Alternative Room Disinfection Modalities –Pros and Cons - Use of Biocidal Surfaces for Reduction of Healthcare Acquired Infections - page 189

There have been a number of chemicals tested for use as fumigants. Examples of
these include chlorine dioxide, hydrogen peroxide vapor, hydrogen peroxide and
silver dry mist, super-oxidized water, or ozone for terminal disinfection of hospitals
contaminated with mold and bacteria [ 37 , 55 - 59 ]. In the past, paraformaldehyde,
has been used to decontaminate biological safety cabinets and in entire buildings
[ 60 ]. Fumigants such as chlorine dioxide and hydrogen peroxide continue to be the
two agents most frequently examined to decontaminate hospitals, animal research
facilities or similar environments. One of the selling points of these products is that
their composition as a gas or vapor allows them to be deposited on hard to reach
areas [ 37 ]. Research has consistently demonstrated the ability of these fumigants to
kill microorganisms in the laboratory; however, there are still concerns for the
safety of patients, workers, or research animals that may be inadvertently exposed
to these toxic chemicals when used in the field. Some of the health effects resulting
from exposure to certain fumigants may include neurological signs and respiratory
damage [ 61 ]. Other symptoms from exposure may include severe nausea, vomiting
and dizziness. Limiting exposure to these toxic chemicals must be considered when
using fumigants in areas where humans or animals may be present.
Another modality that has been used in place of or in addition to chemical
fumigation is ultraviolet (UV) irradiation. Research has shown that the mode of
action of UV is due to damage to nucleotic acids, enzymes, amino acids, phospho-
lipid membranes [ 62 - 64 ]. UV wavelength in the range of 200-295 nm has been
determined to be most effective in damaging cellular DNA (most commercial
lamps primarily produce UV at a 254 nm wavelength.).
UV has a long history of use in healthcare settings. For example, UVA has been
used for many years to cure plastic resins and as a black light. Black lights have
been used to identify the presence of rodent infestations and in hand hygiene
demonstrations (Glo Germ TM ). This same approach has been recently applied by
environmental services to assess the quality of surface disinfection [ 65 ]. UVB is
also being used in phototherapy to treat certain types of skin conditions such as
psoriasis [ 66 , 67 ].
UVC has been used for upper air disinfection in the control of tuberculosis or other
respiratory diseases for over 100 years [ 68 ]. The most effective design involves
upper-room placement of the germicidal lamps that are shielded to reduce human
exposure. Another effective approach is to place the UVC lamps in the exhaust
system ductwork, or they may be used in the disinfection of ventilation system
cooling coils [ 69 - 71 ]. To be most effective, the design of the dilution exhaust
ventilation should bring the airborne pathogens into close proximity to the UVC
germicidal lamps. Chang and Young found that in situations where the UVC radiance
is high, the air turbulence is high, and the air velocities are low, germicidal effec-
tiveness is reduced [ 72 ]. They emphasized the importance of conducting tracer
turbulence studies before considering the use of germicidal UVC to assure that the
airborne microorganisms come into close proximity to the lamps.
While there is a long history of using UVC for upper air disinfection, its use in
surface disinfection is a relatively recent development [ 73 , 74 ]. There are a number
of challenges using this germicidal modality because in general, microbes are easier
to inactivate in the air than on surfaces.