Study On The Transmission And Exposure Risk Of Bioaerosols In One BSL-3 Laboratory

Laboratory-acquired infections(LAIs)are defined as infections of laboratory staff by exposure to pathogenic microorganisms during an experimental procedure.For a biosafety level-3(BSL-3)laboratory with a high potential of exposure,reducing risks and threats relevant to LAIs has become a critical concern,especially after the recent outbreak of Novel Coronavirus causing COVID-19.This study aimed to investigate the spatial-temporal characteristics of bioaerosol dispersion and deposition of two kinds of bioaerosols(Serratia marcescens and phageΦX174).A combination of laboratory experiment and numerical simulation was adopted to explore bioaerosol removal.Three-dimensional concentration iso-surface mapping in conjunction with flow field analysis was employed to elucidate bioaerosol migration and deposition behavior.The total deposition number and unit area deposition ratio were calculated for different surfaces.Vortex flow regions and high-concentration regions were determined,and the most severely contaminated surfaces and locations were identified.The results indicate that bioaerosol concentration remains stable for up to 400 seconds after release,and that almost 70%of all bioaerosol become deposited on the surfaces of walls and equipment.Our results could provide the scientific basis for controlling the time interval between different experiments and also provide guidelines for a laboratory disinfection routine.Reasonable equipment layout is essential for creating a healthy and safe environment,especially in a three-level biosafety laboratory with high potential risk factors of infection.This study investigated the effects of obstacles on exposure infection of staff in a biosafety laboratory with related experimental equipment.The results indicate that although the equipment layout does not affect the bioaerosol removal time,nearly 17%of bioaerosols in the actual laboratory cannot be discharged effectively compared with the ideal situation.These bioaerosols lingered in the lower space under the influence of vortex,which would increase the respiratory risk of operators.In addition,after the experiment a large part of bioaerosols would be captured by equipment and floor,and the deposition rate per unit area is 0.45%/m~2 and 0.8%/m~2,respectively.Although the results show that the equipment layout could reduce the pollution on the floor,disinfection is still an important link after the end of experiment,especially on the surfaces of equipment.Meanwhile,the result also indicates that the action should be light and slow when operating in BSL-3 laboratory,so as to avoid the secondary suspension pollution of bioaerosol particles on the floor.Laboratory-acquired infection caused by improper operation in the course of experimental process is frequently reported,so the exposure risk study of biosafety laboratory has become a top priority.In this study,the infection risk of bioaerosols under three typical improper operations was investigated by means of Computational Fluid Dynamics(CFD)method coupled with Wells-Riley equation.Combined with air-age isosurface map,the potential infection risk and time disinfection law were explored in detail.The results showed that the air recirculation zone of the laboratory is mainly located near the experimental equipment,and the bioaerosol removal efficiency in regions above 1.5 m is low.The risk of infection in different regions varied by more than20 times.In addition,the potential exposure per minute was higher at the beginning of the leak,and the risk value was maintained at about 1%/min after 4 min.The research results show that the experimenters should first avoid the initial exposure of the experiment process,and secondly,they must master the precise high-risk disinfection area.