Biological Monitoring of Ultraviolet Germicidal Irradiation in a Biosafety Level 3 Laboratory

Abstract

Ultraviolet germicidal irradiation (UVGI) lamps are used in biological safety cabinets and laboratory containment rooms as methods of surface decontamination. Although some organizations have discouraged the use of UVGI for disinfection, many scientists continue to request this method. The objective of this study was to assess the reliability of using UVGI produced from UV ceiling lamps as an effective method to decrease microbial agent contamination from floor surfaces in a biosafety level 3 laboratory. Actively growing Bacillus cereus and B. anthracis vegetative cells or spores (Sterne strain-Veterinary Vaccine Formula) were used as biological indicators to assess UVGI effects within the containment laboratory. Studies were conducted using UVGI exposure times ranging from 15 minutes to 2 hours with varying inoculums ranging from 10³ to 10⁹ colony-forming unit per sample. Later in the study an UVGI radiometer was used to determine the UVGI intensity and to measure the correlation between the biological indicator results and mechanical instrument data. Study results showed that ceiling-mounted UVGI lamps were effective in reducing the viability of both B. cereus and B. anthracis vegetative cells and spores after a minimum UVGI exposure time of 1 hour at an intensity as low as 8 uW/cm². Additionally, an UVGI radiometer could be used to determine UVGI effectiveness and a UVGI intensity of 8 uW/cm² to 42 uW/cm² corresponded with the increased disinfection observed.

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