In occupational dust exposure, the term 'respirable dust fraction' refers to particles of which aerodynamic diameter that reach the alveoli?

• A < 1 micron
• B 5-10 microns
• C 1-5 microns ✓
• D 10-15 microns

Explanation

Particles 1-5 microns in aerodynamic diameter are called respirable dust (respirable fraction) — they bypass the upper airway defenses and deposit in the alveoli causing pneumoconiosis. Particles > 10 microns are trapped by nasal vibrissae and mucociliary clearance (inhalable fraction). Particles 5-10 microns deposit in the tracheobronchial region (thoracic fraction). Sub-micron particles (< 1 micron) may be partially exhaled. This size classification underpins occupational exposure limits (OELs) for hazardous dusts such as silica (causing silicosis) and coal dust (causing CWP).

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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