EPA/600/R-06/044F | September 2008 | www.epa.gov/ncea
United States
Environmental Protection
Agency
An Exploratory Study:
Assessment of Modeled Dioxin
Exposure in Ceramic Art Studios
National Center for Environmental Assessment
Office of Research and Development, Washington, DC 20460
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EPA/600/R-06/044F
September 2008
An Exploratory Study: Assessment of Modeled Dioxin
Exposure in Ceramic Art Studios
National Center for Environmental Assessment
Office of Research and Development
U.S. Environmental Protection Agency
Washington, DC 20460
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DISCLAIMER
This document has been reviewed in accordance with U.S. Environmental Protection
Agency policy and approved for publication. Mention of trade names or commercial products
does not constitute endorsement or recommendation for use.
ABSTRACT
The purpose of this report is to describe an exploratory investigation of potential dioxin
exposures to artists/hobbyists who use ball clay to make pottery and related products. Dermal,
inhalation and ingestion exposures to clay were measured at the ceramics art department of Ohio
State University in Columbus, OH. The measurements were made in two separate studies: one
in April 2003 and one in July 2004. This assessment combines the results of these two studies.
Estimates of exposure were made based on measured levels of clay in the studio air, deposited on
media representing food and on the skin of artists. Dioxin levels in the clay were based on levels
reported in the literature for commercial ball clays commonly used by ceramic artists.
Hypothetical dioxin dose estimates were calculated for each subject assuming that all
used a 20% ball clay blend with 162 pg TEQ/g. The single-day total doses across the 10 subjects
ranged from 0.32 to 7.1 pg TEQ/d, with an average of 1.44 pg TEQ/d (SD = 2.0). The dermal
pathway was the major contributor to total dose, exceeding 67% for all subjects. A Monte Carlo
simulation was conducted to explore how doses could vary in a broad population of artists. This
simulation suggested a mean total dose of 6.4 pg TEQ/d (SD = 8.4), median of 3.5 pg TEQ/d,
and 90th percentile of 14.8 pg TEQ/d.
Preferred Citation:
U.S. Environmental Protection Agency (EPA). (2008) An exploratory study: Assessment of modeled dioxin
exposure in ceramic art studios. National Center for Environmental Assessment, Washington, DC;
EPA/600/R-06/044F. Available from the National Technical Information Service, Springfield, VA, and online at
http://www.epa.gov/ncea.
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CONTENTS
LIST OF TABLES v
LIST OF FIGURES vi
LIST OF ABBREVIATIONS AND ACRONYMS vii
PREFACE ix
AUTHORS, CONTRIBUTORS, AND REVIEWERS x
ACKNOWLEDGMENTS xi
1. INTRODUCTION AND BACKGROUND 1
2. APPROACH OVERVIEW 5
2.1. GENERAL STRATEGY 5
2.2. CHARACTERIZATION PROCEDURES 6
2.2.1. Dermal Contact 6
2.2.2. Inhalation 6
2.2.3. Ingestion 7
3. SAMPLING METHODS 8
3.1. SAMPLE COLLECTION 8
3.1.1. Personal Air Sampling 8
3.1.2. Area Air Sampling 9
3.1.3. Skin Sampling 10
3.1.3.1. April 2003 10
3.1.3.2. July 2004 11
3.1.4. Surface Wipe Sampling 11
3.1.5. Surrogate Food and Beverage 12
3.2. SAMPLE PREPARATION AND ANALYSIS 12
3.2.1. Filtration and Drying 12
3.2.2. Gravimetric Analysis 13
3.2.3. Quality Control Samples 13
4. DIOXIN CONTENT OF CLAY AND STUDIO RESIDUES 15
5. DOSE ESTIMATION PROCEDURES 21
5.1. DERMAL CONTACT 21
5.1.1. Estimating Particle Loading on Skin 21
5.1.2. Estimating Monolayer Load 21
5.1.3. Estimating Fraction Absorbed 23
5.1.4. Calculating Dermal Dose 25
5.2. INHALATION 26
5.3. INGESTION 27
5.4. TOTAL DOSE 27
6. QUESTIONNAIRE RESULTS 28
7. COMPARING EXPOSURES ACROSS SUBJECTS 30
iii
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7.1. DERMAL CONTACT 31
7.1.1. Clay Loads on Surfaces 36
7.1.2. Dermatologist Report 37
7.2. INHALATION 37
7.2.1. Particle Levels in Air 37
7.2.2. Inhalation Dose 41
7.2.3. Classroom Exposure 42
7.3. INGESTION 42
7.4. TOTAL DOSE 42
8. MONTE CARLO SIMULATION OF THE EXPOSURE DATA 47
9. UNCERTAINTY 57
9.1 GENERAL UNCERTAINTY ISSUES 57
9.2. DERMAL EXPOSURE UNCERTAINTIES 57
9.2.1. Absorption Fraction 57
9.2.2. Monolayer 60
9.2.3. Exposure Under Clothing 60
9.3. INHALATION UNCERTAINTIES 61
9.4. INGESTION UNCERTAINTIES 63
10. CONCLUSIONS 65
REFERENCES 67
APPENDIX A: SUBJECT QUESTIONNAIRE RESULTS A-l
APPENDIX B: EVALUATION OF CLAY DUST MODELING B-l
APPENDIX C: SEM AND EDS DATA BY SUBJECT C-l
APPENDIX D: ALTERNATIVE METHOD FOR ESTIMATING DERMAL
ABSORPTION D-l
APPENDIX E: SKIN RINSING DATA E-l
APPENDIX F: PICTURES OF ARTISANS PRIOR TO SKIN RINSE
PROCEDURE F-l
APPENDIX G: REAL-TIME PARTICLE CONCENTRATION DATA G-l
APPENDIX H: RESPICON™, CASCADE IMP ACTOR, PDR-1000, CLIMET®
DATA FOR EACH INDIVIDUAL SUBJECT H-l
APPENDIX I: MONTE CARLO CALCULATION OUTLINE 1-1
APPENDIX J: MONTE CARLO SIMULATION RESULT GRAPHICS J-l
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LIST OF TABLES
Table 1. Raw ball clay dioxin concentrations 16
Table 2. Processed ball clay dioxin concentrations (pg/g) 17
Table 3. Percentage ball clay in the clay mixtures used during this study 18
Table 4. Particle size distribution of Tennessee ball clay 22
Table 5. Percent absorbed over time 23
Table 6. Questionnaire questions on duration and frequency of subject' s clay work 28
Table 7. Questionnaire questions about clay work 29
Table 8. Artisan activities of each subject 32
Table 9. Hypothetical estimates of dermal dose 33
Table 10. Percent contribution to dermal dose by body part 35
Table 11. Comparing clay loads on surfaces to clay loads on hands 36
Table 12. Particle concentrations in air and mass median aerodynamic diameter
(MMAD) based on cascade impactor 38
Table 13. Hypothetical estimates of inhalation dose 41
Table 14. Clay deposition and hypothetical estimates of ingestion dose 43
Table 15. Hypothetical estimates of total dioxin dose (pg TEQ/d) 44
Table 16. Percent contribution to total dioxin dose 45
Table 17. Dose estimates by activity 46
Table 18. Monte Carlo simulation input parameters and sampling distributions 48
Table 19. Clothing scenarios based on questionnaire responses 50
Table 20. Descriptive statistics of dioxin doses from ball clay use, based on a Monte Carlo
simulation 51
Table 21. Physical properties of dioxin congeners and concentration in processed clay 59
Table 22. Exposure under clothing 62
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LIST OF FIGURES
Figure 1. Conceptual diagram.
Figure 2. Scanning electron microscopy (SEM) and energy dispersive spectroscopy
(EDS) data 20
Figure 3. Scatter plot of adjusted absorption data versus time with trend line 25
Figure 4. Real-time particle concentration for Subject 3 using the CI-500 particle
counter 39
Figure 5. Sculpture Session 1 with dog present 40
Figure 6. Sculpture Session 2 with dog present 40
Figure 7. Frequency distribution of total dose (pg TEQ/d) based on Monte Carlo
simulation 51
Figure 8. Cumulative probability distribution of total dose (pg TEQ/d) based on Monte
Carlo simulation 52
Figure 9. Sensitivity analysis based on percent contribution to variance for total dose 53
Figure 10. Sensitivity analysis based on percent contribution to variance for dermal dose 54
Figure 11. Sensitivity analysis based on percent contribution to variance for ingestion
dose 55
Figure 12. Sensitivity analysis based on percent contribution to variance for inhalation
dose 56
VI
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LIST OF ABBREVIATIONS AND ACRONYMS
ACGIH American Conference of Governmental Industrial Hygienists
°C degrees Centigrade
CDD chlorinated dibenzo-p-dioxin
CDD/F chlorinated dibenzo-p-dioxin and chlorinated dibenzofurans
CDF chlorinated dibenzofuran
cm centimeter
DI deionized
EDS energy dispersive spectroscopy
ET extrathoracic
g gram
OFF glass fiber filters
HpCDD heptachlorodibenzo-p-dioxin
Hz hertz
HxCDD hexachlorodibenzo-p-dioxin
ICRP International Commission on Radiological Protection
1KB Institutional Review Board
kg kilogram
Kow octanol-water partition coefficient
L liter
LRB laboratory record book
m meter
mg milligram
mL milliliter
mm millimeter
MMAD mass median aerodynamic diameter
MPPD Multiple Path Particle Dosimetry
MSS model sum of squares
NA not available
NIST National Institute of Standards and Technology
vn
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LIST OF ABBREVIATIONS AND ACRONYMS (continued)
NM not measured
OCDD octachlorodibenzo-p-dioxin
OSHA Occupational Safety and Health Administration
OSU Ohio State University
PCB polychlorobiphenyls
PCDD polychlorinated dibenzo-p-dioxin
PeCDD pentachlorodibenzo-p-dioxin
pg pictogram
ppt parts per thousand
PU pulmonary
r2 regression coefficient squared
RIVM National Institute of Public Health and the Environment
RSS residual sum of squares
SD standard deviation
SEM scanning electron microscopy
TB tracheobronchial
TCDD tetrachlorodibenzo-p-dioxin
TEF toxic equivalency factor
TEQ toxic equivalent
TSS total corrected sum of squares
TWA time-weighted average
UMDES University of Michigan Dioxin Exposure Study
U.S. EPA United States Environmental Protection Agency
WHO World Health Organization
jig microgram
|im micrometer
Vlll
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PREFACE
Dioxins were discovered in ball clay in 1996 as a result of an investigation to
determine the sources of elevated dioxin levels in two chicken samples from a national survey of
poultry. The investigation indicated that the contamination source was ball clay added to
chicken meal as an anti-caking agent. The purpose of this study is to evaluate another potential
exposure scenario associated with ball clay, namely its use in ceramic art studios. This
exploratory investigation makes preliminary exposure estimates that can be used to evaluate
whether more detailed follow-up analyses are needed. Hypothetical dioxin exposure estimates
were calculated using an assumption of dioxin levels in the ball clay based on measurements
from other studies. The study was conducted during 2003 and 2004 by the National Center for
Environmental Assessment with contract support provided by Battelle in Columbus, Ohio.
IX
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AUTHORS, CONTRIBUTORS, AND REVIEWERS
PRINCIPAL AUTHOR
John Schaum, National Center for Environmental Assessment, U.S. Environmental Protection
Agency, Washington, DC (U.S. EPA Project Manager)
AUTHORS
Ryan James, Battelle (Battelle Project Manager)
James Brown, National Center for Environmental Assessment, U.S. Environmental Protection
Agency, Research Triangle Park, NC
Dwain Winters, Office of Pollution Prevention and Toxic Substances, U.S. Environmental
Protection Agency, Washington, DC
CONTRIBUTORS
Ian MacGregor and Christine Mattingly of Battelle served as the technicians for the project.
INTERNAL REVIEWERS
Mark F. Boeniger, National Institute for Occupational Safety and Health, Cincinnati, OH
David Crawford, Office of Solid Waste and Emergency Response, U.S. Environmental
Protection Agency, Washington, DC
Mike Dellarco, Office of Research and Development, U.S. Environmental Protection Agency,
Washington, DC
Kim Hoang, Region 9, U.S. Environmental Protection Agency, San Francisco, CA
Chong Kim, Office of Research and Development, U.S. Environmental Protection Agency,
Research Triangle Park, NC
Sid Soderholm, National Institute for Occupational Safety and Health, Washington, DC
Dan Stralka, Region 9, U.S. Environmental Protection Agency, San Francisco, CA
EXTERNAL REVIEWERS
Peter deFur, Environmental Stewardship Concepts, Richmond, VA
Alesia Ferguson, University of Arkansas Medical Sciences, Little Rock, AR
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AUTHORS, CONTRIBUTORS, AND REVIEWERS (continued)
Bruce Hope, Oregon's Department of Environmental Quality, Portland, OR
Clint Skinner, Skinner Associates, Creston, CA
Woodhall Stopford, Duke University, Durham, NC
ACKNOWLEDGMENTS
The authors thank the Ohio State University (OSU) Ceramics Area and the OSU Division
of Dermatology for their cooperation during this study. In addition, the authors thank Joe
Ferrario at the U.S. Environmental Protection Agency/Environmental Chemistry Laboratory
(Stennis Space Center, Mississippi) for his assistance in evaluating dioxin levels in ball clay.
XI
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1. INTRODUCTION AND BACKGROUND
Ball clay is a natural clay mined commercially in the United States, primarily in
Kentucky, Tennessee, and Mississippi. A total of 1.21 million metric tons was mined in the
United States in 2005. Its plasticity makes ball clay an important commercial resource for a
variety of commercial uses. In 2005, it was used as follows: floor and wall tile—40%, sanitary
ware (sinks, toilets, etc.)—25%, exports—17%, ceramics—11%, fillers, extenders and
binders—4%, pottery—1.5%, and miscellaneous purposes—1.9% (USGS, 2007).
Dioxins were discovered in ball clay in 1996 as a result of an investigation to determine
the sources of elevated dioxin levels in two chicken samples from a national survey of poultry
(Ferrario et al., 1997). The investigation indicated that soybean meal added to chicken feed was
the source of the dioxin contamination. Further investigation showed that the dioxin
contamination occurred when ball clay was mixed with the soybean meal as an anti-caking agent
(Ferrario et al., 2000b; U.S. FDA, 2000). In 1997, the U.S. Food and Drug Administration
(FDA) asked producers or users of clay products in animal feeds to cease using ball clay in all
animal feeds and feed ingredients (U.S. FDA, 1997).
During the same time period that the present study was conducted, a completely
independent study called the University of Michigan Dioxin Exposure Study (UMDES) was
being conducted (Franzblau et al., 2008). UMDES measured chlorinated dibenzo-^-dioxins
(CDDs), chlorinated dibenzofurans (CDFs), and polychlorinated biphenyls (PCBs) in serum of
946 subjects who were a representative sample of the general population in five Michigan
counties. The individual with the highest blood level (211 ppt TEQ) among all 946 subjects had
practiced ceramics art in her home for over 30 years. A follow-up analysis was performed to
explore the source of this subject's exposure. Based on the similarity of the congener profile of
the subject's blood and the clay she used, Franzblau et al. concluded that exposure from the
ceramics work was the most likely reason for the elevated blood levels. The clay used by the
subject was a liquid formulation with unknown geologic origin. Sample analysis showed that it
contained 223 ppt TEQ with a profile that matched ball clay. Franzblau et al. concluded that
ceramic clay may be a significant nonfood and nonindustrial source of human exposure to
dioxins and recommended further research to more precisely characterize the routes of exposure.
The purpose of this study is to explore the possible dioxin exposures of artists using ball
clay in ceramic art studios. The study was conducted at a single facility with 10 artists and
therefore cannot be considered to be representative of all possible types of studios and practices.
Ceramic art is conducted in a wide variety of studios ranging from small residential operations to
large commercial facilities. Cleanliness, ventilation, and safety practices also vary widely within
these types of studios. This study was conducted at the Ohio State University (OSU) Ceramics
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Art Department. The OSU studio is a modern facility with excellent ventilation and
maintenance. During the peer review of this study, an industrial hygienist commented that the
OSU studio was an unusually clean and newly renovated facility (Eastern Research Group,
2008). Accordingly, the exposures measured in this study are most representative of similar
university studios. Many different kinds of activities can occur in these studios including mixing
clay, sculpting, operating a wheel, tending kilns, etc. Although many of these practices occurred
at the OSU facility, this study is not representative of all possible ceramic art activities.
This exploratory investigation makes preliminary exposure estimates that can be used to
evaluate whether more detailed follow-up analyses are needed. The limited resources available
for this study required a strategy to base the analysis on existing data to the fullest extent
possible.
Dioxin exposure is primarily a function of the dioxin concentration in the clay and an
individual's level of exposure to the clay. Although studies in the literature provided
information about dioxin levels in clay, no information could be found on clay exposure levels in
ceramic art studios. Therefore, this study was designed to measure total clay exposures in a
ceramic art studio. No dioxin measurements were made in this study, rather the dioxin levels in
ball clay were assumed based on measurements from other studies. Three exposure pathways
were evaluated: inhalation, dermal contact, and incidental ingestion. The evaluations involved
measuring levels of clay particulates in air, clay residues on skin, and clay deposition on media
representing food and beverages. These data provided a basis for estimating potential dioxin
exposures and resulting doses, conducting an initial analysis of which exposure pathways
contribute most to total dose, and evaluating how individual behaviors affect exposure/dose.
Ultimately, the data helped develop distributions for input parameters for conducting a Monte
Carlo analysis to estimate how dioxin exposure/dose may vary across a wide population of
artists. Figure 1 provides a conceptual diagram of the key components of this study.
An alternative way to evaluate dioxin exposures is by blood testing. While this provides
a direct measure of dioxin exposure, it represents exposures from all sources, not just work in an
art studio. Also, a blood study would not have provided any insights about how dioxin
exposures may occur in an art studio. Normal background exposures vary widely and factors
such as diet and age are known to have large impacts on dioxin body burden. Accordingly, a
blood study would require a large number of subjects with controls to reduce the effects of these
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Exposure Data from
Study:
-Clay measurements:
air level, skin load, and
deposition to food
-Questionnaire:
exposure duration, ball
clay in blend
External Data:
-Dioxin concentration in
clay
-Absorption fractions
Deterministic Analysis:
Used point estimates for
all exposure parameters
Monte Carlo Analysis:
Used distributions for all
exposure parameters
Hypothetical
dermal,
ingestion, and
inhalation doses
for 10 subjects
Distribution of
dermal, ingestion,
and inhalation
doses in broad
population of artists
in well maintained
studios
Figure 1. Conceptual diagram.
factors. Also blood tests have very high analytical costs. On the basis of costs alone, blood
testing was beyond the scope of this effort. The clay exposure testing done here provided a low
cost way to explore the problem and gives future researchers an informed basis for deciding if
blood testing or other types of follow-up work are needed.
Dioxin concentrations and exposures are presented in terms of toxic equivalents (TEQs).
TEQs allow concentrations of dioxin mixtures to be expressed as a single value computed by
multiplying each congener concentration by a toxicity weight (toxic equivalency factor or TEF)
and summing across congeners. TEFs are expressed as a fraction equal to or less than 1 with 1
corresponding to the most toxic dioxin congener, 2,3,7,8-tetrachlorodibenzo-p-dioxin
(2,3,7,8-TCDD). The TEQ data presented here are based on TEFs from the 1998 World Health
Organization (WHO) recommendations (Van den Berg et al., 1998). In 2005, WHO updated the
TEFs (Van den Berg et al., 2006). As discussed in Chapter 4, these updates had little impact on
the literature values used here, so no adjustments were made.
The term "dioxins" is used in this study to refer collectively to the tetra- through
octa-chlorinated dibenzo-p-dioxins and chlorinated dibenzofurans (CDD/Fs) with chlorine
substitutions in all of the 2,3,7,8 positions. This term is commonly defined to include the
12 co-planar pentachlorobiphenyls (PCBs) which also demonstrate dioxin-like toxicity.
However, PCBs are not addressed in this study. PCBs have been shown to make up a small
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fraction of the total TEQs in a wide variety of background soils (U.S. EPA, 2007) and, therefore,
are probably not important contributors to TEQs in ball clay.
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2. APPROACH OVERVIEW
While working in a ceramics studio, artists may be exposed to dioxin-contaminated clay
via three pathways: dermal contact, particle inhalation, and incidental ingestion. Exposure could
also occur via open cuts or eyes and this possibility is discussed in Chapter 9 on uncertainty.
The general strategy and procedures used to characterize each pathway are described below.
2.1. GENERAL STRATEGY
The site selected for this study was the Ceramics Area in Hopkins Hall at OSU in
Columbus, OH. The Ceramics Area, housed in the basement of Hopkins Hall, has eight rooms,
including classrooms, studios, a storage area, a glaze-mixing area, a clay recycling area, and a
furnace room. This facility was selected because it offered a convenient location for assessing
exposures during a variety of typical ceramic art activities.
An extensive ventilation system is used through out the studio with hoods located in
several areas such as where clay mixing is conducted. The kilns are located in two rooms which
are isolated from classrooms and other areas frequented by the students. These rooms are
dedicated to kiln operations and no art work is performed in them. The studio has six kilns fired
with natural gas (sizes in cubic feet: 28 [2 units], 40, 70, 7, and 25) and nine electric kilns (sizes
in cubic feet: 60 [2 units], 27, 5 [4 units], 28, and 0.3). The small electric unit is unvented and
used to test the temperature program on small pieces. All other kilns are equipped with
ventilation hoods (vented outside the building). The kilns are generally heated slowly to a
maximum temperature of about 1,200°C (2,200°F) and pieces are baked for about 9 to 15 hours.
They are generally operated 2-3 times/week and daily during busy periods at the end of
semesters.
The exposure measurements were carried out in two separate studies. The first study was
conducted in April 2003 and the second in July 2004. The results of both studies have been
combined in this report. Seven artisans and one nonartisan staff member in the OSU Ceramics
Department were recruited to serve as subjects for the first study, and two additional artisans
were recruited for the second study. An open solicitation was presented to the students and
departmental staff, and the first volunteers were selected. The subjects included three males and
seven females ranging in age from about 20-40 years. Approval for human subjects was
obtained via the Battelle Institutional Review Board (IRB) and the U.S. Environmental
Protection Agency (EPA). Upon approval by the Battelle IRB and EPA, OSU determined that
review by their IRB was not necessary. The testing was conducted while the subjects conducted
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a variety of unscripted tasks, including clay mixing/preparation, sculpting, pottery wheel work,
and molding.
To assess dioxin exposure levels, it is necessary to estimate dioxin levels in the various
exposure media (i.e., clay used by the artists, dust particles suspended in the studio air, and dust
settled onto surfaces). No actual dioxin measurements were made in this study. Rather, dioxin
levels were estimated using literature-reported concentrations of dioxins in ball clay and
information about the amount of ball clay in the clay mixtures used by the artists. Chapter 4
discusses the details about this procedure.
A questionnaire was administered to subjects during the first study to gather information
on their routines involving clay artwork. Chapter 6 summarizes the questionnaire data as
presented in Appendix A.
2.2. CHARACTERIZATION PROCEDURES
The following procedures were used to characterize each exposure pathway.
2.2.1. Dermal Contact
Dermal contact with clay can occur via direct handling of the clay, deposition from the
air onto exposed skin, transfer from surfaces, and splashing during wheel operations. The
amount of clay on skin was measured using rinsing procedures. Additionally, surface wipes
were collected in work areas to evaluate dermal exposures via transfers from surfaces. To
further evaluate dermal exposure, a dermatologist examined the condition of the stratum
corneum, the outermost layer of skin, before and after Subjects 1-8 worked with clay. The
primary focus of this examination was to determine if any damage to skin may have occurred
that would affect dermal absorption.
