- Supporting information –
A Comparative Study of Walking-induced Dust Resuspension using a
Consistent Test Mechanism
Yilin Tian1*, Kyung Sul2, Jing Qian2, Sumona Mondal3 and Andrea R. Ferro2
1
Institute for a Sustainable Environment, Clarkson University, 8 Clarkson Ave, Potsdam, NY,
13699
2
Department of Civil and Environmental Engineering, Clarkson University, 8 Clarkson Ave,
Potsdam, NY, 13699
3
Department of Mathematics, Clarkson University, 8 Clarkson Ave, Potsdam, NY, 13699
Table of Content
Literature review: residential surface dust loading ..................................................................... 2
Photograph of the resuspension mechanism ............................................................................... 5
Carpet type descriptions .............................................................................................................. 5
Volume and number size distributions of house dust ................................................................. 6
Photograph of the seeding system............................................................................................... 6
Summary of average resuspension fractions............................................................................... 7
Summary of ANOVA results ...................................................................................................... 7
Results of Wilcoxon rank sum test ............................................................................................. 8
Emission rate plot ..................................................................................................................... 12
Literature review: residential surface dust loading
Table S1 shows a summary of surface dust loadings measured in U.S residence and offices.
According to table S1, measured residential surface dust loadings varied over several orders of
magnitude: from the minimum value of 0.05 g/m2 reported by Adgate et al. (1995) to the
maximum value of 465 g/m2 provided by Robert et al. (2004). When reporting surface dust
loadings, different size fractions were used in previous studies due to various research purposes,
sampling methods and dust process methods. In the current work, the collected house dust was
sieved to 44 micron to remove debris, hair and fibers which could tangle or block the dust inlet
of the seeding system. There is a need to determine the fractions of less than 44 micron particles
for dust sieved to 150 micron and 500 micron, respectively. Table S2 listed the average size
fractions of house or office dust reported in previous studies. According to table S2, we assumed
that less than 44 micron particles account for 30% and 20% of the bulk dust sieved to 150 micron
and 500 micron, respectively. To estimate the proper surface dust loading for less than 44 micron
particles, these fractions were applied to the median/geometric mean/average surface dust
loadings reported in Table S1. The estimated median/geometric mean/average surface dust
loadings ranged from 0.08 to 4.8 g/m2 (average: 1.4 g/m2; median: 0.8 g/m2). The specific
Grimm 1.108 aerosol spectrometer used in the study had a reduced performance when the
airborne particle concentrations were close to its detection limit of 1 particle/L. Hence, instead of
the median value of 0.8 g/m2, the average value of 1.4 g/m2 (rounded to 2 g/m2) was selected as
the low level of surface dust loading to reduce the error generated by the instrument. The high
level of surface dust loading of 8 g/m2 was selected based on the amount of house dust obtained
from the 18 vacuum bags collected.
2
Table.S1 Surface dust loadings in U.S. homes
Reference
Adgate et al. 1995
Method
Size fraction
216 houses sampled
< 500 µm
0.05-7.0 (GM*: 0.42)
Floor wipe samples
Carpet vacuum samples
Wang et al. 1995
Surface dust loading (g/m2)
0.3-99
73 houses sampled
(GM: 7.8)
< 500 µm
1-136 (Median: 16, SD: 16)
< 150 µm
0.32-14.4 (median: 1.30)
< 150 µm
0.7-21.1 (median:2.9)
< 150 µm
Average: 2.6
Carpet vacuum samples
Robert et al. 1999
9 mid-class houses and 2
small offices
HVS3: carpet
Robert et al. 2004
10 old carpets
HVS3: surface dust
Takaro et al. 2004
214 low-income houses
sampled
(before environmental
intervention)
HVS3: child’s room or
primary play area
*: geometric mean
Table.S2 Particle size fractions of house dust
Reference
Que Hee et al. 1985
Method
Size fraction
Sampling tube + sampling pump
392-833 µm: 11 %
149-392 µm: 13.3 %
44- 149 µm: 58 %
<44 µm: 18 %
(fraction for <53 µm: 24% (<150 µm)
20% (<500 µm)
Lewis et al. 1999
25 middle-class homes sampled
500 µm-2mm: 13.3%
Vacuum samples (~80% carpeted)
150-500 µm: 25.8%
53-150 µm: 33.1%
53-106 µm: 22.7%
<53 µm: 27.8%
(fraction for <53 µm: 33% (<150 µm)
25% (<500 µm)
3
Molhave et al. 2000
7 Danish office buildings
Vacuum samples
>125 µm: 40%
50-125 µm: 41%
<50 µm: 18.8%
(fraction for <53 µm: 31% (<150 µm)
Reference:
Adgate, J., Weisel, C., Wang, Y., Rhoads, G.G. and Lioy, P.J. (1995) Lead in house dust:
Relationships between exposure metrics. Environ. Res., 70, 134-147.
