aerosol exposures due to re-suspension from building ... · slide 1 aerosol exposures due to...

Aerosol Exposures Due to

Re-suspension from Building Reservoir Surfaces (M3.4)

J. Freihaut ,W. Bahnfleth, C. Gomes, Bin Hu, J. Firrantello, P. AumpansubIndoor Environment Center

Dept. of Architectural EngineeringPennsylvania State University

B. ThranU.S. Army Center for Health Promotion and Preventive Medicine

Society for Risk Analysis Annual Meeting 2004:Session M3 – Microbial Dose-Response Assessment for Inhalation Exposures

Objectives: Coupled Literature & Experimental Investigation ofParticle Re-suspension in Indoor Air Systems

1.) Extract Bio-particle Re-suspension Factors, Re-suspension Rates and Deposition Velocities from Literature Reported Investigations

2.) Use Controlled Re-suspension Experiments to Refine and Quantify Selection

3.) Establish Methodology to Relate Particle Re-Suspension and Deposition Rates to Generation and Sink Terms of Contaminant Source Terms in Building Air Flow Simulation Program (CONTAMW)

Aerosol Occupant Risk Assessment Scope

Biological Agents

Urban Air Quality

Natural BiocontaminantsProtein AllergensEndotoxinsAdsorbed Mycotoxins

Diesel exhausts

Occupant Risk AssessmentPrimary Release AersolizationSecondary AerosolizationTransport & Dispersion Occupant ExposureOccupant DosagesEpidemiological Effects

Allergens Can be Natural Bio-contaminants

Asthma related statistics18 million Americans (6% of US population) affected5,000+ death per year in the US13 billion USD per yearContinues to increase

http://aspe.hhs.gov/sp/asthma/overview.htm

Primary vs Secondary (Re-Suspension) Aerosolization Exposure

1

10

100

1000

10000PPM

CFU/M3

Secondary Aerosolization (Occupant Activity or Equipment Cycling):Residue of Primary Aerosolization BWA Attack“Conventional”– Allergens, Toxins, Pathogens, Spores

Primary Aerosolization /Transient Pulse Release:BWA Attack - Near Air Handle Intake or Interior ReleaseSpores - Air Handler Start-upSmoke & Fire AerosolsChemical Spills Aerosols

Time

1 2 3 4 5 6 7 8 9 10Seconds/Minutes1 2 3 4 5 6 7 8 9 10

Hours

Concentration

Inhalation Exposure Paths for Re-suspension Not Known"At present the question of how allergen particles enter the lungs is not resolved, and this issue is of considerable importancesince it may well define the distribution of "inflammation" and airway obstruction."Clearing the Air: Asthma and Indoor Air Exposures, National Academy of Sciences, National Academy Press, p.139, 2000 .

0.05 to 10 microns Aerosols

1.) BWA Deposited during primary Aersolization Event2.) Allergen - containing particles

Respiratory Disease Development

Need to elucidateair re-suspensionmechanisms :1.)Bioaerosol deposited during primary aersolization event;2.)common allergens

GeneticallyPredisposed Individual

IndividualLD50

Population Distribution

DebilitationfromBWA

Bioaerosol

Time

Aerobiology of Re-suspended Indoor Air BiocontaminantsInhalation Exposure Paths and Risk Assessment Require Aerobiological Pathway Quantification

PrimarySources

ReservoirFormation

Dose DiseaseDevelopment

(Individual riskFactors)

Aerosolization:PrimarySecondary

(Resuspension)

ExposureParameters

Occ(t) = occupant present (=1)or not (= 0) during time tin space containing contaminant i

Md = mass of aerosol carrier d = (π/6)ρd3

N i d (t) = # aerosol d/air volume

f i d = i mass fraction of d partilce mass

f d i = fraction of d particles carryiing i

Residue fromPrimary

BWA EventBWA*

Insects,Pets,,PestsFungi,MoldsEndotoxinsMycotoxins

Protein Allergens

Occupant Exposure Mass

EPMid

Dose

RR = Respiration rate occupantηd-capture = lung capture efficiency

DustSurfaces

EpidemiologyStatistics

EPMi = Σd StOcc(t)*Ndi ( t)*Md*f id* fi

dd(t)

