EPA/600/R-16/129 I October 2016
www.epa.gov/homeland-security-research
United States
Environmental Protection
Agency
&EPA
Developing Table of Forces for Human
Activity as It Relates to
Reaerosolization and Exposure to
Bacillus	anthracisSpores from
Outdoor Urban Surfaces
Office of Research and Development
Homeland Security Research Program

-------
This page left Intentionally Blank

-------
EPA/600/R-16/129
October 2016
Developing Table of Forces for Human
Activity as It Relates to Reaerosolization
and Exposure to Bacillus anthracis
Spores from Outdoor Urban Surfaces
Final Report
National Homeland Security Research Center
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711

-------
This page left Intentionally Blank

-------
Disclaimer
The U.S. Environmental Protection Agency (EPA), through its Office of Research and Development's
National Homeland Security Research Center, funded and managed this investigation through contract
EP-C-15-008 WA 0-067 with Jacobs Technology Inc. This report has been peer and administratively
reviewed and has been approved for publication as an EPA document. Note that approval does not
signify that the contents necessarily reflect the views of the Agency. Mention of trade names, products,
services does not convey official EPA approval, endorsement, or recommendation.
Questions concerning this document or its application should be addressed to:
Dr. Russell Wiener
Decontamination and Consequence Management Division
National Homeland Security Research Center
U.S. Environmental Protection Agency (MD-E343-06)
Office of Research and Development
109 T.W. Alexander Drive
Research Triangle Park, NC 27709
Phone: 919-541-1910
Fax: 919-541-0496
E-mail: wiener.russell@epa.gov

-------
Acknowledgments
The authors would like to acknowledge the support of the project team: Russel Weiner, PhD; Sang Don
Lee, PhD; M. Worth Calfee, PhD; and Sarah Taft, PhD of the USEPA National Homeland Security
Research Center. The authors would also like to acknowledge the work performed by Jacobs
Technology Inc., funded under EPA contract EP-C-15-008.

-------
Contents
Disclaimer	i
Acknowledgments	ii
Figures	iii
Acronyms and Abbreviations	iv
Executive Summary	v
1	Introduction	1
1.1 Particle Reaerosolization Forces	1
2	Literature Review	2
2.1	Human Locomotion (Walking/Running)	2
2.2	Driving	3
2.3	Lawn Mowing, Leaf Blowing, Sweeping	4
3	Quality Assurance	5
3.1	Source Selection	6
3.2	Data Quality Objectives	9
3.3	Quality Assurance/Quality Control Checks	9
3.4	Literature Assessment Form	10
4	Summary	11
5	Bibliography	13
Figures
Figure 1. Depiction of particle on surface being acted on by forces. (A) Only adhesion, (B)
adhesion and lifting force, and (C) adhesion, lifting and shear forces	1
Figure 2. Flow chart for information source evaluation	8
Tables
Table 1: Summary Table of Forces and Velocities
12

-------
Acronyms and Abbreviations
B. anthracis	Bacillus anthracis
DCMD	Decontamination and Consequence Management Division
DHS	United States Department of Homeland Security
EPA	United States Environmental Protection Agency
m/s	Meter(s) per Second
NHSRC	National Homeland Security Research Center
N	Newton
ORD	Office of Research and Development
QA/QC	Quality Assurance/Quality Control
QAPP	Quality Assurance Project Plan
jjm	Micrometer
iv

-------
Executive Summary
This report presents the results of an extensive literature review of human-surface interaction forces with
respect to Bacillus spore reaerosolization in the outdoor environment. The areas of focus were activities
such as sweeping, human locomotion (walking/running), driving, bicycling, lawn mowing, leaf blowing,
and playing sports. Mechanical interaction forces and flow fields associated with those activities were
investigated. Human locomotion and driving were the two most studied modes of reaerosolization, and
orders of magnitude for shear stresses and flow fields were determined although studies directly related
to such forces were sparse. Flow fields associated with rolling tires could not be found. The search found
only two studies of flow fields associated with rotating blades in lawn mower decks, any additional studies
were likely conducted by manufacturers and are proprietary. Nozzle velocities for leaf blowers were found
through manufacturer and retailer websites. No relevant information associated with bicycling could be
found although upper limits of trailing wind velocities can likely be estimated through vehicle studies.
Studies involving the interaction forces and flow fields in sweeping were not discovered although
interaction forces were estimated. Due to the relative lack of a fundamental understanding of how
mechanical interaction forces in between contacting surfaces, for example the foot-floor interaction while
walking, contribute to reaerosolization no relation can be drawn at this time between human interaction
forces and resuspended fraction of spores.
v