2.2.2. Inhalation
Both personal and area air-monitoring techniques were used to assess inhalation
exposures. Personal air samplers provide data most representative of an individual's exposure
because they sample the air in a person's breathing zone and reflect changes in concentration due
to their movement. An area sampler provides a general indication of exposure for people in its
vicinity and also can achieve lower detection levels. Both the personal and area-monitoring
techniques provided particle size-selective data, so that the deposition site of the particles in the
respiratory tract (nose/mouth, tracheobronchial airways, and alveolar region) could be
determined.
Two types of personal air samplers were used: real-time and time-integrating. Similarly,
two types of area air samplers were used: real-time and time-integrating. The real-time air
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samplers provided data on particle levels on a nearly continuous basis (every minute). The
integrating samplers collected particles over the entire time period of a work activity, yielding a
time-weighted average (TWA) concentration. In this sampling design, the real-time exposure
monitoring was used to assess frequency, magnitude, and duration of peak exposures as well as
TWA across the entire sampling time, while the integrating samplers provided information on
average exposures.
2.2.3. Ingestion
Inadvertent ingestion of clay or dust can occur in several ways. Clay particles in the air
can deposit on food or in beverages. Deposition onto surrogate food samples (a quartz filter was
used to represent food and a beaker of water was used to represent a beverage, see Section 3.1.5.
for further details) was measured to evaluate this pathway. Ingestion can also occur via transfers
from hands to food or cigarettes (though no smoking was allowed in the OSU studio) and via
transfers to the mouth resulting from wiping the hands or licking the lips. These possibilities
were evaluated qualitatively through observations about individual behaviors. Finally, ingestion
can also occur via particle deposition in the nose, mouth, and tracheobronchial airways;
clearance to the throat; and swallowing. This process was evaluated using inhalation modeling
(see Appendix B).
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3. SAMPLING METHODS
Methods used for collecting, preparing, and analyzing samples are described below.
3.1. SAMPLE COLLECTION
Samples were collected from personal air, area air, skin rinses, surface wipes, and
surrogate food and beverages.
3.1.1. Personal Air Sampling
The Respicon™ Model 8522 particle sampler (TSI Incorporated, Shoreview, MN) is a
two-stage virtual impactor with a three-stage gravimetric filter sampler. The sampler sorts
airborne particulate matter into three size ranges. Each size range is collected on a 37-mm glass
fiber filter (GFF). The particle size collection ranges are as follows: stage 1, aerodynamic
particle diameter (Dae) < 4 jim; stage 2, 4 < Dae < 10 jim; and stage 3, 10 < Dae < 100 jim.
Before the start of sampling, three preweighed GFFs were removed from their protective
polystyrene containers (47-mm Millipore petri slides) and loaded into the Respicon™ using
nonmetallic filter forceps. A unique laboratory record book (LRB) identification number was
assigned to each GFF during tare weighing, and this weight was recorded onto the sampling data
sheet at that time. The Respicon™ was then assembled, and the total flow checker head was
installed. A personal sampling pump (SKC model no. 224-PCXR4, Eighty Four, PA) was
attached to the total flow head, and the flow rate through the Respicon™ was adjusted to 3.11 L
per minute (L/min) + 2%, according to the manufacturer's specifications. All flows were
verified by employing a calibrated National Institute of Standards and Technology
(NIST)-traceable Buck calibrator (Model M5, A.P. Buck, Orlando, FL). After confirmation of
the manufacturer's suggested flow rates at each stage of the sampler, the total flow checker was
replaced with the standard (100 jim) inlet head. A nylon chest harness (TSI Incorporated,
Shoreview, MN) was used to place the Respicon™ in each subject's breathing zone,
approximately 15-20 cm below the chin. The personal sampling pump was attached to the
subject's belt and connected to the Respicon™. Sampling was initiated by starting flow through
the Respicon™ and continued throughout a subject's entire work shift, typically 2-2.5 hours.
The average sampling volume was 387 L. Following sampling, the pump was turned off, the
Respicon™ was disassembled, and the filters were returned to their polystyrene petri dish
containers for transportation back to the laboratory for gravimetric analysis. Quality control
samples, such as field blank samples and matrix spike samples, were collected and analyzed for
each sampling technique (see Section 3.2.3).
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The personal DataRAM-1000 (pDR-1000, Thermo Electron Corporation, Franklin, MA)
sampler was also used to measure personal particle exposure passively. No pump is required for
this instrument; instead, the air surrounding the sampler circulates freely through the open
sensing chamber by natural convection, diffusion, and background air motion. Particle
concentrations are measured using a light-scattering (nephelometry) technique. This instrument
responds optimally to particles with diameters in the range of 0.1-10 jim but will also respond to
a lesser extent to larger diameter particles. Via internal calibration, the sampler converted
particles/m3 to mg/m3 as final data units.
Before the start of sampling, the instrument sensor was zeroed by placing it in a
resealable bag into which particle-free (filtered) air was pumped. All zero operations were
performed successfully. To begin sampling, the instrument was clipped to the subject's waistline
(on the belt or strap holding the SKC pump) and the unit was activated. The pDR-1000 collected
data at 1 Hz and was programmed to record these data as 1-minute averages over the duration of
the sampling period. At the conclusion of sampling (typically 2-2.5 hours), data logging was
stopped and the instrument was turned off. The data were then uploaded to a personal computer
using software provided by the manufacturer and an RS-232 serial port connection.
3.1.2. Area Air Sampling
To assess the particle size and concentration in the ceramic studio's air, a 6-stage Delron®
cascade impactor (Delron Research Products, Powell, OH) was employed. Each stage filters out
successively smaller particles so that the following particle sizes are collected in successive
stages: >32 jim, 16-32 jim, 8-16 jim, 4-8 jim, 2-4 jim, and 0.5-2 jim; the final OFF collects all
particles smaller than 0.5 jam in diameter. Particles accumulate on glass slides underneath each
impactor orifice. To prevent particle loss due to bouncing, a small amount of vacuum grease was
applied to each glass slide. The area coverage of the grease on the slide was determined by the
approximate size of the impactor nozzle below which the slide was to be placed. Correct airflow
rate through the impactor ensures that the correct particle sizes are collected on each stage. A
carbon-vane pump (Gast Co., Benton Harbor, MI), with a critical orifice that provides a pressure
drop of at least 430 mm of mercury, was used to ensure the flow rate of 24 L/min.
Before the start of sampling, preweighed glass slides were removed from their protective
polystyrene petri slide containers and loaded into the impactor using clean forceps or tweezers.
Unique LRB numbers, assigned to each slide during tare weighing, were recorded on sample
data forms. The impactor tower was then assembled and flow was initiated to verify the required
pressure drop. For each sample, the pressure drop was between 480 and 510 mm of mercury.
Flows were also verified using the Buck calibrator. Sampling times were approximately
2-2.5 hours, giving an average sample volume of approximately 2,900 L. Following sampling,
-------
the impactor was disassembled and all slides were returned to their respective petri dish
containers for transportation back to the laboratory for gravimetric analysis.
The Climet® CI-500 innovation laser particle counter (Redlands, CA) was a second
sampling device used to measure area particle concentrations. In a manner similar to the
pDR-1000, the Climet® CI-500 measures particle number concentration using nephelometry. A
self-contained pump sampled air at a constant flow rate of approximately 3 L/min. In the count
mode, the Climet® CI-500 measures particles in six particle size ranges: 0.3-0.5 |im, 0.5-1 |im,
1-2.5 jam, 2.5-5 |im, 5-10 |im, and >10 |im. The sampling frequency for the instrument is 1 Hz,
and the data were logged as 1-minute averages. The particle counts were converted from
particles/m3 to mg/m3 as final data units. The particle counts did not exceed the manufacturer's
recommended maximum (200-250 counts/cm3 at 3 L/min) at any time except for a few minutes
during two of the sampling periods. No instrument zero or span checks were necessary.
Following sampling, the data were uploaded to a computer using an RS-232 serial cable and
software provided by the manufacturer. The Climet® CI-500 was located in close proximity to
the cascade impactor and generally very near the subject. For example, when the subject was
working with clay at a wheel, the two air samplers were placed on the side of the wheel opposite
the subject at a height and distance from the wheel similar to the subject's mouth and nose. The
inlet to the Climet® was oriented in a vertical direction.
3.1.3. Skin Sampling
The total skin area of hands, arms, face, feet, and legs was estimated using a combination
of direct measurements and regression models based on body weight and height (U.S. EPA,
1997). The subject's exposed body parts were rinsed with a dilute soap solution (-2% soap in
deionized [DI] water, by weight). Approximately 100-150 mL of the soap solution was used to
rinse each exposed body part. After each body part was rinsed, the washbasin contents were
transferred to a polypropylene bottle with small amounts of DI water rinses. The bottle was
labeled and sealed with a screw-top cap. The washbasin was then rinsed again, wiped out, and
reused. Between the first and second studies, the procedures differed as described below.
3.1.3.1. April 2003
All subjects wore short-sleeved shirts, long pants, socks, and shoes. Therefore, the only
exposed skin areas were the hands and forearms, and the rinsing was limited to these body parts.
At three times during each subject's work session, the subject's exposed skin was examined for
clay residue. When clay was observed visually, the affected areas of the subject's body were
rinsed. Rinses were performed at approximately equally spaced intervals, and the last rinse
10
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usually coincided with the conclusion of the sampling period. The average of the three
measurements was used to represent the session.
3.1.3.2. July 2004
Both subjects wore short-sleeved shirts, short pants, and sandals. Therefore, the exposed
skin areas included the hands, arms, legs, and feet, and the rinsing was expanded from the first
tests to include all of these body parts. The subjects' faces were also rinsed during these tests.
Although no visible residues were apparent on the faces, this area was included for the sake of
completeness.
The rinse samples were collected in a washbasin using a squirt bottle of soap solution
while the subjects used their hands to gently wipe off the affected area. Rinses were conducted
in the following manner:
• Hands. Moving downward from the wrist, the technician rinsed the residual clay off
both sides of the artisans' hand; the residual clay from each hand was rinsed into separate
containers and analyzed separately.
• Arms. Moving downward from the elbow, the artisans rinsed the residual clay from their
arms.
• Feet. Moving downward from the ankle, the artisans rinsed the residual clay from their
feet.
• Legs. Moving downward from the top of the exposed area of the legs, the artisans rinsed
the residual clay from their legs.
• Face. The artisans rinsed the residual clay from their faces.
Skin rinse samples were collected at the close of each work session. In addition, if at any
point during the work session the subject indicated the need to wash an exposed body part, it was
rinsed into a sample container reserved for that body part.
3.1.4. Surface Wipe Sampling
A 20 x 20 cm horizontal surface near the subject's workspace was selected and cleaned
with dilute soap solution before the subject began working with any clay. These surfaces were
porous concrete tabletops. Wipe samples of this area were taken immediately after cleaning (to
confirm that low levels were present before starting the work session) and at the end of the work
session. The wipe sampling procedure consisted of the following steps. The selected area was
wiped with 10 x 10 cm rayon gauze wipes wetted with ~5 mL isopropanol using the following
11
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procedure. The wipe was secured between the thumb and forefinger of one hand, and the surface
was wiped five times in one direction using evenly applied pressure. The soiled side of the wipe
was folded to the inside and, in an orthogonal direction, the surface was wiped five more times.
This soiled side of the wipe was again folded to the inside and the wipe was placed into its
prelabeled, resealable bag for transportation back to the laboratory for gravimetric analysis. The
entire wiping process above was then repeated using one additional wipe.
3.1.5. Surrogate Food and Beverage
An 85-mm diameter quartz fiber filter and a 125-mL polypropylene jar filled with
100 mL DI water served as surrogates for food and beverage samples, respectively. Before clay
work began, both were placed in a location where the artisan indicated he or she might normally
place food or drink. In most cases, this location was away from the direct work area but still in
the same room. However, occasionally clay workers placed food and beverage directly adjacent
to their work. To begin sampling, the lid of the polycarbonate petri dish containing the food
surrogate and the screw-cap lid on the beverage surrogate were removed. Following the
conclusion of sampling, the lid to the petri dish was replaced and sealed with Teflon® tape, and
the polypropylene jar was secured for transportation back to the laboratory for gravimetric
analysis.
3.2. SAMPLE PREPARATION AND ANALYSIS
Procedures used for sample preparation, analysis, and quality control are described
below.
3.2.1. Filtration and Drying
To collect the clay rinsed from the subject's skin during the skin rinse sampling
procedure and the clay deposited into the surrogate beverage sample, the clay-liquid suspensions
were filtered through a preweighed 85-mm diameter quartz fiber filter in a Buchner funnel using
vacuum filtration. Any remaining clay in the sample container was rinsed with several small
aliquots of DI water to ensure complete transfer of the clay to the filter. All filters from the
vacuum filtration procedure were subsequently placed on clean 10-cm watch glasses and dried
overnight at 100°C (212°F). The gauze wipes for surface residues were dried in this fashion as
well. No drying was required for the 37-mm Respicon™ filters or glass slides.
12
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3.2.2. Gravimetric Analysis
The accuracy of the analytical balance (AT-20, Mettler-Toledo) used for all gravimetric
analyses was confirmed daily with weights approved by NIST. The calibration weights ranged
from 0.001 mg to 100 g. All 37-mm GFFs, 85-mm quartz fiber filter paper, 37-mm glass slides,
and gauze wipes were conditioned in a temperature- and humidity-controlled balance room
(temperature 22-23°C (72-73°F), relative humidity 46-56%) for a minimum of 24 hours before
tare and final weights were recorded. For conditioning, the lid of the container holding the filter
or slide was left slightly ajar, and the resealable bags containing the gauze wipes were left open.
For both kinds of filters and glass slides, three separate weights were recorded to the nearest jig.
The weight was acceptable if the range of the three independent measurements was less than 10
jig. For gauze wipes, the three separate weights were recorded to the nearest tenth of a mg and
the acceptability criterion was that the range of the measurements be less than 1 mg.
3.2.3. Quality Control Samples
At least one field blank sample was collected for each type of gravimetric sample,
including the Respicon™, cascade impactor, food and beverage, and surface wipe samples.
Such samples were collected by transporting the sampling media to the field location and placing
them into their respective sampling device or position for sampling. As soon as the medium was
ready for sampling, it was collected as if the sampling time had come to a close and transported
back to the laboratory for gravimetric analysis. The detection limits for the gravimetric
measurements were determined by multiplying the standard deviation of the field blank net
weights by 3. The detection limits for each type of gravimetric measurement were as follows:
0.0025-0.015 mg/m3 for each stage of the cascade impactor, 0.878 mg/m3 for each stage of the
Respicon™, 10.6 mg for the surface wipes, 0.6-1 mg for the food/beverage deposition samples,
and 0.6-1.6 mg for the dermal rinse samples.
As a quality control check, the skin rinse, surface wipe, and food and beverage sampling
and analysis methods were tested in a controlled laboratory setting (Battelle Laboratory in
Columbus, OH). For the skin rinse method evaluation, approximately 3 g of clay (obtained from
one of the artisan subjects) was handled carefully without dropping any until the entire sample
was spread over the hands and forearms of a Battelle researcher. The skin rinse and analysis
method described above was performed, and recoveries of 87 + 3% of the clay applied were
obtained. This compares favorably with Kissel et al. (1996), who obtained 93% recovery when
rinsing wet soil from the skin of human subjects using a similar sampling method. Similarly, for
the surface wipe method, approximately 1 g of clay was deposited onto a precleaned laboratory
bench, the wipe method described above was performed, and recoveries of 94 + 5% were
obtained. For the food and beverage samples, approximately 50 mg of clay was added to those
13
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sampling matrices and recoveries of 90 and 95%, respectively, were obtained using the
gravimetric analysis procedures described above.
14
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4. DIOXIN CONTENT OF CLAY AND STUDIO RESIDUES
As discussed earlier, this study made no dioxin measurements in clays, dust residues, or
other materials from the Ohio State University ceramics studio. Instead, the possible levels were
estimated on the basis of other studies. A number of studies have measured dioxin levels in raw
and processed ball clay. Raw clay is the clay as it comes out of the ground. Processed clays are
the result of the initial processing, which is usually conducted at or near the mining site before
shipping. This processing typically involves drying with hot air at 120°C and pulverizing in a
series of milling stages (Ferrario and Byrne, 2002). The following studies describe dioxin levels
in raw and processed clay:
• Ferrario and Byrne (2002, 2000). Both papers present data for processed ball clay used
at one ceramics manufacturer. The mean of seven samples of processed ball clay was
3,172 pg/g TEQ. Additional data are presented on dioxin levels in clay mixtures and
fired products. The authors noted that dioxin levels in the dust samples collected at the
facility were the same as those in the unfired clay mixtures.
• Ferrario et al. (2000a). This study compared the mean levels in eight raw clay samples
from Mississippi (see Table 1) to the mean levels in four processed ball clay samples.
This comparison showed that the processed clays had much lower levels of
2,3,7,8- TCDD and higher levels of 1,2,3,4,7,8-hexachlorodibenzo-^-dioxin (HxCDD),
1,2,3,4,6,7,8-heptachlorodibenzo-^-dioxin (HpCDD), and octachlorodibenzo-^-dioxin
(OCDD) than the raw clay. The mean total TEQ of the processed clay (977 pg/g TEQ)
was 37% lower than the raw clay (1,513 pg/g TEQ).
• Ferrario et al. (2000b). This study also presents the data for raw and processed clay
described in Ferrario et al. (2000a). In addition, it presents dioxin levels in a variety of
other types of clays and discusses the evidence of a natural origin for their presence.
• Ferrario et al. (2007, 2004). These studies collected processed ball clay directly from
four art-supply retailers. All ball clay types sold by these retailers were purchased in
22.7-kg (50-pound) bags. One type of ball clay was sold by all four retailers, five types
were sold by two of the retailers, and seven types were sold by only one retailer. Thus, a
total of 21 bags, representing 13 different types of ball clays, were purchased and
sampled. A ceramics expert confirmed that the most commonly used ball clays for
making artware and pottery were represented in these samples. Table 2 summarizes these
data.
15
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Table 1. Raw ball clay dioxin concentrations
Congener
2,3,7,8-TCDD
1,2,3,7,8-PeCDD
1,2,3,4,7,8-HxCDD
1,2,3,6,7,8-HxCDD
1,2,3,7,8,9-HxCDD
1,2,3,4,6,7,8-HpCDD
OCDD
Total
PCDD concentration (pg/g dry weight)
Range
253-1,259
254-924
62-193
254-752
1,252-3,683
1,493-3,346
8,076-58,766
Median
617
492
134
421
1,880
2,073
4,099
Mean
711
508
131
456
2,093
2,383
20,640
Mean TEQ
711
508
13
46
209
24
2
1,513
HpCDD = heptachlorodibenzo-p-dioxin; HxCDD = hexachlorodibenzo-p-dioxin; OCDD =
octachlorodibenzo-p-dioxin; PCDD = polychlorinated dibenzo-p-dioxin; PeCDD = pentachlorodibenzo-p-dioxin;
TCDD = tetrachlorodibenzo-p-dioxin; TEQ = toxic equivalent.
Source: Ferrario et al. (2000a).
Because the data from Ferrario et al. (2007, 2004) represented the types of clays most
likely used in ceramic art studios, these data were selected as the most representative ones to be
used in this study. Accordingly, it was assumed here that the dioxin TEQ levels in clay could
range from 289 to 1,470 pg/g with an average of 808 pg/g. Table 2 shows the TEQs from this
study were calculated on the basis of the WHO-98 TEFs (Van den Berg et al., 1998). In 2005,
WHO updated the TEFs (Van den Berg et al., 2006). These updates increased the TEF for
OCDD from 0.0001 to 0.0003. None of the TEFs for the other six congeners used to estimate
the ball clay TEQs were changed by the WHO update. The increase in the OCDD TEF would
cause the overall average to increase by 6%. It was decided to use the TEQ estimates for ball
clay as originally reported instead of updating it on the basis of the 2005 WHO TEFs. This was
based on two reasons, first the change would have been relatively minor and second it would
have complicated comparisons to exposure estimates which have not yet been updated on the
basis of the new TEFs.
16
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Table 2. Processed ball clay dioxin concentrations (pg/g)
PCDDs
2,3,7,8-TCDD
1,2,3,7,8-PeCDD
1,2,3,4,7,8-HxCDD
1,2,3,6,7,8-HxCDD
1,2,3,7,8,9-HxCDD
1,2,3,4,6,7,8-HpCDD
OCDD
Total
TCDD
PeCDD
HxCDD
HpCDD
Total TEQsb
Average
76
374
335
526
1,480
9,780
254,000
1,450
4,600
13,500
25,000
808
Standard
deviation
60
144
141
204
608
4,480
88,200
606
1,890
5,710
11,700
318
Median
63.5
387
313
523
1,570
8,600
233,000
1,600
4,880
12,800
24,400
771
Minimum
21.8
125
142
167
394
3,940
118,000
412
1,560
4,800
9,320
289
Maximum
291
588
636
944
2,550
19,500
471,000
2,370
7,140
21,900
44,900
1,470
WHO-
TEFa
1
1
0.1
0.1
0.1
0.01
0.0001
Avg
TEQ
76.0
374
33.5
52.6
148
97.8
25.4
808
a World Health Organization Toxic Equivalency Factors (WHO-TEFs) based on Van den Berg (1998)
b The overall average presented by Ferrario et al. (2007) is based on averaging the mean congener levels across
samples. An alternative approach is to compute the average on the basis of the TEQ for each sample. This
approach yields an average of 819 pg/g (SD = 303 pg/g). Similarly, the median TEQ is 810 pg/g based on the
individual samples. The minimum and maximum TEQ values are reported on the basis of the individual samples.
HpCDD = heptachlorodibenzo-p-dioxin; HxCDD = hexachlorodibenzo-p-dioxin; OCDD =
octachlorodibenzo-p-dioxin; PCDD = polychlorinated dibenzo-p-dioxin; PeCDD = pentachlorodibenzo-p-dioxin;
TCDD = tetrachlorodibenzo-p-dioxin; TEQ = toxic equivalent.
Source: Ferrario et al. (2007, 2004).
All of these studies indicate that ball clay has relatively high levels of CDDs and very
low levels of CDFs. Based on Ferrario et al. (2007, 2004), about 95% of the TEQs in processed
clay are contributed by four congener groups: TCDDs (9%), pentachlorodibenzo-p-dioxin
(PeCDDs) (46%), HxCDDs (28%), and HpCDDs (12%).
17
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Artists commonly use a mixture of clays to achieve various physical properties and visual
effects. The percentage of ball clay in the mixture can vary widely. The amount of ball clay in
the mixtures used on days when the testing occurred ranged from 0 to 100% with an average of
21.5% (see Table 3). Although 4 of the 10 subjects used mixtures containing no ball clay on the
test days, on other days these subjects would likely use mixtures that do contain ball clay. This
is because students are required to conduct a variety of projects, and some of these are better
suited to using ball clay and others are not. Accordingly, it was assumed here that the ball clay
portion of clay mixtures used by artists can range from 0 to 100% with an average of 20%.
Furthermore, it was assumed that the dioxin levels in the nonball clays were negligible. This is
supported by Ferrario et al. (2000b), who analyzed 15 different mined clays and concluded their
dioxin levels were significantly lower than levels in ball clay.