Lewis, R.G., Fortune, C.R., Willis, R.D., Camann, D.E. and Antley, J.T. (1999) Distribution of
pesticides and polycyclic aromatic hydrocarbons in house dust as a function of particle size,
Environ. Health Persp., 107, 721-726.
Molhave, L., Schneider, T., Kjaergaard, S.K., Larsen, L., Norn, S. and Jorgensen, O. (2000)
House dust in seven Danish offices, Atmos. Environ., 34, 4767-4779.
Que Hee, S.S., Peace, B., Clark, C.S., Boyle, J.R., Bornschein, R.L. and Hammond, P.B. (1985)
Evolution of efficient methods to sample lead sources, such as house dust and hand dust, in
the homes of children, Environ. Res., 38, 77-95.
Roberts, J.W., Clifford, W.S., Glass, G. and Hummer, P.C. (1999) Reducing dust, lead, dust
mites, bacteria, and fungi in carpets by vacuuming, Arch. Environ. Con. Tox., 36, 477-484.
Roberts, J.W., Glass, G. and Mickelson, L. (2004) A pilot study of the measurement and control
of deep dust, surface dust, and lead in 10 old carpets using the 3-spot test while vacuuming,
Arch. Environ. Con. Tox., 48, 16-23.
Seifert, B., Becker, K., Helm, D., Krause, C., Schulz, C. and Seiwert, M. (2000) The German
Environmental Survey 1990/1992 (GerES II): reference concentrations of selected
environmental pollutants in blood, urine, hair, house dust, drinking water and indoor air, J.
Expo. Anal. Env. Epid., 10, 552-565.
Takaro, T.K., Krieger, J.W. and Song, L. (2004) Effect of environmental interventions to reduce
exposure to asthma triggers in homes of low-income children in Seattle, J. Expo. Anal. Env.
Epid., 14, S133-S143.
Wang, E., Rhoads, G.G., Wainman,T. and Lioy, P.J. (1995) Effects of environmental and carpet
ariables on vacuum sampler collection efficiency. Appl. Occup. Environ. Hyg., 10, 111-119.
4
Photograph of the resuspension mechanism
Figure S1. Resuspension mechanism inside plaxiglass chamber. Toe and heel plates controlled
by electric actuators and pressure controlled by compressed air flow.
Carpet type descriptions
Table.S3 Carpet type descriptions
Characteristic
Carpet LD
Construction
Cut pile
Face weight (kg/m2)
2.12
Pile height (m)
0.02
Density (kg/m3)
101
Face fiber
BCF nylon 6.6
Backing
SoftBac®
BCF: bulked continuous filament
5
Carpet HD
Cut pile
1.65
0.01
138
BCF nylon 6.6
SoftBac®
Carpet Loop
Level loop
1.36
0.009
151
BCF nylon 6.6
SoftBac®
Volume and number size distributions of house dust
Figure S2. Volume and number size distributions of house dust measured by Malven
Mastersizer 2000.