-------
1 Introduction
In the event of a release of biological material in an urban area that would require decontamination for the
purpose of public safety, the potential reaerosolization of said material after it has settled onto surfaces is
of great interest to the U.S. Environmental Protection Agency (EPA). Biological material such as Bacillus
anthracis (B, anthracis) pose an inhalation exposure risk when aerosolized. EPA has the responsibility for
protecting human health and the environment from secondary emission of materials that may have settled
on surfaces. EPA may be required to mitigate, provide consequence management, and decontaminate
the area of concern. To this end, the EPA's Homeland Security Research Program (HSRP) is conducting
research to investigate the reaerosolization of spores.
Understanding the mechanisms of B. anthracis reaerosolization is necessary based on the historic
release by terrorists in the U.S. and the lack of data concerning the ability of spores to re-suspend from
surfaces in quantities of public health concern. There are gaps in understanding the impact of human
activities as it relates to reaerosolization. The goal of this literature review is to evaluate human activity
and associated forces and their thresholds to initiate reaerosolization.
1.1 Particle Reaerosolization Forces
A thorough physical description of the mechanics of reaerosolization is beyond the scope of the review
however a brief description of the mechanics and forces involved is important to understanding the basis
of the literature search. Particles sitting on a surface experience an adhesion force based on the
presence or absence of water vapor, the micro roughness of the substrate, and the particular surface
energies of the particle and the substrate. To remove this particle from the surface this adhesion force
must be overcome. This can be accomplished in two ways shown in figure 1.1.
Lift
Lift
Shear
(A)

-------
that the second method is the most likely method of particle removal and reaerosolization since it requires
significantly less lifting force and, in nature, shear forces generated by wind flow fields and human
interaction tend to be much greater than adhesive forces. (Hu 2008, Vainshtein 1997, Wang 1990,
Ziskind 1995, and Ziskind 1997) Therefore to build any model of particle resuspension due to human
action, lifting forces and shear forces due to those interactions must be known. These forces can come
from flow fields generated by movement, electrostatics, and mechanical applied forces. In addition to
shear and lift, normal forces (forces directed perpendicular into the surface) must be known since normal
forces are directly related to contact area. (Johnson 1985, Persson 2006) This contact area will
determine the number of particles contacted and effected directly by mechanical shear stress.
2 Literature Review
During the past 60 years, numerous experiments have identified the potential for biological agents to
reaerosolize following an initial release. Because only limited quantitative information has been obtained,
it is difficult to predict the reaerosolization hazard that might occur during routine outdoor activities
following a biological attack (Sehmel, 1980; Layshock et al., 2012). This literature review contains the
most relevant information readily available on the mechanical interaction forces, electrostatic forces, and
induced flow fields due to human locomotion (walking/running), driving, lawn mowing, leaf blowing, and
sweeping/raking/mopping and their relation to reaerosolization. These activities were chosen because
they are fairly ubiquitous among different populations and denote the greatest risk for the general public.
2.1 Human Locomotion (Walking/Running)
One of the most thoroughly investigated reaerosolization mechanisms associated with human-induced
particle reaerosolization is locomotion (walking/running) (Qian et al., 2014; Khalifa and Elhadidi, 2007;
Paton, 2015; Hu, 2008; Goldasteh et al., 2014; Sehmel, 1980; Layshock et al., 2012). However, very
few publications have addressed the role of human-interaction forces with respect to particle
reaerosolization, and of those only one has been considered in multiple publications, i.e., the flow field
around the foot as it comes into contact with and leaves the surface. The flow field can easily be shown to
depend on gait. This is clearly variable from person-to-person and activity-to-activity, and an investigation
into averages of foot impact velocities by walking was described to be on the order of 1 meter/second
(m/s) (Gilchrist and Winter, 1996). Experiments on idealized human foot impacts, simulated by falling
disks, showed peak shear velocities of 45 m/s with an impact rate of the disk of 0.5 m/s (Khalifa and
Elhadidi, 2007). However, it was shown that other idealized impact simulations achieved lower peak
shear velocities of approximately 5 m/s. It was mentioned that this could be attributed to differences in
foot shape, impact angle, and specific impact parameters (Kubota et al., 2009). Running impact
velocities were also shown to be on the order of 1 m/s by simple kinematic calculations of objects falling a
short distance without air resistance. Other experiments and simulations of a more realistic walking
motion showed peak shear velocities around the foot impact and removal zone of 2 m/s, however, the
impact rates were much lower than those described above. Still these experiments showed significant
reaerosolization of particles (Eisner et al., 2010; Goldasteh et al., 2014). No fully developed fluid
dynamics simulation of flow fields around real-world walking was found in the literature during this
extensive literature review. The highest shear velocities seen could also be used here as a minimum
value that would be seen for other impact related activities such as bouncing a ball, etc.
2

