Carlos Gomes – Bin Hu – James Freihaut Slide 1 MindBend 2005 Resuspension of allergen-containing particles under mechanical and aerodynamic forces from human walking - Introduction to an experimental controlled methodology Bin Hu Carlos Gomes Advisor: James Freihaut Indoor Environment Center Department of Architectural Engineering Pennsylvania State University April 09, 2005

Carlos Gomes – Bin Hu – James Freihaut Slide 2 Asthma related statistics  18 million Americans (6% of US population) affected  5,000+ death per year in the US  13 billion USD per year  Continues to increase Research Motivation

Carlos Gomes – Bin Hu – James Freihaut Slide 3 Particles-allergen Resuspension dpdp 5-10nm Allergen Carrier particle  m Allergen TypeAnimal/PlantCarrier size range Time to settle in a room Der p 1 Der f 1 House Dust Mite  m 30 minutes Bla g 1, g 2, Per a 1Cockroaches >10  m 30 minutes Fel d 1Cats 50% >9  m 50% <9  m 24 to 48 hours Can f 1DogsSame as cat Amb a I, Bet v IPollen  m 30 minutes Carrier particle Particle size Surface Properties Chemical functional groups Charge distribution Morphology Environmental Conditions %RH Reservoir Perturbation

Carlos Gomes – Bin Hu – James Freihaut Slide 4 Particle Resuspension  Reservoir-air aerosolization pathways Mechanical Shoe Friction Floor Vibration Aerodynamic Velocity Turbulence Electrostatic Human built up to 10,000 V Adhesion + Gravitational Van der Waals Relationship among Force components and Resuspension - Not Understood Electrostatic Field Vibration Air Currents + __ __ + + Friction RF[m -1 ]=C air /C floor RR[min -1 ]=G/(A.C floor )

Carlos Gomes – Bin Hu – James Freihaut Slide 5 Aero-Electro-Mechanical Re-suspension Aerodynamic Driven Re-suspension Resuspension Factor, “Constant,” (m -1 ) Thatcher, et. al. (1995) µm Buttner, et. al (2002) 1.8 x 3.5 µm fungal spores Karlsson, et.al.(1996) 6.0 x 4.0 µm spores Hambraeus, et. al. (1978) Residential Nuclear storage studies (1960’s) Resuspension-Review Findings - Resuspension depends on: Types of activities Intensity activities Reservoir dust load Type of flooring Particle size Type of allergen Relative Humidity ? Sehmel, G.A., 1980, “Particle Resuspension: A Review,” Environment Int., 4, Nicholoson, K.W., 1988, “ A Review of Particle Resuspension,” Atmospheric Environment, 22, 12, Limitations of previous studies: Wide range of conditions and particles type No control or characterization of ambient conditions, floor surface type, dust types, reservoir dust load, activity intensity Particle size relationships among airborne and reservoir sources frequently not given Consequences Not possible to use literature data to make inhalation dose-risk analysis in building simulations and achieve acceptable certainty in trends. Need controlled condition investigations with well characterized perturbations, reservoirs and time- resolved airborne measurements.

Carlos Gomes – Bin Hu – James Freihaut Slide 6 Resuspension Research Controlled: Temperature & Relative Humidity Particle Free Air Sampling Allergen Content Cascade Impactor ELISA Analysis Resuspension Chamber Physical and aerodynamic analysis of: Known Particle Size Known Particle Allergen Content Known Surface Properties Perturbance: Vibration Air Puffs Electrostatic Research Process Particle Counters

Carlos Gomes – Bin Hu – James Freihaut Slide 7 Resuspension Research Overall dimensions: 400x200x200 mm Test plate dimension: 100x100 mm Controlled Ambient Conditions Controlled particulate matter Incorporates mechanical and aerodynamic perturbances Experimental Chamber

Carlos Gomes – Bin Hu – James Freihaut Slide 8 Resuspension Research Floor samples Representative of residential buildings Hardwood, carpet, linoleum Controlled Surfaces Properties

Carlos Gomes – Bin Hu – James Freihaut Slide 9 Resuspension Research Calibrated dust Quartz, aluminum oxide, polymer, silica, etc Allergen dust Roach body parts Cat hair Dog hair Dust mite Controlled Dust Properties Known properties Density Particle size distribution Allergen concentration

Carlos Gomes – Bin Hu – James Freihaut Slide 10 Resuspension Research Floor vibration Simple functions: Sinusoidal, square, triangular, etc. Floor vibration due to human walking Measured in the field

Carlos Gomes – Bin Hu – James Freihaut Slide 11 Resuspension Research Air-puff Air motion due to human walking Published information inexistent Walking experiment with CO 2 vapor Visible horizontal air velocity m/s 1.5 m/s 0.5 – 1.0 m/s m/s

Carlos Gomes – Bin Hu – James Freihaut Slide 12 Resuspension Research Sampling Equipments Optical Particle Counter 0.3 – 2+  m, 8 bins Cascade Impactor 0.4 – 9+  m, 8 stages Particle shape Allergen concentration Determination of resuspended particle size distribution Particle size resolved allergen concentration ELISA Analysis

Carlos Gomes – Bin Hu – James Freihaut Slide 13 Resuspension Research Methodology put together and tested Experiments Test the methodology 26ºC, 45%RH Calibrated quartz and roach dust Carpet and linoleum Vibration, air-puff, vib.+air 12 experiments

Carlos Gomes – Bin Hu – James Freihaut Slide 14 Research – Experiments Results Experimental observations: Resuspension in first two minutes Air had greater impact than vibration Higher resuspension rates on linoleum than carpet Roach dust is easier to resuspend than quartz Maximum: RR=3.22x10 -3 min -1 RF=8.06x10 -5 m -1

Carlos Gomes – Bin Hu – James Freihaut Slide 15 Conclusions and Recommendations Conclusions: Valuable tool to create a database of RR&RF for particle resuspension, e.g. allergens, spores responsible for risk of disease development. First results are consistent with the literature review. Re-suspension parameters used in activity-based inhalation exposure risk models imbedded in building air flow simulations. Recommendations: Improve floor disturbance characterization and expand floor disturbance to include an electrostatic field. Large chamber and field studies to validate the surface disturbance re- suspension data, models. Develop rapid field tests – swab swipe for hard, smooth surfaces and vacuum filtering for rought surfaces – to determine reservoir source strengths at site Sehmel, G.A., 1980, “Particle Resuspension: a review”, Environment International, Vol.4, pp Gomes and Freihaut Resuspension Factor Comparison RF [m -1 ]