Mind Bend 2005 Resuspension of allergen-containing particles under

Mind. Bend 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 1

Research Motivation 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 http: //aspe. hhs. gov/sp/asthma/overview. htm Carlos Gomes – Bin Hu – James Freihaut 2

Particles-allergen Resuspension Allergen dp 5 -10 nm 0. 1 -50 mm Carrier particle Allergen Type Animal/Plant Carrier size range Time to settle in a room Der p 1 Der f 1 House Dust Mite 10 -25 mm 30 minutes Bla g 1, g 2, Per a 1 Cockroaches >10 mm 30 minutes Cats 50% >9 mm 50% <9 mm 24 to 48 hours Fel d 1 Can f 1 Dogs Same as cat Amb a I, Bet v I Pollen 15 -25 mm 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 3

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

Resuspension-Review Sehmel, G. A. , 1980, “Particle Resuspension: A Review, ” Environment Int. , 4, 107 -127 Nicholoson, K. W. , 1988, “ A Review of Particle Resuspension, ” Atmospheric Environment, 22, 12, 2639 -2651 Nuclear storage studies (1960’s) Findings - Resuspension depends on: • • Aero-Electro-Mechanical Re-suspension Karlsson, et. al. (1996) 6. 0 x 4. 0 µm spores Buttner, et. al (2002) 1. 8 x 3. 5 µm fungal spores Limitations of previous studies: Thatcher, et. al. (1995) 1 - 25 µm Hambraeus, et. al. (1978) Residential • • • 10 -8 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 Aerodynamic Driven Re-suspension 10 -10 Types of activities Intensity activities Reservoir dust load Type of flooring Particle size Type of allergen Relative Humidity ? 10 -6 10 -4 10 -2 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 timeresolved airborne measurements. Resuspension Factor, “Constant, ” (m-1) Carlos Gomes – Bin Hu – James Freihaut 5

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

Resuspension Research Experimental Chamber • Overall dimensions: 400 x 200 mm • Test plate dimension: 100 x 100 mm • Controlled Ambient Conditions • Controlled particulate matter • Incorporates mechanical and aerodynamic perturbances Carlos Gomes – Bin Hu – James Freihaut 7

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

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

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 10

Resuspension Research Air-puff Air motion due to human walking • Published information inexistent • Walking experiment with CO 2 vapor • Visible horizontal air velocity 1 -1. 5 m/s Carlos Gomes – Bin Hu – James Freihaut 0. 5 – 1. 0 m/s 1. 0 -1. 5 m/s 11

Resuspension Research Sampling Equipments Optical Particle Counter • 0. 3 – 2+mm, 8 bins Cascade Impactor • Determination of resuspended particle size distribution • Particle size resolved allergen concentration • 0. 4 – 9+mm, 8 stages • Particle shape • Allergen concentration ELISA Analysis Carlos Gomes – Bin Hu – James Freihaut 12

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 13

Research – Experiments Results Maximum: RR=3. 22 x 10 -3 min-1 RF=8. 06 x 10 -5 m-1 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 Carlos Gomes – Bin Hu – James Freihaut 14

Conclusions and Recommendations Resuspension Factor Comparison Gomes and Freihaut 2004 Sehmel, G. A. , 1980, “Particle Resuspension: a review”, Environment International, Vol. 4, pp. 107 -127 10 -10 10 -6 RF [m-1] 10 -3 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. Carlos Gomes – Bin Hu – James Freihaut 10 -2 Recommendations: • Improve floor disturbance characterization and expand floor disturbance to include an electrostatic field. • Large chamber and field studies to validate the surface disturbance resuspension 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 15