DO I HAVE A HIGH-RISK
SILICA PROCESS?
AIOH SILICA HUB
List of potentially high-risk Crystalline Silica Processes (CSP)
Model Work Health and Safety Regulations (Crystalline Silica Substances) Amendment 2024 defines high risk, in relation to the processing of a Crystalline Silica Substance (CSS) as the processing of a CSS that is reasonably likely to result in a risk to the health of a person at the workplace.
These Regulations require that a silica risk control plan be prepared if processing of a CSS is assessed as high risk (Regulation 529CB) and that when determining if the risk could be high there can be no reliance on personal protective equipment or administrative controls that may be used to control that risk. In practical terms this means that when assessing a CSP risk on concrete cutting for example, the on-tool dust extraction and respirators worn do not change the obligation to undertake a risk assessment or identify that task as a high-risk CS process, or not.
In the state of Victoria, regulations also require the identification and control of high risk crystalline silica work . The Victorian definition of high-risk work includes that is reasonably likely to result in an airborne concentration of respirable crystalline silica that exceeds half the exposure standard for respirable crystalline silica or a risk to the health of a person at the workplace.
The table below contains a list of potential high-risk CSP, based on real workplace experience of AIOH occupational hygienists. Actual conditions and specific work practices will influence the potential for exposure and exceedance of a silica WES for the various respirable crystalline silica tasks listed. AIOH has guidance for personal exposure and other air monitoring (link Task 4) as there are various methods of measuring respirable dust. A well-informed CS risk assessment may use multiple methods and sources to understand the risk of exposure and may require specialist advice from a Certified Occupational Hygienist®. Only personal exposure monitoring results assessed in accordance SWA Guidance on the interpretation of WES for airborne contaminants are suitable for comparison with a silica WES.
To assist in the identification of ‘all the processing of a CSS carried out at the workplace that is high risk’ (Regulation 529CB) , AIOH has collated the following list of potential tasks that may be considered high risk for silica exposure in certain industries, workplaces or circumstances. Duration and frequency of exposure are risk factors as is the proportion of silica in a CSS. AIOH guidance on likely CS content of various natural materials and products is here (link Task 8)
In accordance with the Model WHS Regulations and Victorian Occupational Health and Safety Regulations 2017 the use of Respiratory Protective Equipment (RPE) does not alter classification of a task as high-risk.
Table 1: List of potentially high-risk CS processes or tasks
High risk CSP or task
Jackhammering
Shotcreting
Industry / workplace
Construction, construction domestic, demolition, roads, mining
Construction, construction domestic, roads, pool construction,
Grouting Construction domestic and commercial
Scabbling Construction, roads
Road profiling Construction, roads
Road header operation Construction, mining, roads
Operation of Tunnel Boring Machine (TBM)
Cutting/drilling/grindin
g or re-shaping
cement-based building materials
Construction
Task/ work description
Manual jackhammering, concrete and rock-based structures, pile breakback etc
Spray blasting involving adhesion of cement-based material to underground walls, tunnels, ceilings, earthen surfaces etc
Mixing of grout
Scabbling concrete with air driven mechanical tools
Profiling of roads (removal of old road surface) before laying of new asphalt
Tunnelling activities in hard rock, road cuttings
Tunnelling with a TBM
Construction, construction domestic, manufacturing, landscaping,
Dry ingredient mixing Manufacturing, construction domestic, landscaping
Sandblasting Metal industries, automotive repairers, painting, shipbuilding and steel infrastructure repair,
Aggregates handling
Construction, construction domestic, roadbuilding, cement blending,
Brick, tile, paving manufacturing Manufacturing
Dry sweeping and use of compressed air for cleaning
Various
Manual abrasive or cutting of brick, concrete, roof tiles, floor/wall tiles, floor screed, rammed earth, etc.
Dry silica bearing ingredient handling, bulka-bags etc for large range of products. Adhesives, plasters, plasterboards, paint, render, ceramics, glazing compounds, cement manufacturing, precast panels, pipes etc.
Use of sand or particle blasting (such as garnet) to prepare surfaces for other work.
Surface preparation, footings, foundations, landscaping, roadbuilding, drainage, concrete finishing
Blending silica bearing clays and additives, forming to moulds, baking, kilning, storage and handling and associated maintenance.
Use of air blowers to remove dust from surfaces and equipment
Comments
Exposure likely to be higher in trenches or enclosed areas. Significant secondary exposure risk from clothing and poor housekeeping.
