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I’ve
been researching germicidal UV lights which seem to be the right
technology, together with a good filter, to improve my home
environment. In your articles you are dismissing UV as “unlikely to
have beneficial effects” and “not justified” in most cases. However,
I’m not convinced by your argument that it is just the same if I have
alive and thriving indoor germs or dead ones. I also learned that UV
has been incorporated in the Facilities Standards for the Public
Buildings by the U.S. General Services Administration Office of the
Chief Architect to “control airborne and surface microbial growth and
transfer”. My questions are: 1) Why is UV included in the standards by
the Chief Architect if it is “unlikely to have beneficial effects”? and
2) Can you build a convincing argument for not using UV in my home?-Ivan
, Georgia
UV lights are commonly installed in the return air
duct of the furnace/air-conditioning system of a house or other
building. 
As such, it can only kill bacteria, mold and viruses when they are
airborne and passing through the irradiated air stream in the cold air
return duct. When the fan is not operating, no air movement and no
disinfection is occurring.
Effective disinfection of air in a building would
require that the fan be operating continuously. This can significantly
increase one’s monthly electric bill. Such operation would
significantly increase ozone exposures to you and other members of our
family and ozone-sensitive materials in your home. Ozone is a potent
respiratory irritant, and attacks colored materials, rubber compounds
and soft plastics. As such, the use of UV devices that generate ozone
is highly undesirable.
The ozone generating and germicidal spectra of UV
light overlap. I am told by some in the UV light industry that
non-ozone producing devices are available; that is, they use a more
limited portion of the UV spectrum.
The statement you attribute to USGSA “control
surface microbial growth and transfer” indicates that they are proposing
a standard that is not based on good science. The use of UV lights in a
duct system cannot reduce surface microbial growth (except in the duct
where the UV lights are). USGSA people are guilty of some “very fuzzy
thinking.” My sense is this one of those poorly thought out responses
to bio-terrorism concerns. Incidentally UV light is not likely to be
effective in killing anthrax spores.
Killing spores that are airborne has no beneficial
effect. Dead spores are just as allergenic as live spores (indeed a
goodly percentage of airborne mold spores are dead already).
In the case of bacteria, there are few bacteria
types present in buildings that cause a significant disease concern.
Even if UV were effective in killing airborne bacteria, there is no
reason to believe that buildings with UV irradiated air would be any
healthier.
October 31, 2003
Indoor
Environmental Quality (2000), Thad Godish Ph.D., C.I.H
Direct E-mail
00tjgodish@bsu.edu
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