What are cut off for respiratory and aerosol
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aerosol particle size cutoff respiratory tract deposition microns
Respiratory droplets and aerosol transmission
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respiratory droplets vs aerosol transmission particle size cutoff 5 microns
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Here is a comprehensive comparison of respiratory droplet vs aerosol (droplet nuclei) transmission:
Particle Size Cutoffs
| Parameter | Droplet Nuclei (Aerosol) | Respiratory Droplets |
|---|---|---|
| Particle size | 1–5 μm (dried residua of larger particles) | >5–10 μm (commonly >100 μm) |
| WHO definition | <5 μm → aerosols/droplet nuclei | >5–10 μm → respiratory droplets |
Key Distinguishing Features
| Feature | Droplet Nuclei (Aerosol) | Respiratory Droplets |
|---|---|---|
| Settling behavior | Suspended in air indefinitely | Settle within seconds, within ~1 m of source |
| Transmission distance | Long distance (beyond 2 m); risk in enclosed, poorly ventilated spaces | Short range (~2 m / close contact) |
| Microbes per particle | Few microbes per particle | Many microbes per particle |
| Deposition site in airway | Alveolar (deep lung) | Upper airway (nasopharynx) |
| UV-light susceptibility | Susceptible | Resistant |
Example Pathogens
| Transmission Type | Pathogens |
|---|---|
| Aerosol / Droplet nuclei | Measles, TB (M. tuberculosis), Varicella-zoster, SARS-CoV-2 |
| Respiratory droplets | Influenza, RSV, Staphylococcus, SARS-CoV-2, pertussis, pneumococcus |
Note: SARS-CoV-2 is transmitted by both routes. Droplet transmission is the primary route (wet particles within ~2 m), while aerosol transmission occurs over longer distances, especially in poorly ventilated enclosed spaces.
Clinical Relevance for Infection Control
| Precaution | For Droplet Transmission | For Aerosol/Airborne Transmission |
|---|---|---|
| PPE | Surgical mask | N95 respirator |
| Room type | Standard room (door may be open) | Negative pressure / airborne infection isolation room (AIIR) |
| Distance | Maintain >1–2 m | Entire room air is potentially infectious |
| UV light | Less effective (droplets resistant) | Effective (aerosols susceptible) |
Sources:
- Fishman's Pulmonary Diseases and Disorders — Table 130-3: Key Distinguishing Features of Transmission from Droplet Nuclei and Respiratory Droplets
- Robbins, Cotran & Kumar Pathologic Basis of Disease — COVID-19 transmission section
- WHO: Modes of Transmission of SARS-CoV-2
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