HVAC Air Handlingor

Occupant Reservoir Disturbance:

Building Reservoirs

DOcci = Σd RR* η d- capture * η d- release EPMd

iinhalation

[Bio] i indoor air

=[Bio] iindoor

air

K id *[Bio]d ireservoir

dust

K id

K id = fFloor/Duct VibrationWalking ImpactElectrostatics

Turbulence( ( ))

EPMid = SdOcc(t)*[Bio]di (t) d(t)

inhalation

* BWA = chemical, biological warfare agents

Bioaerosols from Surface Reservoirs :Steady State and Transient Components

EPMid = 1* Nd

id ( t)*Md*f i d d(t)

t in

t out

SS

EPM id =

t in

t out

SS 1*[Bio] i d (t) d(t)

[Bio] id

Occupant Activity Based

Steady State Partitioning

t in t outTime

Occupant PresentOcc = 1

Protein Allergen Aerosolization (Resuspension) via Carrier Particles

dp 5-10nm

Allergen

0.1-50µm

Carrier particleAllergen Type Animal/Plant Carrier size range Time to settle in a

room

Der p 1Der f 1 House Dust Mite 10-25µm 30 minutes

Bla g 1 & g 2; Per a 1 Cockroaches >10µm 30 minutes

Fel d 1 Cats 50% >9µm50% <9µm 24 to 48 hours

Can f 1 Dogs Same as cat Same as cat

Amb a I, Bet v I Pollen 15-25µm 30 minutes

Particle sizeSurface Properties

Chemical functional groupsCharge distributionMorphology

Environmental Conditions %RHReservoir Perturbation

Particle Resuspension

Reservoir-air aerosolization pathwaysHuman walking = Aero-electro-mechanical perturbation of reservoir

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

ElectrostaticFieldVibration

Air Currents

+

__ __ __ __

++

Friction

Estimating Field Strengths Required for Air Partitioning of Allergen Carrier Particles

Aerodynamic, FA

Mechanical – Surface Vibration, Fν

Electrostatic Field Over Reservoir, FE

Aerosolization from Reservoir Reservoir Binding

Gravitational, Fg

Electrostatic Adhesion, Fadh

= mag = ρπda3/6

= kHda + KE qsurfaceqar2

= 3πηVada

= maAω2sin(ωt)

= qaE above reservoir = qa[dV/dy)]

where dV/dy = electrostatic voltage gradient

da>0.1 µm

boundary layer velocity profile limited in most conditionsneed directed jet impingement to disrupt

ω limited in most building surfaces (5 – 50 Hz)

human activity, tribology, determined, dV/dy can be large

“Free-ing Allergen Aerosols from Reservoir Surface Boundary Layer into“Bulk” Phase Flows of Room Air

Electrostatic Fields Important Component for Allergen Aerosolization from SurfacesIn Normal Activity Patterns

= [Bio]d iindoo r

air

K id *[Bio] ireservoir

dust

Partitioning of Biocontaminant - Containing Aerosols

{Pseudo Steady StateDescription

[Bio]d iindoor

airK id (m-1) =

[Bio] ireservoir

dust

Standard Vapor-Solid Partitioning Contaminant Containing Aerosol Partitioning

Ki = ΣdKid = Σd([Bio ] id / [Bio] iR)

Aerosol –Reservoir SystemAero-Electromechanical Equilibrium

Contaminant (allergen, virus, spore) i Reservoir of Carrier Particles

Floor/Duct VibrationWalking ImpactElectrostaticsAir Turbulence

Reservoir: Surface adsorbed Gas i

Gas iGas i

Ki (T) = [A i] vapor/ [A i] Adsorbed

NAi(d)

