Internal dose of particles in the elderly-modeling based on aerosol measurements.

The paper presents an integrated methodology that combines experimental and modeling techniques and links exposure to airborne particulate matter (PM) with internal dose in the respiratory system and burden in adjacent tissues over a period of time. The methodology is used to estimate doses in the respiratory systems of elders that reside in 10 elderly care centers (ECCs) in the metropolitan area of Lisbon. Measurements of PM were performed in the ECCs and combined with a time-budget survey for the occupants. This information served as input to the first model that estimated particle doses in the different regions of the respiratory tract of the elderly, and then a second model was used to calculate particle build-up in the alveolar region, the interstitium and the hilar lymph nodes of the elders over a 5-year exposure period. It was found that in 5 years of continuous exposure to the average particle concentration measured over all ECCs, 258 mg of all particles are deposited on the surface of the alveoli of which 79.6% are cleared, 18.8% are retained in the alveolar region, 1.5% translocate to the hilar lymph nodes, and 0.1% are transferred to the interstitium.

Modeling of occupational exposure to accidentally released manufactured nanomaterials in a production facility and calculation of internal doses by inhalation.

BACKGROUND: Occupational exposure to manufactured nanomaterials (MNMs) and its potential health impacts are of scientific and practical interest, as previous epidemiological studies associate exposure to nanoparticles with health effects, including increased morbidity of the respiratory and the circulatory system. OBJECTIVES: To estimate the occupational exposure and effective internal doses in a real production facility of TiO2 MNMs during hypothetical scenarios of accidental release. METHODS: Commercial software for geometry and mesh generation, as well as fluid flow and particle dispersion calculation, were used to estimate occupational exposure to MNMs. The results were introduced to in-house software to calculate internal doses in the human respiratory tract by inhalation. RESULTS: Depending on the accidental scenario, different areas of the production facility were affected by the released MNMs, with a higher dose exposure among individuals closer to the particles source. CONCLUSIONS: Granted that the study of the accidental release of particles can only be performed by chance, this numerical approach provides valuable information regarding occupational exposure and contributes to better protection of personnel. The methodology can be used to identify occupational settings where the exposure to MNMs would be high during accidents, providing insight to health and safety officials.

Computational modeling as part of alternative testing strategies in the respiratory and cardiovascular systems: inhaled nanoparticle dose modeling based on representative aerosol measurements and corresponding toxicological analysis.

The objectives of modeling in this work were (a) the integration of two existing numerical models in order to connect external exposure to nanoparticles (NPs) with internal dose through inhalation, and (b) to use computational fluid-particle dynamics (CFPD) to analyze the behavior of NPs in the respiratory and the cardiovascular system. Regarding the first objective, a lung transport and deposition model was combined with a lung clearance/retention model to estimate NPs dose in the different regions of the human respiratory tract and some adjacent tissues. On the other hand, CFPD was used to estimate particle transport and deposition of particles in a physiologically based bifurcation created by the third and fourth lung generations (respiratory system), as well as to predict the fate of super-paramagnetic particles suspended in a liquid under the influence of an external magnetic field (cardiovascular system). All the above studies showed that, with proper refinement, the developed computational models and methodologies may serve as an alternative testing strategy, replacing transport/deposition experiments that are expensive both in time and resources and contribute to risk assessment.

Facilitating knowledge transfer: decision support tools in environment and health.

The HENVINET Health and Environment Network aimed to enhance the use of scientific knowledge in environmental health for policy making. One of the goals was to identify and evaluate Decision Support Tools (DST) in current use. Special attention was paid to four "priority" health issues: asthma and allergies, cancer, neurodevelopment disorders, and endocrine disruptors.We identified a variety of tools that are used for decision making at various levels and by various stakeholders. We developed a common framework for information acquisition about DSTs, translated this to a database structure and collected the information in an online Metadata Base (MDB).The primary product is an open access web-based MDB currently filled with 67 DSTs, accessible through the HENVINET networking portal http://www.henvinet.eu and http://henvinet.nilu.no. Quality assurance and control of the entries and evaluation of requirements to use the DSTs were also a focus of the work. The HENVINET DST MDB is an open product that enables the public to get basic information about the DSTs, and to search the DSTs using pre-designed attributes or free text. Registered users are able to 1) review and comment on existing DSTs; 2) evaluate each DST's functionalities, and 3) add new DSTs, or change the entry for their own DSTs. Assessment of the available 67 DSTs showed: 1) more than 25% of the DSTs address only one pollution source; 2) 25% of the DSTs address only one environmental stressor; 3) almost 50% of the DSTs are only applied to one disease; 4) 41% of the DSTs can only be applied to one decision making area; 5) 60% of the DSTs' results are used only by national authority and/or municipality/urban level administration; 6) almost half of the DSTs are used only by environmental professionals and researchers. This indicates that there is a need to develop DSTs covering an increasing number of pollution sources, environmental stressors and health end points, and considering links to other 'Driving forces-Pressures-State-Exposure-Effects-Actions' (DPSEEA) elements. Of interest to both researchers and decision makers should be the standardization of the way DSTs are described for easier access to the knowledge, and the identification of coverage gaps.

