The COVID-19 pandemic has reintroduced questions regarding the potential risk of SARS-CoV-2 exposure amongst passengers on an aircraft. Quantifying risk with computational fluid dynamics models or contact tracing methods alone is challenging, as experimental results for inflight biological aerosols is lacking. Using fluorescent aerosol tracers and real time optical sensors, coupled with DNA-tagged tracers for aerosol deposition, we executed ground and inflight testing on Boeing 767 and 777 airframes. Analysis here represents tracer particles released from a simulated infected passenger, in multiple rows and seats, to determine the exposure risk via penetration into breathing zones in that row and numerous rows ahead and behind the index case. We present here conclusions from 118 releases of fluorescent tracer particles, with 40+ Instantaneous Biological Analyzer and Collector sensors placed in passenger breathing zones for real-time measurement of simulated virus particle penetration. Results from both airframes showed a minimum reduction of 99.54% of 1 μm aerosols from the index source to the breathing zone of a typical passenger seated directly next to the source. An average 99.97 to 99.98% reduction was measured for the breathing zones tested in the 767 and 777, respectively. Contamination of surfaces from aerosol sources was minimal, and DNA-tagged 3 μm tracer aerosol collection techniques agreed with fluorescent methodologies.
It is imperative in today's world that harmful airborne or solution-based microbes can be detected quickly and efficiently. Bacillus globigii (Bg) spores are used as a simulant for Bacillus anthracis (Ba) due to their similar shape, size, and cellular makeup. The utility of CE to separate and detect low levels of Bg spore concentrations will be evaluated. To differentiate spores from background particulates, several dyes, including fluorescamine, C-10, NN-127, Red-1c, and indocyanine green (ICG), were utilized as noncovalent labels for proteins on the Bg spore surface, as well as for HSA and homoserine standards. On-column labeling, with dye present in the running buffer, was utilized to obtain greater sensitivity and better separation. CE with LIF detection enables interactions between the dye and spore surface proteins to be observed, with enhanced fluorescence occurring upon binding of the dye to surface protein. Resulting electropherograms showed unique fingerprints for each dye with Bg spores. Migration times were under 10 min for all dye-spore complexes, with net mobilities ranging from 3.5x10(-4) to 6.9x10(-4) cm(2) V(-1) s(-1), and calibration curves yielded correlation coefficients of 0.98 or better for four of the dyes studied.
One issue that has persisted since the beginning of what might be referred to as a modern era of biological aerosol research (since the 1990's), is absence of reference biological aerosols that would permit quantitative comparison among different experimental studies. We believe sufficient technical progress has been made bridging the diverse fields of biology, chemistry, physics and engineering to consider implementing well-characterized biological aerosols as reference standards. Establishment of methods and procedures which result in reliable and repeatable generation of well-characterized biological aerosols would enhance a wide range of different topics under investigation, and permit wider utility for data acquired from individual efforts. In this article we discuss some of the challenges and limitations for two general approaches for biological aerosol generation: solvent evaporation from liquid suspension droplets, and dry powder dispersal. We provide detailed descriptions of an example for each of these two approaches in which sufficient control is demonstrated over particle size distribution, total particle composition, biological constituent quantification and biological state (viability or enzymatic activity) to serve as a comparison among different experimental investigations. These two specific cases are intended as examples, not necessarily as prescriptions.
Following the release of an aerosolized biological agent in a transit venue, material deposited on waiting passengers and subsequently shed from their clothing may significantly magnify the scope and consequences of such an attack. Published estimates of the relevant particle deposition and resuspension parameters for complex indoor environments such as a transit facility are nonexistent. In this study, measurements of particle deposition velocity onto cotton fabric samples affixed to stationary and walking people in a large multimodal transit facility were obtained for tracer particle releases carried out as part of a larger study of subway airflows and particulate transport. Deposition velocities onto cotton and wool were also obtained using a novel automated sampling mechanism deployed at locations in the transit facility and throughout the subway. The data revealed higher deposition velocities than have been previously reported for people exposed in test chambers or office environments. The relatively high rates of deposition onto people in a transit venue obtained in this study suggest it is possible that fomite transport by subway and commuter/regional rail passengers could present a significant mechanism for rapidly dispersing a biological agent throughout a metropolitan area and beyond.
The COVID-19 pandemic has reintroduced questions regarding the potential risk of SARS-CoV-2 exposure amongst passengers on an aircraft. Quantifying risk with computational fluid dynamics models or contact tracing methods alone is challenging, as experimental results for inflight biological aerosols is lacking. Using fluorescent aerosol tracers and real time optical sensors, coupled with DNA-tagged tracers for aerosol deposition, we executed ground and inflight testing on Boeing 767 and 777 airframes.Analysis here represents tracer particles released from a simulated infected passenger, in multiple rows and seats, to determine the exposure risk via penetration into breathing zones in that row and numerous rows ahead and behind the index case. We completed over 65 releases of 180,000,000 fluorescent particles from the source, with 40+ Instantaneous Biological Analyzer and Collector sensors placed in passenger breathing zones for real-time measurement of simulated virus particle penetration.Results from both airframes showed a minimum reduction of 99.54% of 1 µm aerosols from the index source to the breathing zone of a typical passenger seated directly next to the source. An average 99.97 to 99.98% reduction was measured for the breathing zones tested in the 767 and 777, respectively. Contamination of surfaces from aerosol sources was minimal, and DNA-tagged 3 µm tracer aerosol collection techniques agreed with fluorescent methodologies.
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