Hazardous Silica Dust Sources at Work

• Silica is a natural mineral found in materials like stone, sand and clay; it’s hazardous when released as a fine dust known as respirable crystalline silica (RCS).
• RCS is released when materials containing silica are drilled, cut or processed in some way.
• RCS exposure can cause debilitating diseases such as silicosis, COPD and potentially lung cancer.
• Common silica dust sources include quartz, engineered stone, sandstone and concrete.
• High-energy tasks carried out on materials with high silica concentrations pose the greatest risk of harmful exposure.

Silica is found in most types of stone, sand, soil, clay and rock. Unsurprisingly, it’s found in a range of different materials used in agriculture, manufacturing and construction.

In its base form, silica is harmless. But when silica-containing materials are drilled, cut, crushed or used in any other industrial process, silica dust is released. The smallest particles are classified as respirable crystalline silica (RCS).

RCS particles are minuscule; you could fit about 20 of them across the width of a human hair. Their size makes them dangerous for three reasons:

• They hang in the air for hours after release
• They’re invisible to the naked eye
• They’re small enough to inhale

Moreover, silica dust doesn’t make you ill right away. A worker could breathe in RCS without realising it. It might take weeks, months or even years of regular silica exposure before the effects are felt.

Once inhaled, respirable crystalline silica penetrates the deepest parts of our lungs, the alveoli. The alveoli are where oxygen passes from the air in our lungs into the bloodstream. Silica dust scars the tissues inside the alveoli, severely limiting their ability to transfer oxygen. This condition is known as fibrosis, and it makes it extremely difficult, even painful, to breathe.

Fibrosis isn’t the only silica-related condition. Exposure is also known to cause chronic obstructive pulmonary disease (COPD) and silicosis. It’s also been linked to lung cancer.

Chronic obstructive pulmonary disease (COPD) isn’t a single condition. It’s a label used for several lung diseases that narrow airways and cause breathlessness.

COPD is incurable and progressive. Sometimes, symptoms can be managed, but generally, people with the condition suffer more from its effects as time goes on. Few people survive for longer than nine years following a COPD diagnosis.

As the name suggests, silicosis is strongly linked to silica exposure. It develops as a consequence of severe fibrosis. The effects are similar to those of COPD, and, also like COPD, silicosis is incurable, gets worse over time and can prove fatal.

Unlike other silica-related diseases, it’s not entirely understood how silica exposure causes lung cancer. But research consistently shows that high-level (or long-term) exposure to silica dust drastically increases the risk of developing lung cancer.

If it’s an isolated incident, silica exposure isn’t likely to be harmful, even at relatively high levels. Repeated exposures are needed to cause significant lung damage, which is why silica-related diseases typically take years to develop.

Because silica isn’t instantly life-threatening, the Health and Safety Executive (HSE) allows workers to be exposed to low levels of silica dust during a typical workday. The legal workplace exposure limit (WEL) for respirable crystalline silica dust is 0.1 mg/m³ as an 8-hour time-weighted average. But this is the absolute upper limit. Exposure should be kept as far below the WEL as possible at all times.

To ensure workplaces operate safely within the WEL, you must first identify the silica dust sources present.

Different materials contain different levels of silica dust, which should be indicated in any product’s material safety data sheet (MSD).

Substituting products with high silica content for those with little or no silica is one of the most effective ways to prevent harmful exposure in the workplace, so we’ve ranked these silica dust sources by concentration. The percentages included here are averages and might not be accurate for the specific products you use. Refer to MSDs for a definitive answer.

• Quartz is the most potent silica dust source, being almost entirely silica.
• Engineered stone is a close second, containing between 90 – 95% silica.
• Sandstone is another significant hazard, containing around 90% silica.
• Concrete and mortar contain around 70% silica.
• Shale contains 60% silica.
• Chine stone contains 50% silica.

• Granite contains between 40 – 45% silica.
• Ceramic tiles can be anywhere between 15 – 45% silica.
• Slate is typically 40% silica.
• Brick is typically 30% silica.

• Asphalt (containing sand or aggregates) generally comes in under 20% silica.
• Marble and limestone usually only contain between 2 – 5% silica.

Exposure isn’t only a matter of how much silica a material contains; it’s also affected by how much energy is used to process it.

High-energy work releases more silica dust. Grit blasting, saw cutting, and grinding are all examples of high-energy ­– and therefore high-risk – tasks.

If materials containing silica dust are used in your workplace, you must ensure compliance with the Control of Substances Hazardous to Health Regulations (COSHH).

Under COSHH, employers must carry out a hazardous substances risk assessment. This assessment should identify all silica dust sources, the threat they pose and who is at risk. Based on these findings, control measures must be applied to protect workers from harmful exposure.

Employers must follow the established hierarchy of controls when making their workplaces safe. This hierarchy is:

1. Elimination – remove the hazard entirely.
2. Substitution ­– swap materials or work processes for less hazardous versions.
3. Engineering controls – implement physical controls to isolate risks.
4. Administrative controls – change the way people work to reduce risks.
5. Personal protective equipment (PPE) – provide PPE to workers.

Applied to silica dust, the hierarchy of controls might look something like this:

1. Elimination – Remove all silica dust sources.
2. Substitution – Swap high-silica materials for low-silica alternatives.
3. Engineering controls – Install local exhaust ventilation to extract silica dust at its source.
4. Administrative controls – Rotate tasks so exposure is shared among workers.
5. PPE – Provide each at-risk worker with suitable respiratory protective equipment.

When managing risks, you should start at the top (elimination) and consider every way you might remove silica dust sources. If it’s impractical to eliminate all silica-containing materials from your workplace, move on to substitution. Exhaust all possible control measures here before moving on, and so forth.

Protecting workers from the risks of silica dust begins with knowledge. Our online Silica Dust for Duty Holders course is designed to provide employers and supervisors with the essential understanding needed to identify and manage silica dust sources effectively in the workplace.

This course covers silica dust hazards, legal duties and implementing appropriate control measures to reduce risks. After completing the course, you’ll understand how to ensure compliance with COSHH and safeguard your team from silica-related diseases.