Table 3. Percentage ball clay in the clay mixtures used during this study
Subject
1
2
O
4
5
6
7
8
9
10
Percentage ball clay
0
27
48
0
20
0
0
15
100
5
Finally, it was assumed that the dusts suspended in the air and settled onto food or skin
would have the same dioxin levels as the clay. Material other than clay may contribute to these
dusts, further diluting dioxin concentrations. This possibility was evaluated using scanning
electron microscopy (SEM) with energy dispersive spectroscopy (EDS). These techniques were
applied to four types of samples:
18
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• Blank OFF
• Dust on a OFF collected from a storeroom at the Battelle Laboratory (not impacted by
clay)
• Air particles on a Respicon™ GFF collected in the studio
• Clay used by subjects
Figure 2 shows SEM photographs and elemental spectra of samples associated with
Subject 6. A visual comparison of the SEM photographs suggests that the particles on the
Respicon™ filter appear to differ from those in the storeroom dust. Also, the spectra of the
particles on the Respicon™ filters resemble clay more than those of storeroom dust. The clay
samples and Respicon™ filter samples had high abundances of titanium, iron, and aluminum,
which were not seen in the GFF blank or in the storeroom dust sample. Similar results were
found for all eight subjects in the April 2003 tests, as shown in Appendix C. The analysis was
not repeated in the July 2004 tests. These observations suggest that clay dominates the air
particles collected in the studio. On this basis, it was assumed that the studio dust was
dominated by clay and no further dilution factor was needed to adjust dioxin concentrations.
19
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Blank glass fiber filter (OFF)
Dust particles on OFF in Battelle storeroom
0123
Full Scale 1061 cts
0246
Full Scale 885O cts
S 10 12 14 16 18 20
keV
to
o
Sample of clay used by Subject 6
Clay particles on Respicon filter used by Subject 6
1 2 3
Full Scale 2136 cts
keV
Figure 2. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) data.
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5. DOSE ESTIMATION PROCEDURES
This chapter presents the procedures used to estimate the dioxin dose to artisans from all
three routes of exposure: dermal contact, inhalation, and ingestion. Because the dermal dose is
expressed on an absorbed basis, the dose by other pathways must also be expressed on an
absorbed dose basis. This provides an equivalent basis for comparison and addition across
pathways. All doses are presented as daily estimates. No adjustments are made for the
frequency with which artists work with clay. Therefore, these dose estimates should be
interpreted as the dose that could occur on a day that clay work is conducted, rather than as a
long-term average.
5.1. DERMAL CONTACT
A fraction absorbed approach is used to estimate dermal absorption. This method has
been widely used to assess dermal exposures to solid residues and is endorsed in current Agency
guidance (U.S. EPA, 2004, 1992). Kissel et al. (2007) have proposed a more mechanistic model.
This model has not yet been incorporated into Agency guidance and therefore, was not chosen as
the primary basis for this assessment. However, the model is presented in Appendix D with a
discussion of how it could be applied to this situation.
5.1.1. Estimating Particle Loading on Skin
As described earlier, rinsing procedures were used to determine the total amount of clay
on exposed skin. This mass was divided by the exposed skin area to derive a loading in units of
mg/cm2.
5.1.2. Estimating Monolayer Load
The monolayer is the layer of particles immediately adjacent to the skin. According to
the monolayer theory, the only significant dermal absorption comes from chemicals contained in
this first layer (U.S. EPA, 2004, 1992). This theory would not apply in all situations such as
those involving rapid absorption and long exposure times. In such situations the monolayer
could be depleted, and the contaminant in higher layers could diffuse downward and ultimately
be absorbed into the skin. Experimental evidence supporting the monolayer theory has been
published by Duff and Kissel (1996), Roy and Singh (2001), and Touraille et al. (2005). These
studies used exposure times of 24 hours or longer and were conducted with 2,4-D, BaP, and
4-cyanophenol. The similarity of these chemicals to dioxins and the use of exposure times
similar to the ones of concern here, suggest that the monolayer theory should be applicable to
exposure scenarios considered in this study.
21
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To properly apply the dermal absorption fractions, it was necessary to determine whether
residue loads on skin exceeded monolayer loads. The monolayer load for a specific soil can be
estimated on the basis of the median particle size. Assuming spherical particles and
face-centered packing, the monolayer loads can be calculated as follows (U.S. EPA, 2004):
Lmono - K P dp/ 6
(1)
where
Lmono = monolayer load (mg/cm2)
p = particle density (mg/cm3)
dp = physical particle diameter (cm)
The average particle density of the processed clays analyzed by Ferrario et al. (2004) was
2.64 g/cm3. Clays typically have very small particles relative to other components of soil. The
U.S. Department of Agriculture (USD A) defines clays as having less than 2 |im diameter
particles (Brady, 1984). Table 4 shows the particle size specifications for a Tennessee ball clay
(Ceramics Materials Info, 2003). Reviewing the specifications for a variety of commercial ball
clays, median particle sizes ranged from about 0.5 to 1.0 jim (Ceramics Materials Info, 2003).
Table 4. Particle size distribution of Tennessee ball clay
Particle diameter (urn)
% finer than
20
99
10
97
5
93
2
81
1
72
0.5
56
0.2
35
Source: Ceramics Materials Info (2003).
The particle sizes found in the studio air had median physical diameters ranging across
subjects from 8 to 27 |im (this is derived from the mass median aerodynamic diameter [MMAD]
range of 13 to 44 jim described in Appendix B and converted to physical diameters using the
procedure in Appendix B, Footnote 1). These airborne particles appear larger than what would
be expected from the original clay product. This may be explained by the bonding of particles
caused by the addition of water to the clay or the firing process, which fuses particles. Particles
that accumulate on the skin primarily from air deposition are likely to resemble the air particles
more than the original clay particles. Particles that transfer to skin primarily from direct
handling of the clay should more closely resemble the original clay product than the airborne
particles. Accordingly, the particle sizes of the clay residues on skin could vary widely, with
22
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medians ranging from 0.5 to 27 jim. For purposes of the central exposure estimates, the
geometric mean of this range is assumed, i.e., 3.7 jim. This implies a monolayer load of
0.5 mg/cm2. Chapter 9 further discusses the uncertainty resulting from this assumption.
5.1.3. Estimating Fraction Absorbed
Three studies have examined dermal absorption of TCDD from soil (Roy et al., 2008;
Shu et al., 1988; Poiger and Schlatter, 1980). The Roy et al. (2008) data were selected as the
best basis for estimating dermal absorption fractions applicable to the ceramics studio. This was
because the test soil was most fully described allowing comparisons to the clay, and multiple
exposure times were used allowing evaluation of how dose varies with time.
Roy et al. (2008) conducted a variety of experiments in which TCDD was applied to soil
on human skin in vitro, rat skin in vitro, and rat skin in vivo. The experiments were conducted
with both a low organic carbon soil and a high organic carbon soil. Ferrario et al. (2007, 2004)
studied 21 samples of processed ball clay used in ceramics studios. They found that the organic
carbon content of these samples ranged from 0.06 to 1.1% with a median and geometric mean of
approximately 0.4%. This level is very similar to the level in the low organic carbon soil used by
Roy et al. (0.45%). Accordingly, this discussion focuses on the Roy et al. results for the low
organic carbon soil applied to human skin in vitro. For purposes of evaluating human exposure
to TCDD contaminated soil, Roy et al. (2008) made three adjustments to their 24-hour
absorption percentage from the human skin in vitro tests:
• The amount of TCDD found in the skin at the end of the experiment (0.20%) was added
to the amount in the receptor fluid to get total absorption
• The absorption percentage was multiplied by two to reflect the ratio observed between
the rat in vivo tests with low carbon soil and rat in vitro tests with low carbon soil
• The absorption percentage was multiplied by another factor of two to make it applicable
to soil loads less than or equal to the monolayer
Table 5 shows that in the present study, these adjustments were made for each data point.
Finally these adjusted data were fit to a polynomial function relating absorption percentage and
time (see Figure 3). The equation for this function is as follows (converting percent to fraction):
AFdermai = (O.OOOSr2 + O.OSt + 0.7692)7100 (2)
where
23
ai = dermal absorption fraction
t = time (hour)
-------
Table 5. Percent absorbed over time
Time
(hr)
1
2
4
8
24
48
72
96
Receptor Fluid"
(%)
0.02
0.08
0.07
0.02
0.28
0.91
1.54
2.25
Receptor Fluid
+ Skinb (%)
0.22
0.28
0.27
0.22
0.48
1.11
1.74
2.45
Adjusted0
(%)
0.88
1.12
1.08
0.88
1.92
4.44
6.96
9.8
Best Fit"
(%)
0.82
0.87
0.98
1.20
2.26
4.32
6.96
10.18
a Percent absorbed into receptor fluid from human skin in vitro testing by Roy et al. (2008).
b Addition of 0.2% absorbed into skin at end of experiment.
0 Multiplied by a factor of 2 for the in vitro:in vivo ratio and by another factor of 2 for application to soil loads equal
to or less than monolayer.
d Based on Eq. 2.
hr = hour.
24
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8
£
o>
0.
Percent Absorbed vs Time
12 -.
m -
8 -
R -
A -
2 -
0 -
y = O.OOOSx2 + 0.05x + 0.7692
R2 = 0.9956 ^S~
^^r^
^^r^
^^^^
_^s^
^^•^^
^Jt*^1^
_^^
A*"-^"*""^*'^"^
111111
0 20 40 60 80 100 120
Time (hr)
Figure 3. Scatter plot of adjusted absorption data versus time with trend line.
Source: Adapted from Roy et al. (2008).
5.1.4. Calculating Dermal Dose
The rinsing experiments indicated that clay loading exceeded the monolayer load in
some, but not all, cases. The dermal absorption fractions presented above were applied to the
measured loads where these were less than or equal to monolayer loads. At soil loadings greater
than monolayer, the dermal absorption fraction was applied to only the monolayer load.
Accordingly, the dose of dioxins absorbed through the skin of the artisan subjects during this
study was estimated using the following equation for each body part and then summed:
Ddermal =£4 I CAP,
where
£4
L
C
dermal
dermally absorbed dose (pg TEQ/d)
skin area exposed (cm2)
daily clay loading on skin (measured or monolayer, whichever is less)
(mg/cm2-day)
dioxin concentration in clay (pg TEQ/g)
dermal absorption fraction
(3)
25
-------
The approach used in this study assumes that dermal exposure is limited to the
skin area which is not covered by clothing. As discussed in Chapter 9, a number of
studies have shown that dusts can penetrate clothing and deposit on skin. Since none of
these studies were specific to ceramic art studios it is uncertain how they apply in this
situation (see Chapter 9 for a full discussion of the uncertainties associated with this
issue).
5.2. INHALATION
The portion of particles that enter the respiratory tract through the nose or mouth
(inhalability) depends mainly on particle size, route of breathing (through the nose or mouth),
wind speed, and a person's orientation with respect to wind direction. Inhaled particles may be
either exhaled or deposited in the extrathoracic (ET), tracheobronchial (TB), or pulmonary (PU)
airway. The deposition of particles in the respiratory tract depends primarily on inhaled particle
size, route of breathing, tidal volume, and breathing frequency (American Conference of
Governmental Industrial Hygienists, 2004; International Commission on Radiological Protection,
1994). Appendix B presents a detailed discussion of how to consider these factors and estimate
the amount of particulate that deposits in various regions of the respiratory tract.
The absorbed inhalation dose is estimated as follows:
Delation = Dr C AFr (lg/1,000 Hlg) (4)
where
Dinhaiation = inhalation dose (pg TEQ/d)
Dr = dose of particles to region r of the respiratory tract (mg/d)
C = dioxin concentration on particles (pg/g)
AFr = absorption fraction for region r of the respiratory tract
This equation is used to estimate the absorbed dose to the three regions of the respiratory
tract (ET, TB, and PU) and then summed to derive total inhalation dose. In general, particles
deposited in the ET and TB regions clear rapidly (within 1-2 days) to the throat and are
swallowed. Accordingly, the absorption of dioxin from particles deposited in these regions is
treated as if the particles had been ingested with an absorption fraction of 0.3 (U.S. EPA, 2003).
The particles depositing in the PU region remain there a long time, and most of them are
ultimately absorbed directly into the body (assumed absorption fraction of 0.8 based on U.S.
EPA, 2003). Chapter 9 discusses inhalation uncertainties.
26
-------
5.3. INGESTION
The ingestion dose is estimated by assuming that all particles deposited on the surrogate
food and beverage samples are ingested. For both types of samples, the dose was calculated
using the equation below:
J-J ingestion (f ' JJ) U Ar ingestion (
where
Dmgestion = ingestion dose (pg TEQ/d)
F = deposited clay on food (g/d)
B = deposited clay on beverage (g/d)
C = dioxin concentration in clay (pg TEQ/g)
= absorption fraction for ingestion
was assumed to equal 0.3 based on recommendations in U.S. EPA (2003) for
ingestion of dioxin in soil. The ingestion of dioxin from inhaled particles is included in the
inhalation dose as discussed above. Chapter 9 discusses ingestion uncertainties.
5.4. TOTAL DOSE
The total absorbed dose was estimated to be the sum of the dermal absorption, inhalation,
and ingestion doses as shown below:
U total ^dermal ' ^ inhalation ' ^ ingestion (y
where
D total = total dose (pg TEQ/d)
Ddermai = dermally absorbed dose (pg TEQ/d)
D inhalation = inhalation dose (pg TEQ/d)
= ingestion dose (pg TEQ/d)
27
-------
6. QUESTIONNAIRE RESULTS
The complete questionnaire and all responses are presented in Appendix A. The
questionnaire focused on characterizing each subject's work with clay in terms of
frequency/duration, type of activity, clothing worn, and impact on skin. Table 6 summarizes the
questionnaire results for the amount of time that the subjects spent working directly with clay.
The subjects worked with clay, on average, for 30 hours per week and 38 weeks per year over a
6-year period. The times varied widely, however, reflecting the types of students involved. A
student obtaining an advanced degree in ceramics is likely to work with clay daily over many
years. In contrast, a student who takes a pottery class to fulfill a general education requirement
is likely to experience similar exposures, but only for 1-3 hours per day over the duration of the
class (9 months or less).
Table 6. Questionnaire questions on duration and frequency of subject's
clay work
Question (« = 8)
Approximately how many hours
per week do you work with clay?
Approximately how many weeks
per year do you work with clay?
How long (years) have you been
doing clay work with this level of
intensity?
Mean (SD)
30(21)
38(10)
6(8)
Median
23
38
O
Max
70
52
24
Min
10
20
1
SD = standard deviation.
Table 7 summarizes the participants' answers to several questions about their clay work.
Some of the questions address the types of clothing worn, how often the subjects wash their
hands, and whether the subjects could correlate any skin health effects with working with clay.
All eight subjects answered that they have dry skin because of the clay work. In general, the
subjects wash their hands soon after working with clay: their faces and arms within a few hours
and the rest of their bodies within 24 hours. The responses indicate that one subject gets a rash
when using the wheel for throwing, another subject has nasal congestion due to clay work, and
another subject's fingernails do not grow well.
28
-------
Table 7. Questionnaire questions about clay work
Question (« = 8)
What type of clay artwork do you
do?
What types of clothing do you wear
while you work?
What areas of skin typically are
exposed to the clay while you work?
In relation to the time you complete
working with clay, when do you
wash parts of your body that have
been exposed to clay?
How do you wash your skin after you
work with clay?
Do you correlate any skin health
issues with how much you work with
clay? If yes, what?
Summary of answers
(number of subjects with similar answers)
Hand building/sculptural work (7), throwing on wheel
(3), mixing clay, and maintenance work (1).
In general, long sleeves and pants in cool weather and
short sleeves and pants or shorts in warm weather; both
closed-toe shoes and sandals are worn at times.
Always face and hands; arms, legs, and feet when
exposed.
Soon after: hands (8), arms (1), face (1).
Within a few hours: arms (2), face (6).
Within 24 hours: face (1), rest of body (4).
Soap and water or just water (8).
Dryness (8), rash on hands when using wheel (1), nasal
congestion (1), fingernails do not grow well (1).
29
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7. COMPARING EXPOSURES ACROSS SUBJECTS
In this chapter, a hypothetical dioxin dose is estimated for each subject and used to
evaluate which pathways and activities contribute most to total dose. This is done by assuming
that each subject uses clay with the same level of dioxin. More specifically, it is assumed that
each subject uses a clay mixture with 20% ball clay and that the ball clay contains 808 pg TEQ/g
(these are typical values as discussed in Chapter 4). Accordingly, the dioxin levels in the clay
were assumed to be 20% of 808 pg TEQ/g or 162 pg TEQ/g. This concentration was also
assumed to apply to inhaled dust and dust settled onto food. A variety of other factors were also
held constant across subjects to facilitate this analysis:
• Exposure duration. Chapter 6 presents the questionnaire results, which indicate a
median weekly time for clay work of 23 hours. Assuming a 5-day work week, this would
correspond to about 4 hours/day. This value was applied to all subjects.
• Monolayer load. The monolayer load varies depending on particle size but is assumed
here to be 0.5 mg/cm2 for all subjects. This is based on the geometric mean of the range
of possible median particle sizes, i.e., 0.5 to 27 jim (see Section 5.1 for further discussion
of this issue).
• Dermal absorption fraction. This will depend on exposure time, as discussed in
Section 5.1. The time that the skin is exposed to clay will vary with individual behaviors
and body parts. Some body parts (such as hands and faces) are likely to be washed more
frequently than others (such as feet, legs, and arms), resulting in longer exposure times.
The questionnaire data collected during this study (see Chapter 6) suggest that the artists
generally wash their hands soon after working with clay, wash their faces and arms
within a few hours, and wash the rest of their body within 24 hours. Accordingly, the
exposure time for feet and legs was assumed to be 24 hours, and the absorption fraction
corresponding to 24 hours was applied (2.3%). The exposure time for hands, arms, and
face was assumed to be 4 hours with a corresponding 1.0% absorption.
• Ingestion absorption fraction. This was set to 0.3 based on recommendations by EPA
for ingestion of dioxin in soil (U.S. EPA, 2003).
• Inhalation absorption fraction. This was set to 0.3 for ET and TB regions based on the
assumption that the area is rapidly cleared to the gastrointestinal tract. It was set to 0.8
for the PU region based on recommendations by EPA for inhalation of dioxin in air (U.S.
EPA, 2003).
The hypothetical dioxin dose for each subject is calculated using the constant values
described above and their individual exposure conditions (e.g., dust level in air, clay load on
skin, clay load on food). The dose estimates are considered to be hypothetical because they are
30
-------
based on assumed dioxin levels in the various exposure media rather than on studio-specific
measurements. Chapter 8 uses Monte Carlo simulations to analyze the possible variability in
dose resulting from a range of dioxin levels in clay, ball clay mixtures, and exposure factors.
This chapter first addresses each pathway separately (dermal contact, inhalation, and
ingestion) and then addresses total dose. Individual exposures vary widely, and it is important to
consider the subject's activity and clothing in evaluating the results. Table 8 is provided as a
reference for this purpose with summaries of each participant's activities and clothing.
7.1. DERMAL CONTACT
As described in Section 5.1, the mass of clay rinsed from the skin was used to estimate
clay loadings on the skin for each exposed body part. The rinsing data are presented in
Appendix E. Section 5.1 also explains that the skin loading is compared to the monolayer load,
and the absorption fraction is applied to the lower amount. Table 9 shows the dermal absorption
estimate for each subject. Subjects 1 through 8 wore clothing that limited their exposures to only
hands and arms (although arm exposure was detected on only Subjects 1 and 6). The estimates
for Subjects 9 and 10 include hands, arms, legs, and feet because they wore clothing allowing
exposure to these areas. All subjects could have had exposure to the face, but this was evaluated
only for Subjects 9 and 10. Pictures of the clay residues on skin are shown in Appendix F.
Table 9 shows that 6 of the 10 subjects had skin loadings exceeding the monolayer. The
absorbed dose ranged from 0.23 to 7.09 pg TEQ/d with a mean of 1.35 pg TEQ/d (SD = 2.05).
The relationships between the activities of the subjects and their dermal exposure are
discussed below:
• Wheel work (Subjects 6 and 9). This activity led to the highest dermal exposures. The
high exposures were caused by the close proximity of the subjects to the wheel, the
splashing of wet clay onto their bodies, and the use of both hands to mold the clay. The
total dermal dose for Subject 9 was about 4 times greater than that for Subject 6, resulting
primarily from their clothing difference. Both had similar hand and arm exposure, but
Subject 9 had high exposure to legs and feet and Subject 6 had no exposure in these
areas.
31
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Table 8. Artisan activities of each subject
Artisan/staff
(minutes sampled)
Description of activity
Clothing
Test 1, April 2003
Subject I/male
(153 min)
Subject 2/male,
nonartisan staff
(84 min)
Subject 3/female
(124 min)
Subject 4/female
(121 min)
Subject 5/male
(136 min)
Subject 6/female
(123 min)
Subject 7/female
(124 min)
Subject 8/female
(138 min)
Wedged clay on a wedging board to remove air from the
clay before kneading and shaping clay by hand. Used a
wooden press to press the clay into flat, approximately
2.5-cm thick sheets. Also, pounded semi-dry clay into
balls, placed in ball mill for smoothing rough edges.
Poured powdered components into large mixer for clay
manufacture while wearing dust mask and while the dust
removal system was operational. Weighed out portions of
clay, and bagged and stored them. Subject moved to gas
kiln room, where he cut blocks, built the kiln up a bit, and
vacuumed. Finally, subject used compressed air to clean
the dust off himself .
Subject wedged clay and covered a prefabricated mold
with clay using her hands to mold and shape the clay.
Subject cut pre-wedged and formed blocks of clay into
5-cm thick pieces, loaded the blocks into a pneumatic
press, pressed a pattern into each, cut blocks to the proper
shape, and then stacked the finished pieces to be fired.
Subject hand rolled clay into 60-cm long "snake-like"
cylinders, which he then hand-formed into conical pots.
Subject threw a variety of clay items, including a pitcher,
a vase, pots, and bowls on the pottery wheel.
Subject wedged, rolled, cut, and hand-built a variety of
items.
Subject wedged, rolled, shaped, cut, and hand-built large
pieces of clay and placed them on a mold.
Short-sleeved shirt, long
pants, socks, shoes
Short-sleeved shirt, long
pants, socks, shoes
Short-sleeved shirt, long
pants, socks, shoes
Long-sleeved shirt (rolled
up), long pants, socks,
shoes
Short-sleeved shirt, long
pants, socks, shoes
Short-sleeved shirt, long
pants, socks, shoes
Short-sleeved shirt, long
pants, socks, shoes
Short-sleeved shirt, long
pants, socks, shoes
Test 2, July 2004
Subject 9/female,
five sessions
(295-476 min)
Subject 10/female,
three sessions
(406-438 min)
Subject threw a variety of clay items, including plates,
bowls, vases, and cups, on the pottery wheel.
Subject sculpted detailed designs into clay tiles and
plaques; also chipped small bits of excess clay off pieces
of art that had already been fired.
Short-sleeved shirt, short
pants, sandals
Short-sleeved shirt,
3/4-length pants, sandals
min = minute.
32
-------
Table 9. Hypothetical estimates of dermal dose
Body part
Clay load on skin
(mg/cm2) a
Skin area
(cm2)"
Fraction
uncovered
Absorbed dioxin
dose
(PgTEQ/d)c'd'e
Subject 1
Hands
Arms
0.38
0.15
970
2,406
1.0
0.5
Total
0.58
0.29
0.87
Subject 2
Hands
[2.01]
970
1.0
0.77
Subject 3
Hands
[0.51]
865
1.0
0.69
Subject 4
Hands
0.17
855
1.0
0.23
Subject 5
Hands
[2.61]
1,005
1.0
0.80
Subject 6
Hands
Arms
[9.25]
[2.99]
790
2,005
1.0
0.6
Total
0.63
0.95
1.58
Subject 7
Hands
0.26
785
1.0
0.33
Subject 8
Hands
[1.90]
715
1.0
0.57
33
-------
Table 9. continued.
