What do health and safety professionals need to know about silica dust?

Organisations working in the many sectors where silica can be found will need the help of their occupational safety and health (OSH) professional. You will need to work with both managers and workers to help risk assess, implement controls, and eliminate/reduce respirable crystalline silica (RCS) exposures.

You may be required to:

• provide support with the organisational silica risk assessment
• support with identifying and implementing suitable controls by following the ‘hierarchy of control’ – for example, introducing reduction, engineering, administrative controls, or advising upon suitable personal protective equipment (PPE) or respiratory protective equipment (RPE) if adequate control cannot be achieved by other means
• support with the implementation or maintenance of the silica exposure plan
• routinely inspect known RCS tasks and areas
• consult with workers (on a regular basis)
• check that workers are following and understand procedures and safe systems of work
• source and provide suitable silica information and training
  investigate incidents and exposures
• support with health monitoring/surveillance requirements
• support with evaluations and instate any learning lessons to prevent future RCS incidents or exposures.

Control measures

After risk assessment, suitable controls should be identified following the hierarchy of control.

Controls should give preference to those that protect many workers at a time instead of individual worker controls.

Workers should also be consulted when implementing controls, as they will understand and have more experience of the tasks that may generate RCS dust.

Eliminating RCS

Using alternative materials, for example using metallic shot, slag materials or grit instead of sand for abrasive blasting.

Reducing RCS

Reducing exposure to as low as possible by using materials with a lower silica content. For example, limestone or marble (2 per cent silica content) has significantly lower silica levels than engineered stone (90 per cent silica content).

Engineering controls

• Wet-working, which involves suppressing dust and accelerating the weathering process of silica which reduces toxicity. On-tool extraction systems may also be used to capture dust particles when cutting, drilling and grinding.
• Physical barriers or computer numerical control (CNC) machines can be used to isolate areas where dust is created.
• Using H-class (HEPA-filtered) vacuum cleaners for collecting gathered dust – do not dry sweep areas. Note that dust waste bags should be sealed securely and disposed of in the appropriate waste container.

Administrative controls

• Setting up exclusion zones to indicate boundaries to RSC dust areas.
• Signage to indicate warnings, PPE/RPE requirements and other information.
• Organising higher-exposure times to RCS for when fewer workers are onsite or in an area.
• Having regular breaks and shift rotations to reduce the time workers are exposed to RCS.
• Ensuring workers are aware of the importance of washing hands thoroughly after work and before eating or drinking.
• Ensuring good housekeeping that will help to stop dust from gathering and keep work areas clean and free from clutter.

PPE and RPE

Where exposure to RCS cannot be controlled by other means, appropriate PPE and RPE should be provided to all workers. This should include protective clothing such as overalls, gloves and boots. These should not be worn to travel home in, as this will increase the risk of spreading dust within their vehicles, home or on to others.

In relation to RPE, procedures should be put in place to ensure that:

• wearers are face-fit tested and RPE fits correctly
• wearers are clean shaven to ensure a proper skin to RPE seal
• wearers are trained for use of the RPE
• the RPE is cleaned and checked before and after use
  filters and disposable RPE are changed regularly
• RPE is stored correctly
• defects are reported immediately and the RPE is not used if defected or unclean

Exposure measuring and monitoring

RCS levels should be measured and monitored to ensure that exposure limits are not breached. Exposures should be as low as possible and below the legal exposure limit. Real-time dust exposure levels can now be obtained with new technologies.

It is important to remember that any exposure to RCS could be harmful and that exposure limits are not necessarily safe levels of exposure. They are practical guides. Therefore, any exposure should be mitigated and avoided if possible.