The use of ultraviolet radiation to reduce airborne <i>Escherichia coli</i>

Abstract

<b><sc>Abstract.</sc></b> Airborne Escherichia coli (E. coli) originating in poultry houses can be transmitted outside poultry farms through the air, posing risks of barn-to-barn infection through airborne transmission. The objective of this study is to examine the effect of ultraviolet (UV) light on the inactivation of airborne E. coli carried by poultry dust particles under laboratory conditions. To examine the effect of UV light, two testing systems were installed with or without UV lamps. Each system contained two chambers that were connected with an aluminum duct. In the first chamber of the system with UV lamps, airborne E. coli attached to dust particles were aerosolized by a dry aerosolization-based system. An all-glass impinger (AGI-30) and an Andersen impactor were placed in the chamber to collect the viable airborne E. coli. In the aluminum duct, two UV lamps with the wavelength of 253.7 nm were installed. In the second chamber of the system with UV lamps, another set of AGI-30 and Andersen impactor were placed to collect viable airborne E. coli attached to dust particles after being irradiated with UV light. The two chambers had air-in ports which were installed with high efficiency particulate air (HEPA) filters. A vacuum pump was connected with the outlet port of the second chamber. The air filters helped to prevent airborne E. coli and dust particles from spreading to laboratory, and the vacuum pump helped to direct air flow and control the flow speed. By comparing the concentration of airborne E. coli in the two chambers, the reduction rate was calculated. The airborne E. coli reduction was tested at different air speeds (from 20 to 800 feet per minute) in the aluminum duct and UV strength. In the testing system without UV lamp installation, same procedure was repeated, and the results provided data of physical deposition of airborne E. coli during transport in the testing system. The airborne E. coli was reduced significantly for all treatments with UV lamps. The reduction rates varied from over 99.87% and 99.95% at 21 ± 4 ft min^-1 wind speed with 1 and 2 UV lights to 72.90% and 86.60% at 513 ± 7 ft min^-1 wind speed with 1 and 2 UV lights. The UV light level which killed 100% of airborne E. coli was 9160 µW s cm^-2. The designed system was able to create UV irradiation of 6384 µW cm^-2 and 7503 µW cm^-2 for 1 UV light and 2 UV lights, respectively. The findings of this study may provide an understanding of the effect of UV light on the inactivation of airborne E. coli carried by dust particles and help to design an affordable mitigation system for poultry houses.