This safety alert highlights the serious health and safety risks of exposure to high levels of respirable crystalline silica (RCS) for those who work in the stone benchtop industry.
Silicosis is an irreversible and progressive disease that causes fibrosis of the lungs from the inhalation of RCS. The only treatment for advanced disease is lung transplant.
As of February 2019, 99 confirmed cases of silicosis associated with engineered stone benchtop work had been identified in Queensland, Australia. The vast majority of these cases were in workers with no symptoms of disease.
Many of these cases have been consistent with accelerated silicosis, a form of the disease which develops over a short period (1 to 10 years) from inhalation of very high concentrations of RCS.
In New Zealand the prevalence of silicosis is currently unknown. This safety alert has been issued to raise awareness of the risks to those working in the engineered stone industry.
What we know
Engineered stone benchtops have become increasingly popular for kitchens and bathrooms. They are made by mixing finely crushed rock with a polymeric resin, then moulded into slabs and heat-cured. The silica content of engineered stone is approximately 90% silica, which is much higher than natural stones.
Workers may be exposed to RCS while cutting, grinding, sanding and polishing stone benchtops during manufacturing and installation. Accelerated silicosis is one of three forms of silicosis that has been recently reported in workers working with engineered stone.
Accelerated silicosis results from the inhalation of very high concentrations of silica dust. It develops in a pattern similar to that of simple silicosis, except the time from initial exposure to the onset of disease is shorter and the progression to complicated silicosis is more rapid. Specifically, nodules increase in size and merge into large lesions, leading to progressive massive fibrosis and ultimately cardio respiratory failure.
Before starting work using engineered stone, businesses must complete a risk assessment and review their controls. It is important to eliminate uncontrolled dry cutting, grinding or polishing of engineered stone.
If this is not reasonably practicable then exposures must be minimised. Options include:
- substituting engineered stone for materials with a lower silica content
- isolating work areas or tasks that generate dust using physical barriers or computer numerical control (CNC) machines
- using engineering controls, such as local exhaust ventilation (LEV), water suppression (wet cutting), or on-tool dust extraction attachments. Wet sprays should be controlled by guards to prevent dust becoming airborne and wet waste must be managed. LEV system dust collectors or vacuums should be H-class HEPA filtered. Any LEV must be effective, fit for purpose, installed, set up and used correctly and maintained so that it remains effective
- further minimisation controls include administrative controls, such as good housekeeping practice (wet wiping, using an H-class HEPA-filtered vacuum, and low-pressure water cleaning – dry wiping or sweeping is not appropriate).
If a risk still remains, use the appropriate personal protective equipment:
- use a suitable respirator with a filter cartridge with the appropriate assigned protection factor; the appropriate respirator and filter cartridge combination will be informed by exposure monitoring
- ensure the respirator is fit-tested for the worker, cleaned and maintained properly
- wear suitable work clothing such as coveralls that are disposable or can be laundered at the workplace to avoid taking them home.
The current New Zealand Workplace Exposure Standard (WES) for RCS (quartz) is 0.1 mg/m3. We are proposing a new WES 8-hour time-weighted average of 0.05 mg/m3, likely to be introduced at the end of this year.
You can engage an occupational hygienist from the New Zealand Occupational Hygiene Society (NZOHS), or from the Health and Safety Association of New Zealand (HASANZ) Register to measure RCS concentrations and to help evaluate risks to worker health.