When workers are exposed to airborne dust, some particles penetrate far deeper into the lungs than others. Understanding how fine dust reaches the alveoli explains why certain particles are far more hazardous than others, and why respirable dust control remains critical in every dusty trade.

Particle Size and Airflow

As air enters the respiratory system, larger particles are trapped early on by the nose and throat. Mid-sized particles deposit in the upper bronchi, while the smallest particles - those below about 5 micrometres - continue to travel with the airstream down to the alveolar region. This is where gas exchange between blood and air occurs.

How the Body Responds

The lungs have natural defence systems such as mucus and cilia to remove contaminants. However, once particles reach the alveoli, these defences are limited. Macrophage cells attempt to engulf and clear fine dust but can become overloaded. Persistent exposure leads to inflammation and scarring of lung tissue.

Why Size and Solubility Matter

Very fine and insoluble particles present the highest risk because they remain in the lungs for long periods. Respirable crystalline silica is the classic example, but welding fumes and diesel particulate matter behave similarly. The smaller the particle, the deeper it can penetrate and the longer it stays in tissue.

Controlling Exposure at Each Stage

Effective protection targets these fine fractions. Containment during cutting or grinding, extraction close to the source, and correct choice of respiratory protection are all essential. Air monitoring confirms the level of respirable material in the work environment. Educating workers on dust pathways helps reinforce why wearing PPE consistently is vital.

Practical Takeaways

• Respirable particles are under 5 micrometres and reach deep lung tissue
• Prevent release through extraction and wet methods
• Use proper respiratory PPE at all times
• Monitor air and record results for compliance
• Provide worker training on dust behaviour and control

Knowing how fine dust reaches the alveoli helps teams interpret exposure risks more accurately and apply controls that truly protect worker health.