Photograph of the seeding system
Figure S3. Photo of the seeding system
6
Summary of average resuspension fractions
Table.S4 Average resuspension fraction (n=3 for each treatment)
Resuspension fraction ra
Flooring
type
RH
(%)
SDL1
(g m-2)
Carpet HD
40
2
(2.54±0.87)×10-6
(1.30±0.14)×10-6
(5.50±0.72)×10-6
(4.59±0.88)×10-5
(1.56±0.38)×10-4
70
2
-6
(4.59±3.02)×10
-6
(2.64±1.57)×10
-5
(1.57±1.06)×10
-4
(1.12±0.40)×10
(3.72±0.33)×10-4
40
8
(1.12±0.88)×10-6
(7.08±2.92)×10-7
(4.93±3.59)×10-6
(3.85±1.97)×10-5
(1.16±0.35)×10-4
70
8
(1.18±0.28)×10-6
(6.73±1.46)×10-7
(4.29±1.73)×10-6
(6.18±2.80)×10-5
(2.60±1.17)×10-4
40
2
-6
(4.99±3.56)×10
-6
(3.22±2.76)×10
-5
(1.62±0.91)×10
-4
(1.47±0.82)×10
(4.64±3.01)×10-4
70
2
(5.30±3.17)×10-6
(3.39±1.75)×10-6
(2.27±0.77)×10-5
(2.43±1.17)×10-4
(6.63±3.45)×10-4
40
8
-6
(2.41±0.34)×10
-6
(1.53±0.33)×10
-5
(1.53±0.98)×10
-4
(1.27±0.62)×10
(3.73±1.16)×10-4
70
8
(1.62±0.50)×10-6
(1.10±0.10)×10-6
(9.45±4.02)×10-6
(1.20±0.40)×10-4
(3.68±1.33)×10-4
40
2
(3.35±0.66)×10-6
(2.28±0.78)×10-6
(9.41±2.57)×10-6
(5.25±2.56)×10-5
(1.60±0.62)×10-4
70
2
-6
(3.18±1.28)×10
-6
(2.03±1.06)×10
-6
(6.46±1.17)×10
-5
(3.78±1.14)×10
(1.12±0.45)×10-4
40
8
(1.11±0.07)×10-6
(7.42±2.00)×10-7
(4.69±0.69)×10-6
(3.07±0.83)×10-5
(8.93±3.25)×10-5
70
8
-6
(1.04±0.68)×10
-7
(8.02±3.51)×10
-6
(3.69±1.34)×10
-5
(2.40±0.98)×10
(6.94±1.67)×10-5
40
2
(4.44±0.58)×10-6
(1.91±0.50)×10-6
(6.95±2.77)×10-6
(3.23±0.68)×10-5
(6.26±1.51)×10-5
70
2
(2.61±0.86)×10-6
(1.63±0.56)×10-6
(4.12±2.84)×10-6
(2.24±1.05)×10-5
(3.03±0.44)×10-5
40
8
-6
(2.74±1.17)×10
-6
(2.24±0.69)×10
-5
(1.56±0.31)×10
-5
(8.29±1.55)×10
(1.74±0.41)×10-4
70
8
(1.02±0.44)×10-6
(7.77±2.34)×10-7
(4.68±2.59)×10-6
(2.48±1.44)×10-5
(5.93±3.15)×10-5
40
2
-6
(4.16±1.04)×10
-6
(1.50±0.43)×10
-6
(5.98±0.42)×10
-5
(2.28±0.70)×10
(4.27±0.99)×10-5
70
2
(3.76±1.68)×10-6
(2.41±0.37)×10-6
(7.37±0.91)×10-6
(2.67±1.20)×10-5
(6.13±4.20)×10-5
40
8
(2.20±0.67)×10-6
(1.39±0.20)×10-6
(1.11±0.39)×10-5
(6.29±1.41)×10-5
(1.27±0.33)×10-4
8
-7
-7
-6
-5
(3.25±3.93)×10-5
Carpet LD
Carpet Loop
Hardwood
Vinyl
70
0.4-0.5 µm
0.5-1.0 µm
(8.26±3.53)×10
1.0-3.0 µm
(4.82±2.71)×10
3.0-5.0 µm
(2.55±2.52)×10
5.0-10 µm
(1.03±0.80)×10
Summary of ANOVA results
Table.S5 Summary of ANOVA results.
ANOVA
p-value ≤ 0.1
Factor
0.4-0.5
Particle size (µm)
0.5-1.0 1.0-3.0 3.0-5.0
0.027
0.018
0.000
0.017
0.715
0.044
0.022
0.158
0.000
0.131
0.271
0.009
Flooring type
RH
Surface dust loading (SDL)
Flooring type & RH
Flooring type & SDL
RH & SDL
7
0.000
0.010
0.017
0.009
0.041
0.002
0.000
0.048
0.150
0.000
0.080
0.002
5.0-10.0
0.000
0.116
0.635
0.001
0.030
0.040
Results of Wilcoxon rank sum test
Variable: flooring type
Table.S6 Two-sided Mann-Whitney rank sum test results for comparison of resuspension
fractions among different flooring types (n=6, α=0.1) *
LD Carpet vs. HD Carpet
LD Carpet vs. Loop
Carpet
LD Carpet vs. Hardwood
LD Carpet vs. Vinyl
HD Carpet vs. Loop
Carpet
HD Carpet vs. Hardwood
HD Carpet vs. Vinyl
Loop Carpet vs.
