vvEPA
United States
Environmental Protection
Agency
Risk Assessment Guidance for Superfund
Volume I: Human Health
Evaluation Manual
(Part E, Supplemental Guidance for
Dermal Risk Assessment)
Final
Office of Superfund Remediation and Technology Innovation
U.S. Environmental Protection Agency
Washington, DC
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vvEPA
EPA/540/R/99/005
,, ,c OSWER 9285.7-02EP
United States
Environmental Protection PB99-963312
Agencv July 2004
Risk Assessment Guidance for Superfund
Volume I: Human Health
Evaluation Manual
(Part E, Supplemental Guidance for
Dermal Risk Assessment)
Final
Office of Superfund Remediation and Technology Innovation
U.S. Environmental Protection Agency
Washington, DC
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This document provides guidance to EPA Regions concerning how the Agency intends to exercise its discretion
in implementing one aspect of the CERCLA remedy selection process. The guidance is designed to implement
national policy on these issues.
Some ofthe statutory provisions described in this document contain legally binding requirements. However, this
document does not substitute for those provisions or regulations, nor is it a regulation itself. Thus, it cannot impose
legally-binding requirements on EPA, states, or the regulated community, and may not apply to a particular situation
based upon the circumstances. Any decisions regarding a particular remedy selection decision will be made based
on the statute and regulations, and EPA decisionmakers retain the discretion to adopt approaches on a case-by-case
basis that differ from this guidance where appropriate. EPA may change this guidance in the future.
in
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ABOUT THIS DOCUMENT
WHAT IT IS This document is Supplemental Guidance (Part E) to the Risk Assessment Guidance for Superfund,
Volume I: Human Health Evaluation Manual (RAGS). This document incorporates and updates
the principles of the EPA interim report, Dermal Exposure Assessment: Principles and
Applications (DEA) (U.S. EPA, 1992a), released by the Office of Health and Environmental
Assessment (OHEA), in the Office of Research and Development (ORD), in January 1992. Part
E contains methods for conducting dermal risk assessments. EPA has found these methods
generally to be appropriate. However, for each dermal risk assessment, Regions must decide
whether these methods, or others, are appropriate, depending on the facts. Specific information
and data tables and updated or modified assumptions or variables used in this guidance are
available on the following EPA WebPages:
http://www.epa.gov/oswer/riskassessment/
or
http://www.epa.gov/superfund/programs/risk/ragse/index.htm
FOR WHOM This guidance document is for risk assessors, risk assessment reviewers, remedial project
managers (RPMs), and risk managers involved in Superfund site investigations and human health
risk assessments.
WHAT IS
NEW
REVIEW
RAGS Part E updates or expands the following elements in dermal risk assessment methodology:
- updated dermal exposure assessment equations for the water pathway
- updated table for screening contaminants of potential concern (COPCs) from contami-
nants in water
- specific dermal absorption from soil values for ten chemicals and recommended defaults
for screening other organic compounds
- updated soil adherence values based on receptor activities
- updated dermal exposure parameters that are consistent with the Exposure Factors
Handbook (U.S. EPA, 1997a)
- an expanded Uncertainty Analysis section that discusses and compares the contribution
of specific components to the overall uncertainty in a dermal risk assessment.
This guidance document has been reviewed by internal EPA peer review (May 1997), external
peer review (January 1998), and followup external peer review (January 2000). In addition,
specific technical recommendations were provided by a Peer Consultation Workshop organized
by the Risk Assessment Forum (December 1998). EPA received public comments on the draft of
the guidance that was released in December 2001.
IV
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CONTENTS
Page
ABOUT THIS DOCUMENT iv
CONTENTS v
EXHIBITS viii
ACKNOWLEDGMENTS x
PREFACE xi
ACRONYMS/ABBREVIATIONS xii
1. 0 INTRODUCTION AND FLOWCHART 1-1
1.1 INTRODUCTION 1-1
1.2 ORGANIZATION OF DOCUMENT 1-3
1.3 FLOWCHARTS 1-3
2.0 HAZARD IDENTIFICATION 2-1
2.1 CHOOSING CONTAMINANTS OF CONCERN FOR THE
DERMAL-WATER PATHWAY 2-1
2.2 CHOOSING CONTAMINANTS OF CONCERN FOR THE
DERMAL-SOIL PATHWAY 2-1
3.0 EXPOSURE ASSESSMENT 3-1
3.1 ESTIMATION OF DERMAL EXPOSURES TO CHEMICALS IN WATER 3-1
3.1.1 Standard Equation for Dermal Contact with Chemicals in Water 3-1
3.1.2 Exposure Parameters 3-3
3.1.2.1 Permeability Coefficient for Compounds in Water (Kp in cm/hr) 3-3
3.1.2.2 Chemical Concentration in Water 3-7
3.1.2.3 Skin Surface Area 3-8
3.1.2.4 Event Time, Frequency, and Duration of Exposure 3-10
3.2 ESTIMATION OF DERMAL EXPOSURE TO CHEMICALS IN SOIL 3-10
3.2.1 Standard Equation for Dermal Contact with Chemicals in Soil 3-10
3.2.2 Exposure Parameters 3-10
3.2.2.1 Skin Surface Area 3-10
3.2.2.2 Soil-to-Skin Adherence Factors 3-12
3.2.2.3 Recommended Soil Adherence Factors 3-14
3.2.2.4 Dermal Absorption Fraction from Soil 3-17
3.2.2.5 Age-Adjusted Dermal Factor 3-18
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CONTENTS (continued)
Page
3.2.2.6 Event Time, Exposure Frequency, and Duration 3-21
3.3 ESTIMATION OF DERMAL EXPOSURE TO CHEMICALS IN SEDIMENT 3-19
4.0 TOXICITY ASSESSMENT 4-1
4.1 PRINCIPLES OF ROUTE-TO-ROUTE EXTRAPOLATION 4-1
4.2 ADJUSTMENT OF TOXICITY FACTORS 4-2
4.3 CALCULATION OF ABSORBED TOXICITY VALUES 4-2
4.4 DIRECT TOXICITY 4-3
5.0 RISK CHARACTERIZATION 5-1
5.1 QUANTITATIVE RISK EVALUATION 5-1
5.1.1 Risk Calculations 5-1
5.1.2 Risks for All Routes of Exposure 5-1
5.2 UNCERTAINTY ASSESSMENT 5-1
5.2.1 Hazard Identification 5-3
5.2.2 Exposure Assessment 5-4
5.2.2.1 Dermal Exposure to Water - Uncertainties Associated with the Model for
DAevent 5-4
5.2.2.2 Dermal Exposure to Soil 5-5
5.2.3 Toxicity Assessment 5-7
5.2.4 Risk Characterization 5-7
6.0 CONCLUSIONS/RECOMMENDATIONS 6-1
6.1 SUMMARY 6-1
6.2 EXPOSURES NOT INCLUDED IN CURRENT DERMAL GUIDANCE 6-2
6.3 RECOMMENDATIONS 6-2
REFERENCES R-l
APPENDICES
APPENDIX A: WATER PATHWAY A-l
VI
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CONTENTS (continued)
Page
A.I DERMAL ABSORPTION OF ORGANIC COMPOUNDS A-2
A.1.1 Estimation of Kp for Organic Compounds A-2
A. 1.2 Calculation of Other Parameters in DAevent A-7
A. 1.3 Model Adjustment for Lipophilic Compounds Outside EPD A-12
A. 1.4 Model Validation A-13
A.2 DERMAL ABSORPTION OF INORGANIC AND IONIZED
ORGANIC COMPOUNDS A-16
A.3 UNCERTAINTY ANALYSIS A-19
A.4 SCREENING PROCEDURE FOR CHEMICALS IN WATER A-26
A.5 PROCEDURES FOR CALCULATING DERMAL DOSE A-30
A.5.1 Stepwise Procedure for Calculating Dermal Dose Using
Spreadsheets A-39
APPENDIX B: SCREENING TABLES AND REFERENCE VALUES FOR
THEWATERPATHWAY B-l
APPENDIX C: SOIL PATHWAY C-l
APPENDIX D: SAMPLE SCREENING CALCULATIONS D-l
D. 1 SAMPLE CANCER SCREENING CALCULATION FOR DERMAL
CONTAMINANTS IN WATER D-l
D.2 SAMPLE NON-CANCER SCREENING CALCULATION FOR CONTAMINANTS IN
RESIDENTIAL SOIL D-6
APPENDIX E: DISCUSSION ON EVALUATING/DEVELOPING SITE-SPECIFIC DERMAL
ABSORPTION DATA E-l
vn
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EXHIBITS
Page
1-1 RELATIONSHIP OF THE HUMAN HEALTH EVALUATION TO THE CERCLA PROCESS .... 1-2
1-2 WATER PATHWAY 1-4
1-3 SOIL PATHWAY 1-5
3-1 PERMEABILITY COEFFICIENTS FOR INORGANICS 3-5
3-2 RECOMMENDED DERMAL EXPOSURE VALUES FOR CENTRAL
TENDENCY AND RME RESIDENTIAL SCENARIOS - WATER CONTACT 3-8
3-3 ACTIVITY SPECIFIC-SURFACE AREA WEIGHTED SOIL ADHERENCE
FACTORS 3-15
3-4 RECOMMENDED DERMAL ABSORPTION FRACTION FROM SOIL 3-16
3-5 RECOMMENDED DERMAL EXPOSURE VALUES FOR CENTRAL
TENDENCY AND RME RESIDENTIAL AND INDUSTRIAL
SCENARIOS - SOIL CONTACT 3-20
4-1 SUMMARY OF GASTROINTESTINAL ABSORPTION EFFICIENCIES AND
RECOMMENDATIONS FOR ADJUSTMENT OF TOXICITY FACTORS FOR SPECIFIC
COMPOUNDS 4-5
5-1 SUMMARY OF DERMAL RISK ASSESSMENT PROCESS 5-2
5-2 SUMMARY OF UNCERTAINTIES ASSOCIATED WITH DERMAL
EXPOSURE ASSESSMENT 5-3
A-1 EFFECTIVE PREDICTIVE DOMAIN (EPD)
BOUNDARIES FOR K,, ESTIMATION A-5
A-2 COMPOUNDS FROM APPENDIX B WITH PERMEABILITY COEFFICIENTS
OUTSIDE OF THE EFFECTIVE PREDICTION DOMAIN OF THE MODIFIED
POTTS AND GUY CORRELATION A-6
A-3 EFFECTS OF MW AND LOG Kow ON B A-9
A-4 FRACTION ABSORBED (FA) AS A FUNCTION OF SPECIFIC COMBINATIONS
OF B AND Tevent/tsc A-14
A-5 EFFECT OF STRATUM CORNEUM TURNOVER ON FRACTION
ABSORBED (WATER) AS A FUNCTION OF B A-15
A-6 APPARENT PERMEABILITY COEFFICIENTS OF INORGANICS A-17
A-7 STUDENTIZED RESIDUALS OF PREDICTED KP VALUES A-21
viii
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A-8 EVALUATION OF DERMAL/ORAL CONTRIBUTION FOR LIPOPfflLIC COMPOUNDS A-25
A-9 DEFAULT VALUES FOR WATER CONTACT EXPOSURE PARAMETERS A-31
B-l FLYNN DATA SET B-2
B-2 PREDICTED KpFOR ORGANIC CONTAMINANTS IN WATER B-5
B-3 CALCULATION OF DERMAL ABSORBED DOSE FOR
ORGANIC CHEMICALS IN WATER B-l 1
B-4 CALCULATION OF DERMAL ABSORBED DOSE FOR
INORGANIC CHEMICALS IN WATER B-20
C-l BODY PART-SPECIFIC SURFACE AREA CALCULATIONS C-2
C-2 ACTIVITY BODY PART-SPECIFIC SOIL ADHERENCE FACTORS C-4
C-3 OVERALL BODY PART-SPECIFIC WEIGHTED SOIL ADHERENCE
FACTORS C-16
C-4 ESTIMATION OF SOIL ADHERENCE FACTOR AT MONO-LAYER FOR
SOIL CONSERVATION SERVICE (SCS) SOIL CLASSIFICATIONS C-l8
D-l SUMMARY OF DERMAL RISK ASSESSMENT PROCESS D-l
IX
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ACKNOWLEDGMENTS
This guidance was developed by the Superfund Dermal Workgroup, which included regional and headquarters
staff in EPA's Office of Superfund Remediation and Technology Innovation (OSRTI),1 personnel in EPA's Office
of Research and Development (ORD), and representatives from the Texas Natural Resource Conservation Commis-
sion. Jim Konz, Elizabeth Lee Hofmann, Steve Ells, and David Bennett of OSRTI headquarters provided project
management and technical coordination of its development.
OSRTI would like to acknowledge the efforts of all the Superfund Dermal Workgroup members who supported
the development of the interim guidance by providing technical input regarding the content and scope of the
guidance:
Dave Crawford, OSWER/OSRTI
Michael Dellarco, ORD/NCEA
Kim Hoang, previously with ORD/NCEA, currently with Region 9
Elizabeth Lee Hofmann, OSWER/OAA
Mark Maddaloni, Region 2
John Schaum, ORD/NCEA
Dan Stralka, Region 9
Former members:
Ann-Marie Burke, previously with Region 1
Mark Johnson, previously with Region 5
Loren Lund/Steve Rembish, previously with the Texas Natural Resource Conservation Commission
OSRTI would also like to acknowledge the efforts of the peer review panel members who provided input on the
draft version of the document.
Annette Bunge, Colorado School of Mines
John Kissel, University of Washington
James McDougal, Geo-Centers, Inc. (AFRL/HEST)
Thomas McKone, University of California, Berkeley
Environmental Management Support, Inc., of Silver Spring, Maryland, under contract 68-W6-0046, and COM
Federal Programs Corporation, under Contract Nos. 68-W9-0056 and 68-W5-0022, provided technical assistance to
EPA in the development of this guidance.
1 In 2003, The EPA Office of Solid Waste and Emergency Response (OSWER) reorganized. Many of
the functions and responsibilities of the Office of Emergency and Remedial Response (OERR), including
coordinating the development of this guidance, were assigned to the Office of Superfund Remediation
and Technology Innovation (OSRTI).
x
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PREFACE
This guidance is the fifth part (Part E) in the series Risk Assessment Guidance for Superfund: Volume I - Human
Health Evaluation Manual (RAGS/HHEM) (U.S. EPA, 1989). Part A of this guidance describes how to conduct a
site-specific baseline risk assessment. Part B provides guidance for calculating risk-based concentrations that may
be used, along with applicable or relevant and appropriate requirements (ARARs) and other information, to develop
preliminary remediation goals (PRGs) during project scoping. PRGs and final remediation levels can be used
throughout the analyses in Part C to assist in evaluating the human health risks of remedial alternatives. Part D
complements the guidance provided in Parts A, B and C and presents approaches to standardizing risk assessment
planning, reporting and review. Part E is intended to provide a consistent methodology for assessing the dermal
pathway for Superfund human health risk assessments. It incorporates and updates principles of the EPA interim
report, Dermal Exposure Assessment: Principles and Applications (U.S. EPA, 1992a).
Several appendices are included in this guidance to support the summary calculations presented in the main body
of the document (Appendix A), to provide physical constants for specific chemicals (Appendix B), and to provide
tables for screening chemicals for the pathway (Appendix C). Appendix D provides sample calculations.
XI
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ACRONYMS/ABBREVIATIONS
Acronym/
Abbreviation
Definition
a, b, c
ABS
ABSd
ABSGI
AF
ARARs
AT
P
B
CERCLA
BW
CF
COC
COPC
cPAH
CSOil
''tot
cu
cw
DAevent
DAD
De
D0
Dsc
DBA
ED
EF
Correlation coefficients which have been fitted to the Flynn's data to give Equation 3.8
Dermal absorption from soil
Fraction of contaminant absorbed dermally (dimensionless)
Fraction of contaminant absorbed in gastrointestinal tract (dimensionless)
Adherence factor of soil to skin (mg/cm2-event)
Applicable or Relevant and Appropriate Requirements
Averaging time (days)
Constant specific for the medium through which diffusion is occurring
Dimensionless ratio of the permeability coefficient of a compound through the stratum corneum
relative to its permeability coefficient across the viable epidermis (dimensionless)
Comprehensive Environmental Response, Compensation, and Liability Act
Body weight (kg)
Conversion factor (10~6 kg/mg)
Contaminant of Concern
Contaminant of Potential Concern
Carcinogenic polynuclear aromatic hydrocarbons
Chemical concentration in soil (mg/kg)
Total concentration of chemical in the aqueous solution (mg/1)
Concentration of the non-ionized species (mg/1)
Chemical concentration in water (mg/cm3)
Absorbed dose per event (mg/cm2-event)
Dermal absorbed dose (mg/kg-day)
Effective diffusivity of the absorbing chemical in the epidermis (cm2/hr)
Diffusivity of a hypothetical molecule with a molecular volume (MV) = 0 (cm2/hr)
Effective diffusion coefficient of the chemical through the stratum corneum
Dermal Exposure Assessment: Principles and Applications (U.S. EPA, 1992a)
Exposure duration (years)
Exposure frequency (days/year)
xn
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ACRONYMS/ABBREVIATIONS (continued)
Acronym/
Abbreviation
Definition
EFH
EPA
EPC
EPD
EV
FA
FTSA
GI
GSD
HHEM
IR
Kew
Kow
p
p-msd
Kp-pred
lsc
MV
MW
IRIS
NCEA
OERR
OHEA
Exposure Factors Handbook (U.S. EPA, 1997a)
U. S. Environmental Protection Agency
Exposure point concentration
Effective Prediction Domain
Event frequency (events/day)
Fraction absorbed water (dimensionless)
Fraction of total surface area for the specified body part
Gastrointestinal
Geometric standard deviation
Human Health Evaluation Manual
Ingestion rate (for water, liters/day)
Equilibrium partition coefficient between the epidermis and water for the absorbing chemical
(dimensionless)
Octanol/water partition coefficient (dimensionless)
Dermal permeability coefficient of compound in water (cm/hr)
Measured dermal permeability coefficient of compound in water (cm/hr)
Predicted dermal permeability coefficient of compound in water (cm/hr)
Steady-state permeability coefficient through the viable epidermis (ve) (cm/hr)
Equilibrium partition coefficient between the stratum corneum and water (chemical specific
dimensionless)
Effective thickness of the epidermis (cm)
Apparent thickness of stratum corneum (cm)
Molar volume (cm3/mole)
Molecular weight (g/mole)
Integrated Risk Information System
National Center for Environmental Assessment
Office of Emergency and Remedial Response (now known as OSRTI)
Office of Health and Environmental Assessment
Xlll
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ACRONYMS/ABBREVIATIONS (continued)
Acronym/
Abbreviation
Definition
ORD
OSWER
OSRTI
p
A particle
PAH
PCBs
pKa
PRO
RAGS
RfD
RfD0
RME
SA
sc
scs
SEE
SF
SFabs
SF0
SFd
SFSadj
SVOCs
TCDD
THQ
TRL
Office of Research and Development
Office of Solid Waste and Emergency Response
Office of Superfund Remediation and Technology Innovation
Particle density (g/cm3)
Polynuclear aromatic hydrocarbon
Polychlorinated biphenyls
Chemical specific ionization constant
Preliminary Remediation Goals
Risk Assessment Guidance for Superfund (U.S. EPA, 1989)
Reference dose
Absorbed reference dose (mg/kg-day)
Reference dose oral (mg/kg-day)
Reasonable maximum exposure
Skin surface area available for contact (cm2)
Stratum corneum
Soil Conservation Service
Standard error of the estimator
Slope factor
Absorbed slope factor (mg/kg-day)"1
Oral slope factor (mg/kg-day)"1
Dermal cancer slope factor (mg/kg-day)"1
Age-adjusted dermal exposure factor (mg-yrs/kg-event)
Semivolatile organic compounds
Tetrachlorodibenzo-p-dioxin
Lag time per event (hr/event)
Time to reach steady-state (hr)
Event duration (hr/event)
Target Hazard Quotient (non-cancer)
Target Risk Level (cancer)
xiv
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ACRONYMS/ABBREVIATIONS (continued)
Acronym/
Abbreviation
Definition
tsc Turnover time for the stratum corneum (days)
95 % CL 95 % confidence level
95% LCL 95% lower confidence level
95% UCL 95% upper confidence level
xv
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CHAPTER 1
INTRODUCTION AND FLOWCHART
1.1 INTRODUCTION
This guidance is the fifth part (Part E) in the series
Risk Assessment Guidance for Superfund: Volume I -
Human Health Evaluation Manual (RAGS/HHEM)
(U.S. EPA, 1989). Part A of this guidance describes
how to conduct a site-specific baseline risk assessment.