Body part
Clay load on skin
(mg/cm2) a
Skin area
(cm2)"
Fraction
uncovered
Absorbed dioxin
dose
(PgTEQ/d)c'd'e
Subject 9
Hands
Arms
Lower legs
Feet
Face
[10.12]
[1.50]
[0.72]
0.26
0.03
857
2,265
2,161
1,151
374
1.0
0.75
1.0
1.0
1.0
Total
0.68
1.35
3.96
1.09
0.02
7.09
Subject 10
Hands
Arms
Lower legs
Feet
Face
0.20
0.04
0.11
0.03
0.04
783
2,271
2,095
1,109
368
1.0
0.9
0.1
1.0
1.0
Total
0.24
0.13
0.08
0.11
0.02
0.59
a All bracketed loads exceed monolayer of 0.5 mg/cm and were reduced to this value in absorption calculation.
b Skin area is for total body parts; for two-sided parts, it is the sum of right and left sides.
0 Absorption = skin load (mg/cm2-day) x skin area (cm2) x fraction uncovered x dioxin concentration in clay
(pg TEQ/g) x 10~3 mg/g x absorption fraction.
d All calculations assume dioxin concentration in clay = 162 pg TEQ/g and absorption fraction is 2.3% for feet and
legs, and 1.0% for hands, arms, and face.
e Results from Subjects 1 through 8 are based on one work session, from Subject 9 are based on average of five
sessions, and from Subject 10 are based on average of three sessions.
TEQ = toxic equivalent.
34
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• Mixing (Subject 2). Subject 2 was involved in the mixing and handling of dry clays and
furnace/kiln maintenance during the work session. This activity produced relatively large
hand loadings.
• Wedging and molding (Subjects 1, 3, 4, 5, 7, and 8). Wedging clay involves kneading
and hitting clay against a tabletop to purge air pockets from the clay. During the wedging
process, the clay is firm and dry as compared with clay used on the wheel. This activity
produced a wide range of hand loadings (from 0.17 to 2.61 mg/cm2).
• Sculpting (Subject 10). This involved sculpting activities on dry clay. At times, fine
detailing tools were used that involved very little contact with the clay, resulting in low
hand loading.
Table 10 shows the percent contribution to the dermal dose by body part for Subjects 9
and 10. Subjects 9 and 10 were tested in July 2004 and wore summer clothing, which allowed
exposure to their legs and feet. Leg and foot exposure accounted for 71% of the total dose for
Subject 9 and 33% of the total dose for Subject 10. This reflects the relatively large surface
areas and higher absorption fraction (due to longer exposure time) for these parts. The
uncovered portion of Subject 10's lower legs was only 10%, so the leg contribution to total dose
was much less than that of Subject 9. Facial exposures were low, accounting for only 0.2-4% of
total dose.
Table 10. Percent contribution to dermal dose by body part
Body part
Hands
Arms
Legs
Feet
Face
Percentage of dose
Subject 9 (wheel)
10
19
56
15
0.2
Subject 10 (sculpture)
41
22
14
19
4
35
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7.1.1. Clay Loads on Surfaces
The horizontal surfaces in ceramic art studios can have high dust loads resulting from air
deposition. Most clay on the hands of artisans probably results from direct contact with clay, but
some could also result from contact with surfaces. In the interest of exploring this issue, wipe
samples were collected from the work surface of each subject. The sampled surfaces were
porous concrete tabletops. The artisans involved in wedging used a nonporous plastic composite
surface. Table 11 shows the surface sampling results. The surface dust loads ranged from 0.2 to
7 mg/cm2, which are high compared with dust loads on floors in residences (i.e., 0.005 to 0.7
mg/cm2) (Lioy et al., 2002). The efficiency of transfers from surfaces to hands will vary
depending on the type of surface, type of residue, hand condition, force of contact, etc. Rodes et
al. (2001) conducted hand press experiments on particle transfer to dry skin and measured
transfers with central values of about 50% from hard surfaces. Table 11 shows that several of
the ratios of hand loads to surface loads exceed 50% by a wide margin. Subject 6 was working
on a wheel and clearly had hand loads resulting from direct contact with clay. Similarly,
Subjects 5 and 8 had very high hand loads that must have resulted from direct clay contact. The
other subjects had ratios ranging from 0.05 to 0.30, which are in the range that could result from
surface transfers. Observation of the subjects indicated that almost all contact with the work
surface also involved some contact with the clay. Therefore, the hand residues are most likely
derived from a combination of direct clay contact and transfers from surfaces.
Table 11. Comparing clay loads on surfaces to clay loads on hands
Subject
1
2
3
4
5
6
7
8
Clay loading on surface
(mg/cm2)
7.002
NA
2.966
0.572
0.774
0.238
1.206
0.419
Clay load on hand
(mg/cm2)
0.38
2.01
0.51
0.17
2.61
9.25
0.26
1.90
Ratio of hand load to
surface load
0.05
NA
0.17
0.30
3.4
38.9
0.22
4.5
NA = Nonartisan subject was not working at a surface during sampling, so this type of sample was not collected.
36
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7.1.2. Dermatologist Report
The dermatologist did not diagnose any serious skin health problems among the subjects.
Small abrasions and common skin conditions such as dryness and cracking, as the subjects
reported on the questionnaires, were noted, but changes in these conditions could not be detected
based on before and after observations.
7.2. INHALATION
Estimating the inhalation dose involved measuring particle concentrations in air and
modeling deposition to various regions of the respiratory system. Classroom exposures were not
estimated.
7.2.1. Particle Levels in Air
As described in Chapter 3, four different sampling techniques were used during the April
2003 tests to measure clay particle concentrations in air: two personal monitors and two area
monitors. The data from all four devices are shown in Appendices G and H. The Respicon™
personal air sampler normally would have been the best indicator of individual exposures, but
the blanks were high, resulting in a high detection limit and a high frequency of nondetects in the
data. Instead, the cascade impactor was chosen as the best indicator of daily exposure. Although
this is an area sampler, it was located near the subjects and the subjects were generally stationary
during the test. Thus, it should have been a reasonable indicator of individual exposures. Also,
the cascade impactor uses deposition collectors and gravimetric techniques to estimate air
concentrations; consequently, it is a more direct measurement technique than the other two
instruments (pDR-1000 and Climet®), which use light scattering to estimate particle
concentration. These optical devices provide a nearly continuous readout of concentration
levels, making them better suited to evaluating short-term fluctuations in particle levels rather
than long-term concentrations.
Only the cascade and Climet® monitors were used in the July 2004 tests. The instruments
were located even closer to the individuals, i.e., within 30 cm of their breathing zones. The data
were used in a fashion consistent with the April 2003 tests, i.e., daily exposures were based on
the cascade data and the Climet® was used to evaluate short-term fluctuations.
Table 12 presents the air data for each subject on the basis of the cascade measurements.
The MMADs were estimated by fitting the data to log-normal distributions (see the discussion in
Appendix B). Table 12 indicates that the range for total particulate matter is 0.084 to
0.99 mg/m3. Note that the upper end of this range is less than the Occupational Safety and
Health Administration (OSHA) standard for total particulates of 15 mg/m3 (OSHA, 2004).
37
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Table 12. Particle concentrations in air and mass median aerodynamic diameter
(MMAD) based on cascade impactor
Subject
1
2
o
J
4
5
6
7
8
9
10
MMAD dim)
26.9
44.6
18.5
25.0a
25.0a
20.2
13.0
26.7
32.6
16.0
Total concentration (mg/m3)
0.35
0.47
0.99
0.37
0.13
0.61
0.51
0.64
0.084
0.24
"Nondetects prevented calculation of the MMAD for these subjects; they were assumed equal to the average over
the remaining first eight subjects.
Subject 3's concentration was the highest because students were cleaning the floor near the area
samplers (see the discussion below). Subject 9's concentration was the lowest, resulting from a
relatively low activity level during the testing time period. Subject 5's concentration was also
low, likely because a steady breeze entered through an open window in the room in which
sampling was occurring. All of the other subjects had fairly similar concentrations. Subject 2
was the only one who changed room locations during the sampling period and the sampling
equipment was moved with him.
The two subjects using wheels (Subjects 6 and 9) had very different air exposures.
Because a great deal of water is used to moisten clay during wheel molding (the clay was
saturated with water and a pan of water was placed directly next to the artisans for their use), this
setting would not be expected to produce much clay dust, which was observed for Subject 9.
Subject 6, however, had fairly high air levels. Subject 6 was located near a classroom that, as
discussed below, had high activity levels. Therefore, this subject's high air levels may have been
associated more with the classroom activities than the wheel activities.
38
-------
Figure 4 shows the plot of concentration versus time (based on the Climet® CI-500 area
particle counter) for Subject 3, who worked in an area designated for graduate student work
adjacent to a large classroom. Approximately 50 minutes into the sampling session, about
20 students from the adjacent classroom began sweeping and wiping down the surfaces. This
activity continued for approximately 15 minutes and generated a significant cloud of dust.
Figure 4 shows particle levels began rising at about 50 minutes, peaked sharply at
60-70 minutes, and declined to low levels at about 80 minutes.
40
"B>30
o
c
o
o
_©
o
20
£10
•e
re
0
0
25
50 75
Time (min)
100
Figure 4. Real-time particle concentration for Subject 3 using the CI-500 particle
counter.
During two of Subject 10's sculpture work sessions, a small dog was present. The dog's
movement disturbed dust on the floor of the ceramics studio and, in turn, increased the particle
concentration. Figures 5 and 6 are the real-time traces for the Climet® monitor for the sculpting
work sessions during which the dog was present. The dog was present for the entire first
sculpting work session. This was reflected in the relatively constant variation in the particle
concentration throughout the work session. During the second sculpting work session, the dog
did not arrive until 138 minutes into sampling. Note the increase in overall particle
concentration and increase in variability of particle concentration after arrival of the dog. The
presence of a dog in the studios and classrooms is not likely to be a common occurrence,
39
-------
60
120 180 240 300
360
Figure 5. Sculpture Session 1 with dog present.
Figure 6. Sculpture Session 2 with dog present.
40
-------
especially during the regular school year. Therefore, the particle concentrations during the work
sessions when the dog was present (1 and 2) were not used to estimate the exposures for this
subject. It should be noted, however, that pets, which may be present in many ceramic art
studios, can increase the suspended dust levels and spread dust to other areas.
7.2.2. Inhalation Dose
Table 13 shows the absorbed dose in various regions of the respiratory system for all
10 subjects. The total inhalation doses ranged from 0.006 to 0.09 pg TEQ/d with an average of
0.04 pg TEQ/d. Most particle deposition was found to occur in the ET region. Appendix B
presents the modeling to support these estimates.
Table 13. Hypothetical estimates of inhalation dose
Subject
1
2
3
4
5
6
7
8
9
10
Absorbed dose (pg TEQ)a
ETb
0.032
0.033
0.082
0.028
0.012
0.054
0.049
0.048
0.005
0.022
TBb
0.001
0.001
0.002
0.001
0.000
0.001
0.001
0.001
0.000
0.001
PIT
0.003
0.003
0.010
0.002
0.001
0.004
0.006
0.003
0.001
0.002
Total
0.035
0.036
0.094
0.031
0.014
0.059
0.057
0.052
0.006
0.025
aDose calculated using procedures in Appendix B for nasal breathing; subject exposure concentrations from
Appendix H; 4-hour exposure duration and dioxin concentration of 162 pg TEQ/g clay.
b Absorption fraction of 0.3 assumed, since these regions rapidly clear into the gastrointestinal tract.
0 Absorption fraction of 0.8 assumed, in part, due to slow particle clearance from this region.
ET = extrathoracic; PU = pulmonary; TB = tracheobronchial; TEQ = toxic equivalent.
41
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The inhalation exposure estimates assume that no respiratory protection was used.
Generally, this was true, however, Subject 2 used a dust mask while pouring powdered clay into
a mixer for clay preparation. This reduced his inhalation exposures relative to levels reported
here.
7.2.3. Classroom Exposure
Estimating student exposures in a classroom setting was not an objective of this study.
However, some insight on this issue can be gained from the data for Subjects 1, 3, and 6. These
subjects performed their clay activities adjacent to the undergraduate classroom during times
when undergraduate classes of 20-25 students were participating in clay-related activities. The
area particle samples collected for these subjects are generally representative of the inhalation
exposure of students in those classes. As discussed above, students in this class swept the floor
during Subject 3's testing period, producing elevated particle concentrations for about
30 minutes.
7.3. INGESTION
The ingestion dose was calculated by assuming that all deposited material on the
surrogate food and beverage samples was ingested. As Table 14 shows, clay deposition onto the
food and beverage samples reached detectable levels in only 5 out of 16 total samples. The
deposition amounts for the nondetects were assumed to equal half the detection limit. The
resulting ingestion doses ranged from 0.03 to 0.1 pg TEQ/d. The field technicians did not
observe hand-to-mouth activities for any of the subjects. Also, none of the subjects ate food or
smoked without first washing the clay from their hands. No deposition samples were collected
for Subjects 9 and 10.
7.4. TOTAL DOSE
Table 15 lists the hypothetical estimates of total dioxin dose derived by summing across
exposure pathways for each subject. The total doses ranged from 0.32 to 7.10 pg TEQ/d with an
average of 1.44 pg TEQ/d. Table 16 shows the percentage contribution of each exposure
pathway to the total dose of each subject. Dermal absorption is the major contributor to total
dose for all subjects, exceeding 67% for all subjects. Ingestion and inhalation contribute similar
amounts, generally in the range of 1-20%. Table 17 shows the dose estimates by activity. The
highest total doses were associated with wheel activities.
42
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Table 14. Clay deposition and hypothetical estimates of ingestion dose
Subject
1
2
3
4
5
6
7
8
Clay deposited onto
food (mg)
0.71
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Table 15. Hypothetical estimates of total dioxin dose (pg TEQ/d)
Subject
1
2
3
4
5
6
7
8
9
10
Mean (SD)
Median
Minimum
Maximum
Estimated dioxin dose (pg TEQ/d)
Inhalation
0.035
0.036
0.094
0.031
0.014
0.059
0.057
0.052
0.006
0.025
0.041 (0.025)
0.036
0.006
0.094
Ingestion
0.07
0.03
0.03
0.05
0.03
0.03
0.1
0.09
NM
NM
0.05 (0.03)
0.04
0.03
0.10
Dermal absorption
0.87
0.77
0.69
0.23
0.80
1.58
0.33
0.57
7.09
0.59
1.35(2.05)
0.73
0.23
7.09
Total
0.97
0.84
0.81
0.32
0.84
1.67
0.49
0.71
7.10
0.62
1.44(2.02)
0.82
0.32
7.10
NM = not measured; SD = standard deviation; TEQ = toxic equivalent.
44
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Table 16. Percent contribution to total dioxin dose
Subject
1
2
3
4
5
6
7
8
9
10
Percentage of dose
Inhalation
3.6
4.3
11.5
9.9
1.6
3.5
11.7
7.4
0.1
4.1
Ingestion
7.2
3.6
3.7
15.8
3.6
1.8
20.6
12.7
NM
NM
Dermal absorption
89.2
92.1
84.7
74.3
94.8
94.7
67.7
79.9
99.9
95.9
NM = not measured.
45
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Table 17. Dose estimates by activity
Activity
Wedging and
molding
Mixing
Wheel
Sculpting
Subject
1
O
4
5
7
8
2
6
9
10
Inhalation
dose
(pg TEQ/d)
0.035
0.094
0.031
0.014
0.057
0.052
0.036
0.059
0.006
0.025
Ingestion
dose
(pg TEQ/d)
0.07
0.03
0.05
0.03
0.1
0.09
0.03
0.03
NM
NM
Dermal
dose (pg
TEQ/d)
0.87
0.69
0.23
0.80
0.33
0.57
0.77
1.58
7.09
0.59
Total dose
(pg TEQ/d)
0.97
0.81
0.32
0.84
0.49
0.71
0.84
1.67
7.10
0.62
NM = not measured; TEQ = toxic equivalent.
46
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8. MONTE CARLO SIMULATION OF THE EXPOSURE DATA
Chapter 7 presented hypothetical dose estimates for each subject, assuming that all were
using typical amounts of ball clay with average dioxin levels. In this chapter, Monte Carlo
simulations are used to explore the doses that could occur in a broad population of artists with a
wide range of behaviors using ball clay with differing levels of dioxin. The simulations are
based largely on the range of activities observed during this study. As noted in the Introduction,
the OSU studio has a modern ventilation system and is well maintained. Therefore, these
simulations are most representative of how doses may vary in similar facilities. A wider range of
results would be expected across all types of ceramic art facilities. Appendix I provides a
detailed outline of the Monte Carlo procedure.
The general strategy for selecting input value distributions was as follows. The
distribution of skin surface areas across adults in the general population was assumed to be
log-normal with mean and standard deviation from the Exposure Factors Handbook (U.S. EPA,
1997). Similarly, the dioxin concentration in clay was assumed to have a log-normal distribution
with mean and standard deviation from Ferrario et al. (2007, 2004). The rationale for choosing
log-normal distributions was that physiological parameters and environmental media
concentrations are commonly found to have these types of distributions. The remaining
exposure factor parameters were based on observations from this study. These were generally
assumed to have triangular distributions with ranges based on minimum and maximum values
and peaks based on means. The rationale for choosing a triangular distribution was that (1) the
small sample sizes associated with the study observations prevented fitting the data to standard
distributions and (2) it reflected the likelihood that a central value would occur most often. In
some cases (e.g., clay load on face), only two data points were available and a uniform
distribution was assumed. Table 18 lists the distributions assumed for all input variables.
Crystal Ball 7 software was used to conduct 1,000 trial simulations. For each simulation
trial, a set of parameter values was obtained by randomly sampling the parameter distributions
shown in Table 18 and then computing the dioxin dose. Chapter 5 presents the equations used to
calculate the dose. All simulation trials first select a set of values for the dioxin concentration in
ball clay, the fraction of ball clay in the blend used by the artist, gender, and the exposure
duration. Table 18 shows the general parameters. The simulation then calculates the dose from
the dermal, inhalation, and ingestion pathways, as discussed below:
• Dermal. The simulation was designed to first select a total body surface area from
log-normal distributions for females and males. Subsequently, skin surface areas for
47
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Table 18. Monte Carlo simulation input parameters and sampling distributions
Parameter
Distribution
Basis
General parameters
Dioxin concentration in ball clay
(pgTEQ/g)
Fraction of ball clay in blend
Exposure duration (hr/d)
Gender selector
Log-normal (mean = 808,
SD = 318)
Triangular (0, 0.2, 1.0)
Triangular (1,4, 10)
Uniform (0, 1.0)
Ferrario et al. (2007, 2004) (n = 21)
Data in this study (w = 10)
Judgment and data from this study (n = 8)
Used to select male 50% of time, and female
50% of time
Dermal absorption parameters
Total body surface area for
males (cm2)
Total body surface area for
females (cm2)
Clothing selector
Clay load on hand (mg/cm2)
Clay load on arm (mg/cm2)
Clay load on leg (mg/cm2)
Clay load on feet (mg/cm2)
Clay load on face (mg/cm2)
Log-normal (mean= 19,700,
SD = 1,900)
Log-normal (mean = 17,300,
SD = 1,680)
Uniform (0, 1.0)
Triangular (0.1, 3.0, 10)
Triangular (0.04, 0.35, 3.0)
Uniform (0.1, 0.70)
Uniform (0.03, 0.3)
Uniform (0.03, 0.04)
Exposure Factors Handbook (U.S. EPA,
1997) (n = 32)
Exposure Factors Handbook (U.S. EPA,
1997) (n = 57)
This is applied using Table 19. Judgment and
data from this study (n = 8)
Range and mean based on observations from
this study (n = 10)
Data in this study (n = 4)
Data in this study (n = 2)
Data in this study (n = 2)
Data in this study (n = 2)
Ingestion parameters
Clay load on food (mg)
Clay load on beverage (mg)
Triangular (0.3, 0.7, 1.66)
Triangular (0.3, 0.5, 0.72)
Range and mean based on observations from
this study (n = 8)
Range and mean based on observations from
this study (n = 8)
Inhalation parameters
Particle concentration in air
(mg/m3)
Median particle size (um)
Lung parameters
Fraction of time engaged in light
vs. moderate exertion.
Breathing type
Triangular (0.08, 0.44, 0.99)
Triangular (13, 25, 45)
Male— 50%; female— 50%
Uniform (0, 1.0)
Oronasal— 13%; nasal— 87%
Range and mean based on observations from
this study (n = 10)
Judgment and data from this study (n = 10)
Based on general population
Judgment
Brown (2005)
hr = hour; d = day; SD = standard deviation; TEQ = toxic equivalent.
48
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individual body parts were calculated by multiplying the total surface area by the average
percentage of total surface area. These percentages were obtained from U.S. EPA, 1997:
hands—5.2%; arms—14%; legs—31.8%; feet—6.8%; and face—2.5% (assumes face
area equals one-third of head area). This approach ensures that simulation trials have
realistically matched body part areas. Since the body part area calculations give total
areas, a fraction unclothed was used to reduce this to the exposed area. These fractions
were based on four clothing scenarios as shown in Table 19. These clothing scenarios
were based on questionnaire responses and judgment about typical apparel for a moderate
climate. A clothing scenario was selected randomly for each simulation trial according to
the time fractions shown in Table 19. Distributions were also assumed for the clay loads
on skin. These were assumed to be spread uniformly over the entire unclothed area. As
discussed in Section 5.1, dermal absorption was assumed to be limited to the monolayer
that was held constant at the median value of 0.5 mg/cm2 (the impact of changing this
value is discussed as an uncertainty issue in Chapter 9). Finally, the absorption fractions
(as presented in Section 5.1) were applied to derive the absorbed dose from exposed body
parts and then summed to derive total dermal dose.
• Inhalation. Section 5.2 summarizes and Appendix B presents the procedures used to
calculate the inhalation dose. Distributions were used to represent the variability in total
particulate concentration in air and median particle size (see Table 18). Breathing was
assumed to be either oronasal (13%) or nasal (87%), based on Brown (2005). Inhalation
parameters (see Appendix B) were based on gender. The rate of breathing was
determined by the fraction of time engaged in light versus moderate exertion. These
fractions were varied randomly from 0 to 1.0 using a uniform distribution. Depositions to
various parts of the respiratory system were modeled as described in Appendix B,
multiplied by the absorption fraction, and summed to derive the total inhalation dose.
• Ingestion. The variability in ingested dose was simulated using distributions for the
levels of clay in the food and beverages as shown in Table 18. As discussed in
Section 5.3, all deposited material was assumed to be ingested.
Two Monte Carlo stimulations were conducted. The first simulation was designed to
evaluate the influence of clay use only. Accordingly, it was conducted using the distributions for
dioxin concentration in the clay and the fraction of ball clay in the blend used by the artists. All
other inputs were held constant at their central values. The summer clothing scenario was used
(i.e., short-sleeved shirt, short pants, sandals). This simulation produced a mean total dose of
14 pg/d, median of 12 pg/d, and 90th percentile of 28 pg/d. These results are best compared to
the hypothetical dose estimate for Subjects 9 and 10 (see Chapter 7) because they wore summer
clothing matching the simulation assumption. Subject 9 had a dose estimate of 7.1 pg/d,
corresponding to about the 25th percentile of the simulation. Subject 10 had a dose of 0.62 pg/d,
corresponding to about the 2nd percentile of the simulation. This simulation suggests that clay
49
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Table 19. Clothing scenarios based on questionnaire responses
Clothing scenario
Long-sleeved shirt, long pants, shoes
Short-sleeved shirt, long pants, shoes
Short-sleeved shirt, short pants, shoes
Short-sleeved shirt, short pants, sandals
Time fraction
0.2
0.6
0.1
0.1
Fraction unclothed
Arms
0
0.67
0.67
0.67
Legs
0
0
0.67
0.67
Feet
0
0
0
1.0
choice alone can account for a wide range of exposures with the potential to elevate exposures
above the hypothetical estimates for the 10 subjects.