Hardwood
Loop Carpet vs. Vinyl
Hardwood vs. vinyl
0.4-0.5
µm
0.0783
0.5-1.0
µm
0.0400
1.0-3.0
µm
0.0051
3.0-5.0
µm
0.0017
5.0-10.0
µm
0.0051
0.1572
0.7508
0.7508
0.0990
0.5834
0.3408
0.0007
0.0120
0.0050
0.0001
0.0002
0.0001
0.0001
0.0000
0.0000
0.4885
0.2855
0.3408
0.7075
0.1260
0.4025
0.977
0.7075
0.6650
0.0226
0.0531
0.0141
0.0051
0.0014
0.0002
0.9770
0.4357
1.0000
0.5067
0.9770
0.6236
0.5834
0.4357
0.7075
0.7950
0.3408
0.2855
0.1260
0.0531
0.5444
*: H0: 1 = 2; H1: 1 ≠2, where  is the population median.
Table.S7 One-sided Mann-Whitney rank sum test results for comparison of resuspension
fractions among different flooring types (n=6, α=0.1)*. Only the floorings associated with
significantly different ra values were tested.
LD Carpet > HD Carpet
LD Carpet > Loop
Carpet
LD Carpet > Hardwood
LD Carpet > Vinyl
HD Carpet > Loop
Carpet
HD Carpet > Hardwood
HD Carpet > Vinyl
Loop Carpet > Hardwood
Loop Carpet > Vinyl
0.4-0.5
µm
0.0391
0.5-1.0
µm
0.02
1.0-3.0
µm
0.0026
3.0-5.0
µm
0.0008
5.0-10.0
µm
0.0026
0.0786
NA
NA
0.0499
NA
NA
0.0004
0.006
0.0026
0.0000
0.0001
0.0000
0.0000
0.0000
0.0000
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
0.0113
0.0265
0.0071
NA
NA
0.0026
0.0007
0.0001
0.0265
0.0630
*: H0: 1 = 2; H1: 1 >2, where  is the population median.
8
Variable: relative humidity
Table.S8 Two-sided Mann-Whitney rank sum test results for comparison of resuspension
fraction between 40% and 70% relative humidity levels (n=6, α=0.1) *.
Flooring type 0.4-0.5 µm 0.5-1.0 µm 1.0-3.0 µm 3.0-5.0 µm 5.0-10.0 µm
Hardwood
0.0306
0.0306
0.0202
0.0453
0.0306
0.3785
1.0000
0.1282
0.2298
Vinyl
0.0927
0.6889
0.3785
1.0000
0.4712
0.5752
LD Carpet
0.5752
0.4712
0.2298
HD Carpet
0.0656
0.0082
0.6889
0.6889
0.2980
0.2980
0.2980
Loop Carpet
*: H0: 1 = 2 ; H1: 1 ≠2, where  is the population median.
Table.S9 One-sided Mann-Whitney rank sum test results for comparison of resuspension
fractions between 40% and 70% relative humidity levels (n=6, α=0.1) *. Only the floorings
associated with significantly different ra values were tested.
Flooring type 0.4-0.5 µm 0.5-1.0 µm 1.0-3.0 µm 3.0-5.0 µm 5.0-10.0 µm
Hardwood
0.0153
0.0153
0.0101
0.0227
0.0153
0.1892
0.5000
0.1149
Vinyl
0.0641
0.0463
*: H0: 1 = 2; H1: 1 >2, where  is the population median.
Table.S10 One-sided Mann-Whitney rank sum test results for comparison of resuspension
fractions between 40% and 70% relative humidity levels (n=6, α=0.1) *. Only the floorings
associated with significantly different ra values were tested.
Flooring type 0.4-0.5 µm 0.5-1.0 µm 1.0-3.0 µm 3.0-5.0 µm 5.0-10.0 µm
0.2876
0.2356
0.1149
HD Carpet
0.0328
0.0041
*: H0: 1 = 2; H1: 1 <2, where  is the population median.
Variable: surface dust loading
The main effect of surface dust loading on dust resuspension was evaluated for carpets. Because
RH & SDL interaction was significant for hard floorings, the effect of SDL on hard floorings
was evaluated on each RH level separately.
9
Carpets
Table.S11 Two-sided Student t-test results for comparison of resuspension fraction between 2
g/m2 and 8 g/m2 surface dust loadings on carpets(n=6, α=0.1) *.
Flooring type 0.4-0.5 µm 0.5-1.0 µm 1.0-3.0 µm 3.0-5.0 µm 5.0-10.0 µm
0.1282
0.298
0.298
LD Carpet
0.0082
0.0202
0.1735
0.3785
HD Carpet
0.0082
0.0051
0.0927
Loop Carpet
0.0051
0.0131
0.0082
0.0927
0.0453
*: H0: 1 = 2; H1: 1 ≠2, where  is the population median.
