Extractive industries - Silica dust

Topics: Workplace Health, Mining and quarrying, Silica dust

Dust generated from work processes involving natural or artificial stone can cause serious illness.

Latest Northern Ireland estimates suggest that there could be 20 lung cancer deaths per year due to silica dust exposure at work.

What is Respirable Crystalline Silica (RCS)?

Size comparison between a penny and silica dust

Silica is a crystalline (crystal-like), naturally occurring, mineral commonly found in materials such as rock, sand, quartz, clay, granite, and concrete.

When these materials are cut, ground, or otherwise disturbed (for example, during activities like blasting, crushing, mining, or screening), fine dust particles of crystalline silica can be generated.

Respirable crystalline silica (RCS) dust particles are small enough to be breathed deep into the lungs. RCS dust can build up in the lungs and lead to lung damage.

The table below details several different types of stone and the percentage of silica they may contain.

Table of type of stone and percentage of Silica they may contain
Type of stone	Percentage of silica
Sandstone, gritstone, quartzite	Above 70%
Mortar, concrete	25% - 70%
Shale	40% - 60%
China stone	Up to 50%
Granite	20% - 45% (typically 30%)
Slate	20% - 40%
Ironstone	Up to 15%
Basalt, dolerite	Up to 5%
Limestone, chalk	Up to 5% (typically less than 2%)
Marble	Up to 5% (but can contain veins of crystalline silica so the overall content may be a lot higher)

Table note: Information sourced from HSE publication - 'HSG201: Controlling exposure to stone dust' - (hse.gov.uk)

Health risks

Due to the nature of the work, employees in extractive industries are likely to be exposed to fine respirable dust containing crystalline silica.

RCS is found in almost all kinds of rock, sands, clays, shale and gravel.

Workers exposed to RCS are at risk of developing a range of occupational diseases including:

Asthma
Chronic Obstructive Pulmonary Disease (COPD) - (including Chronic Bronchitis)
Lung cancer
Silicosis

Anyone who breathes in RCS should know the damage it can do to the lungs and airways.

Range of exposures for job types calculated as an 8-hour time weighted average concentration in mg/m³
Job title / Description	Respirable dust (4mg/m³) - mg/m³	Respirable crystalline silica (0.1mg/m³) - mg/m³
Quarry manager / Site foreman	0.25 to 1.27	0.05 to 0.22
Plant / Chrusher operator quarry fitter	0.05 to 5.92	0.06 to 1.32
Operator - Shovel, excavator, dumper truck	0.09 to 0.32	<0.02 to 0.08
HSENI Inspector	0.22 to 0.44	0.05 to 0.10

HSE (GB) has produced COSHH essentials advice sheets specific to the quarry sector to help employers control exposure to RCS and protect employees health. For more information, please see the following link:

Quarries silica - COSHH Essentials advice sheets - (HSE website)

Legislative duties

While at work, both employers and employees must comply with:

Employers must:

undertake a suitable and sufficient assessment of the risk to health created by work involving substances hazardous to health
identify, implement, and maintain suitable risk control measures
develop/review a dust action plan:
- identify and detail the issues and remedial action
- detail timescales to complete remedial action
- identify person responsible
involve and inform employees
provide information, instruction and training to employees and others
provide adequate supervision to ensure control measures are used correctly
monitor effectiveness of controls
provide health surveillance (in appropriate cases)

Employees must:

take reasonable care for the health and safety of themselves and of other persons at work
co-operate with employers or others so far as is necessary to comply with applicable legislative duties or requirements

Controls

consider the hierarchy of controls for all dust generating work activities / processes
minimise and suppress the dust - work methods, process control
remove the requirement for the worker to be in the area - design and automate the process
isolate the worker - control rooms, remote from the working area
clean and maintain plant, working area, and vehicle cabs:
- avoid dry brushing
- don’t clean with compressed air
- use a H class vacuum with high efficiency particle (HEPA) filter or wet cleaning methods
Respiratory Protective Equipment (RPE) is a last resort and alone should not be relied upon as a control measure - RPE may be needed in addition to all of the above

Respiratory Protective Equipment must be:

adequate for the amount of dust - P3 Filter or greater if required
suitable for the purpose and compatible with other PPE
face fitted for the individual operator (clean shaven)
worn correctly - filters and disposable masks changed regularly
kept clean, maintained and stored to prevent contamination
regularly examined and tested and records kept
training - to use, check and clean the respirator

Areas of focus

Control rooms:

doors and windows kept closed (maintain seals, self-closing doors)
air conditioning (filter)
reduce dirt / dust being carried into room
floors easy to clean (tiles, linoleum)
clean using vacuum / mop
wet wipes

Vacuum:

choose a H class unit fitted with a HEPA filter
fitted with a low flow indicator
pre-filter fitted
consider waste capacity ie frequency of emptying

Vehicles:

doors and windows kept closed (maintain seals)
air conditioning (filter)
in cab filters (maintenance schedule)
cleaning vehicle cab (vacuum, wet wipes)
seat cover (wipeable fabric)

Welfare facilities:

separate changing area and canteen
overalls removed before entering canteen
lockers provided for storage of PPE
hand washing facilities with warm water, soap and hand drying
suitable floors - tiled, linoleum
walls - tiled, PVC
clean using vacuum / mop
air conditioning (filter)