Lower Airway Exposure to Particulate Emissions from Cooking Oil by a CT-Imaging Based 3D Printed Human Airway Model

Abstract

Formålet ved dette afgangsprojekt er at opnå en dybere forståelse af partikeleksponeringen i de menneskelige luftveje. Dette udføres ved brug af en anatomisk korrekt model af de nedre luftveje udviklet på baggrund af CT-scanningen af en mand. Dette er en innovativ tilgang til at undersøge partikeleksponering fra forskellige forureningskilder, som ikke før er blevet anvendt i takt med den teknologiske udvikling. CT-scanningen har ført til en 3D printet luftvejsmodel, der muliggør en eksperimentel undersøgelse. Luftvejsmodellens geometri bliver ligeledes brugt til en numerisk undersøgelse. De eksperimentelle undersøgelser af partikeleksponeringen i de nedre luftveje tager udgangspunkt i stegning af fire forskellige typer madlavningsolier. I forsøgsopstillingen er luftvejsmodellen placeret tæt på forureningskilden, og partikelkoncentrationen bliver målt i flere lokationer i et "clean room" med fortrængningsventilation. Den eksperimentelle undersøgelse viste en faktor fem til forskel på den maksimalt opnåede massekoncentrationen imellem de forskellige olietyper. Olivenolie genererede den største massekoncentration, og solsikkeolie den mindste. Størrelsesdistributionen på de inhalerede partikler var baseret på talkoncentrationen og viste sig næsten at være ens for de forskellige olietyper, såvel som i løbet af forsøget. Forskellen på massekoncentrationen var altså ikke forårsaget af størrelsesfordelingen på partiklerne, men skyldes nærmere oliernes forskellige røgpunkter. Påvirkningen af den termiske søjle på massekoncentrationen i åndingszonen blev undersøgt ved brug af en termisk mannequin. Denne viste, at der ingen forskelle var i massekoncentrationen grundet den overdøvende varmestrøm fra forureningskilden. Den numeriske undersøgelse omhandler en analyse af partiklers bevægelse samt disses deponering i luftvejene, som ikke er muligt at opnå igennem det eksperimentelle arbejde. Deponeringen blev undersøgt ift. luftvejenes opdeling og ud fra ens-spredte partikler. En stationær CFD simulering blev udført grundet tidsbegrænsningen for projektet. Resultaterne viste, at størstedelen af partiklerne blev deponeret i bronkierne, og at partikler med en aerodynamisk diameter over <2.0mikrometer forårsagede en højere deponeringsfaktor grundet større risiko for impaktion og sedimentation. En sammenligning imellem den eksperimentelle og numeriske undersøgelse viste en stor forskel i den undersøgte deponeringsfaktor. Forskellen skyldes de forskellige antagelser og undersøgelsesmetoder anvendt i forløbet. Samlet set fremmer denne undersøgelse viden om eksponeringen og indtaget af partikler ved implementeringen af ny state-of-the-art teknologi. Denne viden bidrager til fremtidige undersøgelser af kontrolmetoder, der skal minimere de sundhedsmæssige konsekvenser ved husholdningens forureningskilder.

The purpose of this project is to gain a deeper understanding of particle exposure in an anatomically correct model of the lower airways. The model has been developed from the CT-scanning of a human male. This is a new approach to investigating the effect of indoor airborne particles on the human occupants. The CT-scanning is applied to develop a 3D printed model for experimental use and the same geometry was used to conduct CFD simulations in a numerical investigation. The experimental investigation focused on four different types of cooking oil, which generate real polydispersed particles. The 3D printed airway model was placed in close proximity to the emission source and particle concentration was measured in several locations in the displacement ventilated clean room. The duration of the measurement extended from the start of the source-active period until initial conditions were reached. The investigation concluded that the mass concentration varies with a factor of five between peak concentrations of the different oil types. Olive oil generated the most particles and sunflower oil generated the least. The size-resolved distribution of the cooking emitted particles were based on number concentration and showed to be very similar for the different oil types, as well as during the different times of the measurement. Thereby the difference in mass concentration was not due to the sizes of the particles but more likely the smoke points of the various oils. Peak concentration was almost reached simultaneously for the different measurement locations. The effect of the thermal plume on mass concentration in the breathing zone was also investigated by a thermal manikin. This showed no differences in mass concentration due to an overpowering thermal plume generated by the emission source. The numerical investigation was used to analyse the regional particle deposition of monodispersed particles. Steady state CFD simulations were carried out due to time constraints set by the computational power. Results showed that the majority of the particles were deposited in the bronchi. Accumulation particles (0.1 - 2.0 microns) have the smallest deposition fraction in the lower airways. An increase in the aerodynamic diameter (>2.0 microns) of the particles elevated the deposition fraction. A comparison of the deposition fractions from the experimental and numerical investigations showed a big deviation. This is attributed to the different parameters set and assumptions applied in the process. Overall this study advances knowledge on the characteristics of both exposure and intake of particles by the implementation of state-of-the-art technology. This knowledge contributes to future investigations into control methods that minimise the negative health impact of indoor emissions.

A master thesis from Aalborg University

Lower Airway Exposure to Particulate Emissions from Cooking Oil by a CT-Imaging Based 3D Printed Human Airway Model

[Lower Airway Expsoure to Particulate Emissions from Cooking Oil by a CT-Imaging Based 3D Printed Human Airway Model]