Table.S12 One-sided Mann-Whitney rank sum test results for comparison of resuspension
fraction between 2 g/m2 and 8 g/m2 surface dust loadings on carpets(n=6, α=0.1) *.
Flooring type 0.4-0.5 µm 0.5-1.0 µm 1.0-3.0 µm 3.0-5.0 µm 5.0-10.0 µm
0.149
0.149
LD Carpet
0.0041
0.0101
0.0641
0.1892
HD Carpet
0.0041
0.0025
0.0463
0.0867
Loop Carpet
0.0025
0.0065
0.0041
0.0463
0.0227
*: H0: 1 = 2; H1: 1 >2, where  is the population median.
Hard floorings
Under 40% RH level
Table.S13 Two-sided Mann-Whitney rank sum test results for comparison of resuspension
fraction between 2 g/m2 and 8 g/m2 surface dust loadings for hard floorings under 40% RH (n=3,
α=0.1) *.
Flooring type 0.4-0.5 µm 0.5-1.0 µm 1.0-3.0 µm 3.0-5.0 µm 5.0-10.0 µm
0.1904
0.6625
Hardwood
0.0809
0.0809
0.0809
1.0000
Vinyl
0.0809
0.0809
0.0809
0.0809
*: H0: 1 = 2; H1: 1 ≠2, where  is the population median
Table.S14 One-sided Mann-Whitney rank sum test results for comparison of resuspension
fraction between 2 g/m2 and 8 g/m2 surface dust loadings for hard floorings under 40% RH (n=3,
α=0.1) *.
Flooring type 0.4-0.5 µm 0.5-1.0 µm 1.0-3.0 µm 3.0-5.0 µm 5.0-10.0 µm
NA
NA
NA
NA
Hardwood
0.0952
0.5000
NA
NA
NA
Vinyl
0.0404
*: H0: 1 = 2; H1: 1 >2, where  is the population median
10
Table.S15 One-sided Mann-Whitney rank sum test results for comparison of resuspension
fraction between 2 g/m2 and 8 g/m2 surface dust loadings for hard floorings under 70% RH (n=3,
α=0.1) *.
Flooring type 0.4-0.5 µm 0.5-1.0 µm 1.0-3.0 µm 3.0-5.0 µm 5.0-10.0 µm
NA
0.3313
Hardwood
0.0404
0.0404
0.0404
NA
NA
Vinyl
0.0404
0.0404
0.0404
*: H0: 1 = 2; H1: 1 <2, where  is the population median
Under 70% RH level
Table.S16 Two-sided Mann-Whitney rank sum test results for comparison of resuspension
fraction between 2 g/m2 and 8 g/m2 surface dust loadings for hard floorings under 70% RH (n=3,
α=0.1) *.
Flooring type 0.4-0.5 µm 0.5-1.0 µm 1.0-3.0 µm 3.0-5.0 µm 5.0-10.0 µm
1.0000
1.0000
0.6625
Hardwood
0.0809
0.0809
0.1904
0.3827
Vinyl
0.0809
0.0809
0.0809
*: H0: 1 = 2; H1: 1 ≠2, where  is the population median
Table.S17 One-sided Mann-Whitney rank sum test results for comparison of resuspension
fraction between 2 g/m2 and 8 g/m2 surface dust loadings for hard floorings under 70% RH (n=3,
α=0.1) *.
Flooring type 0.4-0.5 µm 0.5-1.0 µm 1.0-3.0 µm 3.0-5.0 µm 5.0-10.0 µm
0.5000
NA
NA
Hardwood
0.0404
0.0404
0.1904
Vinyl
0.0404
0.0404
0.0404
0.0952
*: H0: 1 = 2; H1: 1 >2, where  is the population median
Table.S18 One-sided Mann-Whitney rank sum test results for comparison of resuspension
fraction between 2 g/m2 and 8 g/m2 surface dust loadings for hard floorings under 70% RH (n=3,
α=0.1) *.
Flooring type 0.4-0.5 µm 0.5-1.0 µm 1.0-3.0 µm 3.0-5.0 µm 5.0-10.0 µm
NA
NA
NA
0.5000
0.3313
Hardwood
NA
NA
NA
NA
NA
Vinyl
*: H0: 1 = 2; H1: 1 <2, where  is the population median
11
Emission rate plot
Figure S4. Size-resolved emission for different types of floorings with two levels of initial
surface dust loading. The symbols represent the median values for all tested conditions (n=60,
replicates=6). The upper and lower ends of the error bars represent the 75th and 25th percentiles,
respectively.
12