-------
Other forces that must be considered in regards to locomotion are electrostatic forces associated with
electric field buildup between shoes and the ground, and physical disturbances due to mechanical (non-
hydrodynamic) shear associated with locomotion and other sliding contacts. Only one paper was found
that describes the electric field build up between foot and ground. It was shown, however, that this had a
significant effect on particle reaerosolization and it was discussed as a factor for future investigation by
multiple researchers (Hu, 2008; Gomes et al., 2007; Qian et al., 2014). This can be on the order of
3 kilovolts/centimeter for dry indoor environments. This generates an upward force on micrometer (jjm)
sized particles of 2 orders of magnitude greater than the force of gravity and, with variations in particle
adhesion force, could by itself lead to 1-|jm particle removal from surfaces. It should be noted that this is
highly dependent on the surface and environment and needs to be further investigated in relation to
outdoor environments before any general parameters can be discussed (Hu, 2008).
The role of vertical vibrational disturbance of particles has been investigated and hypothesized to have an
effect as an initiator of reaerosolization. The force of these vibrations have been shown to be on the order
of 5% of the force of gravity with frequencies of 4 to 20 hertz. These would serve to cause wobble in
particles but would be orders of magnitude lower than adhesive forces and would not directly cause
dislocation and reaerosolization (Gomes et al., 2007). These vibrations however cannot be used as an
estimation of direct mechanical disturbances cause by walking or any other sliding interaction, e.g.,
sweeping, mopping, or raking. Mechanical disturbances to particles inside contact areas are inevitable
given shear stresses generated at the microscopic contact level (Persson, 2000). However, to date no
consideration has been given to these mechanisms. This could be due to the complexity associated with
these microscale interactions. It is important to consider the relative size of the forces and shear stresses
to determine if they are significant. Shear forces in walking and running can be as high as 100 Newtons
(N), and, if compared to data concerning rubber contacting rough surfaces, shear stresses could be on
the order of 10 to 100 kilopascal (Addison and Lieberman, 2015; Boyer et al., 2014; Encarnacion-
Martinez et al., 2015; Chen and Lee, 2015; Tanino et al., 2004; Persson, 2000). This could be an order
of magnitude or two above that required for dislocation of particles by wind (Phares et al., 2000; Ziskind,
1995). However, these numbers are highly dependent on surface properties and can only be considered
as estimates.
2.2 Driving
Another widely-studied human activity capable of reaerosolizing particles is that of vehicle motion.
Quantitative research on this mechanism is widely lacking from a first principles standpoint although
emission models exist (Nicholson, 1988,1990; Sehmel, 1980; Tong et al., 2014; Kupiainen, 2007;
Layshock et al., 2012; Mollinger, 1993; Sehmel, 1973; Boulter, 2005). Nicholson's field experiments
showed that for fast-moving vehicles turbulent flow was likely the predominant mechanism for
reaerosolization of 9-|jm particles from dry, paved surfaces, however, tire shear did make a significant
impact over repeated runs. This is not necessarily the case for smaller particles and has not been
investigated. It also might not be the case for slow-moving vehicles, as the wake might not be fast enough
for removal of small particles (Tong et al., 2014; Phares et al., 2000; Ziskind, 1995). Computational fluid
dynamics simulations of model vehicles show that flow fields achieve peak velocities equal to that of the
moving vehicle (Tong et al., 2014). Therefore, the maximum shear velocity associated with the moving
vehicle itself can be said to be its velocity. This assumption can likely be regarded as an upper limit in
regards to motorcycles and bicycles as well. However, this does not take into account the flow field
associated with the rotation of the wheel close to the ground as the air moves away from the leading edge
3