The second simulation used the distributions for all parameters as shown in Table 18.
This simulation produced a mean total dose of 6.4 pg/d, median of 3.5 pg/d, and 90th percentile
of 14.8 pg/d. The standard deviation (8.43) exceeds the mean indicating that the results have a
wide spread. The hypothetical dose estimates of most subjects would have corresponded to low
percentiles of this simulation except Subject 9 (75th percentile). Table 20 shows the simulation
results for each pathway. The simulation means for each pathway exceeded by 3 to 4 times the
pathway means of the hypothetical dose estimates for the 10 subjects. As observed during the
field study, the ingestion and inhalation doses are much smaller than the dermal dose. The total
dose is plotted as a frequency diagram in Figure 7 and as a cumulative probability diagram in
Figure 8. Figure 7 shows a highly skewed distribution with a peak around 2 pg TEQ/d and a
long tail to the right extending to about 28 pg TEQ/d. A detailed report showing all inputs and
outputs for this simulation is presented in Appendix J.
A sensitivity analysis was performed using the Crystal Ball 7 software. Each input
parameter was evaluated using contribution to variance. Figure 9 shows the results of this
analysis applied to the total dose; it shows that the fraction of ball clay in the blend contributed
most to variance (45.2%), followed by clothing selected (36.2%) and dioxin concentration
(13.8%). Figures 10, 11, and 12 show similar sensitivity analyses were also conducted for each
exposure pathway separately.
Overall, the simulation suggests that higher exposures than those reflected in the
hypothetical dose estimates of the 10 subjects may occur. This results from the skewed input
distributions, which generally have long right-hand tails. Also 6 of the 10 subjects had hand
50
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Total Dose (pg/d)
0.12 -
0.10 -
120
100
0.00 4.00
12.00 16.00 20.00 24.00 28.00
Figure 7. Frequency distribution of total dose (pg TEQ/d) based on Monte
Carlo simulation.
Table 20. Descriptive statistics of dioxin doses from ball clay use, based on a
Monte Carlo simulation
Pathway
Dermal dose
(pg TEQ/d)
Ingestion dose
(pg TEQ/d)
Inhalation dose
(pg TEQ/d)
Total dose
(pg TEQ/d)
Mean
6.2
0.14
0.11
6.4
Standard
deviation
8.3
0.10
0.13
8.4
Median
3.2
0.11
0.07
3.5
90th percentile
14.4
0.26
0.26
14.8
pg = picogram; TEQ = toxic equivalent.
51
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Total Dose (pg/d)
1.00 —
0.80 -
1,000
800
600
400
200
0.00
4.00 8.00 12.00 16.00 20.00 24.00 28.00
Figure 8. Cumulative probability distribution of total dose (pg TEQ/d) based
on Monte Carlo simulation.
52
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Sensitivity: Total Dose (pg/d)
0.0% 12.0% 24.0% 36.0% 48.0%
i i i i i
Fraction of ball clay in blend
clothing selector
Dioxin cone in ball clay (p...
13.8%
?.1%
•ft.
Clay load on arm (mg/cm2) 2.1
Total Body Surface Area Fem... 1.3
Gender Selector 0.4%
Particle Concentration in A... -Q.:
Exposure Duration (hr/d) 0.3%
Total Body surface Area Mai... 0.2%
Clay load on face (mg/cm2) 0.1 %
Clay load on food (mg) -0.
Clay load on feet (mg/cm2) O.d%
Figure 9. Sensitivity analysis based on percent contribution to variance for
total dose.
53
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Sensitivity: Total Dermal Dose
0.0% 13.0% 26.0% 39.0% 52.0%
Fraction of ball clay in blend
clothing selector
Dioxin cone in ball clay (p...
Exposure Duration (hr/d) I 1.0%
Clay load on beverage (mg) -O.|%
Gender Selector
Clay load on arm (mg/cm2)
Total Body surface Area Mai...
0.5%
o.:
Clay load on face (mg/cm2) -0.1 %
Breath Selector -0.1%
Clay load on leg (mg/cm2)
0.1%
Total Body Surf ace Area Fern... O.C%
Figure 10. Sensitivity analysis based on percent contribution to variance for
dermal dose.
54
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Sensitivity: Ingestion Dose (pg/d)
0.0% 20.0% 40.0% 60.0%
Fraction of ball clay in blend
Dioxin cone in ball clay (p...
Clay load on food (mg)
Activity selector
Total Body Surface Area Fern...
MMAD (urn)
Total Body surface Area Mai...
Breath Selector
Clay load on hand (mg/cm2)
clothing selector
Clay load on leg (mg/cm2)
Clay load on face (mg/cm2)
N-^^^
4.9%
b.2%
-0.
0.1
lo.
o.c
o.c
o.c
L
1%
%
%
%
%
%
%
%
1
Figure 11. Sensitivity analysis based on percent contribution to variance for
ingestion dose.
55
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Sensitivity: Inhalation Dose
0.0% 15.0% 30.0%
Fraction of ball clay in blend
Particle Concentration in A...
Exposure Duration (hr/d)
Dioxin cone in ball clay (p...
Activity selector
Gender Selector
MMAD (urn)
Clay load on face (mg/cm2)
Breath Selector
Total Body Surface Area Fern...
Clay load on feet (mg/cm2)
Total Body surface Area Mai...
Figure 12. Sensitivity analysis based on percent contribution to variance for
inhalation dose.
exposure only, and the simulation uses a range of clothing that will result in more skin exposure
in most trials.
Many of the input distributions used in this simulation were based on very limited data or
judgment. A number of the distributions were based on data from this study, and the degree to
which the study subjects represented a broader population of artists is unknown. Similarly, the
degree to which the studio conditions observed in this study represent a broader set of studios is
unknown. The simulation should be interpreted as a preliminary indication of how to extrapolate
the study results to a broader population of artists working in well maintained academic
facilities.
56
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9. UNCERTAINTY
This chapter discusses general uncertainty issues and uncertainties related to the three
exposure pathways: dermal, inhalation, and ingestion.
9.1. GENERAL UNCERTAINTY ISSUES
The sensitivity analyses showed that the dioxin concentrations in clay and the fraction of
ball clay used account for a large part of the overall variance in the exposure estimates. Thus, it
is important to consider the uncertainty in the assumptions regarding these two parameters.
The dioxin levels in ball clay were assumed on the basis of the study by Ferrario et al.
(2007, 2004). An important uncertainly issue is whether the ball clay sampled by Ferrario is
representative of the ball clay used in the studio and by the broader community of ceramic
artists. Ferrario et al. (2007, 2004) explained that the major mining companies market a total of
32 ball clay products of which 13 were sampled. Although marketing data were not available to
do true statistical sampling, a ceramics expert confirmed that the most commonly used ball clays
were included in this study. The samples were collected from 22.7-kg (50-pound) bags in the
same form as delivered to ceramic studios. Four of the 21 samples analyzed by Ferrario et al.
(2007, 2004) matched exactly the primary type of ball clay used in the OSU ceramics studio.
As explained earlier, ceramic artists use a wide range of clay blends with ball clay
contents ranging from 0 to 100%. The hypothetical dose estimates were based on the assumption
of 20% ball clay in the blend, which is the average fraction used by the 10 subjects in this study.
It is unknown how representative this is of the wider population of ceramic artists. The ball clay
fraction assumption may also affect other exposure factors. For example, it could affect how
much clay adheres to skin. Soil adherence to skin has been shown to be influenced by moisture
content and particle size. Ball clay is similar to other clays in terms of these properties. The
primary way that ball clay is unique from other clays is its high plasticity. It is not known how
this property would affect skin adherence.
9.2. DERMAL EXPOSURE UNCERTAINTIES
9.2.1. Absorption Fraction
A fraction absorbed approach is used to estimate dermal absorption based on current
Agency guidance. Appendix D presents an alternative approach using a more mechanistic
model. This model predicts an absorbed dose that is about three times higher than the fraction
absorbed approach. The mechanistic model appears very promising but it has had limited
testing, and it is not yet clear whether it provides more realistic estimates.
57
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The exposures in the studio are caused by clay, but the dermal absorption fraction is
derived from soil experiments. An important uncertainty issue is whether clay has properties
that differ significantly from soil and consequently make the soil-derived absorption estimates
invalid for clay. The soil used by Roy et al. (1990) was 16.7% clay. This fraction of the soil
should have properties similar to those of the studio clay. The organic carbon content of the clay
is approximately the same as that of the low organic soil used by Roy et al. In terms of particle
size, clays typically have lower particle sizes than soil and would be expected to more strongly
sorb organic contaminants (e.g., dioxins) as compared with normal soils, all other factors being
equal. As discussed in Chapter 5, commercial ball clay specifications report a median particle
size of about 0.75 jim, which is smaller than that of the Roy et al. (1990) soil (median diameter
of about 10 |im). The particle sizes measured in the studio air had median diameters ranging
from 8 to 27 jim, which are larger than those of the soils used by Roy et al. (1990). This may be
explained by the bonding of particles caused by the addition of water to the clay or the firing
process, which fuses particles. Thus, it appears that the particle size of the soil used by Roy et al.
falls within the range present in the studio.
The residues found on the skin are likely to vary with body location and activity. For
example, a wheel operator will have hand residues similar to the raw clay but the residue on the
face may more resemble room dust. The dermal absorption from these different types of
residues may vary. No information is currently available to account for these types of
differences.
The studies on dermal absorption of dioxin from soil by Roy et al. and other investigators
have exclusively used TCDD. It is important to consider whether results for TCDD can be
extrapolated to the other dioxin congeners found in clay. As mentioned previously, Table 21
lists the compounds of concern in the clay are the tetra- through octa-CDD congener groups.
This table indicates that molecular weight and the octanol-water partition coefficient (Kow)
increase with chlorine substitution. Molecular weight and Kow have been identified as key
chemical properties affecting dermal absorption (U.S. EPA, 1992). These properties also relate
to how tightly bound chemicals are to soils and their release kinetics. The higher chlorinated
congeners would be released from soils more slowly and permeate skin more slowly than TCDD.
Thus, use of TCDD experiments to represent the penta-octa dioxin congeners found in clay
probably leads to some overestimates of dermal absorption, but it is uncertain to what degree.
A related question is whether TCDD-derived dermal absorption values can be applied to
TEQs. Table 21 shows only about 9% of the TEQ in processed clay is derived from TCDD. The
TEFs used to determine TEQs discount the hepta- and octa- congeners much more
58
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Table 21. Physical properties of dioxin congeners and concentration in
processed clay
Congener
TCDD
PeCDD
HxCDD
HpCDD
OCDD
Molecular
weight
322
356.4
390.9
425.3
459.8
Log KoWa
6.1 to 7.1
6.2 to 7.4
6.85 to 7.8
8.0
8.2
Concentration
in processed
clayb
(Pg/g)
76
374
2,341
9,780
254,000
Total
Concentration in
processed clayb
(pg TEQ/g)
76
374
234
97.8
25.4
808
% of total
TEQ
9
46
28
12
3
aU.S. EPA (2000).
b Average values from Ferrario et al. (2007, 2004).
HpCDD = heptachlorodibenzo-p-dioxin; HxCDD = hexachlorodibenzo-p-dioxin; Kow = octanol-water partition
coefficient; OCDD = octachlorodibenzo-p-dioxin; PeCDD = pentachlorodibenzo-p-dioxin; pg = pictogram;
TCDD = tetrachlorodibenzo-p-dioxin; TEQ = toxic equivalent.
than the tetra- and penta- groups. The overestimates of dermal absorption for the higher
chlorinated congeners due to their higher molecular weights and Kow values will be compensated
to some extent by the large discounts during the TEQ calculation and thus make extrapolation of
dermal absorption data from TCDD to TEQs more reasonable.
The amount of chemical that is dermally absorbed has been shown to be related to skin
thickness and whether the skin is dead or alive (U.S. EPA, 1992). Skin thickness varies across
body parts and across individuals. No information was found that could be used to account for
these factors in this analysis.
Another source of uncertainty in the dermal absorption estimates concerns the condition
of the skin. Some of the artists reported dryness and cracking of skin due to clay activities.
These conditions were observed by the dermatologist, but correlation with clay activities could
not be confirmed. Wheel operations involve work with wet clay which would hydrate the skin.
The abrasive nature of this work could also reduce the thickness of the stratum corneum which is
considered the primary barrier to permeation (U.S. EPA, 1992). It is possible that these
conditions would allow more dermal permeation than normal intact skin. However, any
59
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increased permeation would be limited to the surface areas associated with the damaged skin.
Exposure could also occur through the eyes where absorption would likely be greater than intact
skin. This would be limited to particles that contact the eye surface which is probably minimal.
9.2.2. Monolayer
As discussed in Section 5.1, the monolayer calculation is also an important source of
uncertainty for the dermal absorption estimates. The monolayer load is estimated on the basis of
the median particle size and assumption of ideal packing. Actual monolayers will be composed
of a mix of sizes with complex packing that could result in loadings higher or lower than this
theoretical estimate. It is also uncertain how to best characterize the size distribution of particles
on the skin. The particles in the original clay product have a median particle size of about 0.5 to
1.0 jim, and the airborne particles have medians ranging from 8 to 27 jim. The particles on the
skin could more closely resemble either the airborne particles or the clay particles, depending on
the deposition mechanism. Accordingly, particle sizes of the clay residues on skin could vary
widely, with medians ranging from 0.5 to 27 jim. For purposes of the central exposure
estimates, the geometric mean of this range was assumed, i.e., 3.7 jim. This implies a monolayer
load of 0.5 mg/cm2. The monolayer loads corresponding to the upper and lower ends of the
particle size range are 0.07 to 3.7 mg/cm2. This uncertainty is dampened in the dose estimate as
a result of the assumption that absorption occurs from only the monolayer. This dampening is
especially strong for low-exposure subjects. For example, the dose estimates for Subject 4 (who
had the lowest dermal exposure) corresponding to the low and high ends of the monolayer load
range would be 0.1 and 0.23 pg TEQ/d. Thus, a 37-fold variation in monolayer load resulted in
only a 2.3-fold variation in dose. The dampening is less (but still significant) for Subject 9 (who
had the highest dermal exposures). For this subject, the doses corresponding to the low and high
ends of the monolayer load range would be 1.1 and 15.8 pg TEQ/d, respectively. While the
monolayer load assumption has a reduced impact on absorbed dose, it remains an important
uncertainty.
9.2.3. Exposure Under Clothing
The peer reviewers of this study highlighted the possibility of under clothing exposure as
an important uncertainty issue (Eastern Research Group, 2008). Kissel et al. (1998)
demonstrated that clothing can reduce dermal exposure to soil during activities such as planting,
pipe laying and play. However, Kissel's study and others (Fenske, 1988; Fenske et al., 1990;
Raheel, 1991; Kawar et al., 1978) have shown that the clothing is not 100% effective in
preventing dermal exposure. Under clothing exposure can result from both particle penetration
through fabric and direct deposition of particles from air that circulates under loose fitting
60
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clothing. The amount of under clothing exposure depends on the particle characteristics,
clothing type, body location, and individual behavior. Driver et al. (2007) derived clothing
penetration factors from a large exposure database for pesticide handlers. This analysis
suggested a median penetration factor of 10%. No studies were found which were specific to
ceramic artists or clay penetration through clothing. Given the lack of data specific to ceramic
artists, the present study has assumed that any exposure occurring under clothing would be
negligible compared to the amount occurring on unclothed areas. The uncertainty associated
with this assumption is evaluated here using the data collected for Subjects 9 and 10.
Subjects 9 and 10 wore short-sleeved shirts and short pants. The skin surface areas
covered by these articles of clothing were estimated using surface area data presented in U.S.
EPA, 1997. For both subjects, the surface area covered by their shirts is estimated to be half of
the trunk (0.5 x 35% = 17.5% of total body surface area) and 25% of the arms (0.25 x 14%
= 3.5% of the total body area) for a total of 21% (17.5% + 3.5%) of the total body surface area.
Subject 9 wore shorts covering about half of her legs, so the surface area covered by her shorts is
estimated as half of the trunk (0.5 x 35% = 17.5% of total body surface area) plus one-half of the
legs (0.5 x 32% = 16% of total body area) for a total of 33.5% (17.5% + 16%) of the total body
surface area. Subject 10 wore short pants covering about 75% of the legs, so the surface area
covered by her pants is estimated as half of the trunk (0.5 x 35% = 17.5% of total body surface
area) plus 75% of the legs (0.75 x 32% = 24% of total body area) for a total of 41.5% (17.5% +
24%) of the total body surface area.. Both Subjects are assumed to have a total surface area of
17,000 cm2 which is the mean for adult females.
The clay load on the pants is assumed to match the load measured on the lower legs and
the load on the shirt is assumed to match the load measured on the arms. It is assumed that 10%
of the clothing load penetrates to the skin, based on Driver et al. (2007). Based on these
assumptions, the doses occurring from 24-hour exposures under clothing are estimated as 3.5 pg
TEQ/d for Subject 9 and 0.53 pg TEQ/d for Subject 10 (see Table 22). These doses equal 50%
of the dose from the unclothed area for Subject 9 and 58% of the dose from the unclothed area
for Subject 10. These estimates are uncertain, but suggest that exposure under clothing can be
important to consider and should be explored further in future research.
9.3. INHALATION UNCERTAINTIES
Data from the cascade sampler were used to estimate inhalation exposures. These data
were considered to be the most reliable because no samples were below detection limits and the
sampler uses a direct measurement method. The cascade, an area sampler, was located as near
the subject as possible but normally would not represent an individual's exposure as accurately
61
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Table 22. Exposure under clothing
Subject 9
Subject 10
Clothing
Shirt
Pants
Shirt
Pants
Surface area
covered
(cm2)
3,570
5,700
3,570
7,050
Clothing
load
(mg/cm2)
1.50
0.72
0.04
0.11
Skin load
under
clothing
(mg/cm2)
0.15
0.072
0.004
0.011
Absorbed
dose (pg
TEQ/d)
2.0
1.5
0.05
0.3
TEQ = toxic equivalent.
TM
as a personal air monitor. Unfortunately, the data from the Respicon personal monitor were
dominated by nondetects and could not be used. The limited Respicon™ data that were above
detection limits generally indicated higher levels than the cascade, suggesting that personal
exposures may have been higher than those detected by the area monitor. Accordingly, use of
the cascade data may have resulted in underestimates of inhalation exposures.
As discussed in Chapter 7, increases in suspended dust levels were associated with
sweeping and the presence of a dog. It is likely that similar effects could be caused by other
activities such as children playing or vacuuming. A small study, such as this one, cannot capture
the broad range of activities and associated dust levels that may occur in a ceramic art studio.
This study estimated dioxin inhalation on the basis of particulate levels. Additional
inhalation exposure is likely to occur via vapors. Franzblau et al. (2008) conducted a follow-up
study to a large survey of dioxin levels in blood. The highest levels found in the survey were for
an individual who conducted ceramic art activities in her home over thirty years. The study
presents the hypothesis that inhalation of dioxins volatilized from an unvented kiln in her home
was the dominant route of exposure. No measurements could be made to confirm the relative
importance of the possible exposure pathways since the ceramic work was no longer being
conducted and the authors recommended further investigation to confirm their hypothesis. The
kilns at the OSU studio are well vented and therefore likely to be a less important source of
exposure. Further thoughts on the potential for vapor inhalation at the OSU studio are presented
below:
62
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• Under equilibrium conditions at room temperature, about half of the TCDD is partitioned
to particulate and rest is in vapor phase. As chlorination increases, the fraction
partitioned to particulates increases, with PeCDD (dominant contributor to TEQs in ball
clay) over 80% and OCDD almost 100% in particulate phase (U.S. EPA, 2004). So
under equilibrium conditions at room temperature, exposure to dioxin TEQs in vapor
phase would be less than half of dioxin particulate exposure.
• The dioxins in the clay will be vaporized during kiln operations. The OSU studio has
6 kilns fired with natural gas and 9 electric kilns. The kilns are generally heated slowly
to a maximum temperature of about 1,200°C (2,200°F) which is comparable to
commercial incinerators and sufficient to destroy dioxins. Therefore, vapor releases are
of most concern during the initial warm-up phase. The OSU kilns are located in 2 rooms
which are isolated from classrooms and other areas frequented by the students. An
extensive ventilation system is used with hoods located over all kilns except one small
electric unit. Any vapors which escape the kilns would be expected to return to room
temperature equilibrium with particles after transport away from the kiln.
9.4. INGESTION UNCERTAINTIES
The only ingestion pathway quantitatively evaluated in this study was direct ingestion of
clay deposited from the air onto food items. This was estimated by measuring deposition on to
surrogate food/beverage samplers over the testing period (1-2 hours). Two uncertainties
associated with this approach are discussed below:
• Deposition area—An 85 mm diameter (area = 57 cm2) quartz fiber filter was used to
simulate a small sandwich, cookie, bagel or other small snack item. A medium-sized
hamburger bun has a surface area of approximately 62 cm2 and a standard piece of bread
has an area of approximately 100 cm2. So larger snack items could have an area twice
the sampler size. A 125-mL jar (diameter of about 6 cm, area = 28 cm2) filled with
deionized water was used to simulate a beverage such as coffee or soda. The diameter of
the 125-mL jar closely matches that of a typical soda can. Coffee cups have diameters of
70 to 80 mm and a surface area which is about twice that of the 125-mL jar. Thus,
food/beverage items with higher deposition areas could increase ingestion amounts by
over twice the measured values.
• Surface load—Wipe samples were collected from surfaces near the work area of each
subject. These loads ranged from 0.2 to 7 mg/cm2. The maximum clay loading on the
food was 1.66 mg or 0.03 mg/cm2. Thus, the surface loads were much higher than the
food loads. This is likely due to the location of the food samplers which were placed
outside of the immediate work area at a location that the subjects indicated they would
normally place foods or beverages. If food was placed near the work areas, deposition
could increase by 10 times or more than the measured levels.
63
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Clay ingestion may also occur via hand-to-food transfers. Snack foods such as potato
chips, cookies, sandwiches, etc are typically eaten by hand. If hands are not washed prior to
eating, clay on hands can be transferred to the food items and subsequently ingested. While this
behavior may be common, it was not observed during this study. Accordingly, it is not included
in the primary exposure assessment of this study. However, some idea of the possible
importance of this pathway can be evaluated as follows. Hand contact with food is primarily
limited to the fingertips which are assumed to equal 25 cm2 (calculated as 5% of an average adult
male hand—500 cm2—U.S. EPA, 1997). Clay loads on hands measured 0.17 to 10.12 mg/cm2.
If 50% of the clay on fingertips are transferred to the food, then 2 to 125 mg could be ingested.
Additional ingestion could result from multiple contacts with food items after the fingertips are
replenished with clay. The maximum ingestion levels based on deposition was estimated as
about 2 mg of clay. This suggests that hand-to-food transfers could increase ingestion by over
50-fold.
Other possible mechanisms for clay ingestion include hand-to-mouth transfers or
deposition/splattering of clay on to lips and removal by licking. These behaviors were not
observed during this study but could be a common occurrence. Smoking was not allowed in the
study facility, but where this occurs, the potential for hand-to-mouth transfer is increased.