Part B provides guidance for calculating risk-based
concentrations that may be used, along with applicable
or relevant and appropriate requirements (ARARs) and
other information, to develop preliminary remediation
goals (PRGs) during project scoping. PRGs and final
remediation levels can be used throughout the analyses
in Part C to assist in evaluating the human health risks
of remedial alternatives. Part D complements the
guidance provided in Parts A, B and C and presents
approaches to standardizing risk assessment planning,
reporting and review. Part E is intended to provide a
consistent methodology for assessing the dermal
pathway for Superfund human health risk assessments.
Part E incorporates and updates principles of the EPA
interim report, Dermal Exposure Assessment:
Principles and Applications (DBA) (U.S. EPA, 1992a).
The DEA is considered guidance for all EPA environ-
mental programs. Exhibit 1-1 illustrates the correspon-
dence of RAGS/HHEM activities with the steps in the
Comprehensive Environmental Response, Compensa-
tion, and Liability Act (CERCLA) remedial process.
In January 1992, the Office of Health and
Environmental Assessment (OHEA), in the Office of
Research and Development (ORD) of the U.S.
Environmental Protection Agency (EPA) issued an
interim report, Dermal Exposure Assessment:
Principles and Applications (U.S. EPA, 1992a). The
1992 ORD document, from now on referred to as DEA,
provided guidance for conducting dermal exposure
assessments. The conclusions of the DEA were
summarized at the National Superfund Risk Assessors
Conference in January 1992 when regional risk
assessors requested that a workgroup be formed to
prepare an interim dermal risk assessment guidance for
the Superfund program based on the DEA. The Part E
guidance serves to promote consistency in procedures
used by the Regions to assess dermal exposure
pathways at Superfund sites. In August 1992, a draft
Superfund Interim Dermal Risk Assessment Guidance
document was circulated for comment but was never
issued as an Office of Solid Waste and Emergency
Response (OSWER) Directive. This current guidance
supersedes the 1992 Superfund document.
This 2002 Superfund RAGS Part E, Interim
Supplemental Guidance for Dermal Risk Assessment
(from now on referred to as RAGS Part E) is the result
of Superfund Dermal Workgroup meetings from FY 95
through FY 00 on issues associated with the charac-
terization of risk resulting from the dermal exposure
pathway. RAGS Part E updates the recommendations
presented in the DEA, the updated Exposure Factors
Handbook (U.S. EPA, 1997a), and additional infor-
mation from literature as cited. Users of this guidance
are strongly encouraged to review and understand the
material presented in the DEA. This guidance is
considered interim, pending release of any update to
the DEA from ORD. As more data become available,
RAGS Part E may be updated.
It should be noted that this document limits its
guidance on dermal exposure assessment to the
discussion of systemic chronic health effects resulting
from low-dose, long-term exposure. However, acute
chemical injury to the skin should also be examined to
present an accurate and comprehensive assessment of
toxicity through the dermal route. The potential for
direct dermal contact resulting in dermal effects such
as allergic contact responses, urticarial reactions,
hyperpigmentation, and skin cancer should be
discussed qualitatively in the exposure section of the
risk assessment.
This document does not provide guidance on
quantifying dermal absorption of chemicals resulting
from exposure to vapors. The Superfund Dermal
Workgroup agreed with the finding in the DEA report
that many chemicals, with low vapor pressure and low
environmental concentrations, cannot achieve adequate
vapor concentration to pose a dermal exposure hazard.
1-1
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1-1
'RELATIONSHIP OF THE HUMAN HEALTH EVALUATION TO THE CERCLA PROCESS
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For chemicals with the potential to achieve adequate
vapor concentrations, this guidance assumes that they
are primarily absorbed through the respiratory tract.
Additional information on dermal absorption of
chemical vapors can be found in the DBA, Chapter 7.
1.2 ORGANIZATION OF DOCUMENT
This guidance is structured to be consistent with
the four steps of the Superfund risk assessment
process: hazard identification, exposure assessment,
toxicity assessment, and risk characterization.
Chapters 2.0 - 5.0 of RAGS Part E follow these steps:
Chapter 2: Hazard Identification- identifies
those chemicals that make a significant contribu-
tion to exposure and risk at a Superfund site.
Chapter 3: Exposure Assessment- evaluates the
pathways by which individuals could be exposed to
chemicals present at a Superfund site.
Chapter 4: Toxicity Assessment- identifies the
potential adverse health effects associated with the
contaminants of concern identified at the site.
Chapters: Risk Characterization-incorporates
information from the three previous chapters to
evaluate the potential risk to exposed individuals at
the site. This chapter also contains a discussion of
the uncertainties associated with estimating risk for
the dermal pathway.
Chapter 6: Summary and Recommendations-
provides a summary of the main points for each
step in the dermal risk assessment process and
recommendations for future data needs to improve
the evaluation of dermal exposures.
1.3 FLOWCHARTS
The following flowcharts (Exhibit 1-2 and Exhibit
1-3) facilitate the process of performing a dermal risk
assessment, by identifying the key steps and the
locations of specific information. Separate flowcharts
are provided for the water and the soil pathways.
Descriptions of the processes illustrated in both
flowcharts follow.
Dermal Risk Assessment Process for Water
Pathway - The screening process illustrated in
Exhibit 1-2 identifies those chemicals that should
be evaluated for the dermal pathway. The process
identifies those chemicals where the dermal path-
way has been estimated to contribute more than
10% of the oral pathway, using conservative
residential exposure criteria. Screening tables in
Appendix B (Exhibit B-3 for organics and Exhibit
B -4 for inorganics) help provide a recommendation
as to whether the dermal pathway should be
evaluated for a given chemical. If so, the next step
is to determine the rate of migration of the
chemical through the skin, using the dermal perme-
ability coefficient (Kp), derived from either experi-
mentally measured or predicted values. If default
residential exposure assumptions are appropriate
for the risk assessment, then the absorbed dose,
DAevent term, can be extracted from either Exhibit
B-3 or B-4, and used with the chemical concen-
tration to calculate the dermally absorbed dose
(DAD) term. If default residential exposure
assumptions are not appropriate, references to the
specific equations and information sources are
provided in the Exhibit 1-2 flowchart. Finally, the
procedures for the toxicity assessment and risk
characterization steps are also outlined.
Dermal Risk Assessment Process for Soil
Pathway - There is no screening process for
eliminating chemicals in a soil matrix from a
dermal risk assessment, as there is for the water
pathway. The first step in the hazard identification
process illustrated in Exhibit 1-3 is to determine if
quantitative dermal absorption from soil (ABS)
values are available for the chemical to be
evaluated. If not, the decision whether or not to
use default values as surrogates for those
chemicals without specific recommended values
must be made. If data are available, a site-specific
ABS value could be used. Section 3.0, Exposure
Assessment, summarizes exposure parameter
values for a reasonable maximum exposure (RME)
exposure scenario as well as activity-specific
values. The steps in the toxicity assessment and
risk characterization are the same for both the soil
and water pathways.
1-3
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1-2
HAZARD
IDENTIFICATION
EXPOSURE
Are
chemicals
organic or
inorganic?
Is dermal
assessment
recommended,
on Appendix
B-3 Screening
Table?
Is dermal
assessment
recommended,
on Appendix
8-4 Screening
Table?
Identify Kp value from
Exhibit B-4 or use 1Q-3
em/hr defau t va ue
Are default
exposure
assumptions in
Exhibit B-3
appropriate?
No
Is
tev.nl
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1-3 SOIL PATHWAY
HAZARD
IDENTIFICATION
EXPOSURE
ASSESSMENT
Is a
specific soil
absorption (ABS)
value for
chemical in Exhibit
3-4?
Is a
default value or
other date available
to estimate dermal
absorption from
soil?
Is
default
exposure
appropriate?
Discuss the of
sufficient information
about dermal exposure
in the uncertainty section
Select RME exposure
parameter values from
3-5 for EV, EF,
ED, SA, and AF
Identify appropriate activity-specific soil
factor for an adult or child
(Exhibit 3-3), other exposure
(EV, EF, ED, SA) from 3-5
Identify soil absorption value (ABS)
from Exhibit 3-4
I
Calculate Dermal Dose (DAD) with
soil concentration, using eq. 3,10 3.11
TOXICITY
ASSESSMENT
adjustment of
toxicity values
recommended
Exhibit 4-1?
Adjust oral toxicity value using eq, 4,2
(SFABS ) or eq. 4.3 (RfDABS) and Gi
absorption value from Exhibit 4-1
Use oral toxicity values for
and RfDABS
RISK
CHARACTERIZATION
Calculate Dermal Risk using DAD with S
eqs.5.1 and 5.2
. using
I
Characterize uncertainty from potential sources
1-5
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CHAPTER 2
HAZARD IDENTIFICATION
The hazard identification step identifies those
chemicals that contribute to the majority of exposure
and risk at a Superfund site. The "contaminants of
potential concern" (COPCs) are chemicals chosen
because of their occurrence, distribution, fate, mobility
and persistence in the environment. Each chemical's
concentration and toxicity are also considered.
Algorithms, permeability constants and other parameter
values presented in this guidance supersede the dermal
methodology provided in DBA and the Risk Assessment
Guidance for Superfund (RAGS, U.S. EPA, 1989).
2.1 CHOOSING CONTAMINANTS OF
CONCERN FOR THE DERMAL-
WATER PATHWAY
Consideration of the dermal exposure pathway is
important in scoping and planning an exposure and risk
assessment. The assessor should decide the level (from
cursory to detailed) of analysis needed to make this
decision. The screening procedure in Section A.4 of
Appendix A analyzes whether or not the dermal expo-
sure route is likely to be significant compared to the
other routes of exposure. This discussion is based on
the DBA methodology, Chapter 9, using parameters
provided in this guidance. Readers are encouraged to
consult the DBA document for more details. The scre-
ening procedure in Section A.4 is intended to focus
attention on specific chemicals that may be important
for dermal exposure and is provided for the conveni-
ence of the risk assessor. However, risk assessors may
decide not to use the screening and proceed to a
quantitative assessment of all chemicals at a site.
Exhibits B-3 and B-4 in Appendix B provide the
results of applying the Appendix A screening proce-
dure to identify organic and inorganic chemicals that
contribute significantly to the risk for the dermal route
at a site. For this guidance, the Superfund Dermal
Workgroup decided that the dermal route is significant
if it contributes at least 10% of the exposure derived
from the oral pathway. These results are based upon
comparing two main household daily uses of water: as
a source for drinking and for showering or bathing.
This screening procedure is therefore limited to
residential exposure scenarios where both ingestion
and showering/bathing are considered in the site risk
assessment. The screening procedure does not consider
swimming exposures, and thus should not be used for
screening chemicals in surface water where exposure
may be through swimming activity. However, if
swimming is an actual or potential exposure scenario
in the site risk assessment, dermal exposure should be
quantitatively evaluated, using input parameters
described in the document.
Note that the results of this screening procedure are
the actual results of a quantitative exposure assessment
for these two routes of exposure. All calculations
needed for the evaluation of DAD for water, as
described in Chapter 3 and in Appendices A and B,
were performed for the list of chemicals presented in
Exhibit B-3 and Exhibit B-4, using the exposure
conditions specified in each exhibit. These exhibits are
provided as a screening tool for risk assessors to focus
the dermal risk assessment on those chemicals that are
more likely to make a contribution to the overall risk.
The example screening results are provided in two
columns in Exhibit B-3 and Exhibit B-4: the column
labeled "Derm/Oral" gives the actual ratio of the
dermal exposure route as compared to the ingestion
route (two liters of drinking water), and the column
labeled "Chem Assess" gives the result of the
comparison as a Y (Yes) or N (No) using the 10%
criterion discussed above. When these default
exposure assumptions are not appropriate, stepwise
instructions are provided in Chapter 3 and Appendix B
to incorporate site-specific exposure parameters.
2.2 CHOOSING CONTAMINANTS OF
CONCERN FOR THE DERMAL-
SOIL PATHWAY
The number of contaminants evaluated in the risk
assessment for the dermal-soil pathway will be limited
by the availability of dermal absorption values for
chemicals in soil. Very limited data exist in the
2-1
-------
literature for the dermal absorption of chemicals from specific in vitro and in vivo studies, may be considered
soil. Chapter 3 provides recommended dermal absorp- to estimate a dermal absorption value. The EPA risk
tion factors for ten chemicals in soil based on well- assessor should be consulted before conducting site-
designed studies. If a detected compound does not specific dermal absorption studies, to ensure that a
have a dermal absorption value presented in Chapter 3, scientifically sound study is developed and approved
other sources of information, such as new exposure by the Agency.
studies presented in the peer reviewed literature or site-
2-2
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CHAPTER 3
EXPOSURE ASSESSMENT
The exposure assessment evaluates the type and
magnitude of exposures to chemicals of potential
concern at a site. The exposure assessment considers
the source from which a chemical is released to the
environment, the pathways by which chemicals are
transported through the environmental medium, and the
routes by which individuals are exposed. Parameters
necessary to quantitatively evaluate dermal exposures,
such as permeability coefficients, soil absorption fac-
tors, body surface area exposed, and soil adherence
factors are developed in the exposure assessment. In
this chapter, the dermal assessment is evaluated for two
exposure media: water (Section 3.1) and soil (Section
3.2).
EPA's Policy for Risk Characterization (U.S.
EPA, 1995a) states that each Agency risk assessment
should present information on a range of exposures
(e.g., provide a description of risks to individuals in
average and high end portions of the exposure
distribution). Generally, within the Superfund program,
to estimate exposure to an average individual (i.e., a
central tendency), the 95% upper confidence limit
(UCL) on the arithmetic mean is chosen for the
exposure point concentration, and central estimates
(i.e., arithmetic average, 50th percentile, median) are
chosen for all other exposure parameters. This
guidance document provides recommended central
tendency values for dermal exposure parameters, using
updated information from the Exposure Factors
Handbook (Em) (U.S. EPA, 1997a).
In comparison with the average exposure, the "high
end" exposure estimate is defined as the highest
exposure that is reasonably expected to occur at a site
but that is still within the range of possible exposures,
referred to as the reasonable maximum exposure
(RME) (U.S. EPA, 1989). According to the Guidance
on Risk Characterization for Risk Managers and Risk
Assessors (U.S. EPA, 1992b), risk assessors should
approach the estimation of the RME by identifying the
most sensitive exposure parameters. The sensitivity of
a parameter generally refers to its impact on the
exposure estimates, which correlates with the degree of
variability of the parameter values. Parameters with a
high degree of variability in the distribution of para-
meter values are likely to have a greater impact on the
range of risk estimates than those with low variability.
For one or a few of the sensitive parameters, the
maximum or near-maximum values should be used,
with central tendency or average values used for all
other parameters. The high-end estimates are based, in
some cases, on statistically based criteria (95th or 90th
percentiles), and in others, on best professional
judgment. In general, exposure duration, exposure
frequency, and contact rate are likely to be the most
sensitive parameters in an exposure assessment (U.S.
EPA, 1989). In addition, for the dermal exposure route,
the soil adherence factor term is also a very sensitive
parameter. This guidance provides recommended upper
end estimates for individual exposure parameters and
a recommended RME exposure scenario for residential
and industrial settings, using updated information from
the EFH and other literature sources.