-------
of contact and back into the trailing edge. For urban neighborhoods, where speed limits are lower, wheel
rotation and road-tire interaction could prove to be a significant cause of reaerosolization (Layshock et
al., 2012). No simulations of flow fields around the point of contact of a rolling tire and outdoor surfaces
could be identified, and no information could be obtained for reaerosolization of spore-sized particles at
low vehicle speeds. However, information could be found for vehicle shear forces and shear stresses for
rubber tire surface contact. These can be generalized for medium-sized vehicles on asphalt to be on the
order of 1000 to 5000 N and shear stresses of 10 to 1000 kilopascal depending on speed and surface
roughness (Persson, 2000; Persson, 2011; Bian et al., 2014; Dugoff and Brown, 1970; Pacejka,
2006; Nordeen and Cortese, 1964). This does not necessarily mean that the entire area underneath the
tires experiences this shear stress. In fact, the real area of contact underneath all four automobile tires at
any point in time is on the order of 1 square centimeter (Persson, 2000; Persson et al., 2004).
2.3 Lawn Mowing, Leaf Blowing, Sweeping
Studies of lawn-mower blade forces could not be found with the exception of two studies of flow fields
around rotating blades in a lawn-mower deck. Flow-field simulations of double-bladed lawn-mower decks
showed peak shear velocities of 10 to 100 m/s inside the deck area. However, no information for ejection
velocities for mower openings could be located (Chon and Amano, 2004, 2005). Nozzle velocities for
various gas and electric leaf blowers were located from manufacturer specifications on distributer
websites and average on the order of 50 m/s (www.lowes.com. last accessed 3/7/2016).
By far, the most significant information gap is in the range of forces generated by wiping, sweeping,
raking, and mopping. In fact, there are no standards or guidelines available for determining those forces
(Lewis et al., 2012). A study by Sogaard et al. (2001) on ergonomic stresses on hands and arms during
hand scrubbing or mopping with a long pole showed a maximum force generated during these activities
of 50 N. This is a vector sum of shear and vertical forces, and therefore more information is necessary to
break it down into the relevant components. A study by Lewis et al. (2012) used weights of 20 N for hand
wiping and 40 N for mopping simulations. If we assume that the coefficient of friction between the
materials is lower than one (a good assumption considering the coefficient of friction of sandpaper on
wood is on average 0.6 to 0.8), the maximum force necessary for constant velocity sliding would be no
higher than 20 N for hand wiping and 40 N for mopping or sweeping. However, these forces cannot be
directly related to shear stress without knowing significantly more about the surface interaction, i.e., the
real contact area. No flow fields associated with these activities could be found.
4

-------
3 Quality Assurance
The literature search was conducted through a methodical iterative process by which results of a previous
search and review of linking citations informed the next search etc. The search was conducted primarily
through internet searches and through the EPA's library resources. Internet search engines included but
not necessarily were not limited to Web of Science, Google Scholar, and Science Direct. The sources of
data were primarily nationally or internationally recognized scientific publications that went through a peer
review process. The standard of these being primary research and review articles in peer reviewed journals.
Examples of peer reviewed journals relevant to this search are, Journal of Occupational and Environmental
Hygiene, Clinical Biomechanics, Journal of Aerosol Science, and Tribology Letters. Other peer reviewed
sources include dissertations/thesis, government/industry reports, and scientific manuals. Examples of
industry reports can be found in publications of the Society of Automotive Engineers and examples of
government reports can be found through the EPA. Online resources such as the National Institute of
Standards and Technology and the American Society for Testing Materials were also consulted as well as
white papers.
The general process of a literature review begins by defining the question at hand, in this case there were
two: "What research has been conducted in the resuspension of particles (specifically bacterial spores) from
human interaction with outdoor environments?" and "What are the magnitude and direction of interaction
forces and induced flow fields associated with the most common human activities outdoors?" The next step
was to search for previously published review articles relating forces and particle
resuspension/aerosolization, then consult all citing articles and citations from those review articles. Once
review articles were addressed keyword searches for specific human activities were conducted both
attempting to relate forces with resuspension and to determine flow fields and forces independent of research
into resuspension. If articles were found citations and citing articles were investigated for relevant information.
The search parameters were then refined and another search was conducted until no additional variation of
search parameters could be determined.
5