The average-soil-ingestion rate for adults in residential settings is estimated to be
50 mg/day (U.S. EPA, 1997, 1989). This is much higher than the maximum clay ingestion levels
estimated in this study based on deposition (about 2 mg). It is difficult to evaluate how
applicable this soil ingestion rate may be to clay ingestion in a ceramic art studio. However, the
scenarios presented above imply that it may be possible. This was evaluated using a
modification to the Monte Carlo simulation presented in Chapter 8. In this simulation, the
ingestion rate was inputted as a flat distribution from 1 to 50 mg and all other inputs were kept
the same as those described in Table 18. The mean ingestion dose increased by a factor of
17 (from 0.14 to 2.4 pg TEQ) and total dose increased by a factor of 1.3 (from 6.4 to 8.64 pg
TEQ).
The above discussion suggests that a number of plausible scenarios could occur which
would result in greater clay ingestion than observed in this study. The peer reviewers of this
study emphasized their concern that this pathway may have been underestimated (Eastern
Research Group, 2008). This is a high priority issue for future research and demonstrates the
importance of good hygiene practices regarding food placement and hand washing to prevent
these types of exposures.
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10. CONCLUSIONS
Hypothetical dioxin dose estimates were calculated for each subject assuming that all
used a 20% ball clay blend with 162 pg TEQ/g. The single-day total doses across the 10 subjects
ranged from 0.32 to 7.1 pg TEQ/d, with an average of 1.44 pg TEQ/d (SD = 2.0). The dermal
dose was the major contributor to total dose, exceeding 67% for all subjects. Ingestion and
inhalation contributed similar amounts, generally in the range of 1 to 20% of total dose. Hand
and arm exposure accounted for much of the dermal dose for all subjects. The two subjects who
wore summer clothing had foot and leg exposures accounting for about 33 to 71% of the dermal
dose. Facial exposures were low accounting for less than 4% of total dermal dose.
Clay exposure was found to be highly dependent on the type of work being performed.
Throwing clay on the wheel resulted in much higher clay exposures than did any other clay
activities. This is due to the increased contact with clay while working on the wheel and the wet,
sticky consistency of the clay needed for that work. Emptying bags and mixing dried clays also
led to high exposures.
A Monte Carlo simulation was performed to model how doses could vary in a broad
population of artists with exposures outside the hypothetical scenario evaluated in this study.
This simulation produced a mean total dose of 6.4 pg TEQ/d (SD = 8.4), median of 3.5 pg
TEQ/d, and 90th percentile of 14.8 pg TEQ/d. This mean is over times 4 times greater than the
mean of the hypothetical dose estimates for the 10 subjects. All of the 10 subject doses
corresponded to low percentiles of the Monte Carlo simulation except Subject 9 (75th percentile).
Also, it indicated that the fraction of ball clay in the blend, clothing, and dioxin concentration
contributed most to variance in total dose. Many of the input distributions used in this
simulation were based on very limited data or judgment. Therefore, the simulation results are
best interpreted as preliminary indications of how to extrapolate the observations of this study to
a broader population of artists in similar types of studios, i.e., well maintained academic
facilities. It is likely that the range of exposures across all types of ceramic art facilities
(individual, commercial, etc.) is wider than observed here and further study is recommended to
explore this possibility.
This study included a comprehensive uncertainty analysis. The two most important
uncertainties are highlighted below:
• Studies have shown that in a variety of occupational situations, particulates can penetrate
clothing and deposit on skin. It is unclear if and to what extent this may occur in ceramic
art studios. Accordingly, this study assumed that dermal exposure under clothing was
negligible. An evaluation of this issue suggests that if exposure under clothing occurs,
dermal doses may increase by 50% or more.
65
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• The only ingestion pathway evaluated in this study was deposition on to food. Although
not observed during this study, other pathways could occur such as hand-to-food transfers
and hand-to-mouth transfers. Where these occur, ingestion doses could increase
substantially, perhaps by over an order of magnitude relative to the ingestion estimates
presented here.
In the general population, daily intakes of CDD/CDFs are estimated to average 0.65 pg
TEQ/kg-day or 45 pg TEQ/d for a 70-kg adult (Lorber, 2002). More than 90% of this intake is
derived from food ingestion. These intake values are based on the "administered" dose or the
amount taken into the body before absorption. The hypothetical doses presented in this report
are on an absorbed dose basis. Thus, the general population dose must be converted to an
absorbed basis to compare it to the values presented here. Lorber (2002) reports that about 80%
of dioxins in foods are absorbed into the body. Applying this factor, the general population adult
dose on an absorbed basis is 36 pg TEQ/d. Comparing these values to the average of the
hypothetical doses for the 10 subjects estimated here (1.44 pg TEQ/d) indicates that the ball clay
dose is 4% of the general population adult dose (on a TEQ basis). Similarly, the Monte Carlo
simulation suggested a mean dose of 6.4 pg TEQ/d which is 18% of the general population adult
dose (on a TEQ basis). Note that the general population dioxin dose is a long-term average and
the ball clay dioxin doses are estimates for a single day when exposure occurs. Accordingly, this
comparison implies that ball clay use is a frequent event, so that the long-term daily average ball
clay dose is similar to the single-day dose. If ball clay use is infrequent, then the long-term
average dose from ball clay will be reduced and adjustments would be needed to make a valid
comparison to the general population dioxin dose.
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APPENDIX A
SUBJECT QUESTIONNAIRE RESULTS
Table A-l. Subject 1
Question
Approximately how many hours per week do
you work with clay?
Approximately how many weeks per year?
How long have you been doing clay work with
this level of intensity?
What type of clay artwork do you do?
What types of clothing do you wear while you
work?
What areas of skin typically are exposed to the
clay while you work?
Do you correlate any skin health issues with
how much you work with clay? If yes, what?
In relation to the time you complete working
with clay, when do you wash parts of your
body that have been exposed to clay?
How do you wash your skin after you work
with clay?
Do you treat your skin with anything in
particular after working with clay?
Answer
50 hours.
40 weeks.
1 year.
Hand building, sculptural work. Largely
consists of rolling out slabs and assembling
clay parts.
Short sleeve t-shirt and jeans and closed toe
shoes.
Hands and forearms.
Yes. Dryness. No cracking/bleeding. I use
lotion 3-4 times through the day.
Hands:
when rolling slabs — once per hour.
when assembling clay — 3 or more times per
hour.
Face: 1-2 times per day.
Water only.
Yes, Aveeno® brand lotion.
A-l
-------
TableA-2. Subject!
Question
Approximately how many hours per week do
you work with clay?
Approximately how many weeks per year?
How long have you been doing clay work with
this level of intensity?
What type of clay artwork do you do?
What types of clothing do you wear while you
work?
What areas of skin typically are exposed to the
clay while you work?
Do you correlate any skin health issues with
how much you work with clay? If yes, what?
In relation to the time you complete working
with clay, when do you wash parts of your
body that have been exposed to clay?
How do you wash your skin after you work
with clay?
Do you treat your skin with anything in
particular after working with clay?
Answer
10-1 5 hours.
15-25 weeks.
24 years.
Mixing clay and maintenance activities
associated with the OSU Ceramics area.
Long and short sleeves, long pants, work
shoes.
Hands, arms, and face.
Dryness and cracking.
Hands: 2 minutes.
Face: 5 hours.
Soap and water.
Lotion during winter, but when my hands are
very dry a product called Satin Hands® is
used.
A-2
-------
TableA-3. Subjects
Question
Approximately how many hours per week do
you work with clay?
Approximately how many weeks per year?
How long have you been doing clay work with
this level of intensity?
What type of clay artwork do you do?
What types of clothing do you wear while you
work?
What areas of skin typically are exposed to the
clay while you work?
Do you correlate any skin health issues with
how much you work with clay? If yes, what?
In relation to the time you complete working
with clay, when do you wash parts of your
body that have been exposed to clay?
How do you wash your skin after you work
with clay?
Do you treat your skin with anything in
particular after working with clay?
Answer
25 hours.
30 weeks.
14 months.
Functional — thrown on wheel.
Structural — hand built.
Jeans with t-shirt and sandals (summer) or
long sleeves and closed toe shoes (winter).
Hands, arms, face, neck, and feet.
Dry cracking skin and cuticles on hands, red
small-bump rash on backs of hands and
inner forearms when using wheel, nasal
congestion.
Arms and hands: 3 to 5 minutes.
Feet, face, and neck: 1-10 hours.
Water only if returning to work, soap, and
water when finished.
Aveda® hand cream, Neutrogena® Swiss
therapy lotion.
A-3
-------
Table A-4. Subject 4
Question
Approximately how many hours per week do
you work with clay?
Approximately how many weeks per year?
How long have you been doing clay work with
this level of intensity?
What type of clay artwork do you do?
What types of clothing do you wear while you
work?
What areas of skin typically are exposed to the
clay while you work?
Do you correlate any skin health issues with
how much you work with clay? If yes, what?
In relation to the time you complete working
with clay, when do you wash parts of your
body that have been exposed to clay?
How do you wash your skin after you work
with clay?
Do you treat your skin with anything in
particular after working with clay?
Answer
More than 70 hours.
50 weeks.
2 years.
Functional pots, cups, bowls, etc.
Overalls, long/short sleeve shirts and
sneakers.
Face, hands, sometimes arms and legs.
Extremely dry with cracking on fingertips.
Hands: 10 minutes.
Face and body: 10-24 hours.
Water only if returning to work, soap, and
water when finished.
Heavy cream lotion or bag balm at the end
of the day and at intervals throughout the
day.
A-4
-------
TableA-5. Subjects
Question
Approximately how many hours per week do
you work with clay?
Approximately how many weeks per year?
How long have you been doing clay work with
this level of intensity?
What type of clay artwork do you do?
What types of clothing do you wear while you
work?
What areas of skin typically are exposed to the
clay while you work?
Do you correlate any skin health issues with
how much you work with clay? If yes, what?
In relation to the time you complete working
with clay, when do you wash parts of your
body that have been exposed to clay?
How do you wash your skin after you work
with clay?
Do you treat your skin with anything in
particular after working with clay?
Answer
More than 14 hours.
35 weeks.
6 years.
Hand building objects about 1.5 feet tall.
Short sleeves/pants and shoes.
Hands, lower arms, face.
Yes, dryness, sometimes cracking.
Hands: <5 minutes.
Arms: 8 hours.
Face: 0.5-8 hours.
Soap and water.
Lotion.
A-5
-------
Table A-6. Subject 6
Question
Approximately how many hours per week do
you work with clay?
Approximately how many weeks per year?
How long have you been doing clay work with
this level of intensity?
What type of clay artwork do you do?
What types of clothing do you wear while you
work?
What areas of skin typically are exposed to the
clay while you work?
Do you correlate any skin health issues with
how much you work with clay? If yes, what?
In relation to the time you complete working
with clay, when do you wash parts of your
body that have been exposed to clay?
How do you wash your skin after you work
with clay?
Do you treat your skin with anything in
particular after working with clay?
Answer
30-40 hours.
30-40 weeks.
25 weeks.
Throwing objects using wheel, hand
building, and sculptural work.
Short sleeves, pants, shorts, and flip flops
shoes.
Arms, hands, feet, face.
Yes, dry skin on feet and hands and nails
being unable to grow healthily.
Hands: 30 minutes.
Legs, feet, and face: 3-5 hours.
Soap and water.
Lotion.
A-6
-------
Table A-7. Subject 7
Question
Approximately how many hours per week do
you work with clay?
Approximately how many weeks per year?
How long have you been doing clay work with
this level of intensity?
What type of clay artwork do you do?
What types of clothing do you wear while you
work?
What areas of skin typically are exposed to the
clay while you work?
Do you correlate any skin health issues with
how much you work with clay? If yes, what?
In relation to the time you complete working
with clay, when do you wash parts of your
body that have been exposed to clay?
How do you wash your skin after you work
with clay?
Do you treat your skin with anything in
particular after working with clay?
Answer
10 hours.
40 weeks.
4 years.
Clay sculpture. Rolling out slabs, pressing
them into molds. Limited work throwing
objects using wheel.
Short sleeves and pants (winter/spring/fall)
and shorts (summer).
Arms, hands, and face.
Dryness and cracking.
Hands: 1-2 minutes.
Face and legs 1-2 minutes (powdered clay)
or end of day (wet clay).
Soap and water.
Lotion.
A-7
-------
TableA-8. Subjects
Question
Approximately how many hours per week do
you work with clay?
Approximately how many weeks per year?
How long have you been doing clay work with
this level of intensity?
What type of clay artwork do you do?
What types of clothing do you wear while you
work?
What areas of skin typically are exposed to the
clay while you work?
Do you correlate any skin health issues with
how much you work with clay? If yes, what?
In relation to the time you complete working
with clay, when do you wash parts of your
body that have been exposed to clay?
How do you wash your skin after you work
with clay?
Do you treat your skin with anything in
particular after working with clay?
Answer
20 hours.
52 weeks.
6 years.
Large clay sculpture. Rolling out slabs, cut
and bend them and then press them together.
Pants or shorts, short sleeves or tank tops,
sneakers or sandals.
Arms, neck, hands, calves, and shins.
Dryness and cracking.
Hands: 5 minutes.
Face and legs: 4-24 hours.
Soap and water or just water.
Lotion.
A-8
-------
APPENDIX B
EVALUATION OF CLAY DUST INHALATION
The methodology used to evaluate the dose of clay dust and associated dioxin received
via inhalation is discussed in this appendix. The appendix is divided into four sections: clay
dust size distribution, particle inhalability, respiratory deposition of clay dust, and delivered dose
estimates.
B.I. CLAY DUST SIZE DISTRIBUTION
As discussed in the main body of this report, the size distribution of clay dust was
measured using a Delron® cascade impactor and a Climet® during regular daily activities in the
art studio. The Climet® optically determines particle concentration for six size bins with the
associated physical particle diameter (dp) of 0.3-0.5, 0.5-1, 1-2.5, 2.5-5, 5-10, and >10 |im.
Aerodynamic particle diameter (Dae) can be estimated for the Climet®'s size bins by assuming
that the airborne clay dust has a density of 2.6 g/cm3, similar to that of bulk clay.1 Using this
approach, a clay particle with a dp of 10 jim has a Dae of 16 jim. The Delron® cascade impactor
fractionates particles directly, based on their Dae, into the seven ranges of <0.5, 0.5-2, 2-4, 4-8,
8-16, 16-32, and >32 |im.
During normal artisan activities (Subjects 1-8), 64 + 9% (mean + SD) of the aerosol is
associated with particles having a Dae > 16 jim based on average Climet® data. Based on
average impactor data, 63 + 13% of the aerosol is associated with aDae > 16 jim (Subjects 1-8).
The particle size distributions to which the artisans were exposed was assumed to be log-
normally distributed.2 The cascade impactor data were selected for estimating particle size
distributions for the following reasons: (1) the impactor measures particle size based on the
aerodynamic behavior of particles, whereas the Climet® uses light scattering to estimate a
physical particle size; (2) the impactor affords a better characterization of the large particles than
does the Climet® because it contains an additional size bin of 16-32 jim; and (3) particle
deposition in the respiratory tract is a function of Dae. Thus, uncertainty in estimates of
respiratory deposition is reduced by the direct measurement of Dae by the impactor. The clay
1 Dae = dp {(clay density * Cc(dp) )/(H2O density * Cc(Dae) )}05, where: Cc(dp) and Cc(Dae) are the
Cunningham slip correction factor for the physical and aerodynamic particle size, respectively. For more
information, the reader is referred to ICRP (1994), page 239.
2For more information about particle sizing and the log-normal distribution, the reader is referred to Hinds
(1999).
B-l
-------
dust size distribution was not estimated for runs where two or more of the impactor stages were
below the nondetect level.
When engaged in normal artisan activities, the mass median aerodynamic diameter
(MMAD) of clay dust to which artisans were exposed ranged from 13 to 45 jim. Table B-l
provides a characterization of clay dust exposures for each subject. Figure B-l illustrates a
log-probability plot of a typical (i.e., near the average MMAD) clay dust particle size
distribution and a background sample from the studio. The prevalence of fewer large particles in
the background aerosol can be explained easily, based on particle-settling velocities. The
settling velocities for the Dae of 1-, 10-, and 20-|im particles are 3.5 x 10"3, 0.3, and 1.2 cm/s,
respectively. Due to their rapidly settling velocities, large particles (Dae > 10 jim) are
maintained in the air only by active generation or resuspension from surfaces. The substantive
presence of large particles (52% of mass associated with aDae > 10 jim) in the background
sample is suggestive of particle resuspension due to movement (e.g., walking and setting up
sampling equipment in the studio).
Table B-l. Clay dust size distribution and concentration during normal
activities
Subject
1
2
3
4
5
6
7
8
Mean + SD
Size distribution3
MMAD (urn)
26.9
44.6
18.5
NA
NA
20.2
13.0
26.7
25.0+11
<*£
3.9
4.8
4.3
NA
NA
3.0
3.6
o o
J.J
3.8 + 0.7
Total concentration
(mg/m3)
0.35
0.47
0.99
0.37
0.13
0.61
0.51
0.64
0.51+0.25
B-2
-------
a The aerosol size distribution is described in terms of the mass median aerodynamic diameter (MMAD) and
geometric standard deviation (og).
NA = not available.
1
L."
^4—1
i
(0
Q
o n n
— 1 U
t
(0
0.
o
(0
•o
o
1_
(Tj
^^r
0
/'
1 1
*
f
f
2 E
>
^
d'
/
-6
/
/
/
/
r
, 1° 2
/
f
/
f
P
O
n 30,
0 4
/
J
/
'
1'
1
05'°6
V
/
/
3
/
/
^
07°8
T7
X
0 9°9
5 "9
99.9
9
Cumulative Percent Less Than Indicated Size
Figure B-l. Clay dust particle size distribution during normal artisan
activities from analysis of cascade impactor data. Illustrated are the data for
Subject 8 (D ) and a background sample when work was not being done in
the studio (o). The dashed and solid lines illustrate the log-normal
distribution for these respective data. The mass median aerodynamic
diameter (MMAD) of clay dust was 27 um (og= 3.3) for Subject 8, whereas
the background sample had an MMAD of 11 um (og = 4.6).
Data were also available for two subjects during specific activities (i.e., when sculpting
and using a pottery wheel) (see Table B-2). During pottery wheel operations, an average
MMAD of 33 |im with a geometric standard deviation (og) of 5.4 was observed. A dog was
present during two of the sculpting runs. The MMAD with the dog present was 21 jim versus
only 16 um without the dog. The shift toward larger particles when the dog was present appears
to be consistent with particle resuspension due to the dog's movement around the studio.
B-3
-------
Table B-2. Clay dust size distribution and concentration during specific
activities
Subject
Subject 9
(Pottery wheel)
Run 1
Run 2
Run 3
Run 4
Run 5
Mean + SD
Subject 10b
(Sculpting work)
Run 1
Run 2
Run 3
Size distribution3
MMAD (um)
33.7
NA
24.8
NA
39.3
32.6 + 7.3
21.2
20.4
16.0
°g
6.2
NA
4.3
NA
5.6
5.4 + 0.9
3.9
3.2
3.5
Total
concentration
(mg/m3)
0.049
0.046
0.102
0.073
0.152
0.085 + 0.044
0.48
0.24
0.24
a The aerosol size distribution is described in terms of the mass median aerodynamic diameter (MMAD) and
geometric standard deviation (og).
b A dog was present during Runs 1 and 2 but not during Run 3. Therefore, these three runs were not averaged as
was done in the case of the pottery wheel work.
NA = not available
B.2. PARTICLE INHALABILITY
For a given particle size, inhalability is the ratio of the particle concentration that enters
the respiratory tract through the nose or mouth to the concentration of these particles in the
ambient air. Inhalability depends mainly on particle size (i.e., Dae), route of breathing, wind
speed, and a person's orientation with respect to wind direction. Wind speeds in the art studio
were assumed to be 0.3 m/s or less (Baldwin and Maynard, 1998). The artisans were presumed
to move about the studio such that their orientation was random with respect to wind direction.
The clay dust aerosol present under normal activities in the art studio was observed to
have an average MMAD of 25 jim and og of 3.8. Hence, 50% (on average, by mass) of the
airborne clay dust is composed of particles having aDae of >25 jim, a size that is generally
considered to be unable to penetrate the thorax (ACGIH, 2004). These large particles
(Dae >25 |im), if inhaled, will deposit almost completely and exclusively in the extrathoracic
(ET) airways. Thus, determining inhalability is key to estimating the delivered dose of these
B-4
-------
large particles. For smaller particles, inhalability still describes the fraction of airborne particles
that may enter the respiratory tract and thereby the availability of these particles for deposition in
the lung.
Only limited data are available on the inhalability of particles from calm air (wind speeds
of 0.3 m/s and less). Inhalability from calm air depends on the route of breathing. Logistic
functions describing particle inhalability during nasal [P(!N)} and oral [P(Io)] breathing are given
by Menache et al. (1995) and Brown (2005):
(B-l)
+ exp(10.32-3.1141n(£>ae))
1 44
(B-2)
l + 0.44exp(0.0195£>ae)
Note that these equations depend only on aerodynamic particle diameter, Dae. Given by Eq. B-l,
P(IN) begins a rapid decline from 0.95 at Dae =11 |im, to 0.5 at Dae = 27.5 jim, and 0.1 at
Dae= 56 |im. Eq. B-2 predicts a slow decline mP(Io) from 0.95 atDae = 8 jim, to 0.5 at
Dae= 74 |im, and 0.1 atDae =175 jim.
Figure B-2 illustrates particle inhalability predicted by Eqs. B-l and B-2 (shown by solid
lines) along with relevant experimental data. Based on high wind speeds (1-8 m/s), the
American Conference of Governmental Industrial Hygienists (ACGIH) inhalability criterion is
also illustrated (shown by dashed lines) for comparative purposes. Eq. B-l for P(!N) describes
the experimental nasal inhalability data well with an r2 of 0.86 (model sum of squares divided by
the total corrected sum of squares). A negative r2 is obtained for the fit of the ACGIH (2004)
criterion to these data.3 Equation B-2 describes the experimental oral inhalability data with an r2
of 0.69, whereas the ACGIH criterion fit with an r2 of 0.32.
B.3. RESPIRATORY DEPOSITION OF CLAY DUST
Inhaled particles may be either exhaled or deposited in the ET, tracheobronchial (TB), or
pulmonary (PU) airways. The deposition of particles in the respiratory tract depends primarily
3An r2 is calculated as the model sum of squares (MSS) divided by the total corrected sum of squares
(TSS). The MSS equals the TSS minus the residual sum of squares (RSS). In typical linear regressions,
when a model is fitted to a data set, the resulting r2 must be non-negative because the least square fitting
procedure assures RSS < TSS. When r2 is computed on excluded data, i.e., data not used to fit the model,
the RSS can exceed the TSS. In this case, r2 (which is not the square of r) can be negative, indicating that
the mean of the data is a better predictor than the model.
B-5
-------
0,0
10 100
Dae (Mm)
Figure B-2. Particle inhalability from calm air for nasal [P(!N)] and oral
[P(Io)] breathing as a function of aerodynamic particle diameter (Dae). Left
panel [ Eq. B-l, • Breysse and Swift (1990), + Hinds et al. (1998), o Hsu
and Swift (1999), - - - ACGIH (2004)]. Right panel [ Eq. B-2, o Aitken et
al. (1999), • Kennedy and Hinds (2002), - - - ACGIH (2004)].
Table B-3. Breathing patterns used in particle deposition calculations"
Activity
Sitting
Light exercise
VT (mL)
/(min1)
VT (mL)
/(min1)
Males
750
12
1,250
20
Females
464
14
992
21
a Source: ICRP (1994), Table 8.
on inhaled particle size (i.e., Dae\ route of breathing (through the nose or mouth), tidal volume
(Vx), and breathing frequency (f). Reference respiratory values for males and females were
adopted from the International Commission on Radiological Protection (ICRP, 1994). In
addition to breathing patterns (see Table B-3) necessary for deposition calculations, males and
females were assumed to have a functional residual capacity of 3,300 mL and 2,680 mL,
respectively. The majority (70%) of the subjects were female; only Subjects 1, 2, and 5 were
male.
