Scientific Studies Show UV-C Light is Germicidal

B. I. Callies, “SUMMARY REPORT Background levels of viable bacteria and fungi in the indoor air and on surfaces in Ingham Regional Medical Center “before and after” the UVGI-HVAC installation.  Michigan State University, Feb. 2009
The objective of this project was to assess microbial concentrations in air and on fomites in Ingham Hospitals before and after the  installation of a UVGI-HVAC system. Using bacteria and fungi concentrations as a standard of effectiveness of the UVGI-HVAC system, indoor air samples were collected before and after installation and microbial levels were compared. Using  the impingement method as described by Jensen and Schafer (1998) viable microorganisms (E. coli, total bacteria, Staphylococci, MRSA, and fungi) were sampled in the air. This study also
investigated indoor surface contamination because fomites have been shown to act as reservoirs for spreading diseases (Morens, D. M., and V. M. Rash. 1995; Bures et al. 2000; Barker, J. 2001;
Barker et al. 2004; Kramer et al. 2006; Boone and Gerba 2005). Preliminary samples were collected in the summer of 2007 and post UVGI installation samples were collected in the fall of 2008. Both pre/post installation samples were collected in the emergency department waiting room and cardiac intensive care unit of the Greenlawn Campus and in the UCC waiting room
and patient room in 1E at the Pennsylvania Campus.
…and .85 for the Greenlawn campus and
Ingham Regional Orthopedic Hospital, respectively. On both of the campuses of Ingham  Regional Hospital, the UV systems appear to have decreased all organism levels in the post installation tests in the air and on non-touched and touched surfaces.
Mardell, Bucher et. al. “Safety of Upper-Room Ultraviolet Germicidal Air Disinfection for Room Occupants: Results from the Tuberculosis Ultraviolet Shelter Study , Public Health Reports / January–Feb. 2008, Vol. 123.
SYNOPSIS  Objectives. We evaluated the safety of room occupants in the Tuberculosis  Ultraviolet Shelter Study (TUSS), a double-blind, placebo-controlled field trial of upper-room ultraviolet germicidal irradiation (UVGI) at 14 homeless shelters in
six U.S. cities from 1997 to 2004.   RESULTS  Among these subjects, there were 223 reports of eye or skin symptoms. During the active UV period, 95 questionnaires (6%) noted such symptoms, and during the placebo period, 92 questionnaires (6%) did so. In
the 36 remaining cases, either the UV period when symptoms took place was  unknown or the symptoms spanned both periods. There was no statistically significant difference in the number of reports of symptoms between the active  and placebo periods. One definite instance of UV-related keratoconjunctivitis  occurred, resulting from a placement of a bunk bed in a dormitory where a single bed had been used when the UV fixtures were first installed.  CONCLUSIONS These findings demonstrate that careful application of upperroom  UVGI can be achieved without an apparent increase in the incidence of  the most common side effects of accidental UV overexposure.
Nicholson and Galeaon, et. al. “UV Resistance of Bacillus anthracis Spores Revisited: Validation of Bacillus subtilis Spores as UV Surrogates for Spores of B. anthracis Sterne. Applied and Environmental Microbiology, Feb. 2003, p. 1327–1330.
Public Health Reports / January–February 2008 / Volume 123 Copyright © 2003, American Society for Microbiology. All Rights Reserved.   Received 25 July 2002/Accepted 30 October 2002
Recent bioterrorism concerns have prompted renewed efforts towards understanding the biology of bacterial spore resistance to radiation with a special emphasis on the spores  of Bacillus anthracis. A review of the literature revealed that B. anthracis Sterne spores may be three to four times more resistant to 254-nmwavelength
UV than are spores of commonly used indicator strains of Bacillus subtilis. To test this notion, B. anthracis Sterne spores were purified and their UV inactivation kinetics were determined in parallel with those of the spores of two indicator strains of B. subtilis, strains WN624 and ATCC 6633. When prepared and assayed under identical conditions, the spores of all three strains exhibited essentially identical UV inactivation kinetics. The data indicate that standard UV treatments that are effective against B. subtilis spores are likely also sufficient to inactivate B. anthracis spores and that the spores of standard B. subtilis

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