-------
3.1 Source Selection
An assessment of each information source (article, report, website, etc.) was conducted as depicted in
Figure 2 using the following guidelines and questions:
•	Applicability: The extent to which the information is relevant for the intended use (forces induced
by human activity that could result in B. anthracis reaerosolization).
-	How useful or applicable is the scientific theory applied in the study to the intended use of the
analysis?
-	How relevant are the study's purpose, design, outcome measures, and results to the
intended use of the analysis?
•	Soundness: The extent to which the scientific and technical procedures, measures, methods, or
models employed to generate the information is reasonable for and consistent with the intended
application.
-	Is the purpose of the study reasonable and consistent with its design?
-	Is the study based on sound scientific principles?
-	To what extent are the procedures, measures, methods, or models employed to develop the
information reasonable and consistent with sound scientific theory or accepted approaches?
-	How do the study's design and results compare with existing scientific theory and practice?
-	Are the assumptions, governing equations, and mathematical descriptions employed
scientifically and technically justified?
-	How internally consistent are the study's conclusions with the data and results presented?
•	Clarity and Completeness: The degree of clarity and completeness with which the data,
assumptions, methods, quality assurance, and analyses employed to generate the information
are documented.
-	To what extent does the documentation clearly and completely describe the underlying
scientific theory and the analytic methods used?
-	To what extent have key assumptions, parameter values, measures, and limitations been
described and characterized?
-	To what extent are the results clearly and completely documented as a basis for comparing
them to results from other similar tests?
-	If novel or alternative theories or approaches are used, how clearly are they explained and
the differences with accepted theories or approaches highlighted?
-	Is the complete data set accessible, including metadata, data-dictionaries, and embedded
definitions (e.g., codes for missing values, data quality flags)?
-	To what extent are the descriptions of the study design clear, complete, and sufficient to
enable the study or survey to be reproduced?
-	Have the sponsoring organization(s) for the study/information product and the author(s)
affiliation(s) been documented?
-	To what extent are the procedures for quality assurance and quality control of the data
documented and accessible?
6

-------
•	Uncertainty and Variability: The extent to which variability and uncertainty (quantitative and
qualitative) related to results, procedures, measures, methods, or models are evaluated and
characterized.
-	To what extent have appropriate statistical techniques been employed to evaluate variability
and uncertainty?
-	To what extent have the sensitive parameters of models been identified and characterized?
-	To what extent do the uncertainty and variability impact the conclusions that can be inferred
from the data and the utility of the study?
-	What are the potential sources and effects of error and bias in the study design?
-	Did the study identify potential uncertainties such as those due to inherent variability in
environmental and exposure-related parameters or possible measurement errors?
•	Evaluation and Review: The extent of independent verification, validation, and peer review of the
information or of the procedures, measures, methods, or models.
-	To what extent has there been independent verification or validation of the study method and
results?
-	What were the conclusions of these independent efforts, and are they consistent?
-	To what extent has independent peer review been conducted of the study method and
results, and how were the conclusions of this review taken into account?
-	Has the procedure, method or model been used in similar, peer reviewed studies?
-	Are the results consistent with other relevant studies?
-	In the case of model-based information, to what extent has independent evaluation and
testing of the model code been performed and documented?
All information sources that passed the "cite or cite with explanation" evaluation shown in Figure 1 were
subjected to further assessment. The following factors were also considered and documented in the
Literature Assessment Factor Rating form (section 3.4):
•	Focus: The extent to which the work addresses the area of inquiry under consideration.
-	Is the work germane to the issue?
-	Does it contribute to the understanding of the issue?
•	Verity: The extent to which data are consistent with accepted knowledge in the field or, if not, the
new or varying data are explained within the work.
-	Do the data fit within the context of the literature?
-	Is the information intellectually honest and authentic?
7

-------
•	Integrity: The degree to which data are structurally sound and present a cohesive story.
-	Is the design or research rationale iogical and appropriate?
-	Is the information clear, concise, and well presented?
•	Rigor: The extent to which the work is important, meaningful, and non-trivial relative to the field.
-	Does the work exhibit significant depth of intellect rather than superficial or simplistic
reasoning?
The Literature Assessment Factor Rating form was completed for all cited sources to indicate the degree
to which the acceptance criteria have been met. These forms as well as references available as
electronic copies are stored in an EPA sharepoint directory.
Is it applicable?
Yes
No ^


not cite.
Is it peer-reviewed?
Yes
No
I
Address topics not in peer-
reviewed literature?
Provide useful background
information?
Support conclusions found in
peer-reviewed literature?
Yes to one
or more.
No to all.
1
H
Do not cite.
T
Is it sound?
Is it clear''
Is it complete''
Does it document uncertainty
and variability?
Yes to all.
No to one or
more.
I
I
Cite.	Cite with
explanation.
Figure 2. Flow chart for information source evaluation.
8