3.1 ESTIMATION OF DERMAL
EXPOSURES TO CHEMICALS
IN WATER
3.1.1 STANDARD EQUATION FOR DERMAL
CONTACT WITH CHEMICALS IN
WATER
The same mathematical model for dermal
absorption recommended in DEA is used here. The
skin is assumed to be composed of two main layers, the
stratum corneum and the viable epidermis, with the
stratum corneum as the main barrier. A two-
compartment distributed model was developed to
describe the absorption of chemicals from water
through the skin as a function of both the thickness of
the stratum corneum (lsc) and the event duration (tevent).
The mathematical representation of the mass balance
equation follows Pick's second law and is a partial
differential equation with concentration as a function
of both time and distance. The exact solution of this
model is approximated by two algebraic equations: (1)
to describe the absorption process when the chemical
is only in the stratum corneum, i.e., non-steady state,
5-1
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where absorption is a function of tevent1/2; and (2) to
describe the absorption process as a function of tevent,
once steady state is reached. One fundamental
assumption of this model is that absorption continues
long after the exposure has ended, i.e., the final
absorbed dose (DAevent) is estimated to be the total dose
dissolved in the skin at the end of the exposure. For
highly lipophilic chemicals or for chemicals that are
not highly lipophilic but exhibit a long lag time (revent),
some of the chemical dissolved into skin may be lost
due to desquamation during that absorption period. A
fraction absorbed term (FA) is included in the
evaluation of DAevent to account for this loss of
chemical due to desquamation. As shown in Appendix
A, for normal desquamation rates to completely replace
the stratum corneum in about 14 days, only chemicals
with log Kow > 3.5 or chemicals with tevent > 10 hours (at
any log Kow) would be affected by this loss.
The following procedures represent updates from
the DBA and are recommended for the estimation of
the dermal absorbed dose (DAD):
For Organics:
The equation for DAevent is updated to include the
net fraction available for absorption in the stratum
corneum after exposure has ended (FA).
The equation for the permeability coefficient (Kp)
is updated by excluding three data points from the
Flynn data base (Flynn, 1990) in the development
of the correlation equation for Kp. The 95%
confidence intervals are also provided for the
estimation of Kp using this correlation equation.
The screening procedures are updated to include
the new values for Kp and FA in order to provide
guidance when the dermal route would pose more
than 10% of the ingested dose.
A statistical analysis of the correlation equation for
Kp provides the ranges of the octanol-water
partition coefficient (log Kow) and molecular
weight (MW) where the extrapolation of the Kp
correlation equation would be valid.
A discussion of the model validation and
uncertainties related to the dermal absorption
model for chemicals in water is included.
Appendix A gives a detailed discussion of the
above changes.
The spreadsheet ORG04_01 .XLS and Exhibits B-1
through B-3 of Appendix B provide the calcula-
tions of the dermal absorbed dose for over 200
organic chemicals, using a default exposure
scenario.
For Inorganics:
The measured values of the permeability coeffi-
cients for available chemicals are updated based on
the latest literature.
Screening procedures for determining when the
dermal route would pose more than 10% of the
ingested dose are updated to include the relative
fraction absorbed by accounting for the actual
gastrointestinal absorption (ABSGI) of inorganics.
Appendix A gives a detailed discussion of the
above changes.
The spreadsheet INORG04_01 .XLS and Exhibit B-
4 of Appendix B provide the calculations for the
inorganics with available measured Kp or ABSGI.
For chemicals in water, Equations 3.1,3.2,3.3 and
3.4 are used to evaluate the dermal absorbed dose. The
following discussion summarizes the key steps in the
procedure detailed in Appendix A.
For short exposure durations to organic chemicals
in water (Equation 3.2), DAevent is not a function of the
parameter B, which measures the ratio of the
permeability coefficient of the chemical in the stratum
corneum to its permeability coefficient in the viable
epidermis, because neitherthe viable epidermis northe
cutaneous blood flow will limit dermal absorption
during such short exposure durations.
For long exposure times, Equation 3.3 should be
used to estimate DAevent for organic chemicals. The lag
time is decreased because the skin has a limited
capacity to reduce the transport rate of inorganic and/or
highly ionized organic chemicals. In addition, the
viable epidermis will contribute insignificantly as a
barrier to these chemicals. Consequently, for inorganic
and highly ionized organic chemicals, it is appropriate
5-2
-------
where:
Parameter
DAD
SA
EV
EF
ED
BW
AT
Dermal Absorbed Dose - Water Contact
DAD =
DAevent x EV x ED x EF x SA
BW x AT
(3.1)
Definition (units)
Dermally Absorbed Dose (mg/kg-day)
Absorbed dose per event (mg/cm2-event)
Skin surface area availablefor contact
(cm2)
Event frequency (events/day)
Exposure frequency (days/year)
Exposure duration (years)
Body weight (kg)
Averaging time (days)
Default Value
Chemical-specific, see Eq. 3.2, 3.3 and 3.4
See Exhibit 3-2
See Exhibit 3-2
See Exhibit 3-2
See Exhibit 3-2
70 kg (adult) 15 kg (child)
noncarcinogenic effects AT = ED x 365 d/yr
carcinogenic effects AT = 70 yr x 365 d/yr
to assume that Tevent and B are both near zero, which
simplifies Equation 3.3 to Equation 3.4.
Discussions of the permeability coefficient (Kp)
and all other parameters for water media are found in
Section 3.1.2, with more details and data in Appendix
A. Descriptions of the dermal absorption model and
equations for calculating all the parameters to evaluate
the dermal absorbed dose for organics (DAevent in
Equations 3.3 and 3.4) are provided in Appendix A. 1,
and for inorganics (DAevent in Equation 3.4) in Appen-
dix A.2. Appendix B (Exhibits B-3 and B-4) contains
chemical-specific DAevent and DAD values per unit
concentration, using default assumptions. Instructions
for calculating DAevent and DAD values with site-
specific exposure assumptions are provided (see
AppendixA.5), and the spreadsheets (ORG04_01.XLS
and INORG04_01 .XLS), including all the calculations,
will be available at http://www.epa.gov/oswer/
riskassessment/ or http://www.epa.gov/superfund/
programs/risk/ ragse/index.htm.
3.1.2 EXPOSURE PARAMETERS
3.1.2.1 Permeability Coefficient for Compounds in
Water (Kp in cm/hr)
Some discussion of criteria for selecting an
experimental Kp was presented in DEA, Chapter 5.
The procedure recommended by RAGS Part E to
estimate the permeability coefficient (Kp) of a
compound is obtained from updating the correlation
presented in DEA. Three data points which came from
in vivo studies (ethyl benzene, styrene and toluene)
from the Flynn database are now excluded in the
development of the new Kp correlation, limiting its
representation to in vitro studies using human skin.
Updated Kp values for over two hundred common
organic compounds in water are provided, in Appendix
B, as estimated using procedures described below. It is
recommended that these Kp values be used in
Equations 3.2 and 3.3. Kp values for several inorganic
compounds are given, and default permeability
constants for all other inorganic compounds are
provided in Exhibit 3-1, to be used in Equation 3.4.
Organics. The permeability coefficient is a
function of the path length of chemical diffusion
(defined here as stratum corneum thickness, lsc), the
membrane/vehicle partition coefficient of the chemical
(here as octanol/water partition coefficient Kow of the
chemical), and the effective diffusion coefficient (Dsc)
of the chemical in the stratum corneum, and can be
written for a simple isotropic membrane as presented
in Equations 3.5 and 3.6.
In this approach, Kp from Equation 3.7 is estimated
via an empirical correlation as a function of Kow and
5-3
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Dermal Absorbed Dose per event for Organic Compounds - Water Contact
DAevent (mg/cm2-event) is calculated for organic compounds as follows :
where:
Parameter
DAevent =
FA
KP
Cw
^event
t :
Levent
t*
B
K x C
t
1 + B
Definition (units)
Absorbed dose per event (mg/cm2-event)
Fraction absorbed water (dimensionless)
Dermal permeability coefficient of compound
in water (cm/hr)
Chemical concentration in water (mg/cm3)
Lag time per event (hr/event)
Event duration (hr/event)
Time to reach steady-state (hr) = 2.4 ievent
Dimensionless ratio of the permeability
coefficient of a compound through the
stratum corneum relative to its permeability
coefficient across the viable epidermis (ve)
(dimensionless)
= 2 FA x K x C
6 T x t
event event
71
(3.2)
(1 + Bf
Default Value
Chemical-specific, See Appendix B
Chemical-specific, See Appendix B
Site-specific, non-ionized fraction, See
Appendix A for more discussion
Chemical-specific, See Appendix B
See Exhibit 3-2
Chemical-specific, See Eq. A.5 to A.8
Chemical-specific, See Eq. A. 1
(3.3)
MW (Potts and Guy, 1992) obtained from an
experimental data base (the Flynn data base composed
of about 90 chemicals, see DBA, Chapter 4, and
Appendix B of this document) of absorption of
chemicals from water through human skin in vitro.
For ionized organic compounds, Equation 3.8 can
be used to estimate Kp with the appropriate Kow value.
Note that for ionizable organic chemicals, the Kow
value used in Equation 3.8 should be the Kow of only
species that are non-ionized. Similarly, for these
chemicals, the concentration Cw used in Equations 3.2
and 3.3 should be that of the non-ionized fraction. (See
Appendices A and B for more discussion on this topic.)
Organic chemicals which are always ionized (including
ionized but uncharged zwitterions) and ionized species
of ionizable organic chemicals at the conditions of
interest should be treated the same as inorganic
chemicals.
For halogenated chemicals, Equation 3.8 could
underestimate Kp. The Flynn data set from which
Equation 3.8 was derived consists almost entirely of
hydrocarbons with a relatively constant ratio of molar
volume to MW. Because halogenated chemicals have
a lower ratio of molar volume relative to their MW
than hydrocarbons (due to the relatively weighty
halogen atom), the Kp correlation based on MW of
hydrocarbons will tend to underestimate permeability
coefficients for halogenated organic chemicals. To
address this problem, a new Kp correlation based on
molar volume and log Kow will be explored.
Based on the Flynn data set, Equation 3.8 can be
used to predict the permeability coefficient of
5-4
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EXHIBIT 3-1
PERMEABILITY COEFFICIENTS FOR INORGANICS
Compound
Cadmium
Chromium (+6)
Chromium (+3)
Cobalt
Lead
Mercury (+2)
Methyl mercury
Mercury vapor
Nickel
Potassium
Silver
Zinc
All other inorganics
Permeability Coefficient Kp (cm/hr)
1 x ID'3
2xlO-3
1 x ID'3
4xlO-4
1 x ID'4
1 x ID'3
1 x ID'3
0.24
2xlO-4
2xlO-3
6xlO-4
6xlO-4
1 x ID'3
chemicals with Kow and MW within the following
"Effective Prediction Domain" (EPD), determined via
a statistical analysis (see Appendix A, Section A. 1) as
presented in Equations 3.9 and 3.10. Contaminants
outside the EPD are identified with an asterisk (*) in
Appendix B2 and B3. Note that as additional data are
received, the contaminants within the EPD may
change. Therefore, users of this guidance should
review EPA's website at (http://www.epa.gov/oswer/
riskassessment/ or http://www.epa.gov/superfund/
programs/risk/ragse/index.htm) to determine what
contaminants are currently inside (or outside) the EPD.
Strictly, chemicals with very large and very small
Kow values are outside of the EPD. Although large
variances in some data points contributed to the
definition of the EPD, it is defined primarily by the
properties of the data used to develop Equation 3.8.
With no other data presently available for chemicals
with very large and very small Kow, it is appropriate to
use Equation 3.8 as a preliminary estimate of Kp.
For many chemicals with log Kow and MW outside
of the prediction domain, a fraction absorbed (FA) is
estimated to account for the loss of chemicals due to
Dermal Absorbed Dose Per Event for Inorganic Compounds - Water Contact
DAevent (mg/cm2-event) is calculated for inorganics or highly ionized organic chemicals as follows:
C x t.
where:
Parameter
DAevent =
Cw
f
Levent
DA = K
event p
Definition (units)
Absorbed dose per event (mg/cm2-event)
Dermal permeability coefficient of compound
in water (cm/hr)
Chemical concentration in water (mg/cm3)
Event duration (hr/event)
event
(3.4)
Default Value
Chemical-specific, see Exhibit A-6 and
Appendix B
Site-specific, non-ionized fraction, see
Appendix A for more discussion
See Exhibit 3-2
5-5
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Theoretical Derivation of Permeability Coefficient for Organic Chemicals
Kp -
sc/w sc
(3.5)
or:
D
log K = log Kscjw + log
Empirically it has been shown that (Kasting, et al., 1987):
and
(3.6)
DSC=D0 exp(-p MV)
where:
D0 and p are constants, characteristic of the medium through which diffusion is occurring. For hydrocarbons, MV will be
related directly to molecular weight (MW). Combining these two relationships with Equation 3.6 leads to the general form:
log Kp = b + a log Kow - c MW
where:
Parameter Definition (units)
Kp = Dermal permeability coefficient of compound
in water (cm/hr)
Kow = Octanol/water partition coefficient
(dimensionless)
Ksc/w = equilibrium partition coefficient between the
stratum corneum and water (dimensionless)
D0 = Diffusivity of a hypothetical molecule with a
molecular volume (MV) = 0 (cmVhr)
P = Constant specific for the medium through
which diffusion is occurring
Dsc = Effective diffusion coefficient for chemical
transfer through the stratum corneum (cmVhr)
lsc = Apparent thickness of stratum corneum (cm)
a,b,c = correlation coefficients which have been
fitted to the Flynn's data to give Equation 3.8.
MV = Molar volume (cnf/mol)
MW = Molecular weight (g/mole)
(3.7)
Default Value
Chemical-specific, see Appendix B
Chemical-specific, see Appendix B
Chemical-specific
Chemical-specific
Medium specific
Chemical-specific, see Spreadsheet
ORG04_01.XLS (on website given in
Section 3.1.1)
10'3 cm
Chemical-specific
Chemical-specific
the desquamation of the skin, which would decrease
the net amount of chemicals available for absorption
after the exposure event (tevent) has ended. Predictions
of chemical-specific Kp and their use in the estimation
of DAevent, are included in Exhibit B-3 for about two
hundred chemicals.
-------
Empirical Predictive Correlation for Permeability Coefficient of Organics
log K = -2.80 + 0.66 log K - 0.0056 MW (r2 = 0.66)
& p o ow \ '
(3.8)
where:
Parameter
MW
Definition (units)
Dermal permeability coefficient of compounds in
water (cm/hr)
Octanol/water partition coefficient of the non-
ionized species (dimensionless)
Molecular weight (g/mole)
Default Value
Chemical-specific, see Appendix B
Chemical-specific, see Appendix B
Chemical-specific, see Appendix B
Inorganics. Exhibit 3-1 summarizes permeability
coefficients for inorganic compounds, obtained from
specific chemical experimental data, as modified and
updated from DBA, Table 5-3 and from Hostynek, et
al. (1998). Permeability coefficients from these refer-
ences are condensed for each metal and for individual
valence states of specific metals. To be most protective
of human health, the value listed in this exhibit
represents the highest reported permeability coef-
ficient. More detailed information is presented in
Appendix A (Exhibit A-6).
3.1.2.2 Chemical Concentration in Water
One of the issues regarding the bioavailability of
chemicals in water is the state of ionization, with the
non-ionized form being much more readily absorbed
than the ionized form. The fraction of the chemical in
the non-ionized state is dependent on the pH of the
water and the specific ionization constant for that
chemical (pKa). Further information on the formulas
for calculating these fractions is provided in the DBA
and in Appendix A. However, given the complexities
of calculating the non-ionized fraction across multiple
samples and multiple chemicals, it is recommended
that a standard risk assessment should make the health-
protective assumption that the chemical is entirely in
the non-ionized state. Therefore, the total concentration
of a chemical in water samples (Cw) should be equal to
the total concentration of the chemical in water.
Estimates of Cw, and therefore potential impacts of
dermal exposure, may be strongly influenced by the
presence of particulates in the sample. Although filtra-
Boundaries of Effective Prediction Domain
-0.06831 < 0.5103 x 10"4 MW + 0.05616 log Kow < 0.5577
-0.3010 < -0.5103 x 1Q-4 MW + 0.05616 log K < 0.1758
(3.9)
(3.10)
where:
Parameter
TC =
-"-ow
MW
Definition (units)
Octanol/water partition coefficient of the
non-ionized species (dimensionless)
Molecular weight (g/mole)
Default Value
Chemical-specific, see Appendix B
Chemical-specific, see Appendix B
5-7
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EXHIBIT 3-2
RECOMMENDED DERMAL EXPOSURE VALUES FOR CENTRAL TENDENCY AND RME
RESIDENTIAL SCENARIOS - WATER CONTACT
Exposure Parameters
Concentration- Cw
(mg/cm3)
Event frequency- EV
(events/day)
Exposure frequency- EF
(days/yr)
Event duration- tev(,nt
(hr/event)
Exposure duration- ED (yr)
Skin surface area- SA (cm2)
Dermal permeability
coefficient-K,, (cm/hr)
Central Tendency Scenario
Showering/
Bathing
Site-specific
1
350
Adult1
0.25
9
18,000
Child2
0.33
6
6,600
Swimming
Site-specific
Site-specific
Site-specific
Adult
Child
Site-specific
9
18,000
6
6,600
RME Scenario
Showering/
Bathing
Site-specific
1
350
Adult1
0.58
30
18,000
Child2
1.0
6
6,600
Swimming
Site-specific
Site-specific
Site-specific
Adult
Child
Site-specific
30
18,000
Chemical-specific values Exhibits B-3 and B-4
6
6,600
1 Adult showering scenario used as the basis for the chemical screening for the dermal pathway, as shown in Appendix B, Exhibits B-3 and
B-4. Event duration for adult exposure is based on showering data from the EFH (U.S. EPA, 1997a).
2Event duration for child exposure is based on bathing data from the EFH (U.S. EPA, 1997a).
tion of water samples in the field has been used to
reduce turbidity and estimate the soluble fraction of
chemicals in water, existing RAGS guidance (U.S.
EPA, 1989) recommends that unfiltered samples be
used as the basis for estimating the chemical concen-
tration for calculating the oral dose. The rationale is
that particulate-bound chemicals may still be available
for absorption across the gastrointestinal tract. To be
consistent with existing EPA guidance, it is recom-
mended that unfiltered samples also be used as the
basis for estimating a chemical concentration for
calculating the dermal dose.