( ( ))

Thermal Equilibrium

Gas-Solid System

NRSi (d)

Framework for Understanding Secondary AersolizationAerosol Pathways of Inhalation Exposure

ReservoirPerturbation

K i = ΣdKid = Σ d [Bio] id

aerosol

Biocontaminantcontaining dust

Σd[Bio]i aerosol

( )( )Floor/Duct VibrationWalking ImpactElectrostaticsAir Turbulence

K units

mass/l3

l-1

[Bio]d ireservoir

RR, kA

= kA

kD

1/time

kD

l/time

K id is analogous to gas-solid chemical partitioning constants, i.e. is an equilibrium characterization whose value:- is a function of energy distribution in vapor and solid phases in system- varies with the interaction strength between the aerosol carrier particles and the reservoir surface

Re-suspension Literature Summary

Aero-Electro-Mechanical DriveRe-suspension

10-10 10-8 10-6 10-4 10-2

Aerodynamic DrivenRe-suspension

Resuspension Factor, “Constant,” (m-1)

Sehmel, G.A. “Particle Re-suspension: A Review,” Environment Int. 4, 107-127 (1980a)Nicholoson, K.W. “ A Review of Particle Re-suspension,” Atmospheric Environment, 22, No. 12, 2639-2651(1988)

Resuspension due to human activity

Nuclear Facilities (1960’s)• Freshly deposited contamination: 10-6 - 10-3 m-1

• Clean or aged contamination: 10-7 – 10-6 m-1

Residential buildingsResuspension Factors (m-1)

0.E+00

1.E-03

2.E-03

3.E-03

4.E-03

Blowing - 1person

Mopping - 1person

Walking - 4person

Particle size: 3-6µm

Hambraeus et al. 1978


Ratio [occupant activity/inactivity] airborne concentration

0

2

4

6

8

10

12

0.5-1.0 1-5 5-10 10-25

Particle Diameter (µm)Cleaning Walking 5 min Walking 30 min

29Cleaning: vigorous vacuuming and housecleaningWalking: done by 4 people

Residential buildings

Thatcher et al. 1995



Resuspension Rate (min-1)

1.65E-08

6.33E-06

7.33E-09

1.38E-065.67E-07

3.00E-07

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

0.3-0.5 0.5-1 1-5 5-10 10-25 >25

Particle size (µm)

Thatcher et al. 1995

Resuspension of an Indoor Aerosol – Grass Pollen ParticlesKarlsson, E., Fangmark, I., Berglund, T., “Resuspension of an indoor aerosol,”J. Aerosol Science, Vol. 27, Suppl. 1, S441-S442, 1996.

4 persons walking around

N 6.2 µm = 2.6 x107/m2

N 6.2 µm = 1.0 x105/m3 = 1.4 x 10-5 g/m3

= 14µg/m3

Reservoir Containing 6x4 µm Ellipsoidal Pollen Particles

N 6.2 µm = 1.0 x104/m3 = 1.4 x 10-6 g/m3

= 1.4 µg/m3

K 6.2 µm (m-1)=4.0 x10-4 K 6.2 µm (m-1)= 3.95 x10-3

1 person working at a table4hrs 4hrs

M 6.2µm = 3.4 x 10-3 g/m2



0.E+00

2.E+04

4.E+04

6.E+04

8.E+04

0 10 20 30 40 50 60 70

Time (minutes)

Conc

entra

tion

(#/m

3 )

1 person 4 persons

RR=1.8E-5 min-1

RR=2.45E-5 min-1

Karlsson et al. 1999



Buttner et al. 2001

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1E6 cfu/m2 1E7 cfu/m2

cfu/

m3

Vinyl Commer. Carpet Residt carpet

Spores: 1-8>-3.5 mm

Indoor Resuspension Aerosol- Penicillium Chrysogenum Spores

Buttner, M.P., Cruz-Perez, P., Stetzenback., L.D., Garrett, P.J., Luedtke, A.E.,“Measurement of airborne fungal spore dispersal from three types of flooring materials,”Aerobiologia, 18:1-11, 2002.

