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Content archived on 2024-05-28

BIOcontamination Specific Modeling in HAbitats Related to Space

Periodic Report Summary - BIOSMHARS (Biocontamination specific modeling in habitats related to space)

Project Context and Objectives:

On earth, nowadays, people spend more than 90 % of their time indoors or in vehicles. Biocontamination in these closed areas can have significant health impacts. When humans go to space, so do also bacteria. On manned spacecrafts, there is a need for effective biocontamination control measures. Biocontamination in spacecrafts may indeed result both in a risk for the health of the crew and for the on-board equipment.

The BIOSMHARS project intends to develop, to calibrate and to validate a mathematical model to predict the transportation of bioaerosols in a closed environment and the concurrent spread of biocontamination. The long-term objective is to produce a versatile and robust modelling tool for predicting airborne microbial contaminant dispersion and concentration distribution in a spacecraft with applications for closed environments on earth.

In addition to the normal airflow fields and temperature distribution predictions, the objective is that the model takes also into consideration the different types of human bioaerosol emissions. The model to be developed will be a three dimensional computational fluid dynamics (CFD) model utilising a two-equation model for turbulence closure. The calculations will be made first assuming normal gravity but the model will allow the gravity vector to be adjusted in the future to reflect microgravity conditions.

Experiments will be required to check the validity of simplifying assumptions as well as to find out the accuracy, the limitations and the development needs of the model. The initial calibration of the model will be realised in a special test room at the Technical Research Centre's (VTT) laboratory in Finland. The calibration will first be realised using non-viable particles generated by conventional aerosol generators. The model will then be calibrated with biological particles using bacterial and fungal aerosols. The aim will be to ensure that the model provides a reliable picture of bioaerosol behaviour. The model will be refined as required, based on the results of the experiments. Experiments will then be realised in BIOS-3 facility in Krasnoyarsk, which is a closed ecosystem used to conduct confinement studies, for further validation and refinement. These experiments will also be realised in two phases, first with non-viable particles and then with biological particles.

In addition, the project will develop a scientific and technical roadmap to plan further phases.

BIOSMHARS is a joint research effort of Europe and Russia to improve biocontamination control strategies for manned spacecrafts and more generally for closed environments. The consortium is made of six partners: MEDES, the French Institute for Space Physiology and Medicine as coordinator, SCK-CEN - the Belgian Nuclear Research Centre, IBMP - the Russian Institute for Biomedical Problems, bringing their expertise in microbiology related to manned space exploration, the University of Eastern Finland, expert on the medical impact of indoor microbial contamination, VTT - the Technical Research Centre of Finland - bringing expertise on mathematical modelling and IBP - the Russian Institute of Biophysics - operating the BIOS facility. The project, which started in June 2011, will last two years.

Project Results:

The project started by a review of the current issues and procedures related to biocontamination in spacecrafts. Fluctuations in microbial concentration and contamination events suggest the need for continued diligence and evaluation as well as further improvements in engineering systems. Significant improvements could be achieved if a reliable model to predict bioaerosol dispersion in closed habitats would be available to be used to validate habitat design and to develop adequate prevention and monitoring procedures for airborne microbial contamination. BIOSMHARS should contribute to develop such a model. The partners have in parallel reviewed the current knowledge in the area of bioaerosol dispersion modelling and biological indoor air quality control. Human exposure to airborne biocontaminants is mainly affected by the generation and dispersion of bioaerosols and their transport and dilution due to ventilation airflows. Thus the control of bioaerosols is essential in good indoor air quality management. This review shows that reliable simulation tools are urgently needed to correctly describe the biocontamination phenomena.

Scientific papers have been submitted to publish these reviews.

The partners have then defined the requirements of the envisaged model.

The methodology for the modelling was identified in five phases with the description:

1. of the airflow field in enclosed space
2. of the microbial contaminant generation (source description)
3. of the microbial contaminant dispersion
4. of the microbial contaminant deposition on surfaces and
5. of the microbial growth (biofilm formation) on surfaces.

