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Supplemental Materials
Supplemental Information About Study Methods
(a) Study Preparation and Setting
Sealed Plexiglas™ windows were present in the study chamber for external viewing of activities
within the chamber. The chamber was accessed by a door that was located in one corner of the
chamber. On the interior side of the door, an airlock with dimensions of approximately 4 feet
long x 3 feet wide x 8 feet high was located. The airlock was utilized for doffing personal
protective equipment (PPE) and decontaminating study equipment when exiting the chamber.
(b) Description of Chrysotile Asbestos Used
The grade 7T chrysotile was obtained from Thetford Mines (Quebec, Canada). To break
up bundles and generate fibers of respirable size, the chrysotile was dried at 191C for 24 hours
and then processed using a small scale, table top mill (Homeland Housewares; Los Angeles,
CA), a low volume device that separates fibers from the bundles. A small quantity of chrysotile
(a few milligrams) was placed into the mill for one minute. This procedure was repeated three
times with a one-minute rest between each milling event to help prevent thermal degradation.
Bulk analysis of the dried and milled chrysotile used in the study showed that approximately
1.4% of the bulk fibers met the criteria for the fiber size range of interest that is measured
according to OSHA’s specification of PCM fiber dimensions (≥5µm in length, ≥0.25µm in
width, aspect ratio of 3:1 or greater). A majority of the remaining chrysotile in the bulk analysis
was shorter and/or thinner than the PCM OSHA fiber criteria.
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(c) Clothing Selection and Airborne Chrysotile Generation
A total of 36 sets of consistent styles of shirts and pants typically worn in industrial
settings were used in the study. The uniforms were obtained new (Banner Uniform Center; San
Francisco, CA). Half the shirts and pants were composed of 100% cotton, while the other half
was composed of a blend of 65% polyester and 35% cotton (hereafter referred to as cotton/polyblend). Because some workers have described arriving home with dust in their hair as well as on
their clothing, three out of the six mannequins in each loading event were also dressed with
human hair wigs. Human hair was used to avoid potential differences with the electrostatic
properties of plastic or synthetic hair. Wigs of short length were used to represent male workers,
who were more common than women in historical reports of occupational asbestos exposure.
The predried and milled chrysotile was aerosolized in the chamber using a dust
generation system that was controlled remotely. This system consisted of a compressed airassisted media delivery system (Speed Blaster; Unitec Corporation, Washington, USA)
positioned at a height of 3.5 feet with an enclosed hopper for the loose chrysotile and a tubing
delivery system with a diameter of approximately one inch that would not limit the flow of
particulates into the air or alter the nature of the chrysotile through friction forces (i.e., alteration
of the fiber dimensions). The compressed air was discharged into the hopper in short bursts, and
the frequency, duration, and intensity of the air bursts were monitored and adjusted remotely in
order to maintain the desired target airborne concentration of fibers in the chamber. The dust
generation system was run continuously during each loading event and provided short, regular
bursts of chrysotile fibers from the hopper into the chamber. The frequency and duration of the
bursts was adjusted during each run as needed to maintain the desired target loading
concentration in the chamber. The appropriate number of pulses was assessed using a real time
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fiber monitor (Real Time Fiber Monitor Model 7400AD; MSP Corporation, Shoreview, MN,
USA). Four box fans, one on each side of the room at a distance of two feet from each wall, were
placed on blocks facing upward toward the ceiling to help maximize airborne suspension of the
chrysotile fibers for the duration of each loading event.
(d) Safety/Quality Control, Sampling and Isolation/Decontamination Procedures
Air sampling was performed throughout the study for quality control, safety and
environmental purposes in accordance with local, state, and federal laws and regulations.
Background air samples were collected both inside and outside of the chamber prior to clothes
loading and handling and shake-out events. To establish baseline concentrations inside the
chamber, 30-minute air samples were collected prior to each handling/shake-out event. Personal
breathing zone air samples were also collected for study personnel who were working in the
immediate vicinity of the study chamber but never entered the chamber.
Following each loading event, the HEPA-filtered AFD was operated on the high setting
(24 ACH) for a 30-minute period while the chamber remained unoccupied in order to remove
residual airborne fibers from the chamber. This waiting time equated to 12 full air changes in the
chamber before personnel entry. Between loading and shake-out events, the chamber was also
decontaminated to remove settled chrysotile fibers generated during the previous loading events.
The decontamination procedure included wet-wiping of all surfaces in the chamber (including
walls, floor and ceiling) and HEPA vacuuming. Prior to entering the chamber for either
decontamination or the handling and shake-out events, study participants donned personal
protective equipment (PPE), including disposable Tyvek™ coveralls with integrated booties and
hoods, nitrile gloves, and full-face powered air purifying respirators (PAPRs) with P-100 filters.
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All participants who wore respirators during the study were placed into a respiratory protection
program prior to study initiation. This program included medical clearance, training, respirator
selection, and fit testing, as appropriate.
As noted above, a real-time fiber monitor (Model 7400AD; MSP Corporation,
Shoreview, MN, USA) was also used to continuously measure the fiber concentration inside the
study chamber during all study events. The real-time airborne fiber concentration data were used
to support both the study design and participant safety. The instrument selectively measured
fibers with a defined aspect ratio using a method involving electric-field-induced fiber alignment
and oscillation, and reported fiber concentrations consistent with the analytical specifications of
the NIOSH 7400 (PCM) method. Real-time concentration readings were collected at one-minute
intervals during all loading and handling/shake-out events. The instrument was used on a
continuous basis during the study for comparison with other measurement means used to
characterize the estimated fiber concentrations in the chamber during study events and between
events prior to entry.
