Which statement best describes the particle hazard described as the greatest threat?

Which statement best describes the particle hazard described as the greatest threat?

• A. Particles larger than 5 microns
• B. No hazard
• C. Only spherical particles
• D. 3-5 micron diameter particles with length under 0.1 mm

Answer: (D)

The most dangerous particle is the one small enough to reach the deepest parts of the lungs. Particles in the 3–5 micron range are in the respirable size that can bypass nasal defenses and deposit in the alveolar region, where they can cause inflammation and potentially systemic effects. Larger particles, those over about 5 microns, tend to lodge in the upper airways and are cleared more readily, so they pose less risk for deep-lung injury. The length noted as under 0.1 mm helps rule out long, fibrous hazards that behave differently, since long fibers can cause irritation and persistence in the lungs. Shape matters, but size is the primary factor for the depth of inhalation; thus this size range is the most threatening.

The most dangerous particle is the one small enough to reach the deepest parts of the lungs. Particles in the 3–5 micron range are in the respirable size that can bypass nasal defenses and deposit in the alveolar region, where they can cause inflammation and potentially systemic effects. Larger particles, those over about 5 microns, tend to lodge in the upper airways and are cleared more readily, so they pose less risk for deep-lung injury. The length noted as under 0.1 mm helps rule out long, fibrous hazards that behave differently, since long fibers can cause irritation and persistence in the lungs. Shape matters, but size is the primary factor for the depth of inhalation; thus this size range is the most threatening.