-------
3.2 Data Quality Objectives
Our objective was to cite literature that conforms in full to all five criteria in section 3.1. However, from
previous search efforts, we learned that the preponderance of literature on some topics does not fully
conform to all aspects of the outlined criteria, specifically, in the case of non-peer reviewed sources. Non-
peer reviewed references addressing topics not found in the peer reviewed literature, providing useful
background information, or corroborating conclusions in the peer reviewed literature, were cited with clear
explanation. A clear explanation was also offered for references that did not fully conform to one of the
other criteria. However, applicability was deemed the most important criterion for inclusion as data that
has no applicability did not need to be tested further for quality.
3.3 Quality Assurance/Quality Control Checks
Twenty percent of all citations were quality checked against the source for correctness and completeness
with zero tolerance for errors. A minimum of twenty percent of data used to generate human activity
forces was checked against the source citation.
9

-------
3.4 Literature Assessment Form
Rate each factor from 0 (not applicable) to 5 (strongly applicable) and total for the overall rating.
Title of Article:
Name of Reviewer:	Rating (1-5)
Focus
The work not only addresses the area of inquiry under consideration but also
contributes to its understanding; it is germane to the issue at hand.

Verity
The data are consistent with accepted knowledge in the field or, if not, the new or
varying data are explained within the work. The data fit within the context of the
literature and are intellectually honest and authentic.

Integrity
The data are structurally sound and present a cohesive story. The design or
research rationale is logical and appropriate.

Rigor
The work is important, meaningful, and non-trivial relative to the field. It exhibits
sufficient depth of intellect rather than superficial or simplistic reasoning.

Utility
The work is useful and professionally relevant. It makes a contribution to the field
in terms of the practitioners= understanding or decision-making on the topic.

Clarity
The work is written clearly, not dependent on jargon. The writing style is
appropriate to the nature of the study.

Soundness
The extent to which the scientific and technical procedures, measures, methods,
or models employed to generate the information is well documented and
reasonable for, and consistent with, the intended application.

Uncertainty and
Variability
The extent to which the variability and uncertainty (quantitative and qualitative) in
the information or in the procedures, measures, methods, or models are evaluated
and characterized.

Evaluation and
Review
The extent of independent verification, validation, and peer review of the
information or of the procedures, measures, methods, or models.

Total _
Overall Rating:
	35—45 High quality article
	25—34 Moderately high quality article
	15—24 Lower quality article but with some useful information (please explain below)
	<15 Unacceptable/Do not use
Reviewer Comments:
10

-------
4 Summary
This project report describes the results of a literature search to obtain interaction forces, as well as flow
field velocities, for human activities in outdoor urban environments. The largest amount of research that
was found centered on walking and driving, however, research into the specific forces of those activities
was sparse and no experiments linking forces directly with spore resuspension could be found. Very little
information was found for lawn-mowing-induced wind velocities, and no direct information was found for
sweeping activities, though the maximum of the shear forces could be estimated. There is a relative lack
of a fundamental understanding of how mechanical interaction forces in between contacting surfaces, for
example the foot-floor interaction while walking, contribute to reaerosolization. Therefore no relation can
be drawn at this time between human interaction forces and resuspended fraction of spores. Moving
forward experiments should be conducted to directly link these human interaction forces specifically with
spore resuspension. The question should be asked what forces are the most impactful for modeling. For
footfall experiments flow fields should be isolated from lateral sliding forces and normal forces. Sweeping
experiments should be conducted and modeled at multiple sweeping velocities both in contact with the
surface and just out of contact to isolate the sweeping action itself with trailing turbulent wind. A 3 axis
force gauge under surfaces would give normal contact and sliding force information. Particle image
velocimetry could be used to obtain information related to flow fields generated by sweeping.
Resuspension of spores from driving must also be analyzed further to determine the main generating
mechanisms and simulation of flow fields at the lead and trailing edge of a rolling tire close to the ground
must be obtained.
11

-------
Table 1: Summary Table of Forces and Velocities
Action
Normal Force
Shear
Force/Stress
Shear Flow
Velocity
Walking/Running
500 - 2000 N
-100 N
-10-100 kPa
1 - 45m/s
Driving
Average
Midsize Vehicle
~3800 N per tire
-1000-5000 N
-10- 1000 kPa
Trailing Wind -
Vehicle Speed
No Tire Flow
Information
Bicycling
Weight of Rider
and Bike
No Information
Trailing Wind -
Speed of Rider
No Tire Flow
Information
Sweeping
Estimated
20 - 40 N
Estimated
20 - 40 N
No Information
Mowing
N/A
No Information
Inside Deck
10 - 100 m/s
No Nozzle Velocity
Information
Leaf Blowing
N/A
N/A
~50m/s
12