However, it should be noted that particulate-bound
chemicals in an aqueous medium (e.g., suspended
sediment particles) would be considered to be much
less bioavailable for dermal absorption, due to
inefficient adsorption of suspended particles onto the
skin surface and a slower rate of absorption into the
skin. The uncertainty in the estimation of the dermal
dose from a water sample with high turbidity is directly
proportional to the magnitude of the difference in the
concentration between an unfiltered and filtered
sample. The actual bioavailable concentration is likely
to lie somewhere between the unfiltered and filtered
sample concentrations. The impact of this health-
protective assumption and relevant field factors (e.g.,
turbidity) should be discussed in the uncertainty
section. To reduce the uncertainty in estimating the
bioavailable chemical concentration, water sample
collection methods that minimize turbidity should be
employed (U.S. EPA, 1995b, 1996), ratherthan sample
filtration.
3.1.2.3 Skin Surface Area
The surface area (SA) parameter describes the
amount of skin exposed to the contaminated media.
-------
Dermal Absorbed Dose - Soil Contact
DAD =
DA
BW x AT
(3.11)
where:
Parameter
DAD
DAevent =
SA
EV
EF
ED
BW
AT
Definition (units)
Dermal Absorbed Dose (mg/kg-day)
Absorbed dose per event (mg/cm2-event)
Skin surface area available for contact (cm2)
Event frequency (events/day)
Exposure frequency (days/year)
Exposure duration (years)
Body weight (kg)
Averaging time (days)
Default Value
Chemical-specific, see Equation 3.12
See Appendix C and Equations 3.13 to 3.16
See Exhibit 3-5
See Exhibit 3-5
See Exhibit 3-5
70 kg (adult), 15 kg (child)
noncarcinogenic effects AT = ED x 365 d/yr
carcinogenic effects AT = 70 yr x 365 d/yr
The amount of skin exposed depends upon the
exposure scenario. For dermal contact with water, the
total body surface area for adults and children is
assumed to be exposed for both swimming and bathing.
Since body weight and SA are dependent variables, all
SA estimates used 50th percentile values in order to
correlate with the average body weights. The recom-
mended SA exposed to contaminated water for the
adult resident is 18,000 cm2. This SA value was
calculated by incorporating data from Tables 6.2 and
6.3 for the Exposure Factors Handbook (U.S. EPA,
1997a), averaging the 5 0th percentile values for males
and females.
The recommended SA value for exposure to
contaminated water for the child resident is 6,600 cm2.
This SA was calculated by incorporating the data from
the EFH for the 5 0th percentile of the total body surface
area for male and female children, and calculating a
time weighted average surface area for a 0-6 year old
child. The lack of data for all ages led to a conservative
assumption that a 0-1 year old and 1-2 year old had the
same surface area as a 2-3 year old. This recommended
child SA was calculated by averaging the male and
female surface areas.
Dermal Absorbed Dose Per Event - Soil Contact
DAevent (mg/cm2-event) is calculated as follows:
where:
Parameter
DAevent =
CF
AF
ABS,
= r
event ^soil
CF X AF X
Definition (units)
Absorbed dose per event (mg/cm2-event)
Chemical concentration in soil (mg/kg)
Conversion factor (10"6 kg/mg)
Adherence factor of soil to skin (mg/cm2-
event) (Referred to as contact rate in RAGS,
Part A)
Dermal absorption fraction
(3.12)
Default Value
Site-specific
10'6 kg/mg
See Section 3.2.2.3 and Appendix C
See Exhibit 3-4
5-9
-------
where:
Surface Area Exposed for Adult Resident - Soil Contact
Exposed SA (Adult Resident] = SAhead + SAforeams + SAhands + SAlower
legs
(3.13)
Parameter Definition (units)
SA = Skin surface area available for contact (cm2)
Default Value
See Appendix C
where:
Parameter
SA
Surface Area Exposed for Adult Commercial/Industrial - Soil Contact
Exposed SA (Adult Commercial/Industrial) = SAhead + SAfo
forearms hands
(3.14)
Definition (units)
Skin surface area available for contact (cm2)
Default Value
See Appendix C
3.1.2.4 Event Time, Frequency, and Duration of
Exposure
Exhibit 3-2 summarizes the default exposure values
for both surface area and exposure duration, presented
as central tendency and RME. All the central tendency
values were obtained from the EFH, while the RME
values were derived as previously presented. Recom-
mended event duration values are provided for a
showering activity. Even though children may be
bathing for a longer duration, the showering adult
remains the most highly exposed receptor.
3.2 ESTIMATION OF DERMAL
EXPOSURE TO CHEMICALS IN
SOIL
3.2.1 STANDARD EQUATION FOR DERMAL
CONTACT WITH CHEMICALS IN
SOIL
The general guidance for evaluating dermal
absorption of compounds from soil is presented in Risk
Assessment Guidance for Superfund (RAGS, U.S.
EPA, 1989) and is expanded upon in the DEA. This
section briefly discusses the rationale and updates
specific parameters. The standard equation for dermal
contact with chemicals (Equation 3.11) is the same as
that in Section 3.1.1. (Equation 3.1). Equation 3.12
provides DAevent for soil contact.
3.2.2 EXPOSURE PARAMETERS
3.2.2.1 Skin Surface Area
The skin surface area parameter (SA) describes the
amount of skin exposed to the contaminated media.
The amount of skin exposed depends upon the
exposure scenario. Clothing is expected to limit the
extent of the exposed surface area in cases of soil
contact. All SA estimates used 50th percentile values to
correlate with average body weights used for all
scenarios and pathways. This was done to prevent
inconsistent parameter combinations since body weight
and SA are dependent variables. Body part-specific
S As were calculated for adult (> 18 years old) and child
(<1 to <6 years old) residents as described below and
documented in Appendix C.
Adult resident. The adult resident was assumed to
wear a short-sleeved shirt, shorts and shoes; therefore,
the exposed skin surface is limited to the head, hands,
forearms and lower legs. The recommended SA
exposed to contaminated soil for the adult resident is
5700 cm2 and is the average of the 50th percentile for
males and females greater than ISyearsofage. Surface
area data were taken from EFH, Tables 6-2 (adult
male) and 6-3 (adult female). Exposed SA for the adult
3-10
-------
Surface Area Exposed for Child Resident - Soil Contact
Fraction of Total SA
SA fraction
SA fractiona
body part i
ige 1<2
SA fraction^
ige 5<6
(3.15)
Exposed SA = (FTSAkeJ(SAtoJ + (FTSAfarearJ(SAtoJ + (FTSAhcmd)(SAtoJ + (FTSA,omr,egs)(SAtoj + (FTSAfJ(SAMcd) (3 16)
where:
Parameter
FTSA
SA
SAtotal
(FTSA1)(SAtoU)
Definition (units) Default Value
Fraction of total surface area for the See Appendix C
specified body part (cm2)
Skin surface area available for contact (cm2) See Appendix C
Total skin surface available for contact See Appendix C
Surface area for body part "i" (cm2)
resident was calculated using Equation 3.13, docu-
mented in Appendix C with the assumption that the
female adult forearm SA was 45% of the arm SA
(based on the adult male forearm-to-arm SA ratio).
Adult commercial/industrial. The adult commer-
cial/industrial receptor was assumed to wear a short-
sleeved shirt, long pants, and shoes; therefore, the
exposed skin surface is limited to the head, hands, and
forearms. The recommended SA exposed to contami-
nated soil for the adult commercial/industrial receptor
is 3300 cm2 and is the average of the 50thpercentile for
males and females greater than ISyearsofage. Surface
area data were taken from EFH, Tables 6-2 (adult
male) and 6-3 (adult female). Exposed SA for the adult
commercial/industrial receptor was calculated using
Equation 3.14 and is documented in Appendix C with
the assumption that the female adult forearm SA was
45% of the arm SA (based on the adult male forearm-
to-arm SA ratio).
Child. The child resident (<1 to <6 years old) was
assumed to wear a short-sleeved shirt and shorts (no
shoes); therefore, the exposed skin is limited to the
head, hands, forearms, lower legs, and feet. The
recommended SA exposed to contaminated soil for the
child resident is 2800 cm2 and is the average of the 50th
percentile for males and females (<1 to <6 years old).
Body part-specific data for male and female children
were taken from EFH, Table 6-8, as a fraction of total
body surface area. Total body SAs for male and female
children were taken from EFH, Tables 6-6 (male) and
6-7 (female), and used to calculate average male/
female total SA (see Appendix C). Exposed SA for the
child resident was calculated, using Equations 3.15 and
3.16 and is documented in Appendix C with the
following assumptions: (1) because of the lack of data
for certain ages, the fraction of total SA was assumed
to be equal to the next oldest age group that had data
and (2) the forearm-to-arm ratio (0.45) and lower leg-
to-leg ratio (0.4) are equivalent to those of an adult.
These assumptions introduce some uncertainty into the
calculation, but are used in the absence of age-specific
data.
While clothing scenarios described above for the
adult and child residents may not be appropriate for all
regions, the climate in some areas would allow a short-
sleeved shirt and/or shorts to be worn throughout a
majority of the year. In addition, in some regions of the
country, children may remain barefoot throughout a
major portion of the year. These clothing scenarios
were chosen to ensure adequate protection for those
receptors that may be exposed in the warmer climates,
with the realization that risks would likely be over-
estimated for some seasons.
When selecting the surface area, site-specific
conditions should be evaluated in coordination with
the project's risk assessors. For colder climates, the
surface area may be weighted for different seasons.
Because some studieshave suggested that exposure can
occur under clothing (Maddy, et al., 1983), these
3-11
-------
clothing scenarios are not considered to be overly
conservative.
3.2.2.2 Soil-to-Skin Adherence Factors
The adherence factor (AF) describes the amount of
soil that adheres to the skin per unit of surface area.
Recent data (Kissel etal., 1996; Kissel etal., 1998; and
Holmes et al., 1999) provide evidence to demonstrate
that 1) soil properties influence adherence, 2) soil
adherence varies considerably across different parts of
the body; and 3) soil adherence varies with activity.
Given these results, the Workgroup recommends
that an activity which best represents all soils, body
parts, and activities be selected (U.S. EPA, 1997a).
Body part-weighted AFs can then be calculated and
used in estimating exposure via dermal contact with
soil based on assumed exposed body parts. Given that
soil adherence depends upon the body part, an overall
body part-weighted AF must be calculated for each
activity. The assumed clothing scenario determines
which body part-specific AFs are used in calculating
the 5 0th and 95th percentile weighted AFs. The weighted
AFs are used with the relative absorption, exposure
frequency and duration, exposed surface area, body
weight, and averaging time to estimate the dermal
absorbed dose. The general equation used to calculate
the weighted AF for a particular activity is shown in
Equation 3.17.
Adult resident. The adult resident (>18 years old)
was assumed to wear a short-sleeved shirt, shorts and
shoes; therefore, the exposed skin surface was limited
to the face, hands, forearms and lower legs. The
weighted AFs for adult residential activities (e.g.,
grounds keepers, landscapers, and gardeners) were
calculated using Equation 3.18 and are documented in
Appendix C. Note: This calculation differs from that
presented in Section 3.2.2.1 in the areas used for head
and face. In the total surface area calculation presented
earlier, the total head area was used. For the soil-to-
skin adherence factor, empirical measurements were
from the face only and the face surface area was
estimated to be Vb the total head surface area.
Adult commercial/industrial. The adult commer-
cial/industrial receptor was assumed to wear a short-
sleeved shirt, long pants, and shoes. Therefore, the
exposed skin surface was limited to the face, hands,
and forearms. The weighted AFs for adult commercial/
industrial activities (e.g., grounds keepers, landscapers,
irrigation installers, gardeners, construction workers,
equipment operators, and utility workers) were
calculated using Equation 3.19, and documented in
Appendix C.
Child resident. The child resident (<1 to <6 years
old) was assumed to wear a short-sleeved shirt and
shorts (no shoes). Therefore, the exposed skin was
limited to face, hands, forearms, lower legs, and feet.
Weighted AFs for children in day care and "staged"
children playing in dry and wet soil activities were
calculated using Equation 3.20, and documented in
Appendix C.
As noted in Appendix C, body part-specific AFs
for both child and adult receptors were not always
available for all body parts assumed to be exposed.
Weighted adherence factors for receptors were
where:
Parameter
AF
AF
Surface Area Weighted Soil Adherence Factor
(AF, )(SA, ) + (AF2 )(SA2 )+...+ (AFi )(SAi
Weighted AF =
Definition (units)
Adherence factor of soil to skin (mg/cm2-event)
(Referred to as contact rate in RAGS, Part A)
Overall adherence factor of soil to skin
(mg/cm2-event)
Skin surface area available for contact for body
part "i" (cm2)
SA2 + . . . + SAt
Default Value
See Appendix C
See Appendix C
(3.17)
3-12
-------
Surface Area Weighted Soil Adherence Factor for Adult Resident
Wei, toed AF
" el&me" Ar
where:
Parameter Definition (units) Default Value
AF = Adherence factor of soil to skin (mg/cm2-event)
(Referred to as contact rate in RAGS, Part A)
AFj = Overall adherence factor of soil to skin (mg/cm2- See Appendix C
event)
SAj = Skin surface area available for contact for body See Appendix C
part "i" (cm2)
(3.18)
Surface Area Weighted Soil Adherence - Adult/Commercial
Weighted AFadult commemal =
where:
_ (AFface )(SAface ) + (AFforearms )(SAforearms ) + (AFhands )(SAhands
face forearms hands
Parameter Definition (units)
AF = Adherence factor of soil to skin (mg/cm2 -
event) (Referred to as contact rate in RAGS,
Part A)
AFj = Overall adherence factor of soil to skin
(mg/cm2-event)
SAj = Skin surface area available for contact for
body part "i" (cm2)
Default Value
See Appendix C
See Appendix C
(3.19)
Weighted AFcMd
where:
Parameter
AF
AF,
SAi
Surface Area Weighted Soil Adherence Factor - Child
SAface * SAfo,eajm, * SAkand, * SA bwerleg.
Definition (units)
Adherence factor of soil to skin (mg/cm2-event)
(Referred to as contact rate in RAGS, Part A)
Overall adherence factor of soil to skin
(mg/cm2 -event)
Skin surface area available for contact for body
part "i" (cm2)
+ SAfea (6.20)
Default Value
-
See Appendix C
See Appendix C
calculated using only those body parts for which AFs
were available because of the difficulty in trying to
assign an AF for one body part to another body part.
For example, the weighted AF for the children in day
care was based on the forearms, hands, lower legs, and
feet (AFs for the face were not available). However,
the surface area for all exposed body parts was used in
calculating the dermal absorbed dose. For the day care
3-13
-------
child example, the surface area used in estimating the
DAD included the whole head, forearms, hands, lower
legs and feet. Therefore, the body part that may not
have had AF data available was assumed, by default, to
have the same amount of soil adhered as the weighted
AF.
3.2.2.3 Recommended Soil Adherence Factors
This section recommends default soil AFs for the
child resident, the adult resident, and the adult
commercial/industrial worker, and provides the basis
for the recommendations. EPA suggests selecting an
activity from AF data which best represents the
exposure scenario of concern and using the corre-
sponding weighted AF in the dermal exposure
calculations (U.S. EPA, 1997a). To make this selec-
tion, activities with available AFs were categorized as
those in which a typical residential child, residential
adult, and commercial/industrial adult worker would be
likely to engage (see Appendix C). Within each
receptor category, activities were ranked in order from
the activity with the lowest to highest weighted AF
(50th percentile) (Exhibit 3-3). The 50th percentile
weighted AF was used in ranking the activities from
those with the lowest to highest weighted AFs, because
the 50th percentile is a more stable estimation of the
true AF (i.e., it is not affected as significantly by
outliers as the 95th percentile).
As with other contact rates (e.g., soil ingestion), the
recommended default value is a conservative, health
protective value. To maintain consistency with this
approach (i.e., recommending a high-end of a mean),
two options exist when recommending default weight-
ed AFs: (1) select a central tendency (i.e., typical) soil
contact activity and use the high-end weighted AF (i.e.,
95th percentile) for that activity; or (2) select a high-end
(i.e., reasonable but higher exposure) soil contact
activity and use the central tendency weighted AF (i.e.,
50th percentile) for that activity.
It is not recommended that a high-end soil contact
activity be used with a high-end weighted AF for that
activity, as this use would not be consistent with the
use of a reasonable maximum exposure (RME)
scenario. The use of these values also needs to be
evaluated when combining multiple exposure pathways
to insure that an overall RME is being maintained.
Adult resident. Given that there were data
available for a wide variety of activities that an adult
resident may engage in, a high-end soil contact activity
was selected and the central tendency weighted AF
(50th percentile) was derived for that activity. In so
doing, the recommended weighted AF for an adult
resident is 0.07 mg/cm2, and is based on the 50th
percentile weighted AF for gardeners (the activity
determined to represent a reasonable, high-end acti-
vity). The basis for this recommendation is as follows:
(1) although no single activity would represent the
activities an adult resident engages in, a comparison of
the gardener 50th percentile weighted AF with the other
residential-type activities (Appendix C) shows that
gardening represents a high-end soil contact activity;
(2) common sense suggests that gardening represents a
high-end soil contact activity, whereas, determining
which of the other activities (i.e., grounds keeping and
landscaping/rockery) would represent a reasonable,
central tendency (i.e., typical) soil contact activity
would be difficult; and (3) selecting the central
tendency weighted AF (i.e., 50th percentile) of a high-
end soil contact activity is consistent with an RME for
contact rates.
