Know your hazards: Spotlight on silica

The International Agency for Research on Cancer (IARC), part of the World Health Organisation (WHO) of the United Nations, has classified silica as a Class 1 carcinogen, causing lung cancer, renal disease and autoimmune diseases including rheumatoid arthritis.

What is silica dust?

Crystalline silica (quartz) is a naturally occurring mineral found in most rocks, stone, sand and clay, and in brick, concrete, tile and manufactured stone prooducts. When working with these materials, the silica is released as a fine dust. This dust is respirable crystalline silica (RCS), commonly called silica dust.

The workplace exposure standard for RCS is exceeded when the amount of dust a worker breathes over a full shift contains more RCS than the amount shown here next to a five cent piece. However, workers may still suffer adverse health effects from lower levels of exposure.

What is the hazard?

Breathing in RCS can cause:

•• silicosis

•• lung cancer (associated with silicosis)

•• kidney disease

•• increased risk of tuberculosis

•• possible increased risk of autoimmune diseases

•• chronic obstructive pulmonary disease (COPD).

What is silicosis?

Silicosis is an incurable lung disease, with inflammation and scarring of the lungs, causing shortness of breath, coughing, fatigue and other symptoms.

There are three types of silicosis:

•• acute silicosis results from short-term exposure to very high levels of silica over a period of weeks or months to several years

•• accelerated silicosis results from 5-10 years’ exposure to high levels of silica – this is becoming more prevalent in workers who work with engineered stone

•• chronic silicosis results from long term (more than 10 years) exposure to lower levels of silica.

Which work activities have a higher risk of exposure?

Examples of work activities that can generate RCS include:

•• fabrication and installation of composite (engineered or manufactured) stone countertops

Note: Silicosis risks are much greater when working with engineered stone as it contains up to 95% crystalline silicia while natural stone contains 5-50% silica

•• clay and stone processing machine operations

•• paving and surfacing

•• tunnelling

•• construction labouring activities

•• brick, concrete or stone cutting; especially using dry methods

•• abrasive blasting (blasting agent must not contain greater than 1 per cent of crystalline silica)

•foundry casting

•• angle grinding, jack hammering and chiselling of concrete or masonry

•• mining, quarrying and mineral ore treating processes

•• excavation, earth moving and drilling plant operations

•• hydraulic fracturing of gas and oil wells.

What can employers do to protect workers?

Western Australian occupational safety and health legislation requires employers, in consultation with workers, to identify hazards, assess risks and implement practical controls to protect workers’ health and safety.

Managing risks and worker exposures to silica can be achieved by selecting and implementing appropriate control measures. The most effective controls are still elimination and substitution:

•• eliminate, where possible, tasks that generate dust

•• substitute, where possible, with safer products

•• use exhaust ventilation systems to capture and remove dust at the source

•• use dust capture systems on portable tools

•• apply water suppression systems to reduce dust generation

•• follow instructions and controls outlined in safety data sheets and product labels

•• use water or an approved vacuum cleaner (class M or H) to clean up dust and avoid using compressed air or sweeping

•• conduct regular air monitoring to confirm everyone at the workplace is working within safe levels of exposure

•• use well maintained and appropriate personal protective equipment (e.g. face masks).

If there is regular exposure to crystalline silica there may be a health risk (for example, where exposure is frequently at or above 50% of the exposure standard). Health surveillance must be provided to workers in accordance with regulation 5.23 of the Occupational Safety and Health Regulations.

Online resources available

Guidance note – Safe stone product fabrication and installation

The Commission for Occupational Safety and Health has recently released a guidance note on safe stone product fabrication and installation. This guide outlines how to control exposure to airborne RCS dust during fabrication of stone benchtops or similar stone products and the health effects of breathing RCS dust.

Safety alert 11/2018 Stone benchtop workers at risk of fatal silicosis

RCS and the mining sector

In our next issue of ThinkSafe magazine, we will take a closer look at exposures in the mining sector and what mining operations can do to protect their workers.