I've found just the thing, so I'll reiterate my prior input here,
for the sake of future readers, and add what I've located about
bacteria and water vapor.
This article on a study by the Lawrence Berkeley National
Laboratory certainly makes it clear that there are multiple
varieties of airborne bacteria:
"Their goal is to catalog the thousands of types of bacteria
drifting and swirling in the nation's cities, and determine
how each bacterium's relative concentration changes week by
week. When completed, the census will help researchers
differentiate between natural and suspicious fluctuations
in airborne pathogens, which can help deter false alarms.
It will also help scientists refine tests that identify
"'We rely on the statistical significance of many tests
coming up positive," says DeSantis. "The trick was
choosing the 500,000 pieces of DNA that will test for
all 10,000 types of bacteria.'"
As for water vapor, I located this article by Nathan Schiff,
Ph.D., who is the President of Schiff Consulting, a Regulatory
and Environmental Consulting firm. He notes:
"The atmosphere always contains some moisture in the form of
water vapor in it, and the when it holds the maximum amount
at a given temperature, the air is saturated with water,
the level of discomfort is high and bacterial potency is
maintained at a maximum level."
Therefore, in maintaining a healthy work environment, he
recommends keeping the humidity low through the use of
"By reducing the relative humidity throughout a facility to
less than 50%, biological contaminations is reduced many
fold to safe levels whereby bacteria can not proliferate."
More on the page:
Here's United States Patent 5520854 submitted for an invention
to prevent the transmission of bacteria in the water vapor
emitted from a humidifier, which notes that, for humidifiers
without the benefit of the invention:
"...bacteria in both the water and surrounding air accumulate
within the humidifier. As a result, the operational efficiency
of the humidifier is impaired, and more importantly, bacteria
emitted in the water vapor can pose a significant health threat
to people breathing the humidified air."
Here's an article about the importance of 'De-humidification in
Hospitals', by the Bry-Air air conditioning company, which notes:
"In many health care facilities, there is a necessity to assure
good indoor air quality, thus large quantities of outside air
must be brought into the building through the ventilation system.
This outside air can account for over 90% of the moisture load
typically seen in many health care buildings. It is important
to remember that bacteria travels on water vapor in the air so
in order to avoid microbial growth and surgeon/patient discomfort,
this moisture must be removed before the fresh air enters the
building. This is particularly true in warm, humid climates."
And here's a scholarly article, published in U.S. Pharacist
Magazine, and online, titled 'Review of Community-Acquired
Pneumonia in Immunocompetent Adults', by Dawn S. Knudsen,
PharmD and Steven T. Boyd, PharmD, BCPS, CDE, CDM, which
"A suspicion of L. pneumophila can be supported by epidemiologic
evidence in the patient?s medical history or past activity.
Commonly, outbreaks arise at the end of the summer and early
fall. The bacteria is associated with warm, stagnant water
found in certain plumbing systems, hot water tanks, cooling
towers, evaporative condensers of large air-conditioning
systems, and whirlpool spas. Legionella organisms are not
passed from person to person but by inhalation of water vapor
I think that makes the point.
Please do not rate this answer until you are satisfied that
the answer cannot be improved upon by way of a dialog
established through the "Request for Clarification" process.
Additional information may be found from an exploration of
the links resulting from the Google searches outlined below.
Searches done, via Google:
"airborne bacteria" "water vapor"
"bacteria * water vapor"
"water vapor * bacteria"
Searches done, via Google Scholar:
"water vapor * bacteria"
"bacteria * water vapor"
Clarification of Answer by
31 Mar 2006 13:36 PST
Ahh...now I see what you're trying to get at.
The thing is, gas isn't truly a vapor. A gas is defined as:
"The state of matter distinguished from the solid and liquid
states by relatively low density and viscosity, relatively
great expansion and contraction with changes in pressure and
temperature, the ability to diffuse readily, and the spontaneous
tendency to become distributed uniformly throughout any container."
This tendency to expand and diffuse to the limits of the container
is what sets gas apart. A gas such as helium, e.g., will expand on
a molecular level, becoming uniformly distributed within the confines
of its container, or, if it's in the atmosphere, it will expand to
the point of equal distribution and become so rarified as to be
almost immeasurable. Given its molecular structure, it is simply
too miniscule to act as a carrier for bacteria, which are orders
of dimension larger. It is not a liquid, and doesn't offer any
life support to bacteria.
I think of a vapor, on the other hand, as a dispersion of a substance
which is innately liquid or particulate matter, such as fog or smoke,
which doesn't have the same tendency to become equally distributed
as a gas does, by nature. Certainly there is some expansion, but
there is also the tendency for it to become layered in strata based
on temperature, as is seen in cloud formations which maintain a
degree of consistency which a gas would never do.
In that they are essentially particulate liquid or solids, vapors
of water of smoke contain larger particles than gas, and allow for
the capacity to carry something the size of a bacterial cell.
Liquid vapors, such as water, additionally provide nutritional
support for bacteria, in that the water assists in allowing them
to thrive and multiply.
Therefore, in the respiratory field, a gas such as oxygen would
be unable to carry bacteria, due to the molecular size of its
composition, while bronchial mists which are liquid in nature
would be more susceptible to carrying bacteria in suspension
and transmitting bacteria in this way.
This is simply my own reasoning, and seems like common sense
from my understanding of physics. Proving a negative can be
difficult when it comes to internet research, since, if a
thing is not true, it can be impossible to located data that
The following searches, in which an asterisk (*) allows for
any number of intervening words, and all of which return no
results whatsoever, strongly suggest, to me, that gas is not
documented as being involved in the transmission of bacteria:
"transmit bacteria * gas"
"transmission of bacteria * gas"
"gas * transmission of bacteria"
"gas * transmit bacteria"
An additional 8 searches using 'gases' and 'gasses' in the place
of 'gas' for all the searches above, also returned not one result.
Let me know if this satisfies your interests.