-------
5 Bibliography
Addison, B. J. and Lieberman D. E. 2015. Tradeoffs between impact loading rate, vertical impulse and
effective mass for walkers and heel strike runners wearing footwear of varying stiffness. Journal of
Biomechanics. 48(7): 1318-1324.
Bian, M., Chen, L., Luo, Y., and Li, K. 2014. A Dynamic Model for Tire/Road Friction Estimation Under
Combined Longitudinal/Lateral Slip Situation. SAE Technical Paper. 2014-01-0123.
Boulter, P. G. 2005. A Review of Emission Factors and Models for Road Vehicle Non-exhaust Particulate
Matter, project report PPR065, Transport Research Laboratory.
Boyer, E. R., Rooney, B. D., and Derrick, T. R. 2014. Rearfoot and Midfoot Impacts in Habitually Shod
Runners. Medicine and Science in Sports and Exercise. 46(7): 1384-1391.
Chen, W. M. and Lee, P. V. S. 2015. Explicit finite element modelling of heel pad mechanics in running:
inclusion of body dynamics and application of physiological impact loads. Computer Methods in
Biomechanics and Biomedical Engineering. 18(14): 1582-1595.
Chon, W. and Amano, R. S. 2004. Experimental and Computational Studies on Flow Behavior Around
Counter Rotating Blades in a Double-Spindle Deck. KSME International Journal. 18(8): 1401-1417.
Chon, W. and Amano, R. S. 2005. Investigation of Flow Behavior around Corotating Blades in a Double-
Spindle Lawn Mower Deck. International Journal of Rotating Machinery. 1:77-89.
Dugoff, H. and Brown, B.J. 1970. Measurement of Tire Shear Forces, SAE Technical Paper. 700092.
Eisner, A., Rosati, J., and Weiner, R. 2010. Experimental and Theoretical Investigation of Particle-Laden
Airflow Under a Prosthetic Mechanical Foot in Motion. Building and Environment. 45(4):878-886.
Encarnacion-Martinez, A., Perez-Soriano, P., and Llana-Belloch, S. 2015. Differences in ground reaction
forces and shock impacts between Nordic walking and walking. Research Quarterly for Exercise and
Sport. 86(1): 94-99.
Gilchrist, L. and Winter, D. 1996. A Two-Part, Viscoelastic Foot Model for Use in Gait Simulations. Journal
of Biomechanics. 29(6):795-798.
Goldasteh, I., Tian, Y., Ahmadi, G., and Ferro, A. 2014 Human Induced Flow Field and Resultant Particle
Resuspension and Transport During Gait Cycle. Building and Environment. 77:101-109.
Gomes, C., Freihaut, J., and Bahnfleth, W. 2007. Resuspension of Allergen-Containing Particles Under
Mechanical and Aerodynamic Disturbances from Human Walking. Atmospheric Environment. 41:5257-
5270.
http://www.cdc.gov/anthrax/basics/types/inhalation.html
Hu, B. 2008. An Investigation of Walking Induced Electrostatic Field Effects on Indoor Particle
Resuspension. Ph.D. Dissertation, The Pennsylvania State University, College Park, PA.
Johnson, KL. 1985. Contact Mechanics, Cambridge University Press, Cambridge, UK
Khalifa, H. E. and Elhadidi, B. 2007. Particle Levitation Due to a Uniformly Descending Flat Object.
Aerosol Science and Technology. 41 (1): 33-42.
13