N 1.8x3.5 µm = 106 ->107 CFU/m2

Reservoir (tile/carpet) Containing 1.8 x 3.5 µm P. chrysogenum spores

Vinyl tileCommercial carpet (cut pile)Residential carpet (loop pile)

Floor substrates investigated

One person walking 1 minute

K 1.8-3.5 µm

K(m-1) 106 CFU/m2 Reservoir

Vinyl Ccarpet Rcarpet Air Sampler

0.00001 0.00002 0.00200 Anderson

0.00056 0.00020 0.01000 Buckcard

K(m-1) 107 CFU/m2 Reservoir

Vinyl Ccarpet Rcarpet Air Sampler

0.00008 0.00009 0.00900 Anderson

0.00010 0.00080 0.31650 Buckcard

1 x 10-5 < K Anderson < 9 x 10-3

M 1.8 x 3.5 µm = 4.5 x 10-5 g/m2 -> 4.5x10-4 g/m2

Quiescent, “Steady State” Partitioning of Indoor Allergens

K d Allergen i

Allergen i Aero. Conc. [ng/m3 air]Can f 1 10Fel d 1 10Der p 1 <0.0 – 2.0Rat n 1 * 1 – 20Mus m 1* 0.5 – 15Mus m 1 NRGuinea Pig 3 – 20Bla g 1 NR

“Quiescent” ConditionsPerturbation strength = 0Primary sources present

Allergen i Reservoir Conc. [µ gm/gm dust]Can f 1 100 - 700Fel d 1 100 - 3000Der p 1 1 - 60Rat n 1 * 350 - 850Mus m 1* NRMus m 1 05. – 2.0Guinea Pig NRBla g 1 10 – 104 Units ( ND – 400 µg/gm dust)

* = Animal Laboratory facilitiesNR = not reported

Note: Allergen investigationsdo not typically give reservoirsurface coverage (gms/m2,

Particles/m2 ) data forallergen containing dusts

Reservoir Perturbation Induced Partitioning of Allergens

K d Allergen iReservoirPerturbation

Allergen i Aero. Conc. [ng/m3 air]Can f 1 NR Can f 1** 300**Fel d 1 50 – 1000 **Der p 1 5 - 100Rat n 1 * 10 – 80*Mus m 1* NR*Mus m 1 NRGuinea Pig 5000 - 17000Bla g 1 NR

Allergen i Reservoir Conc. [µ gm/gm dust]Can f 1 100 - 700Fel d 1 100 - 3000Der p 1 1 - 60Rat n 1 * 350 - 850Mus m 1* NRMus m 1 05. – 2.0Guinea Pig NRBla g 1 10 – 104 Units ( ND – 400 µg/gm dust)

** I Cat or Dog Housing Facility * = Animal Laboratory facilitiesNR = not reported


Aero-Electro-MechanicalRe-suspension

10-10 10-8 10-6 10-4 10-2



Thatcher, et. al. (1995) 1- 25 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)


Literature review findings:• Different types of activities => Different Resuspension Factors• Higher intensity perturbation=> Higher Resuspension Rates,

Factors• Reservoir Loading => Resuspension rates proportional• Resuspension rates higher for super-micron particles• Different allergens => Different particle size distributions• Lower the Relative Humidity => Higher the Resuspension

rates??

