Monitoring exposure to crystalline silica
Where workers are exposed, suspected of being exposed or are concerned about exposure to crystalline silica, the person conducting the business or undertaking (PCBU) has a duty to arrange a health monitoring appointment for the worker(s) with the registered medical practitioner.
Workers should undergo a medical examination annually. The medical examination should include:
- records of personal exposure
- physical examination
- standardised respiratory questionnaire and pulmonary function tests in accordance with appropriate quality guidelines, and
- chest X-Ray full posterior-anterior (PA) view (as indicated, see below).
Respiratory function tests
Respiratory function testing should be conducted in accordance with appropriate quality guidelines. Tests should be performed as a baseline and annually.
Individuals with progressive decreases in respiratory function beyond that normally associated with age should be reviewed more frequently or referred to an accredited respiratory physician with experience in occupational health.
Cigarette smoking can significantly exacerbate lung function loss attributable to silica dust exposure. The smoking history and status of the worker should be recorded and considered during the health monitoring program. Advice regarding the impact of smoking on the symptoms of disease should also be provided to the worker.
Chest X-rays should be carried out as a baseline measure. The frequency of follow up X rays should be based on exposure levels.
X-rays should be taken in a specialist radiology practice or hospital department . The X-rays should be read by a radiologist who meets the reporting requirements and competencies of the RANZCR (the Royal Australian and New Zealand College of Radiologists recommends using a specialist radiology practice or hospital radiology department accredited under Diagnostic Imaging Accreditation Scheme (DIAS) for Medicare and meeting the quality criteria of the ILO classification, so it may be used later for comparison) or is qualified as a B reader.
For lower risk occupations and industries, a chest X-ray is recommended to be carried out every five years for the first 20 years of work. An abnormal X-ray, increased or prolonged exposure (above the exposure standard or greater than 20 year work history) may warrant X-rays on a more frequent basis (for example, three yearly). Where a worker has experienced very heavy exposure, annual X-rays may be warranted.
The WHS Regulations prescribe an X-ray as a minimum, but another type of health monitoring may be undertaken where the registered medical practitioner considers it is equal or better. For high risk occupations and industries, such as the composite stone industry, a high-resolution computed tomography (HRCT) should be considered. X-rays are less sensitive in detecting accelerated silicosis.
At a minimum, if not HRCTs, annual X-rays should be considered for high risk occupations and industries, such as the composite stone industry, rather than every five years.
NOTE: Registered medical practitioners should be aware of the potential for excessive X rays where the worker has worked for multiple employers, particularly in the construction and mining industries.
Other health monitoring methods including use of high-resolution CT
High-resolution computed tomography (HRCT) has been demonstrated to be more sensitive than X-rays in detecting early dust lung disease. Use of a HRCT scan of the chest (non-contrast) may be considered depending on the worker’s history and levels of individual silica exposure. If the worker’s role involves a very high level of silica exposure (such as composite stone countertops) or a high level of silica exposure for over three years, then HRCT should be used as a replacement or adjunct to X-ray.
With the identification of rapidly progressive silicosis and advanced disease in high risk workers, notably those that work with composite stone, there may be a need to conduct more rigorous respiratory function testing. For example, incorporating measurement of the diffusing capacity of the lungs for carbon monoxide (DLCO). This is a more recent test that may not be available in regional and rural areas and may only be offered through specialist respiratory laboratories.
Workplace exposure standard
The workplace exposure limit for crystalline silica (all forms) is:
- eight-hour time weighted average (TWA) of 0.05 mg/m3.
A physical examination and respiratory function testing may be required if the results of air monitoring indicate frequent or potentially high exposure (for example, half of the TWA or above). The results of air (dust) monitoring should be provided to the registered medical practitioner to inform the frequency of testing.
Removal from work
There is evidence that disease may continue to progress even after exposure to crystalline silica dust has ceased. Where the results of a medical examination indicate the worker is displaying signs or symptoms of exposure to crystalline silica, the registered medical practitioner should consider recommending the worker be removed from crystalline silica-related work.
When removal from crystalline silica-related work is indicated the registered medical practitioner must provide the PCBU with the following recommendations:
- the worker should be removed from work with crystalline silica, and
- the PCBU should review control measures and carry out recommended remedial action.
Where recommended by the registered medical practitioner, the PCBU should ensure that:
- the control measures are reviewed and the recommended remedial actions are followed to minimise the exposure,
- the worker must be informed of the results of the health monitoring, and
- if the health monitoring report indicates that worker may have contracted a disease or illness, the PCBU must provide a copy of the health monitoring report to the WHS regulator.
Return to work
Should a worker be removed from crystalline silica-related work, they must not return until the registered medical practitioner has:
- assessed them as medically fit, and
- made a recommendation to the PCBU that the worker can return to remediated crystalline silica-related work.
The assessment from the registered medical practitioner should consider:
- the clinical condition of the worker
- the resolution of symptoms, and
- remediation of the circumstances that led to the symptoms if possible.
The PCBU should provide advice to the registered medical practitioner about workplace monitoring undertaken and that the control measures and all recommended remedial actions are in place (for example through a revised risk assessment). The PCBU should ensure that the worker is returned to remediated work only after PCBU has received formal notification from the registered medical practitioner.