Child resident (<1 to <6 years old). Available
data on soil AFs for children were limited to children
(l-6!/2 years old) playing indoors and outdoors (3.5-4
hours) at a day care center (reviewed in U.S. EPA,
1997a) and children (8-12 years old) playing for 20
minutes with an assortment of toys and implements in
a preconstructed 8'x8' soil bed (i.e., "staged" activity)
containing dry or wet soil (see Kissel et al., 1998, and
Appendix C). Therefore, it was not possible to identify
a reasonable worst-case soil contact activity as was
done for the adult resident. As such, both of the
following approaches were used in determining the
appropriate weighted AF for children: (1) selecting a
central tendency (i.e., typical) soil contact activity
using the high-end weighted AF (i.e., 95th percentile)
for that activity; and, (2) selecting a high-end soil
contact activity using the central tendency weighted AF
(i.e., 50th percentile) for that activity. The recom-
mended weighted AF for a child resident (<1 to <6
years old) is 0.2 mg/cm2 and is based on the 95th
percentile weighted AF for children playing at a day
care center (central tendency soil contact activity) or
the 50th percentile for children playing in wet soil
(high-end soil contact activity).
3-14
-------
EXHIBIT 3-3
ACTIVITY SPECIFIC-SURFACE AREA WEIGHTED SOIL ADHERENCE FACTORS
Exposure Scenario
CHILDREN1
Indoor Children
Daycare Children (playing indoors and outdoors)
Children Playing (dry soil)
Children Playing (wet soil)
Children-in-Mud5
RESIDENTIAL ADULTS2
Grounds Keepers
Landscaper/Rockery
Gardeners
COMMERCIAL/INDUSTRIAL ADULTS3
Grounds Keepers
Landscaper/Rockery
Staged Activity: Pipe Layers (dry soil)
Irrigation Installers
Gardeners
Construction Workers
Heavy Equipment Operators
Utility Workers
Staged Activity: Pipe Layers (wet soil)
MISCELLANEOUS ACTIVITIES4
Soccer Players #1 (teens, moist conditions)
Farmers
Rugby Players
Archeologists
Reed Gatherers
Soccer Players #2 (adults)
Age
(years)
1-13
1-6.5
8-12
8-12
9-14
>18
>18
>16
>18
>18
>15
>18
>16
>18
>18
>18
>15
13-15
>20
>21
>19
>22
>18
Weighted Soil Adherence Factor (mg/cm2)
Geometric Mean
0.01
0.04
0.04
0.2
21
0.01
0.04
0.07
0.02
0.04
0.07
0.08
0.1
0.1
0.2
0.2
0.6
0.04
0.1
0.1
0.3
0.3
0.01
95th Percentile
0.06
0.3
0.4
3.3
231
0.06
0.2
0.3
0.1
0.2
0.2
0.3
0.5
0.3
0.7
0.9
13
0.3
0.4
0.6
0.5
27
0.08
3-15
-------
EXHIBIT 3-3 (continued)
ACTIVITY SPECIFIC-SURFACE AREA WEIGHTED SOIL ADHERENCE FACTORS
1 Weighted AF based on exposure to face, forearms, hands, lower legs, & feet.
2 Weighted AF based on exposure to face, forearms, hands, & lower legs.
3 Weighted AF based on exposure to face, forearms, & hands.
Note: this results in different weighted AFs for similar activities between residential and commercial/industrial exposure scenarios.
4 Weighted AF based on all body parts for which data were available.
5 Information on soil adherence values for the children-in-mud scenario is provided to illustrate the range of values for this type of activity.
However, the application of these data to the dermal dose equations in this guidance may result in a significant overestimation of dermal
risk. Therefore, it is recommended that the 95th percentile AF values not be used in a quantitative dermal risk assessment.
See Exhibit C-4 for bounding estimates.
Children playing at a day care center represent a
central tendency (i.e., typical) activity given that: (1)
the children played both indoors and outdoors; (2) the
clothing worn was not controlled (i.e., some subjects
wore long pants, long-sleeve shirts, and/or shoes); and
(3) soil conditions were not controlled (e.g., other soil
types, moisture content, etc., could result in higher
AFs). The 95th percentile weighted AF for children
playing at the day care center is a known, reasonable,
"real-life" activity that represents the majority of the
population, given that children 1 to 6 years old are
either in day care or at home and are likely engaging in
activities similar to those at the day care center, and
represents a high-end of a typical activity.
EXHIBIT 3-4
RECOMMENDED DERMAL ABSORPTION FRACTION FROM SOIL
Compound
Arsenic
Cadmium
Chlordane
2,4-Dichlorophenoxyacetic acid
DDT
TCDD and other dioxins
-if soil organic content is >10%
Lindane
Benzo(a)pyrene and other PAHs
Aroclors 1254/1242 and other PCBs
Pentachlorophenol
Semivolatile organic compounds
Dermal Absorption
Fraction (ABSJ1
0.03
0.001
0.04
0.05
0.03
0.03
0.001
0.04
0.13
0.14
0.25
0.1
Reference
Wester, etal. (1993a)
Wester, etal. (1992a)
U.S. EPA (1992a)
Wester, etal. (1992b)
Wester, etal. (1996)
Wester, etal. (1990)
U.S. EPA (1992a)
Duff and Kissel (1996)
Wester, etal. (1990)
Wester, etal. (1993b)
Wester, etal. (1993c)
1 The values presented are experimental mean values.
3-16
-------
The "staged" activity of children playing in wet
soil for 20 minutes under controlled conditions (i.e., all
subjects were clothed similarly, the duration of soil
contact was controlled, and the soil properties were
characterized) is a high-end soil contact activity
because: (1) the children were in direct contact with
soil for the full duration of the activity; and (2) the
children played in wet soil, which is known to have
higher AFs than dry soil, for the duration of the
activity. The 50th percentile weighted AF for children
playing in wet soil is a central tendency estimate of a
high-end soil contact activity.
Use of the 95th percentile weighted AF for children
playing at a day care center (0.3 mg/cm2) or the 50th
percentile for children playing in wet soil (0.2 mg/cm2)
as a recommended weighted AF for a child resident (< 1
to <6 years old) is consistent with recommending a
high-end of a mean for contact rates.
While this value (0.2 mg/cm2) is at the lower end
of the range of soil adherence factors reported in DBA
and based on Lepow et al. (1975) and Roels et al.
(1980) studies, those studies were not designed to study
soil adherence and only allowed calculation of soil
adherence to hands. In addition, the central-tendency
adherence factor of 0.2 mg/cm2 estimated here is based
on soil adherence studies for all of the relevant body
parts (i.e., head, hands, forearms, lower-legs, and feet).
Kissel et al. (1998) reports soil adherence factors for
children's hands of 0.5-3 mg/cm2 (median of 1 mg/cm2)
for relatively moist soil, which is comparable to the
range of values previously reported for soil adherence
to children's hands (0.5-1.5 mg/cm2; U.S. EPA, 1997a).
Exhibit C-2 contains data used to calculate the central
tendency and high end AFs for children.
Commercial/industrial adult worker. Given that
there were data available for a wide variety of activities
that a commercial/industrial adult worker may engage
in, a high-end soil contact activity was selected and the
central tendency weighted AF (50th percentile) derived
for that activity. In so doing, the recommended
weighted AF for a commercial/industrial adult worker
is 0.2 mg/cm2 and is based on the 50th percentile
weighted AF for utility workers (the activity deter-
mined to represent a high-end contact activity). The
bases for this recommendation are as follows: (1)
although no single activity would be representative of
activities a commercial/industrial adult worker engages
in, a comparison of the utility worker 50th percentile
weighted AF with other commercial/industrial-type
activities (Exhibit 3-3) shows that the utility worker
represents ahigh-end soil contact activity (i.e., grounds
keepers, landscaper/rockery, irrigation installers,
gardeners, construction workers); (2) a combination of
common sense and data on the weighted AFs supports
the assumption that utility worker activities represent
a high-end soil contact activity, whereas, determining
which of other measured activities might represent a
reasonable, central tendency (i.e., typical) soil contact
activity would be difficult; and (3) selecting the central
tendency weighted AF (i.e., 50th percentile) of a high-
end soil contact activity is consistent with a RME
forcontact rates.
Recreational. No specific default values are being
recommended for a recreational scenario since many
site-specific concerns will impact the choice of
exposure variables, such as, climate, geography, loca-
tion, and land-use. The risk assessors, in consultation
with the project team, should reach consensus on the
need to evaluate this scenario and the inputs before
incorporating this into the risk assessment. The EFH
should be consulted to obtain appropriate exposure
estimates.
3.2.2.4 Dermal Absorption Fraction from Soil
DEA (Chapter 6) presents a methodology for
evaluating dermal absorption of soil-borne
contaminants. In that document, ORD reviewed the
available experimental data for dermal absorption from
contaminated soil and presented recommendations for
three compounds/classes. Recommendations were
presented as ranges to account for uncertainty which
may arise from different soil types, loading rates,
chemical concentrations, and other conditions. In
RAGS Part E, selection of a single value is based on
recommended ORD ranges to simplify this risk calcu-
lation. In addition, recommended values for other
compounds according to review of literature and
default values for classes of compounds are provided.
For tetrachlorodibenzo-p-dioxin (TCDD), sufficient
data allow specific recommendations based on organic
content of the soil.
Values in Exhibit 3-4 have been determined to be
applicable using the Superfund default human exposure
assumptions, and are average absorption values. Other
3-17
-------
values will be added to this list as results of further
research become available. However, as an interim
method, dermal exposure to other compounds should
be treated qualitatively in the uncertainty section or
quantitatively using default values after presenting the
relevant studies to the regional risk assessors so that
absorption factors can be agreed upon on a site-specific
basis before the start of the risk assessment. Particular
attention should be given to dermally active
compounds, such as benzo(a)pyrene, and they should
be addressed fully as to their elevated risk by this route
of exposure.
This guidance provides a default dermal absorption
fraction for semivolatile organic compounds (SVOCs)
of 10% as a screening method for the majority of
SVOCs without dermal absorption fractions. This
fraction is suggested because the experimental values
in Exhibit 3-4 are considered representative of the
chemical class for screening evaluations. If these are
used quantitatively, they represent another uncertainty
that should be presented and discussed in the risk
assessment. There are no default dermal absorption
values presented for volatile organic compounds nor
inorganic classes of compounds. The rationale for this
is that in the considered soil exposure scenarios,
volatile organic compounds would tend to be
volatilized from the soil on skin and should be
accounted for via inhalation routes in the combined
exposure pathway analysis. For inorganics, the
speciation of the compound is critical to the dermal
absorption and there are too little data to extrapolate a
reasonable default value.
Although Equation 3.12 implies that the ABSd is
independent of AF, this independence may not be the
case. Experimental evidence suggests that ABSd may
be a function of AF (Duff and Kissel, 1996 and Yang,
1989). Specifically, ABSd has been observed to
increase as the AF decreases below the quantity of soil
necessary to completely coverthe skin in athin layer of
soil particles, which is discussed in the DEA as the
mono-layer concept. This mono-layer will vary
according to physical characteristics of the applied soil,
e.g., particle size. Most significantly, nearly all
experimental determinations of ABSd have been
conducted at loading rates larger than required to
completely cover the skin, while the recommended
default values for AF for both adult and children are at
or less than that required to establish a mono-layer. The
absolute effect of soil loading on these parameters is
not sufficiently understood to warrant adjustment of
the experimentally determined values. Consequently,
actual ABSd could be larger than experimentally
determined and the effect of this uncertainty should be
appropriately presented in the risk assessment.
Equation 3.12 includes no explicit effect of
exposure time, which also adds to the uncertainty and
consequently assumes exposure time is the same as in
the experimental study that measured ABSd. For values
presented, the exposure time per event is 24 hours.
Site-specific exposure scenarios should not adjust
ABSd per event but rather adjust the exposure
frequency (EF) and exposure duration (ED) to account
for site conditions.
A discussion of theoretical models that estimate
DAevent on the basis of a soil permeability coefficient
rather than ABSd is presented in DEA. The
permeability coefficient approach offers some
advantages in that the partitioning coefficient from soil
should remain constant over a wider range of
conditions, such as the amount of soil on the skin and
the concentration of the contaminant in the soil.
However, as soil partitioning procedures are not well
developed, the Workgroup recommends that the
absorbed fraction per event procedures presented in
this guidance be used to assess dermal uptake for soil.
3.2.2.5 Age-Adjusted Dermal Factor
An age-adjusted dermal exposure factor (SFSadj) is
used when dermal exposure is expected throughout
childhood and into adult years. This accounts for
changes in surface area, body weight and adherence
factors over an extended period of time. The use of
SFSadj incorporates body weight, surface area, exposure
duration and adherence factor parameters from the risk
equation. To calculate SFSadj, assumptions recom-
mended above for the child (age 0-6 years) and adult
(age 7-30 years) were calculated using data from the
EFH and the methodology described for the residential
child. The recommended age-adjusted dermal factor is
calculated using Equation 3.21.
3.2.2.6 Event Time, Exposure Frequency, and
Duration
This guidance assumes one event per day, during
which a percentage of a chemical quantity is absorbed
3-18
-------
Age-Adjusted Dermal Exposure Factor
SFS
adj
where:
Parameter
SFSad =
AF7.3
SA7.31
ED,., =
ED7.31 =
BW,.6 =
BW7.31 =
(3.21)
2)(0.2mg/cm 2-evenf)(6yf) (5700cm 2)(0.07mg/cm2-event)(24yr')
SFSad. = 360 mg-yrs/kg-event
Definition (units)
Age-adjusted dermal exposure factor
(mg-yrs/kg-events)
Adherence factor of soil to skin for a child
(1-6 years) (mg/cm2-event) (Referred to as
contact rate in RAGS, Part A)
Adherence factor of soil to skin for an adult
(7-31 years) (mg/cm2-event) (Referred to as
contact rate in RAGS, Part A)
Skin surface area available for contact during
ages 1-6 (cm2)
Skin surface area available for contact during
ages 7-31 (cm2)
Exposure duration during ages 1-6 (years)
Exposure duration during ages 7-31 (years)
Average Body weight during ages 1-6 (kg)
Average Body weight during ages 7-31 (kg)
Default Value
0.2 (EFH, EPA 1997a)
0.07 (EFH, EPA 1997a)
2,800
5,700
6
24
15
70
systemically, and exposure time is the same as in the
experimental study that measured ABSd (i.e., 24 hours),
as recommended in Exhibit 3-4.
Limited data suggest that absorption of a chemical
from soil depends on time. However, information is
insufficient to determine whether that absorption is
linear, sublinear or supralinear with time. Whether
these assumptions would result in an over- or under-
estimate of exposure and risk is unclear. Site-specific
exposure scenarios should not scale the dermal absorp-
tion factor of the event time. The exposure frequency
for the RME is referenced from RAGS Part A (U.S.
EPA, 1989) but may be adjusted to reflect site-specific
conditions.
The recommended central tendency and RME
values for exposure duration (Exhibit 3-5) are
referenced from RAGS Part A (U.S. EPA, 1989), but
may be adjusted to reflect site-specific conditions.
3.3 ESTIMATION OF DERMAL
EXPOSURES TO CHEMICALS
IN SEDIMENT
Exposures to sediment will differ from exposures
to soil due to potential differences in the chemical and
physical properties between the two media and
differing conditions under which these types of expo-
sures occur. Since studies of dermal exposure to sedi-
ments are limited, it is recommended that the same risk
assessment approach described in this document for
soil exposures be used for sediments, with the follow-
ing considerations:
3-19
-------
EXHIBIT 3-5
RECOMMENDED DERMAL EXPOSURE VALUES FOR CENTRAL TENDENCY AND RME
RESIDENTIAL AND INDUSTRIAL SCENARIOS - SOIL CONTACT
Exposure Parameters
Concentration- Csoll (mg/kg)
Event frequency (events/day)
Exposure frequency (days/yr)
Exposure duration (yr)
Skin surface area
(cm2)
Soil adherence
factor (mg/cm2)
Adult
Child
Adult
Child
Dermal absorption fraction
Central Tendency
Residential
Industrial
RME Scenario
Residential
Industrial
site-specific values
1
site-specific
9
5,700
2,800
0.01
0.04
1
219
9
3,300
NA
0.02
NA
1
350
30
5,700
2,800
0.07
0.2
1
250
25
3,300
NA
0.2
NA
chemical-specific values (Exhibit 3-4)
NA: not applicable
Sediment samples must be located in areas in
which individuals are likely to come into direct
contact with the sediments. For wading and
swimming, this includes areas which are near shore
and in which sediments are exposed at some time
during the year. Sediments which are consistently
covered by considerable amounts of water are
likely to wash off before the individual reaches the
shore.
Since data are generally reported in dry weight, the
impact of moisture content in the in situ sample
(i.e., wet weight) on exposure and uptake should be
considered and discussed in the Uncertainty
Section. The greater the moisture content of a
sediment sample, the greater the difference in dry
vs. wet weight contaminant concentration.
Measures of sediment adherence reflect wet
weight, therefore dose estimations utilizing
sediment concentration recorded in dry weight will
serve to over-estimate risk in direct proportion to
the moisture content of the sediment sample.
When applying standard equations for DAevent (Eq.
3.12) and DAD (Eq. 3.11) to sediment scenarios,
assumptions about surface area exposed,
frequency, and duration of exposure will depend
on site-specific conditions.
The amount of chemical absorbed from sediment
is dependent on a number of chemical, physical
and biological factors. The relative importance of
some of these factors on absorption may differ
between soils and sediments. Until more
information becomes available, the same dermal
absorption fraction for soils (Exhibit 3-4) should
be applied to sediments. The uncertainties
associated with this approach should be discussed
in the Uncertainty Section of the risk assessment.
The adherence factor is perhaps, the most
uncertain parameter to estimate for sediment
exposures. Increasing moisture content will
increase the ability of sediments and soils to
adhere to skin, as demonstrated by comparing soil
adherence for the same activity in wet and dry soil.
The increased moisture content may also affect the
relative percent absorbed.
3-20
-------
In addition, assumptions about soil loading (or
adherence) will affect absorption estimates For
example, as soil loading increases, the fraction
absorbed will be constant until a critical level is
reached at which the skin surface is uniformly
covered by soil (defined as the mono-layer) (Duff
and Kissel, 1996). The soil loading at which a
mono-layer exists is dependent on grain size. It is
recommended that the value chosen for adherence
be consistent with the activity and surface area
assumptions as well as the mono-layer concept.