A novel method for the generation of multi-block computational structured grids from medical imaging of arterial bifurcations.

In this study a description of a new approach, for the generation of multi-block structured computational grids on patient-specific bifurcation geometries is presented. The structured grid generation technique is applied to data obtained by medical imaging examination, resulting in a surface conforming, high quality, multi-block structured grid of the branching geometry. As a case study application a patient specific abdominal aorta bifurcation is selected. For the evaluation of the grid produced by the novel method, a grid convergence study and a comparison between the grid produced by the method and unstructured grids produced by commercial meshing software are carried out.

A methodology to generate structured computational grids from DICOM data: application to a patient-specific abdominal aortic aneurysm (AAA) model.

This study presents the generation of a multi-block structured grid on a real abdominal aortic aneurysm (AAA) acquired from Digital Imaging and Communication in Medicine (DICOM) data. With the use of a computed tomography exam (or medical images in standard DICOM format), the shape of a human organ is extracted and a structured computational grid is created. The structured grid generation is done by utilising Floater's and Gopalsamy et al.'s algorithm. The proposed methodology is applied to the AAA case, but it may also be applied to other human organs, enabling the scientist to develop an advanced patient-specific model. More importantly, the proposed methodology provides a precise reconstruction of the human organs, which is required in an AAA, where small variations in the geometry may alter the flow field, the stresses exerted on the walls and finally the rupture risk of the aneurysm.

Dynamics of flow in a mechanical heart valve: the role of leaflet inertia and leaflet compliance.

In this work, we examine the dynamics of fluid flow in a mechanical heart valve when the solid inertia and leaflet compliance are important. The fluid is incompressible and Newtonian, and the leaflet is an incompressible neo-Hookean material. In the case of an inertialess leaflet, we find that the maximum valve opening angle and the time that the valve remains closed increase as the shear modulus of the leaflet decreases. More importantly, the regurgitant volume decreases with decreasing shear modulus. When we examined the forces exerted on the leaflet, we found that the downward motion of the leaflet is initiated by a vertical force exerted on its right side and, later on, by a vertical force exerted on the top side of the leaflet. In the case of solid inertia, we find that the maximum valve opening angle and the regurgitant volume are larger than in the case of an inertialess leaflet. These results highlight the importance of solid compliance in the dynamics of blood flow in a mechanical heart valve. More importantly, they indicate that mechanical heart valves with compliant leaflets may have smaller regurgitant volumes and smaller shear stresses than the ones with rigid leaflets.

A simple mechanistic model of deposition of water-soluble aerosol particles in the mouth and throat.

Aerosol drugs are usually delivered to the lung by inhalation via the oral route, since aerosol deposition is much lower in the oral than in nasal airways. In the present study a practical, non-CFD-based, mechanistic model is developed, which permits an efficient calculation of deposition along the oral route with simple computational means. A simplified geometrical description of the mouth and throat region is used, based on a sequence of conducting ducts. The numerical model takes into account aerosol dynamics, which enables to express the impact on aerosol transport and deposition of the hygroscopic growth of water-soluble particles. Simulations are made for coarse particles in the range 1-17 microm, and the model predictions are found in good agreement with the available experimental data. The model predicts inertial impaction to be the dominant mechanism, and correctly reproduces the increase in the deposition with an increasing flow rate and particle diameter. Higher deposition is calculated in the oropharyngeal region than the laryngeal region, due to the significant flow direction change and constriction at the end of the oral cavity. According to the model, highly soluble particles may deposit up to 50% more than inert aerosols in the mouth-throat region. The proposed model will be useful for quick, practical calculations of deposition with a full account of aerosol dynamical processes.