Dust and fibres

When a person breathes, inhalable particles suspended in the air enter their body. Most large particles are stopped in the nose, but smaller respirable particles reach the lungs.

Dusts can contain hazardous materials for which a workplace exposure standard exists.

One of the most common dusts encountered on mine sites, in construction and in some manufacturing workplaces is quartz (crystalline silica), which is a mineral found in many ore bodies, sand, concrete, bricks and engineered stone. Excessive exposure to respirable crystalline silica can cause silicosis, a serious and potentially fatal respiratory condition.

Several varieties of asbestiform minerals may be encountered during exploration activities for iron ore, base metals and gold and subsequent mining. Welding and abrasive blasting can also generate toxic dusts and fumes. During construction work, risks associated with asbestos in the built environment, and hazardous chemicals such as lead in old paint, may present a hazard.

Where are they found?

Mining

People can be exposed to dust almost anywhere on a mine site, but activities such as drilling, blasting, hauling, stockpiling and crushing of ore have the potential to create unacceptable dust exposures if not controlled.

Wet ore or concentrates will reduce dust exposure, but people can be exposed to dust from dried spilled material, or generated from tailings storage facilities, product stockpiles and during product transfer.

Some metals that are mined or present as processing reagents are potentially toxic if inhaled or ingested, such as lead, arsenic and mercury. Hazardous gases and mists such as sulfur dioxide, hydrogen sulfide, hydrogen cyanide and ammonia can also be generated in process plants and refineries. Fibrous minerals such as crocidolite asbestos, chrysotile asbestos and grunerite can be encountered during exploration and mining.

Mineral exploration drilling
- Mineral exploration drilling - code of practice - This code is a practical guide to assist those involved in mineral exploration to develop and implement safe systems of work for drilling operations, particularly in remote areas. It was issued under the Mines Safety and Inspection Act 1994 and is still an approved Code under WHS laws due to transitional legislation.
Guidance about fibrous mineral hazards
- Frequently asked questions on fibrous minerals in Western Australia - information sheet - This information sheet outlines the frequently asked questions on fibrous minerals in Western Australia.
- Frequently asked questions on cracker dust - information sheet - This information sheet outlines the frequently asked questions on cracker dust.
General industries

Dust and fibres are found in a wide range of general industries, such as:
- Construction – from earthworks, demolition, handling insulation, mixing concrete, mortar or plaster, waste handling, abrasive blasting and welding;
- Manufacturing – from welding, grinding, abrasive blasting, cleaning, waste handling, recycling, and material (eg wood, metal, stone) processing;
- Agriculture – from grain handling, pesticides, plant materials, manure; soil handling;
- Transport – from material handling (eg grain, cement, bulk foods, ore, chemicals, sand);
- Waste and recycling – from handling or processing of waste/recyclable materials.
Diesel engines can emit diesel particulate matter (DPM), exhaust gases, including a wide range of organic vapours, and a small amount of metallic compounds, which are collectively referred to as diesel emissions.

The potential short- and long-term health effects from exposure to diesel emissions are well documented (for example by Safe Work Australia) and range from irritation to nausea, increased allergy risks and increased risk of heart or lung disease, including lung cancer. Exposure may occur in vehicle workshops and where diesel equipment is used in confined areas, such as underground, in ore and concentrate storage sheds or in large tanks.

Guidance about underground air quality and ventilation
- Management of diesel emissions in Western Australian mining operations - guideline: This guideline should be used by anyone planning or conducting underground mining where diesel engines are likely or are being used.
- Guide to managing risks of exposure to diesel engine exhaust in the workplace – Safe Work Australia - This Guide provides information on how to manage risks associated with exposure to diesel exhaust in the workplace.
Legionella pneumophila is a bacteria found in cooling towers, air conditioners and other water systems. In rare cases, the inhalation of contaminated aerosols may cause Legionnaires’ disease, which is a form of pneumonia caused by an acute bacterial infection of Legionella.
- Prevention and control of Legionnaires’ disease - code of practice - This code of practice provides general guidance on the identification and control of safety and health hazards and risks associated with Legionnaires’ disease. While this Code was approved under previous legislation, it remains an approved WHS Code due to transitional legislation.

How can dusts and other airborne contaminants be managed?

Substantial dust can be generated during drilling operations, particularly if undertaken in dry conditions. The generation of dust needs to be minimised as much as practicable.

Control measures include:
- fitting drills with a water injection or dust extraction system (or both) suitable to control or extract the dust at the hole during drilling
- where dust is being discharged through ducting, positioning the ducting so dust will not blow back on the operators or others working in the vicinity
- controlling dust at the source if using a cyclone sample collector and during the crushing and splitting of samples
- operating drill rigs from a well-sealed HEPA filter air-conditioned cabin
- regularly replacing filters or cleaning filtration devices and systems to prevent dust build-up.
Samplers and other operators who may be exposed to dust will require suitable personal protective equipment (PPE), which should be selected, worn and maintained in accordance with Australian Standards AS/NZS 1715 Selection, use and maintenance of respiratory protective equipment and AS/NZS 1716 Respiratory protective devices.

Australian Standards are available from Standards Australia.
Dust needs to be controlled during the loading of broken material such as ore or waste into trucks, and on haulage roadways.

Controls can be provided through:
- wetting down of haul roads and blasted piles
- installing water sprays at dump pockets
- dust extraction at conveyor tipping points, crushers, and screens
- providing HEPA filter air-conditioned cabins in plant equipment.
For air-conditioned plant, the cabin doors, windows and any other access point such as cabling routes should be well sealed to prevent dust ingress.
Dust needs to be effectively controlled at each crusher, mill and grinder, with dust control appliances fitted at the primary crusher feed hopper as well as secondary and tertiary crushers plus screens. Conveyor belt transfer points and stockpile tunnels may also require dust control measures.

Any spillage and dust build up on and around the plant and equipment needs to be monitored and removed as necessary. After processing, dust control will be required at stockpile stackers and reclaimers, and during loading and unloading operations (e.g. ship, train, road train).

Dust management is assisted by having wet process streams and dust extraction on transfer points.
Most mine sites have a sample preparation and laboratory area, where crushing, screening and analysis of samples is routinely undertaken. This work is also conducted in general industries by assay laboratories. Exposure to dusts (including silica) and hazardous reagents found in the laboratory needs to be controlled. Effective local ventilation is required for fume cupboards, fire assay areas where lead is handled, and sample preparation areas.

Personal monitoring may be required to confirm controls are effective, and biological monitoring may be required in areas such as assay laboratories using hazardous reagents, such as litharge (lead oxide).

Guidance
Welding and cutting operations are common in industry, and generate metal and other fumes. Local extraction systems may be required to ensure fumes are not discharged into other work areas.

Abrasive blasting occurs at many mines and in general industry. The abrasive agent used to clean equipment can generate considerable dust. Open-air abrasive blasting should be done away from working areas with appropriate dust control measures. The operators must be suitably provided with protective equipment with a clean air supply. There are limits on the amount of silica and other contaminants allowed in the abrasive material.

The aim is to reduce dust generation - PPE should be used as a last line of defence against exposure.
- Code of Practice – Abrasive blasting

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