The latter will not be modelled within the current project. The first phase started with the modelling of the geometry and of the airflow inlets and outlets, with realistic boundary conditions. The first developed geometry is based on the Columbus module of the international space station (ISS).

For the calibration tests, VTT has been preparing a special test room, reproducing similar volumes and air flow generation as within the Columbus module, with specific equipment for the measurements to check the model as well as to generate the calibrated aerosols of physical particles (non-viable).

In parallel, to prepare the biological calibration and validation, the partners have been working on the generation of well calibrated. The selected microorganisms are: the fungus Penicillium expansum, the bacteria Staphylococcus epidermidis and Bacillus subtilis , which are well representative of the microbial flora found on ISS. The tested strains have been isolated from samples retrieved from ISS by IBMP. The generation of the bioaerosol has already started, first with the dry generation for fungi. The performance of the bioaerosols is being tested with characterisation of stability, source strength and size distributions of the generated aerosols, examination of agglomeration stage and the purity of the generated aerosol.

For the validation of the model, the objective was to carry out experiments in a facility similar to spacecraft environment. The BIOS-3 facility has been considered as a unique facility for such experiments. IBP, operating the BIOS-3 facility has been upgrading the facility, especially in terms of sensors and is preparing the airflow generation system for the envisaged experiments. The physical validation experiments in BIOS are planned in September 2012.

The partners have also started to design the experiments for the biological validation that will be realised in BIOS in 2013. This design is regularly reviewed along with the progress of the work on the bioaerosol characterisation.

Finally, the partners have started to disseminate the project, in particular through the public website and participation to congresses.

Potential Impact:

BIOSMHARS should deliver a preliminary predictive model for biocontamination in confined environments. The model should enable to describe and to predict the airborne microbial contamination dispersion profile in confined habitats. The model will be calibrated and validated both with non-biological and biological aerosols and the validation will be realised in relevant spacecraft environmental conditions in a space habitat analogue, i.e. the BIOS facility.

Due to the 'predictive capacity' of the model, it will have high value as a tool for a 'risk assessment' of microbial contamination for long duration missions in space. The predictive model could indeed be used to screen spacecraft design, to reduce possible sites prone to support microbial contamination and should help to define an improved strategy to deal with the biocontamination issue.

The complex phenomena of microbial dispersion through air and deposition onto surfaces in a confined environment are also a topic of interest in numerous areas like in hospitals, airplanes, pharmaceutical and food industry. The BIOSMHARS project should provide insights for further developments (space related and non space related) in different disciplines of human health related to biocontamination. It is a proven fact that an important change of the environmental microbial flora increases the risk of infectious diseases. To better understand the dispersion of airborne microbial contamination and to assess a possible necessity for countermeasures for intolerable changes of the microbial flora, research is needed. The outcome will provide important information on the adaptation and changes of the bio-burden for closed areas like hospital departments, surgery wards in hospitals, clean rooms and habitats, public buildings and lead to a better understanding of the development and evolution of microbial communities (nosocomial disease, cross-infection risk, etc.). As for public area, the interest of this know-how for clean room design and quality control, including pharmaceutical plants is very promising.

Furthermore, such a model will have the potential to be extended to predict the release of non-biological material emissions, or chemical contamination, e.g. volatile organic compounds (VOCs) and particles released by the microbes.

The proposed work may also be of interest for safety measures against for instance biochemical or biological terrorism.

The generation of a calibrated bioaerosol will also be a progress in the general area of biocontamination in indoor environments.

In terms of facilities, the adaptation of BIOS, a ground based facility representative of spacecrafts and well characterised, for experiments on biocontamination, is a significant contribution for future studies on the issue of biocontamination in space and more generally, in close habitats.

Finally, BIOSMHARS will develop a European - Russian strategy to deal with biocontamination in spacecrafts and will provide a roadmap defining the detailed scientific and technical achievements required, to solve this issue.

Except from BIOS, these tools are 'open', meaning that they will be reusable for further phases of the project, either by the partners of the consortium, or by other institutions.

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