UV-C Decontamination of Aerosolized and Surface-Bound Single Spores and Bioclusters

Kesavan, Jana; Schepers, Deborah; Bottiger, Jerold R.; Edmonds, Jason M.

doi:10.1080/02786826.2014.889276

Cited by 27 publications

(58 citation statements)

References 21 publications

(28 reference statements)

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“…Proposed models for the tailing effect have been published by Clark (1968), Qualls and Johnson (1985), Grant (1995), Pennell et al (2008), Jensen (2010) and Kesavan et al (2014). Handler (2016) developed a novel model of aerosolized clustered micro-organisms as aggregated spheres and has also proposed a mechanistic model based on varying damage probability (Handler 2019).…”

Section: Introductionmentioning

confidence: 99%

The cluster model of ultraviolet disinfection explains tailing kinetics

et al. 2019

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Aims To develop a new mathematical model derived from first principles to define the kinetics of ultraviolet disinfection and to explain the phenomenon known as tailing. The theory presented interprets tailing as the result of photoprotection due to cumulative Mie scattering effects in clustered populations of micro‐organisms. Methods and Results Mie scattering effects at ultraviolet wavelengths are used to compute a shielding constant for each micro‐organism based on the average projected diameter. An intrinsic rate constant, hypothesized to be a characteristic property of the microbial genome alone, is computed. The cluster model is fitted to tailing data from 30 ultraviolet inactivation studies and results are compared with the classic two stage multihit model. Conclusions The cluster model demonstrates a statistically significant improvement in the mean adjusted R2 values of the tested data sets (P < 0·0001). Tailing in survival curves is the direct consequence of the Gaussian distribution of cluster sizes and the intrinsic rate constant is a real and critical parameter that defines ultraviolet susceptibility. Significance and Impact of the Study The ultraviolet dose–response behaviour of micro‐organisms can now be explained in terms of parameters that have physical meaning and provide deep insight into the disinfection process.

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Section: Introductionmentioning

confidence: 99%

The cluster model of ultraviolet disinfection explains tailing kinetics

et al. 2019

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“…Therefore, realistic hazard assessments and UVGI effectiveness evaluation require understanding the danger posed by clusters of spores in the size range from one to ten microns. Clustering of spores can protect the inner spores from the effects of the UV radiation and enhance survivability of the spores and thus affect hazard estimates for outdoor releases as well as effectiveness of UVGI system designs (Kesavan et al 2014). The net impact of clustering of spores (such as anthrax) on hazards presented to humans by outdoor releases depends on a number of factors in addition to just UV survivability.…”

Section: Introductionmentioning

confidence: 99%

“…A previous paper (Handler and Edmonds 2015) considered the net impact of all of the above factors on hazards presented by outdoor releases of clustered spores of various diameters up to 10 mm and compared the results to hazards presented by single spores. A simplified form of the model presented in this article was used, also based on the data from Kesavan et al (2014), and only aerosolized UV decay was considered. The result was that release of clustered spores can present significantly greater hazards to humans, depending on the meteorological conditions, downwind distance, and amount of solar irradiance.…”

Section: Introductionmentioning

confidence: 99%

“…The data obtained by Kesavan et al (2014) shows (see Figure 1) that when clusters of spores up to 4.4 microns in diameter are exposed to narrow band UV-C, the fraction of the spores inside the clusters that are killed reaches and slightly exceeds 99%. This is despite the fact that more than half of the spores inside the clusters (more than 75% for the case of spores exposed on a surface) are completely shielded from direct exposure by spores on the surface and in the intervening distance between the inside spore and the cluster outer shell of spores.…”

Section: Introductionmentioning

confidence: 99%

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Modeling ultraviolet dose–response ofBacillusspore clusters in air

Handler¹

2016

Aerosol Science and Technology

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This article presents a new way to model the narrow band ultraviolet (UV-C, 254.7 nm) radiation dose-response behavior of Bacillus spores in clusters based on knowledge of the UV-C doseresponse behavior of the single spores. The approach is demonstrated using experimentally obtained survival rates for Bacillus atrophaeus var. globigii (BG) spores and BG spore clusters of several sizes exposed to UV-C fluence when aerosolized and when deposited on dry surfaces. These results are modeled to derive predicted survival rates for spores in clusters of arbitrary cluster diameter under similar conditions. The essential feature of the approach is accurate accounting for attenuation of incident UV fluence within the spore cluster to derive the fluence incident on individual spores within the cluster. The results suggest that UV fluence attenuation by bacterial spores may increase with increasing fluence, a phenomenon that has not been previously reported for bacterial spores. The results are of utility in estimating dispersed biological hazards and evaluating the effectiveness of ultraviolet germicidal irradiation (UVGI) systems.

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“…The test particles were 5 μm AD clusters of Bacillus atrophaeus spores, where each cluster contained approximately 150 spores (Kesavan et al 2013). The spores are oblate spheroids (Carrera et al 2007) with an AD of approximately of 1 μm.…”

Section: Evaluation and Verification Of Apparatus Ijag Particle Countmentioning

confidence: 99%

Comparison of Particle Number Counts Measured with an Ink Jet Aerosol Generator and an Aerodynamic Particle Sizer

Kesavan

Bottiger

Schepers

et al. 2013

Aerosol Science and Technology

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Aerodynamic particle sizer (APS) users typically calibrate the particle sizing capabilities, but not the counting efficiency upon which aerosol concentration results are based. Herein, comparisons were made between the counts provided by an ink jet aerosol generator (IJAG) with those measured by an APS. Near-monodisperse (geometric standard deviation of about 1.06) liquid or solid aerosols in the size range of 0.95 to 13.3 μm aerodynamic diameter (AD) generated with an IJAG were released into the inner inlet-tube of the APS in a manner that rendered APS wall and aspiration losses negligible. For most experiments, the IJAG generated 75 particles/s, which rate was maintained by the IJAG system through control of electrical pulses applied to its ink jet cartridge. For particles in the size range of 2-13.3 μm AD, the ratio of relative detection efficiency (ratio of the number of particles counted by the APS to the number reported as generated by the IJAG) was 99.3 ± 1.4%; however, for test particles between 0.95 and 2 μm AD, the relative detection efficiency was somewhat lower, but the drop off was less than about 2%. This slight drop off is likely associated with the light scattering detection approach and corresponding counting algorithm of the APS. Tests were conducted where the IJAG produced 7.0 μm AD particles at rates of 1 to 500 s -1 and the results showed essentially a 1:1 correspondence between IJAG and APS counts. The presence of smaller-sized background particles did not affect the measured APS counts of larger-sized challenge particles.

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UV-C Decontamination of Aerosolized and Surface-Bound Single Spores and Bioclusters

Abstract: The results of this study demonstrate that the decay rate of spores contained in clusters is proportional to the overall particle size, and that it is harder to inactivate large clusters on surfaces.

Cited by 27 publications

References 21 publications

The cluster model of ultraviolet disinfection explains tailing kinetics

The cluster model of ultraviolet disinfection explains tailing kinetics

Modeling ultraviolet dose–response ofBacillusspore clusters in air

Comparison of Particle Number Counts Measured with an Ink Jet Aerosol Generator and an Aerodynamic Particle Sizer

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