WHAT DO I NEED TO KNOW ABOUT AIR MONITORING?
AIOH SILICA HUB
ALICIA GORMAN
Air Monitoring for Crystalline Silica (CS):
Methods and Considerations
Requirements for Persons Conducting a Business or Undertaking (PCBUs) in relation to crystalline silica substances (CSS) are effective on 1 September 2024. PCBU must engage a competent person in relation to respirable dust and respirable crystalline silica (RCS) risk assessment. This involves planning, sampling, analysis, interpretation of air monitoring results and development of risk control plans based on air monitoring.
Air monitoring is critical to assess Respirable Crystalline Silica (RCS) exposures in workplaces, ensuring compliance with exposure standards and protecting worker health. This information sheet provides guidance on various air monitoring methods, their applications, and other considerations during monitoring.
1. Purpose of Air Monitoring
Air monitoring for RCS aims to quantify airborne concentrations in the breathing zone of workers, validate the effectiveness of control measures and ensure regulatory compliance with applicable Workplace exposure standards (WES) for airborne contaminants published by Safe Work Australia (SWA)
There is no single WES for RCS; in fact there four WES that may be applicable to CS work. This is because there are different polymorphs (or types) of crystalline silica (CS) that could become airborne during work involving crystalline silica. The most common type of CS in nature is α-Quartz and the respirable dust from CS work is the air contaminant most monitored however cristobalite is also present at some level in natural and engineered stones A list of common natural and industrial materials that might release CS into the air at a workplace can be found here.
Table 1: Crystalline silica WES and their values.
2. Methods of Air Monitoring
There are various methods of measuring respirable dust from crystalline silica. A wellinformed CS risk assessment may use multiple methods to better understand the risk of exposure.
However, only personal exposure monitoring results assessed in accordance SWA Guidance on the interpretation of WES for airborne contaminants can be used to evaluate compliance against a WES.
Table 2 summarises the 3 common methods, their function and specific considerations.
Table 2: Summary of Air Monitoring Methods for RCS
• Assesses workgroup exposure based on representative amount of individual samples.
• Requires equipment and process to meet Australian Standard AS2985 method for sampling and analysis of respirable dust.
Involves using personal samplers worn by workers in breathing zone to measure RCS exposure during shifts, including breaks.
• Evaluates compliance against WES or whether exposure from CS processing reasonably likely to exceed 50% of WES as per Reg 529CA.
• May indicate future workgroup exposures, if statistically valid data is captured.
• Requires analysis by a NATA-accredited lab using validated methods such as Xray Diffraction (XRD) or FourierTransform Infra-Red (FTIR)
• AIOH recommends this type of air monitoring be undertaken and interpreted by persons with specific competencies.
Method
Static (fixed) sampling
Measures RCS levels in specific areas to identify sources and assess process control effectiveness
Real-time monitoring
Uses direct-reading devices for immediate dust concentration measurements.
• Useful for verifying engineering controls and prioritizing dust management efforts.
• Helpful to identify sources of CS and whether they are releasing RCS.
• Indicates dust concentrations in a work area or during a work task over time
• Supports real-time control adjustments.
• Investigate dust sources.
• Detect peak exposures.
• Not all monitors are specific to CS. More commonly they measure all dust particles
3. Engaging a Specialist
• Locations of static sampling points should be well-documented for repeatability.
• Results inform control effectiveness but cannot be used for demonstrating compliance with a WES.
• AS2985 method for sampling and analysis of respirable dust still applies.
• Allow for rapid response as provides real-time dust results typically displayed on a digital interface or screen.
• Cannot be used for demonstrating exposure against a WES.
• Useful for indicating how long dust concentrations remain airborne and for when controls need to be increased for example respirators worn.
• Competence in operation and knowledge of limitations of particulate real time monitors is essential
RCS risk assessment (including planning, sampling, analysis and interpretation of air monitoring results) should be undertaken by a competent person with the relevant skills, knowledge, and experience to carry out the task For example, a Certified Occupational Hygienist (COH®) or recognised equivalent is suitably qualified to establish sampling programs and interpret exposure results, whilst an occupational hygiene technician may be suitable to undertake sampling when under the direction of a COH®. Further information regarding occupational hygiene competencies is outlined in the AIOH Guide for Selecting Occupational Hygiene Services
4. Elements of
RCS Monitoring
When undertaking RCS air monitoring, due diligence must be undertaken to ensure that data collected is valid and reliable. Here are some key elements that should be considered when assessing RCS exposures
Planning
• Before monitoring, workers should be categorised into Similar Exposure Groups (SEG) with similar exposure scenarios.
• Sampling plans should be developed based on SEG, considering variability in work conditions and exposure potential.
• A sufficient number of samples should be collected to ensure results are reliable and representative. A COH can advise on the number of samples appropriate for the CS process (CSP) scenario. The aim is to collect a statistically valid number of samples to evaluate workgroup exposure and compliance with applicable WES.
• Appropriate considerations should be made to minimise any uncertainties which may arise in the sampling and analysis process.
Sampling
• Sampling must be undertaken in accordance Australian Standard 2985-2009, Method for sampling and gravimetric determination of respirable dust.
• Exposure monitoring should be conducted for the entire duration of the shift so far as is reasonably practicable.
• Sufficient observations should be recorded during sampling to inform exposure evaluation, such as tasks undertaken by the worker, interfacing activities, site conditions, effectiveness of implemented control measures and appropriate use of respiratory protection
• Invalid samples should be resampled at the next available opportunity.
This short video contains AIOH Top 5 Tips for Assessing Exposure in the Workplace
More detail on the specifics of personal exposure monitoring for CS may be found in the AIOH Technical Paper Minimising Uncertainties When Sampling and Analysing Respirable Crystalline Silica (RCS) (2024).
Sample Analysis
• Laboratory analysis of samples should be undertaken by in accordance with National Health and Medical Research Council (NH&MRC, 1984)) Methods for Measurement of Quartz in Respirable Airborne Dust by Infrared Spectroscopy and Xray Diffractometry. The laboratory should be NATA accredited for the analysis method.
The analysis method should be selected with consideration of the specific characteristics of the workplace, forms (polymorphs) of RCS present, and limitations of the method. Further guidance from AIOH on measurement CS concentration in various natural and industrial materials and the estimation of RCS is here.
Data Analysis
• Exposure sampling data should be analysed by a competent person, using validated statistical methods where appropriate, to interpret results accurately.
• Real time monitoring data will not be appropriate for statistical analysis of compliance with the WES
5. Specific Considerations for Crystalline Silica Processes (CSP)
As of 1 September 2024, the Model Work Health and Safety Regulations (Crystalline Silica Substances) Amendment 2024 comes into effect, providing stronger regulation of crystalline silica substances (CSS):
• Air monitoring for RCS must be undertaken for the processing of a CSS that is high risk (Regulation 529CE)
• RCS air monitoring will also assist in determining whether the processing of a CSS is considered to be high risk, by informing “whether the airborne concentration of RCS is reasonably likely to exceed half the WES” (Regulation 529CA (2)(e)).
Determining risk to health from airborne contaminants and accurately measuring airborne CS requires specific expertise. Experts in assessing RCS exposure risk, can be found through AIOH directory here.