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Supplemental Figure S1. Depiction and Chamber Design for Clothes Loading Events
(Simulated Work Environment)
Corner
Area
Sample
24”
Corner
Area
Sample
Area
Sample
6’
Area
Sample
6’
6’
24”
6’
Area
Sample
Corner
Area
Sample
airflow
HEPA Air
Filtration
Device (AFD)
6’
Dust
Generator/Center
Area Sample
24”
Area
Sample
6’
Airlock
24”
Corner
Area
Sample
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Supplemental Figure S2. Airborne Fiber Measurements During Clothes Loading Events by
Sample Location in the Test Chamber
PCM using NIOSH 7400 (A&B) and TEM using NIOSH 7402 (C&D) fiber concentrations
measured during loading events Low #1 and Low #2 (A&C) and during loading events Medium
#1, Medium #2, High #1, and High #2 (B&D). Data are shown for samples taken on mannequin
lapels (white), near mannequins (light grey), in corners of the chamber (dark grey), and in the
center of the chamber (black). Only one sample was taken per loading event in the center of the
chamber. The PCM center samples were invalid for loading events Medium #1, Medium #2, and
High #2 because of overloading, as were the TEM center samples for events Medium #1 and
High #2.
A
B
PCM Loading Concentrations
0.035
7
0.030
6
Concentration (f/cc)
Concentration (f/cc)
PCM Loading Concentrations
0.025
0.020
0.015
0.010
5
4
3
2
1
0.005
0
0.000
Low
#1
Medium
#1
Low
#2
Medium
#2
High
#1
High
#2
Loading Concentration Level
Loading Concentration Level
C
D
TEM Loading Concentrations
TEM Loading Concentrations
0.025
16
Concentration (f/cc)
Concentration (f/cc)
14
0.020
0.015
0.010
12
10
0.005
8
6
4
2
0
0.000
Low
#1
Medium
#1
Low
#2
Medium
#2
High
#1
Loading Concentration Level
Loading Concentration Level
6
High
#2
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Supplemental Figure S3. Box Plot Distributions of the PCM (NIOSH 7400) and TEM
(NIOSH 7402) Airborne Concentrations for Each Loading Event
Distribution of the PCM and TEM data for each loading event showing the median, quartiles, 5th
percentile, and 95th percentile values (box plots), as well as the arithmetic mean (black circles).
Asterisk (*) indicates loading events for which the mean PCM concentration was significantly
greater than the mean TEM concentration (Gehan test [non-parametric], p<0.05).
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Supplemental Table SI. Loading Event Sample Numbers, Concentrations, and Standard
Deviations (PCM, TEM, and PCME)
Durations, numbers of samples; numbers of samples with detectable fibers; arithmetic mean fiber
concentrations (PCM, TEM, and calculated PCME); and standard deviations associated with
each of the six loading events (Low, Medium, and High).
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Supplemental Table SII. First and Second 15-Minute Clothes Handling and Shake-Out
Event Sample Numbers, Concentrations, and Standard
Deviations (PCM, TEM, and PCME)
Personal samples collected for the clothes handler during the 15 minutes of active clothes
handling and the 15 minutes immediately following active clothes handling (no activity).
Includes number of samples; number of samples with detectable fibers; arithmetic mean of the
PCM, TEM, and calculated PCME concentrations (f/cc); and standard deviations.
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Supplemental Table SIII. Thirty-Minute Clothes Handling and Shake-Out Event Sample
Numbers, Concentrations, and Standard Deviations (PCM,
TEM, and PCME)
Personal samples collected on the clothes handler for the 30-minute clothes handling period and
the concurrent 30-minute area samples (bystander samples). The 30-minute period included 15
minutes of active clothes handling immediately followed by 15 minutes of no activity. Includes
number of samples; number of samples with detectable fibers; arithmetic mean of the PCM,
TEM, and calculated PCME concentrations (f/cc); and standard deviations.
PCM
TEM
Number of Number
Mean
Standard Number of Number
Samples of Detects
(f/cc)
Deviation Samples of Detects
30 Minute Personal Sampling (15 min Active Clothes Handling + 15 min Inactivity)
Loading Event
Low #1
2
2
0.379
0.003
2
0
Low #2
2
2
0.223
0.021
2
0
Medium #1
2
2
0.166
0.048
2
1
Medium #2
4
4
0.265
0.089
4
0
High #1
2
2
0.193
0.022
2
2
High #2
2
2
0.159
0.045
2
2
30 Minute Bystander Sampling (15 min Active Clothes Handling + 15 min Inactivity)
Loading Event
Low #1
4
4
0.069
0.016
4
1
Low #2
4
4
0.095
0.024
4
0
Medium #1
4
3
0.052
0.054
4
3
Medium #2
4
4
0.051
0.028
4
0
High #1
4
4
0.060
0.029
4
4
High #2
4
4
0.058
0.024
4
3
10
Mean
(f/cc)
Calculated PCME
Standard Number of Mean
Standard
Deviation Samples
(f/cc) Deviation
0.007
0.007
0.021
0.006
0.050
0.063
0.003
0.003
0.018
0.002
0.021
0.067
2
2
2
4
2
2
0.000
0.000
0.017
0.000
0.051
0.073
0.000
0.000
0.024
0.000
0.026
0.077
0.003
0.002
0.008
0.003
0.006
0.011
0.002
0.001
0.007
0.000
0.003
0.010
4
4
4
4
4
4
0.001
0.000
0.006
0.000
0.006
0.013
0.002
0.000
0.010
0.000
0.002
0.012