Implications Literature Review Summary

Limitations of previous studies: • Experiments run under wide range of conditions and particle types• Wide variation in re-suspension rates & constants appears due to

wide variation in, but often uncharacterized, reservoir characteristics, reservoir perturbations, environmental conditions

• Particle size relationships among airborne and reservoir sourcesfrequently not given

• Allergen carrier particle resuspension data normalized differently than nuclear, agricultural data

Consequences• Not possible to use literature data to make inhalation dose-risk

analysis in buildling simulations and achieve acceptable certainty in trends

• Need controlled condition investigations with well characterizedperturbations, reservoirs, and time-resolved airborne measurements

Research

Controlled Temperature &

Relative HumidityParticle Free Air

Sampling

AllergenContent

CascadeImpactor

ELISAAnalysis

Experimental Chamber

Physical and aerodynamic analysis of:• Known Particle Size• Known Particle Contaminant (allergen) Content• Known Surface Properties

Perturbance:• Vibration• Air Puffs• Transient Electro-static Fields

Research Process

ParticleCounters

Controlled Re-suspension Experimental Chamber

• Overall dimensions: 400x200x200 mm• Test plate dimension: 100x100 mm• Controlled Ambient Conditions• Controlled particulate matter• Inlet & outlet flow: 32.4 lpm (laminar)

uniformily distributed• Incorporates mechanical and aerodynamic

perturbances• Applied pressurization and no infiltration

Controlled Particle Size and Compositional 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• Contaminant (allergen)

concentration

Preparing Allergen Containing Reservoir Dusts

Steps• Initial grinding• Sieving 38<dp<355 µm• Secondary grinding• Separation in cascade

impactor stagesCascade ImpactorAerodynamic Cut-offs:• 0.4-0.7 µm• 0.7-1.1 µm• 1.1-2.1 µm• 2.1-3-3 µm• 3.3-4.7 µm• 4.7-5.8 µm• 5.8-9.0 µm• +9.0 µm

Known Allergen Concentration In Dusts: ELISA technique

Standard curveStandard curve

0.0000.2000.4000.6000.8001.0001.200

0.001 0.010 0.100 1.000 10.000

Concentrations (U/ml)

Mea

sure

d O

.D.

Allergen curveAllergen curve

0.0000.2000.4000.6000.8001.000

0.100 1.000 10.000 100.000 1000.000

Concentrations (mg/ml)

Mea

sure

d O

.D.

Establishing Uniform Reservoir Dust Samples

Distribution of dust on floor samples

• Overall dimensions: 760x760x420 mm• 25 floor samples (90x90 mm each)• Dust dispersed in mixing conditions• Uniform dust distribution (∆≤10%)• Floor sample covered by protection lids before removal

Use Field Recorded Waveforms for Vibration Energy Input

Floor vibration

Vibration Signal

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0

Time (sec)

Am

plitu

de

Simple functions:• Sinusoidal, square, triangular, etc.

Floor vibration due to human walking

• Measured and digitallyrecorded in the field

Use Smoke Test Visualization for Near Floor Air Current Distubance Velocity Approximation

Air-puff

Air motion due to human walking• Published information inexistent• Performance of walking experiment• Visible horizontal air velocity 1-1.5 m/s

1.5 m/s0.5 – 1.0 m/s

1.0-1.5 m/s

Optical and Impactor Train Sampling of Re-suspended Particles

Sampling Equipment

Optical Particle Counter• 0.3 – 2+µm, 8 bins

Condenser Particle Counter• 0.02 – 1µm

Cascade Impactor• 0.4 – 9+µm, 8 stages• Particle shape• Allergen concentration

• Determination of resuspended particle size distribution

• Particle size resolved allergen concentration

Re-suspension Experimental Results

Experimental observations:• Resuspension greatest in first two minutes perturbation• Air had greater impact than vibration; but vibration important

contributing component• Higher resuspension rates on linoleum than carpet• 0 – 15 µm roach allergen particles easier to resuspend than quartz• Current resuspension factors and rates indicte E field likely significant

contributing component

Carpet Linoleum

Quartz

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

Vibr Air Vibr+Air

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

Vibr Air Vibr+Air

Roach dust

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

Vibr Air Vibr+Air1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

Vibr Air Vibr+Air

Maximum:RR=2.73E-4 min-1

RF=6.81E-5 m-1

No E(t) field

Literature:RR=1E-8 ->7.8E-2 min-1

RF=1E-7 -> 8E-2 m-1

Conclusions and Recommendations

Conclusions:• Methodology is able to determine particle

resuspension for different types of dust, flooring, ambient conditions and floor disturbance type and intensity.

