What Is Respirable Crystalline Silica?

Crystalline silica occurs naturally in materials such as stone, sand, concrete, mortar, bricks and tiles. Cutting, drilling, grinding, crushing or breaking these materials can release very fine particles into the air.

The smallest particles are known as respirable crystalline silica. They are small enough to travel deep into the lungs, where they can cause inflammation, tissue damage and permanent scarring.

RCS particles may be too small to see, so the absence of a visible dust cloud does not mean that the air is safe.

Silicosis: An Incurable Lung Disease

The disease most commonly associated with silica dust is silicosis. Silicosis is a serious and irreversible lung disease caused by breathing in respirable crystalline silica.

When silica particles become trapped in the lungs, they can trigger inflammation and fibrosis. Fibrosis is the thickening and scarring of lung tissue, which gradually reduces the lungs' ability to function properly.

Symptoms of silicosis may include:

• A persistent cough.
• Increasing breathlessness.
• Weakness and extreme tiredness.
• Chest discomfort.
• Difficulty walking or climbing stairs.

In advanced cases, silicosis can cause severe disability and premature death. There is currently no cure, and the damage can continue to develop after exposure has ended.

Different Forms of Silicosis

Silicosis can develop at different rates depending on the concentration of silica dust and the length of exposure.

Chronic Silicosis

Chronic silicosis is generally associated with repeated exposure over an extended period. Symptoms may take many years to become noticeable.

Accelerated Silicosis

Accelerated silicosis can develop more rapidly following exposure to higher concentrations of respirable crystalline silica.

Acute Silicosis

Acute silicosis is rare but can occur following short-term exposure to exceptionally high concentrations of silica dust. It can develop quickly and may be life-threatening.

Silica Dust and Lung Cancer

Occupational exposure to respirable crystalline silica is associated with an increased risk of lung cancer. Crystalline silica in the form of quartz or cristobalite dust is classified by the International Agency for Research on Cancer as carcinogenic to humans.

The risk generally increases with the amount of silica dust inhaled and the duration of exposure. Workers who develop silicosis have a particularly increased risk of lung cancer.

Effective controls used to prevent silicosis also help reduce the risk of silica-related lung cancer.

Chronic Obstructive Pulmonary Disease

Exposure to respirable crystalline silica can also cause chronic obstructive pulmonary disease, commonly known as COPD. COPD is a group of long-term lung conditions that restrict airflow and make breathing increasingly difficult.

COPD includes conditions such as:

• Chronic bronchitis, involving long-term inflammation of the airways.
• Emphysema, involving damage to the air sacs within the lungs.

Common symptoms include:

• A long-term cough.
• Producing sputum or phlegm.
• Shortness of breath.
• Wheezing.
• Reduced ability to undertake physical activity.

COPD can be disabling and can substantially reduce a person's quality of life. Smoking further increases the risk of serious lung disease and can compound the harm caused by occupational dust exposure.

Other Health Conditions Associated With Silica Dust

Silica exposure and silicosis may also be associated with an increased risk of other serious medical conditions, including:

• Tuberculosis.
• Kidney disease.
• Certain forms of arthritis and autoimmune disease.
• Long-term respiratory impairment.

Other hazardous construction dusts may also contribute to occupational asthma and additional respiratory conditions. A worker can be exposed to several types of harmful dust during the same task.

Why Silica-Related Diseases Can Be Difficult to Detect

The harm caused by silica dust often develops gradually. During the early stages, a worker may feel well and have no obvious symptoms despite damage occurring inside the lungs.

Symptoms such as coughing or breathlessness may initially be mild, intermittent or mistaken for ageing, smoking or a lack of fitness. By the time significant symptoms appear, the lung damage may already be permanent.

The absence of symptoms does not prove that exposure has been safe or that no damage has occurred.

Can Short-Term Silica Dust Exposure Cause Harm?

Silica-related diseases are not limited to older workers or people who have been exposed for an entire working lifetime. The level of risk depends on several factors, including:

• The concentration of respirable crystalline silica in the air.
• The frequency and duration of exposure.
• The type of work being undertaken.
• The silica content of the material.
• The effectiveness of the control measures.
• Whether suitable respiratory protective equipment is correctly used.

Short-term exposure to very high concentrations can cause acute silicosis, while repeated exposure can contribute to diseases that become apparent years later.

Preventing Silica-Related Lung Disease

Because silica-related lung damage can be irreversible, prevention is essential. Employers and managers must assess the risks and prevent or adequately control exposure.

Suitable control measures may include:

• Using alternative materials or less dusty working methods.
• Applying suitable water-suppression techniques.
• Using effective on-tool dust extraction.
• Maintaining and testing dust-control equipment.
• Restricting access to dusty work areas.
• Providing suitable RPE where additional protection is necessary.
• Providing information, instruction, training and supervision.
• Arranging health surveillance where required under COSHH.

Silica-related diseases are preventable when exposure is properly controlled. Employers and managers must act before workers develop symptoms, as waiting until illness appears may be too late to prevent permanent harm.