Exhibit C-4 presents upper bound estimates calcu-
lated for the Soil Conservation Service classifi-
cations using mean particle diameters and a
simplified packing model. These values can be
used as bounding estimates in constructing site-
specific exposure parameters. The impact of the
adherence factor assumptions on absorption should
be discussed in the Uncertainty Section.
3-21
-------
CHAPTER 4
TOXICITY ASSESSMENT
4.1 PRINCIPLES OF ROUTE-TO-
ROUTE EXTRAPOLATION
Dermal contact with contaminants can result in
direct toxicity at the site of application and/or
contribute to systemic toxicity via percutaneous
absorption. The issue of direct toxicity is addressed in
Section 4.4. Ideally, a route-specific (i.e., dermal)
toxicity factor would not only consider portal-of-entry
effects (i.e., direct toxicity) but would also provide
dosimetry information on the dose-response relation-
ship for systemic effects via percutaneous absorption.
In the absence of dermal toxicity factors, EPA has
devised a simplified paradigm for making route-to-
route (oral-to-dermal) extrapolations for systemic
effects. This process is outlined in Appendix A of
RAGS/HHEM (U.S. EPA, 1989). Primarily, it
accounts for the fact that most oral reference doses
(RfDs) and slope factors are expressed as the amount
of substance administered per unit time and body
weight, whereas exposure estimates for the dermal
pathway are expressed as absorbed dose. The process
utilizes the dose-response relationship obtained from
oral administration studies and makes an adjustment
for absorption efficiency to represent the toxicity factor
in terms of absorbed dose.
This approach is subject to a number of factors that
might compromise the applicability of an oral toxicity
factor for dermal exposure assessment. The estimation
of oral absorption efficiency, to adjust the toxicity
factor from administered to absorbed dose, introduces
uncertainty. Part of this uncertainty relates to
distinctions between the terms "absorption" and
"bioavailability." Typically, the term absorption refers
to the "disappearance of chemical from the gastro-
intestinal lumen," while oral bioavailability is defined
as the "rate and amount of chemical that reaches the
systemic circulation unchanged." That is, bioavail-
ability accounts for both absorption and pre-systemic
metabolism. Although pre-systemic metabolism in-
cludes both gut wall and liver metabolism, for the most
part it is liver metabolism or liver "first pass" effect
that plays the major role.
In the absence of metabolic activation or detoxi-
fication, toxicity adjustment should be based on
bioavailability rather than absorption because the
dermal pathway purports to estimate the amount of
parent compound entering the systemic circulation.
Metabolism in the gut wall and skin can serve to
complicate this otherwise simplified adjustment
process. Simple adjustment of the oral toxicity factor,
based on oral absorption efficiency, does not account
for metabolic by-products that might occur in the gut
wall but not the skin, or conversely in the skin, but not
the gut wall.
More importantly the oral administered dose
experiences the liver "first pass"effect. The efficiency
of "first pass" metabolism and whether this is an
activating or detoxifying process determines the nature
of the impact this effect has on route-to-route
extrapolations. One example is a compound that
exhibits poor oral systemic bioavailability due to a
prominent "first pass" effect which creates a highly
toxic metabolite. The adjusted dermal toxicity factor
may overestimate the true dose-response relationship
because it would be based upon the amount of parent
compound in the systemic circulation rather than on the
toxic metabolite. Additionally, percutaneous absorp-
tion may not generate the toxic metabolite to the same
rate and extent as the gastrointestinal route.
Toxicity is a function of contaminant concentration
at critical sites-of-action. Absorption rate, as well as
extent of absorption, determines contaminant concen-
tration at a site-of-action. Differences in the anatomic
barriers of the gastrointestinal tract and the skin can
affect rate as well as the extent of absorption; there-
fore, the route of exposure may have significant dose-
rate effects at the site-of-action.
4-1
-------
4.2 ADJUSTMENT OF TOXICITY
FACTORS
Methodologies for evaluating percutaneous absorp-
tion, as described in DEA give rise to an estimation of
absorbed dose. However, Integrated Risk Information
System (IRIS)-verified indices of toxicity (e.g., RfDs,
slope factors) are typically based on administered dose.
Therefore, to characterize risk from the dermal
exposure pathway, adjustment of the oral toxicity
factor to represent an absorbed rather than admini-
stered dose is necessary. This adjustment accounts for
the absorption efficiency in the "critical study," which
forms the basis of the RfD. For example, in the case
where oral absorption in the critical study is essentially
complete (i.e., 100%), the absorbed dose is equivalent
to the administered dose, and therefore no toxicity
adjustment is necessary. When gastrointestinal absorp-
tion of a chemical in the critical study is poor (e.g.,
1%), the absorbed dose is much smaller than the
administered dose; thus, toxicity factors based on
absorbed dose should be adjusted to account for the
difference in the absorbed dose relative to the
administered dose.
In effect, the magnitude of toxicity factor
adjustment is inversely proportional to the absorption
fraction in the critical study. That is, when absorption
efficiency in the critical study is high, the absorbed
dose approaches the administered dose resulting in
little difference in a toxicity factor derived from either
the absorbed or administered dose. As absorption
efficiency in the critical study decreases, the difference
between the absorbed dose and administered dose
increases. At some point, a toxicity factor based on
absorbed rather than administered dose should account
for this difference in dose. In practice, an adjustment
in oral toxicity factor (to account for "absorbed dose"
in the dermal exposure pathway) is recommended when
the following conditions are met: (1) the toxicity value
derived from the critical study is based on an
administered dose (e.g., delivery in diet or by gavage)
in its study design; (2) a scientifically defensible
database demonstrates that the gastrointestinal (GI)
absorption of the chemical in question, from a medium
(e.g., water, feed) similar to the one employed in the
critical study, is significantly less than 100% (e.g.,
<50%). A cutoff of 50% GI absorption is recom-
mended to reflect the intrinsic variability in the
analysis of absorption studies. Thus, this cutoff level
obviates the need to make comparatively small
adjustments in the toxicity value that would otherwise
impart on the process a level of accuracy that is not
supported by the scientific literature.
If these conditions are not met, a default value of
complete (i.e., 100%) oral absorption may be assumed,
thereby eliminating the need for oral toxicity-value
adjustment. The Uncertainty Analysis could note that
employing the oral absorption default value may result
in underestimating risk, the magnitude of which being
inversely proportional to the true oral absorption of the
chemical in question.
The recommended GI absorption values (ABSGI)
for those compounds with chemical-specific dermal
absorption factors from soil are presented in Exhibit 4-
1. For those organic chemicals that do not appear on
the table, the recommendation is to assume a 100%
ABSGI value, based on review of literature, indicating
that organic chemicals are generally well absorbed
(>50%) across the GI tract. Absorption data for
inorganics are also provided in Exhibit 4-1, indicating
a wide range of absorption values for inorganics.
Despite the wide range of absorption values for
inorganics, the recommendation is to assume a 100%
ABSGI value for inorganics that do not appear in this
table. This assumption may contribute to an under-
estimation of risk for those inorganics that are actually
poorly absorbed. The extent of this underestimation is
inversely proportional to the actual GI absorption.
These criteria are recommended for the adjustment of
toxicity values for the assessment of both soil and
water contact.
Equation 4.1 indicates that as the ABSGI value
decreases, the greater is the contribution of the dermal
pathway to overall risk relative to the ingestion
pathway. Therefore, the ABSGI can greatly influence
the comparative importance of the dermal pathway in
a risk assessment.
4.3 CALCULATION OF ABSORBED
TOXICITY VALUES
Once the criteria for adjustment have been met and
a specific ABSGI value has been identified, a toxicity
factor that reflects the absorbed dose can be
4-2
-------
where:
Parameter
ABSra
Impact of Oral Absorption Efficiency on the Ratio of Dermal to Ingestion Risk
Dermal Risk
1
Ingestion Risk ABS
(4.1)
Gl
Definition (units)
Fraction of contaminant absorbed in
gastrointestinal tract (dimensionless) in the
critical toxicity study
Default Value
Chemical-specific, see Exhibit 4-1 and
Appendix B
calculated from the oral toxicity values as presented in
Equations 4.2 and 4.3.
The RfDABS and SFABS should be used in the
calculation of dermal risk, as described in Chapter 5.
4.4 DIRECT TOXICITY
The discussion in Section 4.2 on toxicity factor
adjustment is based on the evaluation of chronic
systemic effects resulting from GI absorption. Chapter
3 of this document provides a methodology for
estimating a systemically absorbed dose secondary to
dermal contact with chemicals in water and soil.
However, dermal contact with a chemical may also
result in direct dermal toxicity, such as allergic contact
dermatitis, urticarial reactions, chemical irritation, and
skin cancer. EPA recognizes that the dose-response
relationship for the portal-of-entry effects in the skin
are likely to be independent of any associated systemic
toxicity exhibited by a particular chemical. However,
at this time, chemical specific dermal toxicity factors
are not available. Therefore, this dermal risk assess-
ment guidance does not address potential dermal
toxicity associated with direct contact. The dermal risk
assessment methodology in this guidance may be
revised to incorporate additional information on portal-
of-entry effects as it becomes available.
Derivation of Cancer Slope Factor Based on Absorbed Dose
SF
SF.
o
ABS
ABSGI
where:
Parameter
spr =
ABSGI :
Definition (units)
Absorbed slope factor
Oral slope factor (mg/kg-day)"1
Fraction of contaminant absorbed in
gastrointestinal tract (dimensionless) in the
critical toxicity study
(4.2)
Default Value
Chemical-specific, See Exhibit 4-1
Chemical-specific
Chemical-specific, see Exhibit 4-1 and
Appendix B
4-3
-------
Derivation of Reference Dose Based on Absorbed Dose
RfDABS = RfD0 x ABSGI (4.3)
where:
Parameter Definition (units) Default Value
RfDABs = Absorbed reference dose (mg/kg-day) Chemical-specific, see Exhibit 4-1
RfD0 = Reference dose oral (mg/kg-day) Chemical-specific
ABSGI = Fraction of contaminant absorbed in Chemical-specific, see Exhibit 4-1 and
gastrointestinal tract (dimensionless) in the Appendix B
critical toxicity study
4-4
-------
EXHIBIT 4-1
SUMMARY OF GASTROINTESTINAL ABSORPTION EFFICIENCIES AND RECOMMENDATIONS FOR
ADJUSTMENT OF TOXICITY FACTORS FOR SPECIFIC COMPOUNDS
Compound
GI Absorption
Ref1
Species
Dosing Regimen
% Absorbed
ABSGI
IRIS Critical Toxicity Study
Species
Dosing
Regimen
Toxicity
Factor
Adjust?
Organics
Chlordane
2,4-
Dichlorophenoxyacetic
acid (2,4-D)
DDT
Pentachlorophenol
Polychlorinated
biphenyls (PCBs)
Polycyclic aromatic
hydrocarbons(PAHs)
Ewing, 1985
Ohno, 1986
Knopp, 1992
Pelletier, 1989
Keller, 1980
Korte, 1978
Meerman, 1983
Albro, 1972
Muhlebach, 1981
Tanabe, 1981
Chang, 1943
Hecht, 1979
Rats
Rats
Rats
Rats
Rats
Rats
Rats
Rats
Rats
Rats
assume aqueous
gavage
assume aqueous
gavage
vegetable oil
diet
water
squalene
emulsion
corn oil
starch solution
diet
80%
>90%
70-90%
76%
100%
96%
80%
81%
58%
89%
Mice
Mice
Rats
Rats
Rats
Rats
Mice
diet
inhalation
diet
dissolved in
oil, mixed
with diet
diet
diet
diet
SF
RfD
RfD
RfD
RfD
SF
SF
No
No
No
No
No
No
-------
EXHIBIT 4-1 (Continued)
SUMMARY OF GASTROINTESTINAL ABSORPTION EFFICIENCIES AND RECOMMENDATIONS FOR
ADJUSTMENT OF TOXICITY FACTORS FOR SPECIFIC COMPOUNDS
Compound
TCDD
Other Dioxins/
Dibenzofurans
All other organic
compounds
GI Absorption
Ref1
Fries, 1975
Piper, 1973
Rose, 1976
ATSDR, 1994a
Species
Rats
Rats
Rats
Dosing Regimen
diet
diet
corn oil
multiple studies
multiple references
% Absorbed
ABSGI
50-60%
70%
70-83%
>50%
generally
>50%
IRIS Critical Toxicity Study
Species
Dosing
Regimen
Toxicity
Factor
under review
under review
multiple studies
RfD or SF
Adjust?
No
No
No
Inorganics
Antimony
Arsenic (arsenite)
Barium
Beryllium
Cadmium
Chromium (III)
Waitz, 1965
Bettley, 1975
Cuddihy and Griffith,
1972
Taylor, 1962
Reeves, 1965
IRIS, 1999
Donaldson and
Barreras, 1996
Keim, 1987
Rats
Human
Dog
Rats
Human
Human
Rats
water
assume aqueous
water
water
diet
water
diet/water
15%
95%
7%
0.7%
2.5%
5%
1.3%
Rat
Human
Human
Rat
Human
Rat
water
water
water
water
diet and
water
diet
RfD
SF
RfD
RfD
RfD
RfD
Yes
No
Yes
Yes
Yes
Yes
Yes
-------
EXHIBIT 4-1 (Continued)
SUMMARY OF GASTROINTESTINAL ABSORPTION EFFICIENCIES AND RECOMMENDATIONS FOR
ADJUSTMENT OF TOXICITY FACTORS FOR SPECIFIC COMPOUNDS
Compound
Chromium (VI)
Cyanate
Manganese
Mercuric chloride
(other soluble salts)
Insoluble or metallic
mercury
Methyl mercury
Nickel
Selenium
Silver
GI Absorption
Ref1
Donaldson and
Barreras, 1996
MacKenzie, 1959
Sayato, 1980
Farooqui and Ahmed,
1982
Davidsson, 1989
IRIS, 1999
Ruoff, 1995
IRIS, 1999
ATSDR, 1994b
Aberg, 1969
Elakhovskaya, 1972
Young, 1982
Furchner, 1968
IRIS, 1999
Species
Rats
Rats
Human
Rats
Human
Human
Human
Human
Dogs
Dosing Regimen
water
assume aqueous
diet/water
water
acute inhalation
of Hg vapor
aqueous
diet/water
diet
aqueous
% Absorbed
ABSGI
2.5%
>47%
4%
7%
74-80%
95%
4%
30-80%
4%
IRIS Critical Toxicity Study
Species
Rat
Rat
Human
Rat
Human
Human
Rat
Human
Human
Dosing
Regimen
water
diet
diet/water
oral gavage
in water;
2X/week
Inhalation
diet
diet
diet
i.v. dose
Toxicity
Factor
RfD
RfD
RfD
RfD
RfC
RfD
RfD
RfD
RfD
(based on
estimated
oral dose)
Adjust?
Yes
No
Yes
Yes
No
No
Yes
No
Yes
-------
EXHIBIT 4-1 (Continued)
SUMMARY OF GASTROINTESTINAL ABSORPTION EFFICIENCIES AND RECOMMENDATIONS FOR
ADJUSTMENT OF TOXICITY FACTORS FOR SPECIFIC COMPOUNDS
Compound
Thallium
Vanadium
Zinc
GI Absorption
Ref1
Lie, 1960
Conklin, 1982
ATSDR, 1994c
Species
Rats
Rats
Human
Dosing Regimen
aqueous
gavage
diet
% Absorbed
ABSGI
100%
2.6%
highly
variable
IRIS Critical Toxicity Study
Species
Rat
Rat
Human
Dosing
Regimen
water gavage
diet as V2O5
diet
supplement
Toxicity
Factor
RfD
RfD
RfD
Adjust?
No
Yes
No
1 Literature references are listed here by first author. Complete citations are provided in Reference Section.
OO
-------
CHAPTER 5
RISK CHARACTERIZATION
5.1 QUANTITATIVE RISK
EVALUATION
5.1.1 RISK CALCULATIONS
In contrast to the calculation of average lifetime
dose for the oral and inhalation routes of exposure,
which typically are based on an administered dose, the
evaluation of exposure for the dermal route typically is
based on an estimated absorbed dose, or dermal
absorbed dose (DAD). The DAD term generally is
calculated separately for the water and soil pathways,
as described in Chapter 3. In Chapter 4, the oral
toxicity values generally are adjusted according to the
estimated extent of gastrointestinal absorption in
critical toxicity studies. Once the DAD and the
adjusted toxicity values have been derived, the cancer
risk and hazard index for the dermal route should be
calculated using Equations 5.1 and 5.2. For evaluating
the risk, the age-adjusted child/adult receptor typically
is the most sensitive receptor for cancer endpoints. For
non-cancer endpoints, the child typically is the most
sensitive receptor.
The steps involved in the dermal risk assessment
are summarized in Exhibit 5-1.
5.1.2 RISKS FOR ALL ROUTES OF
EXPOSURE
Endpoints for assessment of risk for the dermal
pathway generally are based on induction of systemic
toxicity and carcinogenesis, as they are for the oral and
the inhalation routes of exposure. Therefore, the
estimate of total risk for exposure to either soil or water
contaminants is based on the summation of individual
risks for the oral, the inhalation, and the dermal routes.
5.2 UNCERTAINTY ASSESSMENT
The importance of adequately characterizing
uncertainty in the risk assessment is emphasized in
several U.S. EPA documents (U.S. EPA, 1992b; U.S.
EPA, 1995a; U.S. EPA, 1997a; U.S. EPA, 1997b).
EPA's 1995 Policy for Risk Characterization calls for
greater clarity, transparency, reasonableness and
consistency in Agency risk assessments. To ensure
transparency and clarity, the Workgroup recommends
that an assessment of the confidence, uncertainties, and
influence of these uncertainties on the outcome of the
risk assessment be presented.
Several sources of uncertainty exist in the
recommended approach for estimating exposure and
risks from dermal contact with water and soil. Many of
these uncertainties are identified in the DEA, Chapter
10. Exposure parameters with highly variable distribu-
tions are likely to have a greater impact on the outcome
of the risk assessment than those with lower variability.