-------
Kubota, Y., Hall, J. W., and Higuchi, H. 2009. An Experimental Investigation of the Flowfield and Dust
Resuspension Due to Idealized Human Walking. Journal of Fluids Engineering. 131:081104.
Kupiainen, K. 2007. Road Dust from Pavement Wear and Traction Sanding. Monographs of the Boreal
Environment Research. No. 26.
Layshock, J. A., Pearson, B., Crockett, K., Brown, M. J., Cuyk S. V., Daniel, B., and Omberg, K. M. 2012.
Reaerosolization of Bacillus SPP. in Outdoor Environments: A Review of the Experimental Literature.
Biosecurity and Bioterrorism: Biodefense Strategy, Practice, and Science. 10(3): 299-303.
Lewis, R. D., Ong, K. H., Emo, B., Kennedy, J., Brown, C. A., Condoor, S. and Thummalakunta L. 2012.
Do New Wipe Materials Outperform Traditional Lead Dust Cleaning Methods?, Journal of Occupational
and Environmental Hygiene. 9:8 524-533.
Mollinger, A. M., Nieuwstadt, F. T. M., and Scarlett, B. 1993. Model Experiments of the Resuspension
Caused by Road Traffic. Aerosol Science and Technology. 19(3):330-338.
Nicholson, K. W. 1988, A Review of Particle Resuspension. Atmospheric Environment. 22(12):2639-
2651.
Nicholson, K. W. and Branson, J. R. 1990. Factors Affecting Resuspension by Road Traffic. Science of
the Total Environment. 93:349-358.
Nordeen, D. and Cortese, A. 1964. Force and Moment Characteristics of Rolling Tires, SAE Technical
Paper. 640028.
Pacejka, H. B. 2012. Tire and Vehicle Dynamics, 3rd Edition, Butterworth-Heinemann, UK.
Paton, S., Thompson, K. A., Parks, S. R., and Bennett, A. M. 2015. Reaerosolization of Spores from
Flooring Surfaces to Assess the Risk of Dissemination and Transmission of Infections. Applied and
Environmental Microbiology. 81 (15):4914-4919.
Persson, B. N. J. 2000. Sliding Friction: Physical Principles and Applications, 2nd Ed.; Springer New York.
Persson, B. N. J., Albohr, O., Tartaglino, U., Volokitin, A. L., and Tosatti, E. 2005. On the Nature of
Surface Roughness with Application to contact Mechanics, Sealing, Rubber Friction, and Adhesion.
Journal of Physics: Condensed Matter. 17(1):R1.
Persson, B. N. J. 2006. Contact Mechanics of Randomly Rough Surfaces. Surface Science Reports.
61(4): 201-207
Persson, B. N. J. 2011. Rubber Friction and Tire Dynamics. Journal of Physics: Condensed Matter. 23(1):
015003.
Phares, D. J., Smedley, G. T., and Flagan, R. C. 2000. Effect of particle Size and Material Properties on
Aerodynamic Resuspension from Surfaces. Journal of Aerosol Science. 31(11):1335-1353.
Qian, J., Peccia, J. and Ferro A. R. 2014. Review: Walking-Induced Particle Resuspension in Indoor
Environments. Atmospheric Environment. 89:464-481.
Sehmel, G. A. 1973. Particle Resuspension from an Asphalt Road Caused by Car and Truck Traffic.
Atmospheric Environment. 7(3):291-309.
Sehmel, G. A. 1980. Particle Resuspension: A Review. Environment International. 4: 107-127.
14

-------
Sogaard, K, Laursen B, Jensen BR and Sjogaard G. 2001. Dynamic Loads on the Upper Extremities
During Two Different Floor Cleaning Methods. Clinical Biomechanics. 16(10): 866-879.
Tanino, Y., Tanabe, S., Daikuya, S., and Ito, A. 2004. Mechanical stress in knee joint during running at
various speeds and step lengths. Japanese Journal of Physical Fitness and Sports Medicine. 53(1): 167-
181.
Tong, X., Luke, E. A., and Smith, R. 2014. Numerical Validation of a Near-Field Fugitive Dust Model for
Vehicles Moving on Unpaved Surfaces. Proceedings of the Institution of Mechanical Engineers, Part D:
Journal of Automobile Engineering. 228(7): 747-757.
Vainshtein, P., Ziskind, G., Fichman, M., and Gutfinger, C. Kinetic Model of Particle Resuspension by
Drag Force. Physical Review Letters. 78(3): 551-554
Wang, H. 1990. Effects of Inceptive Motion on Particle Detachment from Surfaces. Aerosol Science and
Technology. 13(3): 386-393.
Ziskind, G., Fichman, M., and Gutfinger, C. 1995. Resuspension of Particulates from Surfaces to
Turbulent Flows - Review and Analysis. Journal of Aerosol Science. 26(4): 613-644.
Ziskind, G., Fichman, M., and Gutfinger, C. 1997. Adhesion Moment Model for Estimating Particle
Detachment from a Surface. Journal of Aerosol Science. 28(4): 623-634
15

-------
vvEPA
United States
Environmental Protection
Agency
PRESORTED STANDARD
POSTAGE & FEES PAID
EPA
PERMIT NO. G-35
Office of Research and Development (8101R)
Washington, DC 20460
Official Business
Penalty for Private Use
$300

-------