1932: The first use of the term 'Aerosol'

Many asthmatics participate in what is sometimes referred to as Aerosol Therapy. When you take a breathing treatment you are basically aerosolizing medicine so it can be inhaled.  While aerosols are present through history, the term wasn't used until the 1930s.

It was first used in 1932 by R. Whitlaw and E. Gray Patterson.  The term is derived in the following manner (1, page 173):

• Aer = air
• sol = solution

In subsequent years various generic terms have also been used, which include the following (1, page 173, (2 page 5):

• Mist
• Micromist
• Fog
• Fume
• Spray
• Haze
• Smog

The term aerosol basically refers to "the suspension of a liquid or solid particle in a gaseous medium. The term originated as the gas phase analogue to hydrosols (meaning 'water particle' in Greek) and refers to suspension of particles in a liquid." (2, page 3)  Most "theories describing aerosol behavior assume the particles are spherical." (2, page 6)

Aerosolized particles generally average in size from barely larger than a molecule to as large as 100 micrograms.  Although for the purpose of aerosolized particles to reach the respiratory tract, the following is necessary (3):

1. Greater than 10 um deposits in the nose
2. Greater than 5 um deposits in the mouth
3. 5-10 um deposits in the first six generations of bronchi (large airways)
4. 1-5 um deposits in the last 5-6 generations (small airways)
5. Greater than 3 um have a tendency to impact the conducting airways
6. 0.8-2 um are optimal for alveolar deposition

Bronchospasm, as what occurs in asthma, generally occurs in the smaller airways. For this reason, the ideal particle size is 2-5 um for best airway deposition. This is the particle size that is generally created by most hand held nebulizers. Particle size less than 2 um are too small to be therapeutic.

Particles smaller than 10 micrograms generally hold their contents well, so the medicine is not likely to be lost upon aeroslization.  (2, page 9)  It's for this reason respiratory medicine can be mixed together in the same solution.

References:

1. Korting, Monika Schafer, editor, "Drug Delivery," 2010, Germany, Springer-Verlag Berlin Heidelberg.  The reference used for this information is Aiche, 1990)  Although a more specific reference would be Whitlaw-Gray, R, and Patterson, H.S., in "Smoke: A Study of Aerial Disperse Systems," (Arnold, London, 1932), 192 pages
2. Kulkarni, Pramod, Paul A. Baron, Klaus Willeke, editors, "Aerosol Measurement: Principles, Techniques and Applications," 3rd edition, 2011, Wiley
3. Elliot, Deborah, Patrick Dunne, "A Guide to Aerosolized Drug Delivery," American Association of Respiratory Care, page 9.  I wrote about this at RT Cave as you can see here.