1. Thrust 2. 0: Effect of Human Activity on Exposure PM Pollutants T2
Thrust 2.0: Effect of Human Activity on Exposure PM Pollutants T2.A: PM Source Characterization
Jing Qian, Clarkson University
Andrea Ferro, Clarkson University
Jensen Zhang, Syracuse University

2. Health Concerns for Indoor PM
Exposure to PM contaminants indoors can constitute a potential health hazard.
Resuspension events due to mechanical forces tend to result in short-term, elevated PM concentrations (Long et al., 2000, Ferro et al., 2004).
Short-term (1-8 h) PM exposures have been associated with asthma symptoms, chronic obstructive pulmonary disease, and decreased heart rate variability (Delfino et al., 1998; Morgan et al., 1998; Gold et al., 2000).  
Resuspended soil and dust contain pollutants and biological agents of concern, including PCBs, PAHs, phthalates, molds, pet allergens, dust mites, bacteria, lead and other heavy metals (Roberts and Dickey, 1995; Rudel et al., 2003).

3. Motivation for T2.A
Resuspension is a major source of indoor airborne particles (Thatcher and Layton, 1995, Ferro et al. 2004)
Indoor particle concentrations most sensitive to resuspension rate and track-in rate (Schneider et al., 1999). Very few field data exist for estimating resuspension rates.
A wide range of resuspension rate from human activity: hr-1 for supermicron particles and 10-7 hr-1 for µm particles (Thatcher and Layton, 1995; Qian et al., 2006).
The resuspension rate depends on many factors, such as the type of surface covering material (Thatcher et al., 2002), and the strength and pattern of activity (Ferro et al., 2004)

4. Objectives for T2.A
Task 2.A designed to provide data for better estimates of resuspension rates from human activity and to characterize flow and PM movement
Chamber study provides more control to determine impacts of factors such as particle loading, flooring type, ventilation conditions, RH, and person-to-person variability.

5. Hypotheses
Exposure to PM2.5 in a mixing ventilation is higher than that in a displacement ventilation.
Resuspension of particles is greater from old and fabric flooring material than from hard flooring.
Lower relative humidity correlates with higher resuspension rate.

6. Experiments Conducted (n = 54)
Mixing
Displacement
Unseeded
Seeded H N O N* O* 1 4 7 9 3 5
Notes: H = hard floor; N = new carpet; O = old carpet
* Experiments failed QC criteria due to the detachment of return air duct

7. Experimental methods Experimental Methods
Floorings seeded with Arizona Test Dust ( mm)
Participant performs prescribed activities in a chamber
Measure airborne particle concentration and size distribution using array of optical counters
Measure vibration frequency and amplitude on raised floor
Measure airflow velocity and temperature in space using an array of hot sphere probes

8. Chamber Instrumentation
Temp = 23oC
RH = 30-50%
ACH = 0.5 h-1
: Probes measuring airflow velocity at 1 m and 1.5 m high. : Color index for the distance particle samplers are above the elevated floor Black: 3 cm; grey: 1.0 m; white: 1.5 m.
Legend
p: pDR-1000AN
R: pDR-1200
G: Grimm

9. Prescribed Activities
30-minutes
background measurement …
Sitting motionless
Seated, tapping feet
Seated, tapping feet, upper body motions
walking

10. Particle Distribution in Carpet Fibers by SEM
Pile overall
middle
top
bottom

11. Particle Concentration: Unseeded New Carpet

12. Particle Concentration: Seeded New Carpet

13. Particle Concentration: Unseeded Old Carpet

14. Particle Concentration: Seeded Old

15. Particle Concentration: Seeded Hard Floor

16. Two-compartment Model
(1)
(2)
(3)

17. Time-dependence of Resuspension Rate

18. Time-Dependence of Resuspension Rate
(Jian et al., 2006)

19. Distribution of Resuspension Rate - Log Scale (n = 48)
Tukey’s Multicomparision (a = 0.05)  The mean resuspension rates among the size ranges of mm are not statistically different from each other, but are all different from that in the range of mm.

20. Comparison of Seeded Floorings: Mixing Ventilation
Other conditions: RH = 30%; Vibration Freq. = 1.0 Hz
No significant difference among the flooring types.
No significant size effect for resuspension from hard floor.

21. Comparison of Seeded Floorings: Displ. Ventilation
Other conditions: RH = 40%; Vibration Freq. = 0.5 Hz
Significant difference among the flooring types (2-way ANOVA gives p = )
Size effect found between 1-2 and 5-10 mm for new carpet; 5-10 and mm for old carpet.

22. Results for Old Seeded Carpet, Displ. Vent., Rep. = 3
Two-way ANOVA (a = 0.05) p-value = 0.97
No significant difference between r for 30% and 40% RH

23. Exposure to PM2.5 for Various Exp. Conditions

24. Measured Amplitude of Vibration during Walking
Nydist

25. Vibrational Frequency Comparison
Seeded old carpet; Disp. Ventilation; RH = 44%; 52 vs. 50 kg
Frequency is the Nyquist frequency found to be 0.52 ± 0.42 from 42 people’s walking
(at which the signal produces the strong peaks.)
Two-way ANOVA  p-value = 0.15, only 2 expt.s are compared, no conclusion drawn

26. Conclusions
Resuspension varied under different experimental conditions, varied from person-to-person
Size-resolved resuspension rates in size ranges of 0.4-1, , , and mm were found ranging from hr-1, with highest resuspension rates associated with mm particles.
Difference observed among carpet types, but not statistically significant.
No significant effect from the two types of ventilation, or RHs of 30% and 40%.

27. Future work Complete data analysis.
Collect real carpet fibers and compare dust loading with the test carpets (analyze 10 samples using SEM).
EPA 04: Test resuspension of real dust particles from real floorings