Which exposure parameters will vary the most will
depend on the receptor, (i.e., residential adult,
commercial adult, adolescent trespasser) and chemical
evaluated. For the dermal-soil pathway, the adherence
factor and the value used to represent the concentration
Calculation of Dermal Cancer Risk
Dermal cancer risk = DAD x SF
where:
Parameter
DAD
Dfinition (units)
Dermal Absorbed Dose (mg/kg-day)
= Absorbed cancer slope factor (mg/kg-day)"1
ABS
(5.1)
Default Value
See Equation 3.1 or Exhibit B-3 (water)
See Equations 3.11 and 3.12 (soil)
See Equation 4.2
5-1
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where:
Parameter
DAD
Dermal hazard quotient =
Definition (units)
Dermal Absorbed Dose (mg/kg-day)
Calculation of Dermal Hazard Quotient
DAD
= Absorbed reference dose (mg/kg-day)
(5.2)
Default Value
See Equation 3.1 or Exhibit B.3 (water)
See Equations 3.11 and 3.12 (soil)
See Equation 4.3
EXHIBIT 5-1
SUMMARY OF DERMAL RISK ASSESSMENT PROCESS
Risk Assessment Process
Hazard ID
Exposure
Assessment
Child or
Adult
Age-adjusted
Child/Adult
SFS ADJ
Toxicity Assessment
Risk Characterization
Cancer Risk
Section 2
Water Dose
Section 3.1,
Equations 3.1-
3.4
See Note
Soil Dose
Section 3.2,
Equations
3.11/3.12
Section 3.2.2.5,
Equation 3.21
Section 4, SFABS Equation 4.2
Section 5.1, Equation 5.1
DAD x SFABS
Hazard Index
Section 2
Water Dose
Section 3.1,
Equations
3.1-3.4
See Note
Soil Dose
Section 3.2,
Equations
3.11/3.12
Section 3.2.2.5,
Equation 3.21
Section 4, RID^, Equation 4.3
Section 5.1, Equation 5.2
DAD/RfDABs
Uncertainty Analysis, Section 5.2
Note: The calculations used in developing the screening tables in Appendix B (Exhibits B-3 and B-4) for the water pathway determined that the
adult receptor experiences the highest dermal dose. Therefore, the adult exposure scenario is recommended for screening purposes.
However, if an age-adjusted exposure scenario for the dermal route is selected to be consistent with methods for determining the risk of other
in soil are likely to be sensitive variables regardless of
the receptor. For the dermal-water pathway, the Kp and
the value used to represent the concentration in water
are likely to be sensitive variables.
A detailed analysis of the uncertainty associated
with every exposure model and exposure variable
presented in this guidance is not possible due to
insufficient data. RAGS Part E recommends that a
qualitative evaluation of key exposure variables and
models, and their impact on the outcome of the
assessment, be conducted when the database does not
support a quantitative Uncertainty Analysis. Below is
a discussion of key uncertainty issues associated with
the recommended approach for dermal risk assessments
in this guidance. Exhibit 5-2 summarizes the degree of
5-2
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uncertainty associated with the dermal exposure
assessment.
5.2.1 HAZARD IDENTIFICATION
Uncertainty is associated with the assumption that
the only chemicals of concern in the risk assessment
for the dermal-water pathway are those which
contribute 10% or more of the dose that is achieved
through the drinking water pathway. Although this is a
reasonable assumption for exposure assessments in
which the drinking water pathway is evaluated, this
may result in a slight underestimate of the overall
exposure and risk. In addition, the selection of
chemicals of concern for the dermal-soil pathway is
limited by the availability of dermal absorption values
for soil. If soil dermal absorption values are not avail-
able, a chemical may be dropped out of the quantitative
evaluation of risk, which could potentially result in an
underestimate of risk. The recommended default
screening value of 10% for semi volatile organic
chemicals should limit the degree of underestimation
associated with this step of the dermal risk assessment
approach.
EXHIBIT 5-2
SUMMARY OF UNCERTAINTIES ASSOCIATED WITH DERMAL EXPOSURE
ASSESSMENT
Exposure Factor
COPC selection for dermal-water pathway
Cw - exposure point concentration
Cw - ionization state
Event duration for showering (tevent )
KP
Csoil - exposure point concentration
Event time for dermal-soil pathway
Surface area (SA) - dermal-soil pathway
Exposure frequency (EF)
Adherence Factor (AF)
Default dermal-soil absorption values and lack of
absorption values for other compounds (ABSd )
Lack of dermal slope factor for cPAHs and other
compounds
Lack of info on GI absorption (ABSGI)
High
Medium
Low
X
site-specific, data-dependent
X
X
X
site-specific, data-dependent
X
X
X
X
X
X
X
Above are general statements about the uncertainty associated with each parameter. The actual degree of uncertainty is
dependent on the specific chemical, exposure pathway or statistic utilized.
5-3
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5.2.2 EXPOSURE ASSESSMENT
5.2.2.1 Dermal Exposure to Water - Uncertainties
Associated with the Model for DAevent
When evaluating uncertainties, it is important to
keep in mind that the model used to estimate exposure
can contribute significantly to uncertainty. Uncertainty
in model predictions arises from a number of sources,
including specification of the problem, formulation of
the conceptual model, interpretation, and
documentation of the results. Although some attempts
have been made to validate the model for DAevent
utilized in this document, a greater effort and more
formal process will be necessary before a more
accurate assessment of the sources of uncertainty
associated with the model can occur. A detailed
discussion of the model for DAevent, its validation and
remaining uncertainties is presented in Appendix A,
Sections A. 1.4 and A.3.
Concentration in water (Cw). The value used for Cw
in the equation for DAevent is dependent on several
factors, including the method for estimating the
exposure point concentration (EPC) (e.g., 95% upper
confidence limit of the mean [95%UCL], a maximum
concentration, etc.); and the physico-chemical
characteristics of the water-borne chemicals. The
Superfund program advocates the use of the 95%UCL
in estimating exposure to contaminants in
environmental media. This policy is based on the
assumption that individuals are randomly exposed to
chemicals in soil, water, sediment, etc., in a given
exposure area and that the arithmetic mean best
represents this exposure. To develop a conservative
estimate of the mean, a 95% UCLis adopted. However,
when data are insufficient to estimate the 95%UCL,
any value used for Cw (such as the maximum value or
arithmetic mean) is likely to contribute significantly to
the uncertainty in estimates of the DAevent. The degree
to which the value chosen for the EPC contributes to an
over- or under-estimate of exposure depends on the
representativeness of existing data and the estimator
used to represent the EPC.
The bioavailability of a chemical in water is
dependent on the ionization state of that chemical, with
the non-ionized forms more readily available than the
ionized forms. To be most accurate in estimating the
dermally absorbed dose, the DAevent should be equal to
the sum of the DAevent values for the non-ionized and
ionized species (see Section 3.1.2.2). For most
Superfund risk assessments, however, the DAevent is
most likely to be based on a Cw which is derived
directly from a laboratory report. The value presented
in a laboratory report represents the total concentration
of ionized and non-ionized species and thus does not
provide the information necessary to calculate separate
DAevent values for ionized and non-ionized groups. A
slight overestimate of exposure for organic chemicals
of low molecular weight is likely to occur if the
equations presented in Section 3.1.2.1 are not utilized.
Another factor affecting bioavailability of
chemicals in water is the aqueous solubility of the
chemical and adsorption to particulate material.
Although filtration of water samples in the field has
been used to reduce turbidity and estimate the soluble
fraction of chemicals in water, the use of data from
filtered samples is not recommended for either
ingestion or dermal exposure assessments. Therefore,
data from unfiltered samples should be used as the
basis for estimating the chemical concentration (Cw) for
calculating the dermal dose. The use of data from
unfiltered samples may tend to overestimate the
concentration of chemical that is available for
absorption, the extent of the overestimate determined
by the magnitude of the difference between the filtered
and unfiltered sample. However, water sample collec-
tion methods should be employed that minimize
turbidity, rather than relying on sample filtration. The
impact of this health-protective assumption can be
discussed in the Uncertainty Analysis.
In addition, since the concentration of some
compounds in water decreases greatly during shower-
ing, the impact of volatilization should be considered
when estimating Cw for the dermal-water pathway. The
exposure analysis for the inhalation pathway should
account for compounds which volatilize.
Exposure Time. The recommended default assump-
tions for exposure time in showering/bathing scenarios
are 15 minutes for the central tendency scenario and 35
minutes for the RME scenario. This is consistent with
the recommended 50th and 95th percentiles for
showering presented in EPA's EFH. If a showering/
bathing scenario exceeded 35 minutes (the
recommended central tendency and RME exposure
parameters for bathing time are 20 and 60 minutes,
5-4
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respectively), the default assumption for exposure time
might result in a slight underestimate of risk. The
degree of underestimation is dependent on the actual
showering time.
Permeability coefficients (Kp). Permeability coeffi-
cients have been identified as major parameters
contributing uncertainty to the assessment of dermal
exposure for contaminants in aqueous media (DBA).
Two major groups of uncertainties can be identified.
The Flynn database, upon which the predictive Kp
correlation is derived, includes in vitro data for
approximately 90 compounds. The log Kow and MW
of these compounds and the experiments designed to
measure their Kp values introduce some measures of
uncertainty into the correlation coefficients. Using this
correlation to predict Kp introduces several other
uncertainties. Accuracy of Kow (whether measured or
estimated) would affect both the correlation coefficient
of Equation 3.8 and the predicted Kp of specific
chemicals. Different interlaboratory experimental
conditions (e.g., skin sample characteristics, tempera-
ture, flow-through or static diffusion cells, concentra-
tion of chemicals in solution) influence the value of the
resulting measured Kp included in the Flynn database.
Since the variability between the predicted and
measured Kp values is no greater than the variability in
interlaboratory replicated measurements, this guidance
recommends the use of predicted Kp for all organic
chemicals. This approach will ensure consistency
between Agency risk assessments in estimating the
dermally absorbed dose from water exposures. The
Flynn database contains mostly smaller hydrocarbons
and pharmaceutical drugs which might bear little
resemblance to the typical compounds detected at
Superfund sites. Predicting Kp from this correlation
is uncertain for highly lipophilic and halogenated
chemicals with log Kow and MW which are very high
or low as compared to compounds in the Flynn
database, as well as for those chemicals which are
partially or completely ionized. Alternative approaches
are recommended for the highly lipophilic and
halogenated chemicals, which attempt to reduce the
uncertainty in their predicted Kp values.
Another major source of uncertainty comes from
the use of Kp obtained from in vitro studies to estimate
(in vivo) dermal exposure at Superfund sites. Ths
could introduce further uncertainty in the use of
estimated Kp in the assessment of exposure and risk
from the dermal-water pathway.
5.2.2.2 Dermal Exposure to Soil
Concentration in soil (Csoil). The Superfund program
advocates the use of the 95% UCL in estimating
exposure to contaminants in environmental media. This
policy is based on the assumption that individuals are
randomly exposed to chemicals in soil, water,
sediment, etc., in a given exposure area and that the
arithmetic mean best represents this exposure. To
develop a conservative estimate of the mean, a 95%
UCL is adopted. However, when there are insufficient
data to estimate the 95% UCL, any value used for Csoil
(such as the maximum value or arithmetic mean) is
likely to contribute significantly to the uncertainty in
estimates of the DAevent. The degree to which the value
chosen for the EPC contributes to an over- or under-
estimate of the exposure is dependent on the
representativeness of the existing data and the
estimator used to represent the EPC.
Event time (EV). In order to be consistent with
assumptions about absorption, the equation for DAD
presented in this guidance assumes (by default) that the
event time is 24 hours, (i.e., that no washing occurs and
the soil remains on the skin for 24 hours). This
assumption probably overestimates the actual exposure
time for most site-specific exposure scenarios and is
likely to result in an overestimate of exposure. The
degree to which exposure could be overestimated is
difficult to determine without information on
absorption rates for each chemical.
Surface area and frequency of exposure. Default
adherence values recommended in this guidance are
weighted by the surface area exposed and are based on
the assumption that adults will be wearing short
sleeved shirts, shorts and shoes and that a child will be
wearing a short-sleeved shirt, shorts and no shoes. This
may not match the year-round exposure scenario
assumed to exist at every site. For instance, there is a
four-fold difference between the surface area exposed
for a residential adult based on the default assumption
of clothing worn versus an assumption that an adult is
wearing a long-sleeved shirt, and long pants. There is
also a four-fold difference between the surface area
exposed of a residential child based on the default
assumption of clothing worn versus an assumption that
5-5
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a child is wearing a long-sleeved shirt, long pants,
shoes and socks. The value chosen for surface area can
introduce a moderate degree of uncertainty into
exposure and risk estimates. Risk assessors may need
to adjust defaults depending upon site conditions such
as climate and activity patterns.
The value chosen for frequency can also introduce
moderate amounts of uncertainty into exposure and risk
assessment estimates. For instance, it is assumed that
a resident comes into contact with residential soils 350
days/yr. If the actual frequency is significantly less
(for instance one day per week, equivalent to 52 days/
yr), a seven-fold difference occurs, which directly
impacts exposure and risk estimates.
Adherence factors. Although RAGS Part E provides
dermal adherence factors for several different types of
receptors, the conditions at a particular site may not
match the conditions in the study upon which the
default dermal adherence factor is based, (i.e., specific
activity, clothing worn, soil type, soil moisture content,
exposure duration, etc). For example, Kissel, et al.
(1996) has found that finer particles adhere prefer-
entially to the hands unless soils are greater than 10%
moisture. Some studies have found that soil particles
greater than 250 microns do not adhere readily to skin.
Thus the soil type, including moisture content, can
affect the adherence of soil. In addition, the specific
activity which occurs in the site-specific exposure
scenario may not directly match the activities for which
adherence factors are available in this guidance. All of
these factors can introduce significant uncertainties
into the exposure assessment. Each of these factors
should be carefully evaluated in each risk assessment
conducted for the dermal pathway.
Dermal-soil absorption factors. The amount of
chemical absorbed from soil is dependent on a number
of chemical, physical and biological factors of both the
soil and the receptor. Examples of factors in soil
which can influence the amount of chemical that is
available to be absorbed include; soil type, organic
carbon content, cation exchange capacity, particle size,
temperature, pH, etc. For example, increasing particle
size has been found to correspond with decreased
absorption across the skin for some chemicals.
Chemical factors which can affect absorption include
lipid solubility, chemical speciation, aging of the
chemical, etc. Physical factors which can impact
absorption include soil loading rate, surface area
exposed to soil, soil contact time and soil adherence.
For example, fraction absorbed from soil is dependent
on the soil loading. In general, as the soil loading
increases, the fraction absorbed should be constant,
until one gets above a critical level at which the skin
surface is uniformly covered by soil (i.e., the mono-
layer). Since nearly all existing experimental deter-
minations of fraction absorbed have been conducted
above the mono-layer, the actual fraction absorbed
could be larger than experimentally determined.
Biological factors which can affect absorption include
diffusivity of skin, skin blood flow, age of the receptor,
etc. The exact relationship of all of these factors to
dermal absorption is not known. Thus, there is uncer-
tainty in the default dermal absorption factors. This
discussion should be presented in the risk assessment,
but until more is understood quantitatively about this
effect, adjustment of the dermal-soil absorption factors
is not warranted.
Default Dermal Absorption Values for Semivolatile
Organic Chemicals. This guidance identifies a default
dermal absorption value of 10% for semi volatile
organic compounds as a class. This suggested value is
based on the assumption that the observed experi-
mental values presented in Exhibit 3-4 are represen-
tative of all semivolatile organic compounds for which
measured dermal-soil absorption values do not exist.
Chemicals within classes vary widely in structure and
chemical properties. The use of default dermal absorp-
tion values based on chemical class can introduce
uncertainties into the risk assessment which can either
over- or under-estimate the risk.
Lack of dermal-soil absorption values. The ability
to quantify the absorption of contaminants from
exposure to soil is limited. Chemical-specific
information is available for only a few chemicals. For
most chemicals, no data are available, so dermal
exposures have not been quantified. This lack of data
results in the potential underestimation of total
exposure and risk. The degree of the underestimation
is dependent on the chemical being evaluated.
5.2.3 TOXICITY ASSESSMENT
Oral reference doses and slope factors for dermal
exposures. Quantitative toxicity estimates for dermal
exposures have not been developed by EPA.
5-6
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Therefore, oral reference doses and oral cancer potency
factors are used to assess systemic toxicity from dermal
exposures. The dermal route of exposure can result in
different patterns of distribution, metabolism, and
excretion than occur from the oral route. When oral
toxicity values for systemic effects are applied to
dermal exposures, uncertainty in the risk assessment is
introduced because these differences are not taken into
account. Since any differences between oral and
dermal pathways would depend on the specific
chemical, use of oral toxicity factors can result in the
over- or underestimation of risk, depending on the
chemical. It is not possible to make a general statement
about the direction or magnitude of this uncertainty.
Lack of a dermal slope factor for polynuclear
aromatic hydrocarbons (PAHs) and other
chemicals. This guidance focuses on the expected
systemic effects of dermal exposure from chemicals in
soil and water. EPA does not have recommended
toxicity values for the adverse effects that can occur at
the skin surface. This lack of dermal toxicity values is
considered to be a significant gap in the evaluation of
the dermal pathway, particularly for carcinogenic
PAHs. The statement in RAGS claiming that "it is
inappropriate to use the oral slope factor to evaluate the
risks associated with exposure to carcinogens such as
benzo(a)pyrene, which causes skin cancer through
direct action at the point of application" should not be
interpreted to mean that the systemic effects from
exposure to dermally active chemicals should not be
evaluated. In fact, there is a significant body of
evidence in the literature to generate a dose-response
relationship for the carcinogenic effects of PAHs on
the skin. In addition, PAHs have also been shown to
induce systemic toxicity and tumors at distant organs.
For these reasons, the lack of dermal toxicity values
may significantly underestimate the risk to exposure to
PAHs and potentially other compounds in soil. Until
dermal dose-response factors are developed, EPA
recommends that a quantitative evaluation be
conducted for systemic effects of PAHs and other
compounds and that a qualitative evaluation be
conducted for the carcinogenic effects of PAHs and
other compounds on the skin.