Particle deposition in the respiratory tract was predicted using the publicly available
Multiple Path Particle Dosimetry (MPPD) model.4 The MPPD model was developed by the
4 The MPPD program is available on request from the CUT Centers for Health Research
().
B-6
-------
CUT Centers for Health Research (CUT), United States, in collaboration with the National
Institute of Public Health and the Environment (RIVM), the Netherlands, and the Ministry of
Housing, Spatial Planning and the Environment, the Netherlands. The MPPD model may be
used to predict the deposition in the human respiratory tract for particles between 0.01 and
20 |im in diameter. In the lung, the model considers deposition by the mechanisms of impaction,
sedimentation, and diffusion. Additional model details are available elsewhere
(de Winter-Sorkina and Cassee, 2002). For the size of the clay dust, only impaction and
sedimentation are of concern.
Using the MPPD model, deposition was predicted for the ET, TB, and PU regions of the
respiratory tract. Particle deposition was estimated individually for oral and nasal breathing.
During oral breathing, deposition in the TB airways did not always reach zero by a Dae of 20 jim
(the upper limit for the MPPD model). For Dae > 20 jim, deposition in the TB airways was
estimated by a best fit polynomial (3rd or 4th degree) determined using CurveExpert 1.3
(112B Crossgate St., Starkville, MS 39759). This polynomial function was fitted to TB
deposition fractions for Dae from 10 to 20 jim. The predicted ET deposition during oral
breathing for a Dae > 20 jim was taken as one minus the TB deposition fraction for oral
breathing. For nasal breathing, these additional steps were unnecessary because TB deposition
was well under 1% at aDae of 20 jim.
External to the MPPD model, all of the predicted deposition fractions were corrected for
particle inhalability using Eqs. B-l and B-2. The current version of MPPD model offers an
inhalability correction for nasal breathing only. For a given Dae, an inhalability corrected
deposition fraction is the product of the uncorrected deposition fraction and the predicted
inhalability for thatDae. Unless otherwise specified, all mention of particle deposition fractions
in the main body of this report and subsequently in this appendix refer explicitly to inhalability
corrected deposition fractions.
The deposition fraction (DFr) of an aerosol in a region of the respiratory tract is the
integral of the deposition fractions across all particle sizes in the aerosol:
CO
DFr (MMAD, ag ) = \DFr (dt) p(dt) Sdt (B-3)
B-7
-------
where
DFr(di) = the deposition fraction in region, r, of particles having an aerodynamic
diameter of dt
p(di) = the mass fraction associated with the interval Sdt
The total deposition fraction for the respiratory tract is the sum ofDFr for the ET, TB, and
PU regions. Eq. B-3 can be approximated by summing the particle deposition fractions at known
intervals or percentiles of the particle size distribution. Here, the interval of 1% was used and
the approximation is
1 0.99
DFr (MMAD, ag ) « ]T DFr (di) (B-4)
100P=aoi
where
DFr(di) = the deposition fraction in region, r, of particles having an aerodynamic
diameter dt (the particle size associated with a given percentile, P, of the size
distribution).
For a log-normal distribution, dt is given by
d^MMADa2^ (B-5)
where
z(P) = the normal standard deviate for a given probability
Table B-4 provides the predicted regional deposition fractions for the clay dust in the
respiratory tract of each subject for oral and nasal breathing at two activity levels. These
deposition fraction estimates were based on each subject's measured aerosol exposure size
distribution (see Tables B-l and B-2). Subjects 4 and 5 lacked aerosol size distribution data and
were assumed exposed to an aerosol with an MMAD of 25 jim and og of 3.8, this being the
average for artisans during normal activities (see Table B-l). The deposition fraction estimates
for Subject 10 were based on Run 3, when the dog was not present in the studio.
B-8
-------
B.4. DELIVERED DOSE ESTIMATES
The rate of particle deposition in a region of the respiratory tract may be expressed as:
= C(t)f(t)VT(t)DFr(t)
(B-6)
where
Dr = the rate of deposition per unit time in region r
C = the exposure concentration
/ = breathing frequency
VT = tidal volume
DFr = the deposition fraction in region r
Note that all of the variables in Eq. B-6 may vary with time. The dose to a respiratory region is
determined by integrating Eq. B-6 over the exposure duration.
Table B-4. Regional deposition fractions (corrected for inhalability) for clay
dust in the respiratory tract
Subject
1
2
o
6
4
5
6
7
8
9
10
Sitting
Nasal breathing
ET
0.441
0.336
0.472
0.447
0.458
0.526
0.549
0.451
0.368
0.533
TB
0.015
0.011
0.028
0.021
0.016
0.023
0.035
0.018
0.020
0.030
PU
0.022
0.016
0.033
0.022
0.023
0.022
0.041
0.017
0.023
0.033
Oral breathing
ET
0.473
0.412
0.431
0.471
0.479
0.521
0.432
0.507
0.396
0.462
TB
0.082
0.059
0.104
0.091
0.086
0.108
0.128
0.087
0.077
0.118
PU
0.058
0.042
0.067
0.050
0.061
0.053
0.085
0.041
0.047
0.072
Light exercise
Nasal breathing
ET
0.473
0.360
0.531
0.487
0.492
0.566
0.622
0.483
0.410
0.593
TB
0.006
0.004
0.010
0.007
0.006
0.007
0.013
0.005
0.007
0.010
PU
0.011
0.008
0.020
0.013
0.011
0.012
0.025
0.010
0.014
0.020
Oral breathing
ET
0.516
0.442
0.486
0.521
0.523
0.581
0.498
0.557
0.437
0.525
TB
0.060
0.044
0.074
0.064
0.063
0.075
0.090
0.061
0.054
0.083
PU
0.052
0.037
0.075
0.056
0.054
0.059
0.095
0.046
0.053
0.081
ET = extrathoracic; PU = pulmonary; TB = tracheobronchial.
B-9
-------
By assuming that aerosol characteristics and an individual's activity levels are fairly
constant over discrete periods of time, the dose to a respiratory region may be approximated by:
D =
(CT)i [FmDFmr
(B-7)
where
Dr
VT and/
C and T
Fm and FN
DFmir and DFNir
Constant 0.06
= the dose (jig) to region r of the respiratory tract
= tidal volume (mL) and breathing frequency (min"1) for a specified
activity j
= exposure concentration (mg/m3) and duration (hr) during activity j
= the fraction of a breath entering the respiratory tract through the mouth
and nose, respectively, during activity j
= the deposition fraction for oral and nasal breathing, respectively, in
region r of the respiratory tract while performing activity j
= a unit conversion parameter
As expressed, an "activity" in Eq. B-7 could be associated with changes in exposure
concentration, the particle size distribution, and/or an individual's exertion level. For simplicity,
only two exertion levels (sitting and light exercise) and a single particle size distribution (see
Tables B-l and B-2) were considered for each subject.
The fraction of flow through the mouth (Fm in Eq. B-7) increases with activity level and
varies between individuals. For the two activity levels considered here, most people (87%) will
breathe through their nose (Niinimaa et al., 1981). Hence, for these people, Fm = 0 and FN = 1 in
Eq. B-7. However, 13% of people will be oronasal breathers even at rest, i.e., they will breathe
simultaneously through the nose and mouth (Niinimaa et al., 1981). This latter group is
commonly referred to in the literature as "mouth breathers" (e.g., ICRP, 1994). Derived from
Niinimaa et al. (1981), the fraction of air respired through the mouth (Fm) is well described by a
modified exponential function in the form of
Fm = a exp
r
(B-8)
B-10
-------
where
Ve = minute ventilation
a =0.748
7 = -7.09 (r2 = 0.997) in mouth breathers for 10 < Ve< 80 L/min
7 = -18.3 (r2 = 0.998) in normal augmenters for 35.3 < Ve < 80 L/min
For Ve < 35.3 L/min, normal augmenters breathe entirely through the nose, i.e., Fm = 0.
FA? is one minus Fm regardless of the activity.
Table B-5 gives the estimated clay dust doses to regions of the respiratory tract for each
subject during nasal and oronasal breathing. Estimates are for a 4-hour exposure assuming that
the exposed individual spent 50% of his or her time sitting and 50% engaged in light exercise.
For oronasal breathing in Table B-5, there is a small positive bias in ET doses and a
corresponding negative bias in TB doses calculated by Eq. B-7. In other words, this method of
calculating ET and TB doses shifts the pattern of deposition toward the head relative to the
real-life pattern of deposition. This shift occurs due to deposition being calculated at a higher
airflow rate through the nose and mouth than actually occurs during oronasal breathing. The
deposition calculations presumed that all inhaled airflow was through the nose or mouth. In
reality, inhaled air is partitioned between the nose and the mouth, and the actual flows (for sitting
and light exercise) are roughly half of that used in the deposition calculations. For breathing by
a single route (nasal or oral), changing activity from sitting to light exercise approximately
triples flow rates but only slightly increases ET deposition and modestly decreases TB
deposition (see Table B-4). The effect of using Eq. B-7 for calculating doses during oronasal
breathing should similarly affect the pattern of deposition. Ultimately, particles deposited in the
ET and TB regions will typically be cleared to the throat and swallowed within 24 to 48 hours
postdeposition (ICRP, 1994). Hence, the exact site of deposition (i.e., ET versus TB) is of little
significance because both regions effectively contribute to ingested doses.
B-ll
-------
Table B-5. Regional doses (ug) of clay dust in the respiratory tract3
Subject
1
2
3
4
5
6
7
8
9
10
Mean
SD
Nasal breathing
ET
664
678
1,677
580
256
1,114
1,011
997
110
455
754
460
TB
12
11
47
13
4.6
22
30
18
2.9
12
17
13
PU
20
19
75
19
7.7
29
49
24
4.5
18
27
21
Oronasal breathing
ET
693
757
1,612
598
264
1,126
917
1,067
114
431
758
445
TB
53
52
143
45
21
85
90
72
8.8
39
61
39
PU
48
47
154
41
19
70
100
57
9.2
39
58
42
a Doses calculated by Eq. B-7 as described in the text.
ET = extrathoracic; PU = pulmonary; TB = tracheobronchial.
Table B-6 provides estimates of the dioxin absorption in each subject for nasal and
oronasal breathing. Particles deposited in the ET and TB regions clear rapidly (within 1-2 days)
to the throat and are swallowed. The absorption of dioxin from particles deposited within the ET
and TB regions was treated as if the particles had been ingested. Dose estimates for oronasal
breathing are slightly more conservative from a safety or risk perspective than presuming nasal
breathing. However, nasal breathing may be considered as representative of the majority of the
population (87%). Oronasal breathing is thought to represent 13% of healthy individuals
(Niinimaa et al., 1981). In contrast to healthy subjects, Chadha et al. (1987) found that the
majority (11 of 12) of patients with asthma or allergic rhinitis breathe oronasally even at rest.
On average across all the subjects, dioxin doses are about 1.2 times greater for oronasal than for
nasal breathing.
B-12
-------
Table B-6. Estimates of dioxin absorption" (pg TEQ)
Subject
1
2
3
4
5
6
7
8
9
10
Mean
SD
Nasal breathing
ETand
TBb
0.033
0.034
0.084
0.029
0.013
0.055
0.051
0.049
0.005
0.023
0.038
0.023
PUC
0.003
0.003
0.010
0.002
0.001
0.004
0.006
0.003
0.001
0.002
0.004
0.003
Total
0.035
0.036
0.094
0.031
0.014
0.059
0.057
0.052
0.006
0.025
0.041
0.026
Oronasal breathing
ETand
TBb
0.036
0.039
0.085
0.031
0.014
0.059
0.049
0.055
0.006
0.023
0.040
0.023
PUC
0.006
0.006
0.020
0.005
0.002
0.009
0.013
0.007
0.001
0.005
0.007
0.006
Total
0.043
0.045
0.105
0.037
0.016
0.068
0.062
0.063
0.007
0.028
0.047
0.029
a Dioxin concentration was assumed to be 162 pg toxic equivalent (TEQ) per gram clay.
b Absorption fraction of 0.3 assumed, extrathoracic (ET) and tracheobronchial (TB) rapidly clear into the
gastrointestinal tract.
0 Absorption fraction of 0.8 assumed, due to slow clearance from pulmonary (PU) region.
B-13
-------
REFERENCES FOR APPENDIX B
ACGIH (American Conference of Governmental Industrial Hygienists). (2004) TLVs and BEIs: based on the
documentation of the threshold limit values for chemical substances and physical agents and biological exposure
indices. Cincinnati, OH: ACGIH Worldwide.
Aitken, RJ; Baldwin, PEJ; Beaumont, GC; et al. (1999) Aerosol inhalability in low air movement environments.
J Aerosol Sci 30:613-626.
Baldwin, PEJ; Maynard, AD. (1998) A survey of wind speeds in indoor workplaces. Ann Occup Hyg 42:303-313.
Breysse, PN; Swift, DL. (1990) Inhalability of large particles into the human nasal passage: in vivo studies in still
air. Aerosol Sci Technol 13:459-464.
Brown, JS. (2005) Particle inhalability at low wind speeds. Inhal Toxicol 17:831-837.
Chadha, TS; Birch, S; Sacker, MA. (1987) Oronasal distribution of ventilation during exercise in normal subjects
and patients with asthma and rhinitis. Chest 92(6):1,037-1,041.
de Winter-Sorkina, R; Cassee, FR. (2002) From concentration to dose: factors influencing airborne paniculate
matter deposition in humans and rats. Bilthoven, The Netherlands: National Institute of Public Health and the
Environment (RIVM); report no. 650010031/2002. Available online at
http://www.rivm.nl/bibliotheek/rapporten/650010031.html
Hinds, WC. (1999) Aerosol technology: properties, behavior, and measurement of airborne particles (2nd ed.).
New York, NY: Wiley-Interscience.
Hinds, WC, Kennedy, NJ, and Tatyan, K. (1998) Inhalability of large particles from mouth and nose breathing.
J Aerosol Sci 29(l):277-278.
Hsu, DJ; Swift, DL. (1999) The measurement of human inhalability of ultralarge aerosols in calm air using
manikins. J Aerosol Sci 30:1,331-1,343.
ICRP (International Commission on Radiological Protection). (1994) Human respiratory tract model for
radiological protection: a report of a task group of the International Commission on Radiological Protection.
Oxford, United Kingdom: Elsevier Science Ltd. ICRP publication 66; Annals of the ICRP. Vol. 24, pp. 1-482.
Kennedy, NJ; Hinds, WC. 2002. Inhalability of large solid particles. J Aerosol Sci 33:237-255.
Menache, MG; Miller, FJ; Raabe, OG. (1995) Particle inhalability curves for humans and small laboratory animals.
Ann Occup Hyg 39:317-328.
Niinimaa, V; Cole, P; Mintz, S; et al. (1981) Oronasal distribution of respiratory airflow. Respir Physiol 43:69-75.
B-14
-------
APPENDIX C
SEM AND EDS DATA BY SUBJECT
O
. » i, : . , . |. , . , , . , |, . , , > > . . |.
1 2 3
Full Scale 1314cts
3 9
Figure C-la. Sample of clay used by Subject 1.
1 2
Full Scale 3934 cts Cursor: 1.622 keV (125 tits)
Figure C-lb. Clay particles on Subject 1's Respicon
Filter.
1 2
-ull Scale 8SSO cts Cursor: O.OOO keV
Figure C-2a. Sample of clay used by Subject 2.
1 2
-all Scale 1 3229 cts Cursor: 9.533 keV (1 7
Figure C-2b. Clay particles on Subject 2's Respicon
Filter.
-------
o
to
1 2 3
Full Scale 251 23 cts
8
keV
Figure C-3a. Sample of clay used by Subject 3.
4
6
Full Scale 25579 cts
Figure C-4a. Sample of clay used by Subject 4.
123
Full Scale 31 955 cts
8
heV
Figure C-3b. Clay particles on Subject 3's Respicon
Filter.
1 2
Full Scale 1 41 47 cts
8
keV
Figure C-4b. Clay particles on Subject 4's Respicon
Filter.
-------
1 2 3
Full Scale 14395 cts
' ' " I • •
8
keV
Figure C-5a. Sample of clay used by Subject 5.
1 2
Full Scale 21 36 cts
KeV
Figure C-6a. Sample of clay used by Subject 6.
1 2
Full Scale 930 ds
keV
Figure C-5b. Clay particles on Subject 5's Respicon
Filter.
1 2
Full Scale 795 cts
Figure C-6b. Clay particles on Subject 6's Respicon
Filter.
-------
o
123
Full Scale 5201 cts
8 9
10
keV
Figure C-7a. Sample of clay used by Subject 7.
10
Full Scale 751 6 cts
keV
Figure C-8a. Sample of clay used by Subject 8.
-1 2 3
Full Scale 1344 cts
10
keV
Figure C-7b. Clay particles on Subject 7's Respicon
Filter.
10
Full Scale 9593 els
keV
Figure C-8b. Clay particles on Subject 8's Respicon
Filter.
-------
APPENDIX D
ALTERNATIVE METHOD FOR ESTIMATING DERMAL ABSORPTION
This document uses the fraction absorbed approach to estimate dermal absorption, which
is the method recommended in current U.S. Environmental Protection Agency guidance (U.S.
EPA, 2004, 1992). The discussion below presents an alternative approach using a more
mechanistic model.
Kissel et al. (2007) present a flux based model for estimating an upper limit of dermal
absorption from soil:
AbsDose= C^L ^([l-exp(-1 (Jmulti /Cmu!ti) (Cm^sat ICsml^l L)] (EM)
where
AbsDose = absorbed dose (pg)
CSOii,o = concentration of dioxin in soil at t = 0 (pg mg"1)
L = soil load on exposed skin (mg cm"2)
A = area of skin exposed (cm2)
t = exposure time (hr)
Jmuiti = flux rate of chemical through skin from multi layer experiment (ng cm"2 hr)
= concentration of chemical in soil used in multi layer experiment (ng mg"1)
= saturation concentration of chemical in soil used in multi layer experiment
(ng mg"1)
= saturation concentration of chemical in soil used in exposure scenario
(ng mg"1)
This equation was derived from a mass balance of the chemical on the soil and assumes that the
flux is proportional to the concentration. The model uses the exponential term to represent the
decline in absorption rate that occurs over time as the contaminant is depleted from the soil.
Kissel et al. (2007) suggest estimating the ratio of the saturated soil concentrations on the
basis of the ratio of organic carbon concentration in the soil used in the experiment to the organic
carbon concentration in the soil used in the exposure scenario. As discussed in Section 5, this
report derives the dermal absorption properties of dioxin from Roy et al. (2008), who measured
dermal absorption of tetrachlorodibenzo-p-dioxin (TCDD) in soil with an organic carbon content
of 0.45% and applied at supermonolayer coverage (monolayer estimated as 3 mg/cm2 and
amount applied was 6 mg/cm2). Since the carbon content of the soil used in the Roy et al. tests
was essentially identical to that of the clay, this ratio is one and it drops out of the equation.
If the amount of dioxin absorbed is less than about 10% of the original amount on the
skin, then Eq. D-l can be approximated as
D-l
-------
AbsDose = Crf>0 A t (Jmulti /Cmultl ) (D-2)
For purposes of comparing this approach to the absorption fraction method, Eq. D-2 was
applied to exposure scenario for Subject 2. The exposure conditions for Subject 2 were as
follows:
Csoll,o = 162 pg g1 = 0.162 pg mg1
A = 970 cm2
T =4hr
The 4-hour average flux rate from Roy et al. (2008) was calculated as follows:
sollL/t (D-3)
where
-i
AF = Absorption Fraction = 0.0027 (for 4 hr, includes amount in skin)
Cso,i = 1 ng mg
L = 6 ni|
t =4hr
This yields a flux estimate of 0.004 ng cm"2 hr"1. The experiment was conducted at 1 ppm or
1 ng mg"1. Thus, the term (Jmuit/Cmuiti) m Eq. D-2 is equal to 0.004 mg cm"2 hr"1. Substituting
into Eq. D-2, the absorbed dose is calculated as 2.5 pg which is higher than the value reported in
Table 9 (0.77 pg) based on the fraction absorbed approach. Note that the amount of dioxin in the
monolayer can be estimated as 79 pg (0.162 pg mg"1 x 0.5 mg cm"2 x 970 cm2). This means that
the absorbed dose is less than 10% of the applied dose and Eq. D-2 is approximately equivalent
toEq. D-l.
The Kissel et al. model is conceptually different from the absorption fraction method in
that it assumes that the fluxes measured in the supporting experiment (and normalized by
concentration) can be applied to the exposure scenario of concern. Whereas, the absorption
fraction method assumes that the absorption fraction measured in the supporting experiment can
be applied to the exposure scenario of concern. In the present document, the absorption fraction
method is refined by adjusting the experimentally derived absorption fraction on the assumption
that the absorption occurs exclusively from the monolayer and applying this to the monolayer (or
actual soil load on skin if less than monolayer) in the exposure scenario of concern. The flux
based approach has a stronger scientific basis and has the advantage that it is less dependent on
D-2
-------
uncertain monolayer calculations. Additionally, in the form presented by Kissel et al., it can
account for reductions in flux rate as the chemical is depleted from the soil. Accordingly, this
approach has significant advantages over the absorption fraction method and is likely to become
the preferred approach in the future. Further research is recommended for the continued
development and validation of this promising approach.
D-3
-------
REFERENCES FOR APPENDIX D
Kissel JC, Spalt EW, Shirai JH, Bunge AL. (2007) Dermal absorption of chemical contaminants from soil (book
chapter) in Dermal Absorption and Toxicity Assessment, 2nd ed. (Roberts, MS and KA Walters, eds). Marcel
Dekker Inc, New York,
Roy, TA; Hammerstrom, K; Schaum, J. (2008) Percutaneous absorption of 2,3,7,8-tetrachlorodibenzo-/>-dioxin
(TCDD) from soil. J Toxicol Environ Health, Part A (Accepted).
U.S. EPA (Environmental Protection Agency). (1992) Dermal exposure assessment: principles and applications.
Office of Science Policy, Office of Research and Development, Washington, DC; EPA/600/8-91/01 IB. Available
online at http://www.epa.gov/osa/spc.
U.S. EPA (Environmental Protection Agency). (2004) Risk assessment guidance for Superfund. Vol. I: human
health evaluation manual (part E, supplemental guidance for dermal risk assessment). Office of Superfund
Remediation and Technology Innovation, Washington, DC; EPA/540/R/99/005. Available online at
http://www.epa.gov/superfund/programs/risk/ragse/index.htm.
D-4
-------
APPENDIX E
SKIN RINSING DATA
Table E-l. Weight of clay rinsed from skin of each subject during each
individual skin rinse (g)
Subject
1
2
3
4
5
6
7
8
Rinse 1
0.321
2.957
0.558
0.139
2.908
9.893
0.158
0.443
Rinse 2
NAa
2.804
0.427
0.126
1.919
12.522
0.149
1.018
Rinse 3
0.773
0.083
0.333
0.18
3.042
10.319
0.313
2.618
a Sample lost during analysis.
NA = not available.
E-l
-------
Table E-2. Residual clay (mg)
Subject
Subject 9
Wheel
Subject 10
Sculpture
Right Hand
9,750
1,874
4,059
1,536
1,367
70
83
74
Left Hand
11,243
2,352
4,270
2,845
3,426
14
65
98
Arms
398.55
790.25
388.60
5,005.35
8,630.60
33.50
58.50
131.80
Legs
509.80
596.25
1,276.70
958.50
273.95
8.40
42.85
9.20
Feet
214.40
144.00
267.20
220.65
2,991.50
17.40
42.65
14.10
Face
16.70
0.00
4.35
9.60
524.60
0.00
9.80
25.70
E-2
-------
APPENDIX F
PICTURES OF ARTISANS PRIOR TO SKIN RINSE PROCEDURE
Figure F-l. Subjects 1-4.
