through a light beam or laser and the
number and size of particles are measured in real time.
Occupational Hygiene Monitoring of Dust
6. Personal Monitoring
Occupational Hygiene Monitoring of Dust
Respirable Dust &
Crystalline Silica Sampling
Cyclone Sampler – to only collect the
finer fraction of dust (<4µm)
IOM Samper – to collect
all dust size fractions
Filter Cassettes & Filters
Samples should be collected over the full work shift, or for as long as reasonably possible.
7. Occupational Hygiene Monitoring of Dust
How do we analyse the samples?
Sample filters are weighed before and after sampling.
The amount of dust on the filter is determined by the change in weight
The filter can then be further analysed to determine dust composition
(eg. for metals, crystalline silica).
Samples should be analysed by an accredited laboratory.
Inhalable Dust Filter
Respirable Dust Filters
8. Occupational Hygiene Monitoring of Dust
Aim: Personal Exposure Sampling Results <50% of the Workplace Exposure Standard.
What do the results mean?
Details recorded during sampling (flow rate, sampling time, shift length etc) are used to determine a dust result expressed as
concentration in air (mg/m3).
The result is then directly comparable to Workplace Exposure Standards – if a PERSONAL sample was collected.
A Workplace Exposure Standard is the airborne concentration of a chemical that is not expected to cause an effect on the
health of an exposed worker. They are calculated to account for workplace exposures over an 8-hour work day, 40-hours per
week, over a working lifetime.
Each WES is expressed as an 8-hour Time Weighted Average (TWA)
The 8-hour TWA WES can be adjusted to allow for extended work shifts (eg 10hr,
12hr shifts) and different work rosters.
Current WES’s for dust are:
Inhalable Dust 10mg/m3 8hr TWA
Respirable Dust 3mg/m3 8hr TWA
Respirable Crystalline Silica 0.05mg/m3 8hr TWA
9. Occupational Hygiene Monitoring of Dust
Resource Regulators’ Sampling & Monitoring Assistance Program:
Personal dust sampling was offered to Operators of small mines and quarries to assess
potential high exposure activities or areas at their sites.
Program Progress Status:
• Offer extended to 572 small mines / quarries
• A total of 19 sites responded and requested monitoring
• Sampling completed at 9 sites to date
• A further 10 sites scheduled for sampling prior to end December 2020
• 35 respirable dust and crystalline silica samples collected to date
The main types of dust are defined by the size of the particles that are in the dust.
Inhalable dust is usually expelled by the bodies natural defence system, for example mucous in nose and sneezing etc.
Thoracic dust is the dust that slightly smaller in size and is capable of reaching the larynx.
Respirable dust is less than about 3 micron in size. In comparison, a grain of sand is around 90 microns and a human hair is around 60 microns in size.
Pneumoconiosis are lung diseases caused by breathing in dust particles which damage your lungs. The main types are asbestosis (from asbestos fibres), silicosis (from silica dust) and coal workers pneumoconiosis (or black lung) (from coal dust).
Personal Exposure monitoring – the monitor must be placed so that the air that is sampled is from the workers Breathing Zone. The breathing zone is a 30cm sphere around the nose and mouth.
Monitoring is preferably undertaken for the full duration of the work shift.
Static or Area monitoring – used as an indicator of airborne contaminants, not directly comparable to Workplace Exposure Standards as it is not sampled from the Workers breathing zone.
Active Sampling – a measured volume of air is drawn onto a filter using a sampling pump. The filter is then analysed for the amount of dust collected on it.
Advantage – you can find out what the dust is made up of. Disadvantage - results are not known until the sample is analysed.
Real Time Monitors – a beam of light or a laser is used to shine on the air and detects the number of particles and the size of the particles. This is recorded or logged in the device.
Advantage – you can see the dust concentration in the air in real time. Disadvantage – you don’t know what the dust particles are comprised of, the unit only looks at the amount and size of the particles.
Show the audience the two different types of sampling trains – Inhalable & Respirable
The Inhalable sampler collects all sizes of dust in the breathing zone, while
The Respirable sampler only collects the fine particles (median particle size of ~4µm). The larger particles drop down into the "grit pot" at base of cyclone.
Note the “even coverage’ of particulate matter on the Inhalable Dust Filter (remember this filter is made up of all of different size fractions of dust),
the Respirable dust filters, which show a higher concentration of particulate in the centre of the filter. This is due to the ‘cyclonic effect’ of the air, which separates out the larger fractions, so only the finer fractions are collected on the filter.