• Methodology is able to use reference allergen dusts, spores – in well defined perturbation conditions..

• Valuable tool to create a database of RF for particle resuspension, e.g. allergens, responsible for risk of disease development

• Contribute to development of activity-based human exposure risk models imbedded in building air flow simulations

Recommendations:• Improve floor disturbance

characterization methodology• Expand floor disturbance to include

an electrostatic field• Large chamber and field studies to

validate the surface disturbance re-suspension data, models

• Development of broader range of dust preparation protocols

In Process:• Implementation of results in building

air flow simulation models and human respiratory models (e.g. CONTAMW)


Aero-Electro-MechanicalRe-suspension

10-10 10-8 10-6 10-4 10-2



Thatcher, et. al. (1995) 1- 25 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 facility studies (1960’s)

Gomes, Freihaut, et. al. (2004)0.5 – 10 µm quartz calibration particles0.5 – 10 µm+ roach allergen carrier particlesControlled:

Particle sizeReservoir surface material%RH environmentReservoir ω and g-vibrationAero-dynamic swirl

NO ELECTROSTATIC FIELD TRANSIENT

Sehmel, G.A. “Particle Re-suspension: A Review,” Environment Int. 4, 107-127 (1980a)Nicholoson, K.W. “ A Review of Particle Re-suspension,” Atmospheric Environment, 22, No. 12, 2639-2651(1988)

Modeling Occupant Exposure Mass , EPMdi(t)

Occ = 1 Occ = 0

Time

[Bio] id

Occ = 0

t in t out

EPMid =Σj

t in j

t out j

SS 1*[Bio] i d (t) d(t)

Time

Occupant Interacts with Local Environments to Create Aerosol FiOccupant Interacts with Local Environments to Create Aerosol Fields Causing Exposureelds Causing Exposure

j = Reservoir

[Bio] id

QuiescentBackground

OccupantInduced

j =1 j = 2

j =1

j = 3

Time

Using CONTAM to Assess Re-suspension Occupant Exposure

CONTAMW Vapor Contaminant Source Term: S = G- D*C (mass/time)

Gi = airborne contaminant i generation rate via particle re-suspension rateDi*Ci = contaminant i deposition (sink) rate on surfaces

where Ci = mass fraction of vapor in airDi = k(time-1)*ρair*Vzone

Gi = RAi(t) = AA(π/6)ρdS [kA

i(d) * d3 * fdi(d) * fi

d(d) *NRS(d)] d(d)

Fraction of reservoir particles containing i

Mass fraction of i in particles containing i Particle distribution function onReservoir surface/area

Ki = ΣdKid = Σ d [Bio] id

aerosol

[Bio]d ireservoir

= kA

kDReservoir Perturbation (CONTAMW) :

Linked to occupancy schedules ofAA specified by mulitiplier factor

e.g.

kA, kDfrom Literature, Experimental,

Estimated (e.g. deposition velocities)

Expected Research Impact

Particle and AllergenExposure Simulation• CFD Analysis

• ContamW

Healthier Indoor

Environment

Decrease of AllergenResponse Syndrome

including AsthmaBetter Quality of Life Increase of Work

Productivity

Building Remediation

Building Construction

Development of Database

Resuspension Factors Allergen Concentration of Airborne Particles

New Technology:•Biocontaminant sensors• Ventilation Systems• Filtration• Allergen Deactivation

• Dust Properties• Floor Properties• Human Activity•Ambient Conditions

Acknowledgements

Pennsylvania State University Institutes of the Environment

U.S. Army Center for Health Promotion and Preventive Medicine

Indoor Biotechnologies Corporation, Dr. Martin Chapman

aerosol exposures due to re-suspension from building ... · slide 1 aerosol exposures due to...

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