F-l
-------
Figure F-2. Subjects 5-8.
F-2
-------
Figure F-3. Subject 9.
F-3
-------
Figure F-4. Subject 10.
F-4
-------
APPENDIX G
REAL-TIME PARTICLE CONCENTRATION DATA
Personal Particle Concentration
using the pDR-1000 Particle Counter
0 20 40 60 80 100 120 140 160
Time (min)
Area Particle Concentration
using the CI-500 Particle Counter
0 20 40 60 80 100 120 140 160
Time (min)
Figure G-l. Subject 1.
G-l
-------
0
Personal Particle Concentration
using the pDR-1000 Particle Counter
Mixing and bagging
of powdered clay
Subject cleaned off
using compressed air
20 40 60
Time (min)
80
100
14
8 6
0)
£ 4
I 2
0
Area Particle Concentration
using the CI-500 Particle Counter
/V i
^ \i
Mixing and bagging
ot powdered clay
t
I
\
l/\
\ A A A A i[
Uv^rK/v^
Subject cleaned off
using compressed air
/
0 20 40 60
Time (min)
80
100
Figure G-2. Subject 2.
G-2
-------
Personal Particle Concentration
using the pDR-1000 Particle Counter
1
"E 0.8 -
O>
E
J 0.6 -
c
o
20.4-
.0
|0.2-
0 -
1
1
/
11
/
n
\ 1
/
J
1
0
1
ll tin/
W
L JL /H
/ ^ \PA/ \ / '
,AA, A/I M ^ ^ /
wv v VAAAjy v-^jw
i i i i
25 50 75 100 125
Time (min)
Area Particle Concentration
using the CI-500 Particle Counter
« 35
E
J25-
C O/"\
o ^u "
* 15 -
o
I10"
o -
1
i
k
\ll
/ V
/ \
A » \
J V
^-^-^AJ^^/^ "^N^S^^^^^^WS
0
1 1 1 1
25 50 75 100 125
Time (min)
Figure G-3. Subjects.
G-3
-------
Personal Particle Concentration
using the pDR-1000 Particle Counter
0 20 40 60 80
Time (min)
100 120
Area Particle Concentration
using the CI-500 Particle Counter
0
0 20 40 60 80 100 120
Time (min)
Figure G-4. Subject 4.
G-4
-------
0.3
0.25
0.2
0.15
o 0.1
0.05
0
0
Personal Particle Concentration
using the pDR-1000 Particle Counter
20
40
60 80
Time (min)
100 120 140
Area Particle Concentration
using the CI-500 Particle Counter
0 20 40 60 80 100 120 140
Time (min)
Figure G-5. Subject 5.
G-5
-------
Personal Particle Concentration
using the pDR-1000 Particle Counter
0
0 30 60 90
Time (min)
Area Particle Concentration
using the CI-500 Particle Counter
120
0 20 40 60 80 100 120
Time (min)
Figure G-6. Subject 6.
G-6
-------
1=4
3
o
o
Personal Particle Concentration
using the pDR-1000 Particle Counter
10
20
Time (min)
30
40
Area Particle Concentration
using the CI-500 Particle Counter
0 20 40 60 80 100 120
Time (min)
Figure G-7. Subject 7.
G-7
-------
Personal Particle Concentration
using the pDR-1000 Particle Counter
u
1°
u
o 3
u
o 2
t
n 1
i
n -
N
^WXjVv^/l/A/^jA^/Lwx^^
0 20 40 60 80 100 120 140
Time (min)
Area Particle Concentration
using the CI-500 Particle Counter
0
0 20 40 60 80 100 120 140
Time (min)
Figure G-8. Subjects.
G-8
-------
Wheel Session 1
*?
E
O)
o
u
0)
u
r
re
Q.
0.05
120
180 240
Time (min)
300
360
420
Wheel Session 2
120 180
Time (min)
240
300
Figure G-9. Subject 9.
G-9
-------
Wheel Session 3
4.5
£ 3.5
I 3
y 2.5
8
1.5
1
0.5
0
JYS-^.
It-
UAJVA*
60 120 180 240 300 360 420 480
Time (min)
Wheel Session 4
60 120 180 240 300 360 420
Figure G-9. continued.
G-10
-------
Wheel Session 5
*?
E
O)
re
Q.
0.6
0.5
0.4
0.3
0.2
0.1
60 120 180 240 300 360 420 480
Time (min)
Figure G-9. continued.
G-ll
-------
Sculpture Session 1
120
180 240
Time (min)
Sculpture Session 2
300
360
420
60
120
180 240
Time (min)
300
360
420
Figure G-10. Subject 10.
G-12
-------
Sculpture Session 3
1 d. -
« ^2
E
o) 1 n -
I 8 -
§
0)
* 4
o .
0
OJ -
En T
O)
0
8 n?-
0)
o
P n 1 ^ -
0-1
n -
0
.1 LI, 1 h II 1
^ v^^UJLJly^lUUJbJJ^
60 120 180 240 300 360 420
Time (min)
Background Particle Concentration
1 , lijf
n A fffl
1- - \\W
'I^11^K>WV^^A-WV(^^AV>^*1^^A^^^ V
SO 120 180 240 300 350 42
Time (min)
Figure G-10. continued.
G-13
-------
APPENDIX H
TTM
RESPICON , CASCADE IMP ACTOR, PDR-1000, AND CLIMET* CI-500,
DATA FOR EACH INDIVIDUAL SUBJECT
Table H-l. Concentration by particle diameter (um) as measured by the
Respicon™ Air Sampler (mg/m3)3'b
Aerodynamic
diameter
Subject 1
Subject 2
Subjects
Subject 4
Subject 5
Subject 6
Subject 7
Subject 8
Background0
<4
-------
Table H-2. Concentration by particle diameter (um) as measured by the Cascade
Impactor Air Sampler (mg/m3)3'b
Aerodynamic
diameter
Subject 1
Subject 2
Subject 3
Subject 4
Subject 5
Subject 6
Subject?
Subjects
Background0
0.5-2
32 jim
0.18
0.31
0.39
0.22
0.10
0.23
0.15
0.31
0.085
Total
0.35
0.47
0.99
0.37
0.13
0.61
0.51
0.64
0.13
aDL (DetectionLimit) = 0.015 mg/m3.
b !/2 DL was used in place of the
-------
Table H-3. Particle concentration as measured by the pDR-1000 Air
Sampler (mg/m3)
Subject 1
Subject 2
Subjects
Subject 4
Subject 5
Subject 6
Subject 7
Subject 8
Mean
0.75
0.57
0.30
0.14
0.049
1.22
0.32
0.34
Maximum
8.42
8.33
0.84
0.81
0.27
7.70
3.51
5.14
Minimum
0.047
0.016
0.093
0.027
0.019
0.078
0.080
0.015
Table H-4. Concentration by particle diameter (um) as measured by the
3\a
Climet CI-500 Air Sampler (mg/mj)
Physical
diameter
Subject 1
Subject 2
Subject 3
Subject 4
Subject 5
Subject 6
Subject 7
Subject 8
Background13
0.3-0.5
0.001
0.001
0.002
0.002
0.008
0.011
0.005
0.006
0.009
0.5-1.0
0.005
0.002
0.009
0.003
0.002
0.006
0.010
0.004
0.005
1.0-2.5
0.026
0.016
0.058
0.013
0.003
0.029
0.054
0.021
0.002
2.5-5.0
0.222
0.166
0.411
0.124
0.025
0.260
0.377
0.186
0.010
5.0-10
0.560
0.535
1.214
0.323
0.055
0.679
0.631
0.578
0.010
>10.0
1.499
1.747
3.756
0.964
0.167
1.746
0.817
1.878
0.019
Total
2.313
2.467
5.450
1.429
0.260
2.731
1.895
2.672
0.055
a Concentration calculations assume particle density of 2.6 g/cm3.
b Based on measurements taken late at night when no students were present in building.
H-3
-------
Table H-5. Average concentrations by particle diameter ranges (um)
measured by the Cascade Impactor Air Sampler (mg/m3)3'b
Aerodynamic
diameter
Subject 9
Session 1
Subject 9
Session 2
Subject 9
Session 3
Subject 9
Session 4
Subject 9
Session 5
Subject 10
Session 1°
Subject 10
Session 2C
Subject 10
Session 3
Background11
0.5-2
0.004
32
0.024
0.024
0.044
0.053
0.081
0.198
0.092
0.079
0.005
Total
0.049
0.046
0.102
0.073
0.152
0.480
0.237
0.241
0.023
aDL (Detection Limit) = 0.0025 mg/m3.
b !/2 DL was used in place of the
-------
Table H-6. Concentration by particle diameter ranges (urn) measured by the
Climet® CI-500 Air Sampler (mg/m3)a
Physical
diameter
Subject 9
Session 1
Subject 9
Session 2
Subject 9
Session 3
Subject 9
Session 4
Subject 9
Session 5
Subject 10
Session lb
Subject 10
Session 2b
Subject 10
Session 3
Background0
0.3-0.5
0.008
0.010
0.006
0.012
0.011
0.018
0.003
0.006
0.012
0.5-1.0
0.003
0.005
0.004
0.007
0.008
0.015
0.005
0.008
0.009
1.0-2.5
0.005
0.003
0.005
0.011
0.004
0.067
0.031
0.039
0.003
2.5-5.0
0.026
0.014
0.026
0.055
0.018
0.353
0.172
0.181
0.011
5.0-10
0.042
0.027
0.054
0.113
0.026
0.746
0.367
0.341
0.012
>10.0
0.070
0.058
0.124
0.240
0.048
1.430
0.700
0.656
0.016
Total
0.155
0.117
0.220
0.439
0.115
2.629
1.278
1.231
0.064
a Concentration calculations assume particle density of 2.6 g/cm3.
b Concentration not adjusted for presence of dog.
0 Based on measurements taken late at night when no students were present in building.
H-5
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APPENDIX I
MONTE CARLO CALCULATION OUTLINE
1.1. SELECT GENERAL EXPOSURE PARAMETERS
Dioxin concentration in clay (C) from distribution
Fraction ball clay in blend (Fuend) from distribution
Exposure duration (ED) from distribution
Select value for gender selector (0 to 0.5 means male, >0.5 to 1.0 means female)
Total body surface area males (SA) from distribution
Total body surface area females (SA) from distribution
1.2. COMPUTE DERMAL DOSE
Table 1-1. Select value for clothing selector and determine fraction of body
unclothed
Clothing Selector
0 to 0.2
0.2 to 0.8
0.8 to 0.9
0.9 to 1.0
Fraction Unclothed (Ft/)
f U arm
0
0.67
0.67
0.67
FUJes
0
0
0.67
0.67
FUfeet
0
0
0
1.0
Monolayer load (ML) = 0.5 mg/cm2
Dermal absorption fraction for feet (DAFfeet) = 0.0226 (assumes 24-hour exposure)
Dermal absorption fraction for legs (DAFiegs) = 0.0226 (assumes 24-hour exposure)
Dermal absorption fraction for hands (DAFhand) = (0.0005 ED2 + 0.05 ED + 0.7692)7100
Dermal absorption fraction for arms (DAFarms) = (0.0005 ED2 + 0.05 ED + 0.7692)7100
Dermal absorption fraction for face (DAFface) = (0.0005 ED2 + 0.05 ED + 0.7692)7100
Select clay load on hand (Lhand) from distribution
Adjust Lhand. if'Lhand > ML, then Lhand = ML, ifLhand < ML, then Lhand = Lhand.
1-1
-------
Total hand surface area (SAhand) = 0.052 SA
Dose to hand (Dhand) = (C Fbiend DAFhand Lhand SAhand) 0.001
Select clay load on arm (Larm) from distribution
Adj ust Larm : if Larm > ML, then Larm = ML, if Larm < ML, then Larm = Larm
Total arm surface area (SAarm) = 0.014 SA
Dose to arm (Darm) = (C Fbiend DAFarm Larm SAarm FUarm) 0.001
Select clay load on leg (Lieg) from distribution
Adjust Lieg. if Lieg > ML, then Lieg = ML, if L/eg < ML, then Lieg = Lieg.
Total hand surface area (SAieg) = 0.3 18 SA
Dose to hand (Dieg) = (C F^end DAFieg Lieg SAieg FUieg) 0.001
Select clay load on feet (Lfeet) from distribution
Adjust Lfeet: if Lfeet > ML, then Lfeet = ML, if Lfeet < ML, then Lfeet = Lfeet.
Total feet surface area (SAfeet) = 0.068 SA
Dose to feet (Dfeet) = (C Fbiend DAFfeet Lfeet SAfeet FUfeet) 0.001
Select clay load on face (Lface) from distribution
Adjust Lface: if Lface > ML, then Lface = ML, ifLface < ML, then Lface = Lface.
Total face surface area (SAface) = 0.025 SA
Dose to face (Dface) = (C Fbiend DAFface Lface SAface) 0.001
Total dermal dose (Dder) = Dhand + Darm + Dieg + Dfeet + Dface
1.3. COMPUTE INGESTION DOSE
Ingestion absorption fraction (Fing) = 0.3
Clay load on food (Lfood) from distribution
Clay load on beverage (Lbev) from distribution
Total ingestion dose (Dmg) = CFbiendFmg (Lfood + Lbev) 0.001
1.4. COMPUTE INHALATION DOSE
Particulate concentration in air (Cair) from distribution
Mass mean aerodynamic particle size (MMAD) from distribution
Geometric SD for particle distribution = 4
1-2
-------
Select value for activity selector (AS) from distribution
Walk time^S ED
Light exertion time (LET) = ED (1 -AS)
Table 1-2. Set respiration parameters
Tidal volume (TV) (mL)
Breathing frequency F
(times/min)
Ventilation rate Ve
(1pm)
Residual lung capacity
(mL)
Slow walk
Female
464
14
7y*F/l,000 = 6.5
2,680
Male
750
12
7y*F/l,000 =
9
3,300
Light exertion
Female
992
21
7y*F/l,000 = 21
2,680
Male
1,250
20
7y*F/l,000 =
25
3,300
Select value for Breath Selector
0 to 0.13 means oralnasal breather, >0.13 to 1.0 means nasal breather
Compute regional doses using MPPD Subroutine (see below where Dn = dose to nose, Dm = dose
to mouth, Dtb = dose to tracheal bronchial and Dpu = Dose to pulmonary)
Absorption fraction for nose, mouth, and TB = 0.3
Absorption fraction for PU = 0.8
Compute total inhalation dose (A«/0 = 0.3(DW +Dm+ Dtb) + Q.8Dpu
1.5. COMPUTE TOTAL DOSE (DTOTAi) = DDER + DING + DINH
MPPD Subroutine
MPPD (plus extrapolation curves for particles over 20 jim, see Appendix B) used to generate
deposition fractions over a range particle sizes for each respiratory region and scenario based on
breathing pattern, tidal volume, breathing frequency and residual lung capacity. The deposition
fractions for each particle size (based on aerodynamic diameter or Dae) are multiplied by the
inhalation fraction:
1-3
-------
Inhalation Fraction oral breather, I0= 1.44 / (1 + 0.44exp (0.0195£>ae))
Inhalation Fraction nasal breather, /„ = 1- (1.0 / (1 + exp (10.32-3.114 lnDae))
This results in eight sets of MPPD outputs for deposition fractions in ET, TB, and PU (corrected
for inhalation) which are stored in the spreadsheet:
Table 1-3. Output categories for deposition fractions
Male
Female
Slow Walk
Nasal
1
5
Oral
2
6
Light Exertion
Nasal
O
7
Oral
4
8
The particle size distribution is divided into 100 intervals and DFto each region is computed by
summing the deposition fraction over each interval
Deposition to each region are calculated for slow walk and light exertion and then summed. For
example, deposition to the nose, Dn is calculated as follows:
Dn = Cair [VtFED DFJlight + Catr [VtFED £>F«
1-4
-------
APPENDIX J
MONTE CARLO SIMULATION RESULT GRAPHICS
Crystal Ball Report - Full
Simulation started on 7/23/2008 at 10:07:17
Simulation stopped on 7/23/2008 at 10:15:22
Run preferences:
Number of trials run 1,000
Monte Carlo
Random seed
Precision control on
Confidence level 95.00%
Run statistics:
Total running time (sec) 485.46
Trials/second (average) 2
Random numbers per sec 37
Crystal Ball data:
Assumptions 18
Correlations 0
Correlated groups 0
Decision variables 0
Forecasts 4
J-l
-------
Forecasts
Worksheet: [VarDp-Dep monte6.xls]Monte
Forecast: Ingestion Dose (pg/d)
Summary:
Entire range is from 0.005 to 1.001
Base case is 0.058
After 1,000 trials, the std. error of the mean is 0.003
0.05
0.04
Ingeslion Dose (pg/d)
0000 O.OSO 0.100 0.150 0.200 0.250 0.300 0.350 0.400
Statistics:
Trials
Mean
Median
Mode
Standard Deviation
Variance
Skewness
Kurtosis
Coeff. of Variability
Minimum
Maximum
Range Width
Mean Std. Error
Forecast values
1,000
0.135
0.110
0.102
0.010
2.08
11.29
0.76
0.005
1.001
0.997
0.003
J-2
-------
Forecast: Ingestion Dose (pg/d) (cont'd)
Percentiles: Forecast values
0% 0.005
10% 0.035
20% 0.053
30% 0.073
40% 0.092
50% 0.110
60% 0.133
70% 0.161
80% 0.202
90% 0.258
100% 1.001
J-3
-------
Forecast: Inhalation Dose
Summary:
Entire range is from 0.00 to 1.12
Base case is 0.03
After 1,000 trials, the std. error of the mean is 0.00
D.OO
Inhalation Dose
005
0.10
0.15
020
0.25
030
0 35
0.HO
045
pg/g
Statistics:
Trials
Mean
Median
Mode
Standard Deviation
Variance
Skewness
Kurtosis
Coeff. of Variability
Minimum
Maximum
Range Width
Mean Std. Error
Forecast values
1,000
0.11
0.07
0.13
0.02
2.78
14.10
1.10
0.00
1.12
1.11
0.00
J-4
-------
Forecast: Inhalation Dose (cont'd)
Percentiles: Forecast values
0% 0.00
10% 0.02
20% 0.03
30% 0.04
40% 0.06
50% 0.07
60% 0.09
70% 0.12
80% 0.17
90% 0.26
100% 1.12
J-5
-------
Forecast: Total Dermal Dose
Summary:
Entire range is from 0.14 to 91.63
Base case is 3.32
After 1,000 trials, the std. error of the mean is 0.26
O.QO
Total Dermal Dose
400
a.00
12.00
16.00
20.00
24 00 2B.OO
pg/g
Statistics:
Trials
Mean
Median
Mode
Standard Deviation
Variance
Skewness
Kurtosis
Coeff. of Variability
Minimum
Maximum
Range Width
Mean Std. Error
Forecast values
1,000
6.18
3.23
8.32
69.30
3.71
23.60
1.35
0.14
91.63
91.48
0.26
J-6
-------
Forecast: Total Dermal Dose (cont'd)
Percentiles: Forecast values
0% 0.14
10% 0.96
20% 1.42
30% 1.90
40% 2.45
50% 3.23
60% 4.46
70% 6.07
80% 8.90
90% 14.42
100% 91.63
J-7
-------
Forecast: Total Dose (pg/d)
Summary:
Entire range is from 0.17 to 92.39
Base case is 3.41
After 1,000 trials, the std. error of the mean is 0.27
0.12
Q.10
>•• 0.08
-
-d 0.06
0.04
O.O2
0.0d>
0.00
Total Dose (pg/d)
400
8.00
12.00 16.00
2000
24.00
28.00
Statistics:
Trials
Mean
Median
Mode
Standard Deviation
Variance
Skewness
Kurtosis
Coeff. of Variability
Minimum
Maximum
Range Width
Mean Std. Error
Forecast values
1,000
6.43
3.50
8.43
71.03
3.67
23.22
1.31
0.17
92.39
92.22
0.27
J-8
-------
Forecast: Total Dose (pg/d) (cont'd)
Percentiles: Forecast values
0% 0.17
10% 1.07
20% 1.55
30% 2.08
40% 2.73
50% 3.50
60% 4.69
70% 6.36
80% 9.15
90% 14.80
100% 92.39
End of Forecasts
J-9
-------
Assumptions
Worksheet: [VarDp-Dep monte6.xls]Monte
Assumption: Activity selector
Uniform distribution with parameters:
Minimum
Maximum
0.00
1.00
Assumption: Breath Selector
Uniform distribution with parameters:
Minimum
Maximum
0.00
1.00
Assumption: Clay load on arm (mg/cm2)
Triangular distribution with parameters:
Minimum
Likeliest
Maximum
0.04
0.35
3.00
Assumption: Clay load on beverage (mg)
Triangular distribution with parameters:
Minimum
Likeliest
Maximum
0.30
0.50
0.72
i'lny loud on hcv<:r:i<]c (mi])
J-10
-------
Assumption: Clay load on face (mg/cm2)
Uniform distribution with parameters:
Minimum
Maximum
0.030
0.040
nnylondonlni^mq/cmT)
Assumption: Clay load on feet (mg/cm2)
Uniform distribution with parameters:
Minimum
Maximum
0.03
0.30
Assumption: Clay load on food (mg)
Triangular distribution with parameters:
Minimum
Likeliest
Maximum
0.30
0.70
1.66
Assumption: Clay load on hand (mg/cm2)
Triangular distribution with parameters:
Minimum
Likeliest
Maximum
0.10
3.00
10.00
fiLiy lo,nt on hnnrl (mq/cm?)
J-ll
-------
Assumption: Clay load on leg (mg/cm2)
Uniform distribution with parameters:
Minimum
Maximum
0.10
0.70
Assumption: clothing selector
Uniform distribution with parameters:
Minimum
Maximum
0.00
1.00
Assumption: Dioxin cone in ball clay (pg/g)
Lognormal distribution with parameters:
Mean 808.00
Std. Dev. 318.00
Assumption: Exposure Duration (hr/d)
Triangular distribution with parameters:
Minimum
Likeliest
Maximum
1.00
4.00
10.00
J-12
-------
Assumption: Fraction of ball clay in blend
Triangular distribution with parameters:
Minimum
Likeliest
Maximum
0.00
0.20
1.00
of hall cluym blend
Assumption: Gender Selector
Uniform distribution with parameters:
Minimum
Maximum
0.00
1.00
flendcr Selecl
Assumption: MMAD (um)
Triangular distribution with parameters:
Minimum
Likeliest
Maximum
13.00
25.00
45.00
Assumption: Particle Concentration in Air(mg/m3)
Triangular distribution with parameters:
Minimum 0.08
Likeliest 0.44
Maximum 0.99
J-13
-------
Assumption: Total Body Surface Area Females (cm2)
Lognormal distribution with parameters:
Mean 17,300.00
Std. Dev. 2,100.00
eAieitl cmi*s\<<3ii?)
Assumption: Total Body surface Area Males (cm2)
Lognormal distribution with parameters:
Mean 19,700.00
Std. Dev. 1,900.00
I nlnl llorty \ur1mie Are* MitkM (crnT)
End of Assumptions
J-14
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vvEPA
United States
Environmental Protection
Agency
National Center for Environmental Assessment
Office of Research and Development
Washington, DC 20460
Official Business
Penalty for Private Use
$300
PRESORTED STANDARD
POSTAGE & FEES PAID
EPA
PERMIT NO. G-35
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