Exposure likely to be greater in enclosed areas such as underground mines and tunnels.
Exposure likely to be greater in enclosed areas, or where Local Extraction Ventilation is not in use.
Exposure likely to be greater in enclosed areas. Less dust exposure if low pressure water scabbling is used, more dust if high pressure water used.
Potential exposure of profile machine operator and workers in general area
Higher exposures in high silica content soil or where high silica containing rock is present
Higher exposures when tunnelling in high silica content soil or where high silica containing rock is present
Exposure risk is dependent on both blast medium and substrate. WHS Regulation WHS Regulation 381 restricts CS content to 1% or less wt/wt. Use of recycle abrasive medium presents high risk from CS and other toxic materials.
Dried waste material presents a significant exposure risk.
Blowers and brooms disturb settled dust create exposure risk for cleaners and maintainers as RCS remains airborne.
High risk CSP or task
Mixing glazing compounds
Working with, sieving, milling and Bagging silica flour
Mineral extraction
Mineral processing (crushing and screening)
Industry/workplace
Manufacturing
Manufacturing, quarrying
Quarrying, mining
Quarrying, mining
Task /work description Comments
Mixing of dry silica in glazing compounds
Processing, milling, bagging of silica flour products
Removal of hard rock form mine, or quarry face or pit. Includes drilling, loading/prep of blasting etc.
Breaking of extracted minerals to various screen sizes. Primary, secondary, tertiary and quaternary crushers, various screen mills. Includes operation of conveyor belt systems
Many methods depending on ore body –picking, blasting, breaking, etc. Addition of silica containing stemming material to blast holes.
Many levels of crushing and screening have different risk profiles.
Mineral load-out and transport
Maintenance of mineral processing equipment
Waste processing
Quarrying, mining, retail landscape suppliers
Quarrying, mining
Material testing
Engineered stone * processing with CNC Operator
Engineered stone * polishing and edging
Engineered stone * surface lamination and cutouts
Engineered stone * cutting and grinding
Engineered stone * installation
Landfills, general recycling, solid inert construction waste recycling
Universities, manufacturing, mining/quarrying
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Loading of bulk aggregates to trucks, unloading at site, stockloading to rail etc..
Any maintenance work associated with extractive industry equipment (incl trucks, loaders, drill units, conveyors, crushers and screens).
Screening and processing of waste from various unknown sources, includes large scale recycling of concrete and brick/masonry rubble from demolitions sites.
Use of breakers and crushers to test properties of silica bearing minerals or products
Operation of automated computer numeric control (CNC)
Use of hand-held tools
Use of powered hand-held tools
Use of powered hand-held tools
Wet enclosed process; likely lower exposures than other machinists but still gives rise to secondary exposure
Exposures are high in wet and dry processing
Exposures are high in dry processing
Can result in high exposure over short amount of time when dry-cutting at installation site
* From July 1st, 2024, the manufacture, supply, processing and installation of engineered stone benchtops, panels and slabs is banned in Australia In Model WHS Regulations, engineered stone is a Crystalline Silica Substance as it contains 1% or more crystalline silica (as a weight/weight concentration) AIOH warns that engineered stone containing < 1% w/w of crystalline silica polymorphs may still contain amorphous silica and other hazardous substances that pose a risk to health in respirable form. AIOH recommends sampling and analysis as explained ( link to task 9) to determine composition and concentration of all CSS.
References
Exposure to Particulate Matter and Respirable Crystalline Silica in Tunnel Construction Workers Using Tunnel Boring Machines - PubMed (nih.gov)
Silica Exposure Estimates in Artificial Stone Benchtop Fabrication and Adverse Respiratory Outcomes | Annals of Work Exposures and Health | Oxford
Academic (oup.com)
Occupational Health and Safety Regulations 2017 (legislation.vic.gov.au)
Model WHS Regulations | Safe Work Australia
Hedges, et al, Correlating Exposure to Respirable Crystalline Silica (RCS) with Loss of Lung Function: Treatment of Data and Statistical Analysis, Medical Sciences, Vol 1 Issue 2 September 2021 MCMS-01-010.pdf (themedicon.com)
Longitudinal Analysis of the OSHA IMIS Database for Worker Exposure to Crystalline Silica Dust by Industry and Comparisons to the OSHA PEL, ACGIH TLV and NIOSH REL | Professional Development Conference and Exposition | OnePetro
SWSA UoA Engineered Stone Benchtops Final Report for open access.pdf (figshare.com)