5.2.4 RISK CHARACTERIZATION
Lack of information for GI absorption. One issue in
the dermal-soil risk assessment approach presented in
this guidance is how would the route comparison (i.e.,
oral to dermal) change if the GI tract absorption
fraction were much less than the assumed 100%. As
discussed in Chapter 10 of the DBA, cancer slope
factors are intended to be used with administered dose.
Since dermal doses are absorbed, it is necessary to
convert the SF to an absorbed basis which can be done
in an approximate way by dividing it by the GI tract
absorption fraction. When AB SGI is high, adjustment of
the SF to an absorbed dose is not as important and the
earlier conclusions for when the dermal dose exceeds
the ingested dose do not change. However, when
ABSGI is low, the adjustment of the SF to an absorbed
dose can substantially increase the importance of the
dermal route relative to the ingestion route and it is
important to consider. In the absence of information on
gastrointestinal absorption, the risk characterization for
the dermal pathway has used unadjusted reference
doses and slope factors. This may result in under-
estimation of risk for dermal exposures to both soil and
water.
5-7
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CHAPTER 6
CONCLUSIONS/RECOMMENDATIONS
6.1 SUMMARY
The following summary presents the major points
made in each chapter of this guidance.
Hazard Identification
For the dermal-water pathway, only those
chemicals which contribute to more than 10% of
the dose from the oral (drinking water) pathway
should be considered important enough to carry
through the risk assessment.
For the dermal-soil pathway, the limited
availability of dermal absorption values is expected
to result in a limited number of inorganic
contaminants being considered in a quantitative
risk assessment. An important decision for the risk
assessor is whether the default value of 10%
dermal absorption from soil, for all organic
compounds without specific absorption values,
should be applied to a quantitative risk assessment.
Exposure Assessment
Since the Kp parameter has been identified as one
of the major parameters contributing to uncertainty
in the assessment of dermal exposures to
contaminants in aqueous media, it is important that
risk assessments be consistent when estimating this
parameter. Since the variability between the
predicted and measured Kp values is no greater
than the variability in inter-laboratory replicated
measurements, this guidance recommends the use
of predicted Kp values (Appendices A and B)
based on the equations in Chapter 3. However,
there are some chemicals (Exhibit A-l) that fall
outside the Effective Prediction Domain for
determining Kp, particularly those with a high
molecular weight and high Kow values. To address
these chemicals, a fraction absorbed (FA) term
should be applied to account for the loss of
chemical due to the desquamation of the outer skin
layer and a corresponding reduction in the
absorbed dermal dose. For halogenated chemicals,
Equation 3.8 could underestimate Kp due to the
lower ratio of molar volume related to molecular
weight for these halogenated compounds as
compared to those included in the Flynn database.
A new Kp correlation based on molar volume and
log Kow will be explored.
This guidance presents recommended default
exposure values for all variables for the dermal-
water and dermal-soil pathways in Exhibits 3-2 and
3-5, respectively.
For dermal-water exposures, the entire skin surface
area is assumed to be available for exposure when
bathing and swimming occurs. The assessor
should note that a wading scenario may result in
less surface area exposed. For dermal-soil expo-
sures, clothing is expected to limit the extent of
exposed surface area. For the adult resident, the
total default surface area should include the head,
hands, forearms and lower legs. For a residential
child the default surface area should include the
head, hands, forearms, lower legs and feet. For an
adult commercial/industrial worker, the total
default surface area should include the head, hands
and forearms.
During typical exposure scenarios, more soil is
dermally contacted than is ingested. The default
soil adherence factor (AF) for RME adult
residential activities (0.07 mg/cm2 ) should be
based on the central tendency value for a high-end
soil contact activity (e.g., a gardener). The default
AF value for a RME child resident (0.2 mg/cm2)
should be based on both the high end estimate for
an average soil contact activity (i.e., children
playing in dry soil) and the central tendency AF
estimates for a high-end soil contact-intensive
activity (i.e., children playing in wet soil). The
default AF value for a commercial/ industrial adult
worker (0.2 mg/cm2) should be based on the central
tendency estimate for a high-end soil contact
activity (i.e., utility worker).
The contribution of dermal absorption of chemicals
6-1
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from soils to the systemic dose generally is
estimated to be more significant than direct inges-
tion for those chemicals which have a soil absorp-
tion fraction exceeding about 10%.
Dermal-soil absorption values for ten compounds
are provided in this guidance. Screening absorp-
tion values are provided for semi-volatile organic
compounds as a class. No screening values are
provided for inorganic compounds, due to the lack
of sufficient data on which to base an appropriate
default screening level for inorganics other than
arsenic and cadmium. As new information on
dermal absorption from soil becomes available,
this guidance will be updated.
Toxicity Assessment
Before estimating risk from dermal exposures, the
toxicity factor should be adjusted so that it is based
on an absorbed dose. Usually, adjustments of the
toxicity factor are only necessary when the GI
absorption of a chemical from a medium similar to
the one employed in the critical study is
significantly less than 100% (i.e., 50%). Recom-
mended GI absorption values are presented in
Exhibit 4-1.
6.2 EXPOSURES NOT INCLUDED IN
CURRENT DERMAL GUIDANCE
This guidance does not explicitly recommend
exposure parameters for contact with contaminated
sediment. This exclusion is due to the high degree
of variability in sediment adherence and duration
of sediment contact with the skin. However,
information is included in the guidance document
that would allow a risk assessor to assess sediment
exposure on a site-specific basis.
This guidance does not specifically address dermal
toxicity, either acute or chronic. The dermal dose
derived with this methodology provides an
estimate of the contribution of the dermal pathway
to the systemic dose. The exclusion of dermal
toxicity should be considered an uncertainty issue
that could underestimate the total risk.
Current studies suggest that dermal exposure may
be expected to contribute no more than 10% to the
total body burden of those chemicals present in the
vapor phase. Therefore, this guidance does not
include a method for assessing dermal absorption
of chemicals in the vapor phase, with the
assumption that inhalation will be the major
exposure route for vapors. An exception may be
workers wearing respiratory protection but not
chemical protective clothing.
The methodology described in this guidance does
not cover the exposure associated with dermal
contact with contaminated surfaces.
6.3 RECOMMENDATIONS
The dermal risk guidance uses a mathematical
model to predict absorption and risk from
exposures to water. Contaminants for which there
are sufficient data to predict dermal absorption
with acceptable confidence are said to be within
the model's effective predictive domain (EPD).
Although the methodology can be used to predict
dermal exposures andriskto contaminants in water
outside the EPD, there appears to be greater
uncertainty for these contaminants. OSWER and
the workgroup, which developed this guidance, do
not recommend that the model be used to quantify
exposure and risk to contaminants in water that are
outside the EPD in the "body" of the risk
assessment. Rather, it is recommended that such
information be presented in the discussion of
uncertainty in the risk assessment. OSWER and the
workgroup recommend that experimental studies to
generate data for these chemicals be planned and
completed during remedial investigations on
Superfund sites where dermal exposures to these
chemicals may occur, using site-specific exposure
conditions as appropriate.
OSWER and the dermal workgroup also encourage
experiments to generate additional data on the soil
dermal absorption fraction (see Appendix E). The
dermal workgroup will work with regional risk
assessors on the development of the study designs
and will review study results submitted to it.
Additional details, recommendations, and a few
references are provided in Appendix E.
The Superfund Dermal Workgroup will be avail-
able for consultation on dermal risk assessment
6-2
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issues. It is recommended that the Workgroup
be consulted before dermal absorption values
other than those listed in Exhibit 3-4 or in
Appendix B are used in quantitative risk
assessments. In the future, risk assessors are
encouraged to provide the Workgroup with
new information regarding chemical-specific
studies of dermal absorption from soil, or
water, as well as any other exposure factors for
the dermal pathway.
Areas where additional research would provide
much needed information for addressing the
dermal exposure pathway include: 1)
quantification of dermal absorption from soil
(percent absorbed) for high priority compounds,
including inorganic compounds, using both in vivo
and in vitro techniques, 2) determination of the
effect of soil type/size on bioavailability of soil-
bound compounds, and 3) methods for assessing
risks associated with direct dermal toxicity of
chemical exposures.
A Peer Consultation Workshop on Issues
Associated with Dermal Exposure and Uptake was
held December 10-11, 1998. The Workshop was
sponsored by the EPA Risk Assessment Forum. A
report summarizing the proceedings and
recommendations of the Workshop can be obtained
from the Risk Assessment Forum Web site (http://
www.epa.gov/ncea/raf/rafrprts.htm).
Many of the Workshop recommendations for
immediate action were incorporated into this
guidance document. EPA is considering the
development of a dermal database to be located on
the EPA Web site that would provide information
on chemico-physical properties, soil absorption
and permeability coefficients of specific chemicals
and information on dermal exposure parameters.
Additional long-term recommendations, particu-
larly the development of a unified model for
assessing dermal exposure from multiple media
(e.g., water and soil), will be considered for future
research initiatives.
6-3
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(203Hg) Compounds in Man. Arch Environ. Health 19:453-484.
Albro, P.W. and Fishbein, L. (1972) Intestinal Absorption of Polychlorinated Biphenyls in Rats. Bull. Environ.
Contam. Toxicology 8:26-31.
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APPENDIX A
WATER PATHWAY
General guidance for evaluating dermal exposure at Superfund sites is provided in Risk Assessment
Guidance for Superfund (RAGS), Human Health Evaluation Manual (HHEM), Part A (U.S. EPA, 1989a).
Dermal Exposure Assessment Principles and Applications (DEA) (U.S. EPA, 1992a) details procedures for
estimating permeability coefficients of toxic chemicals and for evaluating the dermal absorbed dose. Section
A.I summarizes equations to evaluate the absorbed dose per event (DAevent) in Equations 3.2 and 3.3 and other
equations from the DEA. It also updates the regression model to predict the water permeability coefficient for
organics. Statistical analysis of the regression equation provides the range of octanol/water partition coefficients
(Kow) and molecular weights (MW) where this regression model could be used to predict permeability coeffici-
ents (Effective Prediction Domain - EPD), as recommended by the Science Advisory Board review in August
1992. Predictive values of the dermal permeability coefficient (Kp) for over 200 compounds are provided with
the 95% lower and upper confidence level in Appendix B (Exhibit B-2).
For chemicals with MW and Kow outside the EPD, a model for predicting the fraction absorbed dose (FA)
is proposed for those chemicals with high K^, taking into account the balance between the increased lag time of
these chemicals in the stratum corneum and the desquamation of the skin during the absorption process; the
consequence of which results in a net decrease in total systemic absorption.
Because the variability between the predicted and measured Kp values is no greater than the variability in
interlaboratory replicated measurements, this guidance recommends the use of predicted Kp for all organic
chemicals. This approach will ensure consistency between Agency risk assessments in estimating the dermal
absorbed dose from water exposures. The Flynn database (Flynn, 1990) contains mostly hydrocarbons which
might bear little resemblance to the typical compounds detected at Superfund sites. Predicting Kp from this
correlation is uncertain for highly lipophilic and halogenated chemicals with log Kow and MW values which are
very high or low as compared to compounds in the Flynn database, as well as compounds for those chemicals
which are partially or completely ionized. Alternative approaches are recommended for the highly lipophilic and
halogenated chemicals, which attempt to reduce the uncertainty in their predicted Kp. Complete calculation of
dermal absorbed dose (DAD) for the showering scenario using default assumptions is performed for over 200
compounds, and included in Appendix B (Exhibit B-3). For inorganics, Section A.2 provides permeability
coefficients of several metals. Section A.3 discusses the uncertainty of the parameters used in the estimation of
the dermal dose. Section A.4 provides the assumptions and calculations for the screening provided in Chapter 2:
-------
Hazard Identification. Section A.5 summarizes the calculation procedures as well as the instructions for using
the spreadsheets, which are provided on the Internet at the following URL: http://www.epa.gov/superfund/
programs/risk/ragse/index.htm
A.1 DERMAL ABSORPTION OF ORGANIC COMPOUNDS
A.1.1 ESTIMATION OF Kp FOR ORGANIC COMPOUNDS
As discussed in DBA, the thin outermost layer of skin, the stratum corneum, is considered to be the main
barrier to percutaneous absorption of most chemicals. The stratum corneum can be described as sheets of dead,
flattened cells containing the protein keratin, held together by a lipoidal substance. Numerous studies, presented
in the DBA, show that when this stratum corneum serves as the limiting barrier to diffusion through the skin, the
permeability coefficient of a compound in water through the skin can be expressed as a function of its oil/water
partition coefficient (Kow, or most often, log Kow), and its molecular weight (MW). This correlation was
presented in the DBA as the Potts and Guy's equation (DBA: Equation 5.8), obtained based on the Flynn
database (Flynn, 1991), shown in Exhibit B-l of Appendix B.
In RAGS Part E, the Potts and Guy correlation has been refined to the following equation by excluding
the three in vivo experimental data points in DEA, Table 5-8: ethyl benzene, styrene, and xylene, to limit the
Flynn database to in vitro studies using human skin. The new algorithm results in Equation 3.8.
log K = -2.80 + 0.66 log Kow - 0.0056 MW
(r2 = 0.66)
(3.8)
where:
Parameter
KP
Kow
MW
Definition (units)
Dermal permeability coefficient of compound in
water (cm/hr)
Octanol/water partition coefficient (dimensionless)
Molecular weight (g/mole)
Default Value
Chemical-specific, see Appendix B
Chemical-specific, see Appendix B
Chemical-specific, see Appendix B
A-2
-------
As can be seen from Equation 3.8, the molecular weight and polarity described by the octanol/water
partition coefficient are the sole predictors of Kp. The above equation containing predicted values of Kp was
evaluated against actual experimentally determined values for Kp and was found to correlate reasonably well,
with few exceptions that may be attributed to experimental or analytical error. In DBA, it was recommended that
the predicted values be used over the experimental measurements for the following two reasons: 1) for consis-
tency with chemicals without an experimental measurement of Kp and, 2) to minimize inter-laboratory differen-
ces. Recently, Vecchia (1997) examined almost twice as many permeability coefficient values as those in the
Flynn data set and found that replicated experimental measurements often vary by one to two orders of magni-
tude. This finding confirms the current continued recommendation that, for organics in water, the predicted
values for Kp obtained from the above algorithm be used instead of actual measured values.
To determine the range of MW and log Kow, where Equation 3.8 would be valid for extrapolation to other
chemicals given that the physico-chemical properties used in the Kp correlation (MW and log Kow) are not
completely independent of each other, the following Effective Prediction Domain (EPD) is determined using
Mandel's approach (Mandel, 1982, 1985) for collinear data. This approach uses experimental data points in the
derivation of the regression equation (here, the Flynn database, presented in Exhibit B-l) to determine the
specific ranges of MW and log Kow where the predictive power of the regression equation would be valid. This
analysis uses the software MLAB (Civilized Software, Bethesda, MD, 1996).
Using Mandel's analysis (Mandel, 1985), the following boundaries of MW and log Kow for the above
regression correlation were determined and are presented by Equations 3.9 and 3.10.
-0.06831 < 0.5103 x 1(T4 MW + 0.05616 log K < 0.5577
-0.3010 < -0.5103 x 1(T4 MW + 0.05616 log K < 0.1758
where:
Parameter Definition (units)
Kow = Octanol/water partition coefficient
(dimensionless)
MW = Molecular weight
Default Value
Chemical-specific, see Appendix B
Chemical-specific, see Appendix B
(3.9)
(3.10)
A-3
-------
The points defining the EPD are shown in Exhibit A-l. The axes shown in the middle of the exhibit are
obtained by translating the original axes (defined at 0 for both MW and log Kow) to the center of the Flynn data
set. The actual boundaries of the EPD are constructed by rotating these axes by 45°, then by drawing lines
through the EPD points parallel to the new axes. All of Flynn's data would fall within the EPD, using the above
exact solutions given by Equations 3.9 and 3.10.
From the list of 200 common pollutants, those which are outside the EPD, as defined by Equations 3.9
and 3.10, are summarized in Exhibit A-2 . The compound characteristics for which the modified Potts and Guy
correlation would not apply would be those with a combination of log K^ and MW satisfying those two
equations.
The permeability coefficients of two classes of chemicals with very low Kow and very high Kow have been
known not to correlate well with the log Kow (Leahy, 1990). Correlations like those in Equation 3.8 are based on
the assumption that chemical absorption is primarily through a dissolution-diffusion process in the lipid material
of the stratum corneum. Chemicals with low Kow will have limited permeability through the lipid material of the
stratum corneum, and penetration by other routes (e.g., appendages such as sweat glands or hair follicles or
through regions of the stratum corneum with even minor damage) may contribute significantly. Permeability
coefficients reported in the Flynn data set are measured at steady-state (i.e., tevent > 2.4 Tevent). Consequently, for
chemicals with very high log Kow, experimental values of permeability coefficients will include contributions of
the viable epidermis.
Exhibit B-2 summarizes the predicted Kp for over 200 organic chemicals. Results of the current EPD
analysis points out that for about 10% of those chemicals, this prediction would not be valid, according to the
current use of Flynn's data set as the basis for the correlation equation between Kp and log Kow and MW.
Strictly, chemicals with very large and very small Kow are outside of the EPD of Equation 3.8. Although large
variances in some data points contributed to the definition of the EPD, it is defined primarily by the properties of
the data used to develop Equation 3.8. With no other data presently available for chemicals with very large and
very small Kow, it is appropriate to use Equation 3.8 as a preliminary estimate o
A-4
-------
Exhibit A-l
Effective Prediction Domain (EPD)
Boundaries for Kp estimation
800
g>
JD
jo
3
o
_0)
o
-3-2-1012345678
Log Ko/w Partition Coefficient
Predicted
Flynn's data ~B EPD boundaries
A-5
-------
EXHIBIT A-2
COMPOUNDS FROM APPENDIX B WITH PERMEABILITY COEFFICIENTS OUTSIDE OF
THE EFFECTIVE PREDICTION DOMAIN OF THE MODIFIED POTTS AND GUY
CORRELATION
Log Kow < -2
Chemicals
Urea
Hydrazine H-sulfate
Log Kow
-2.11
-2.07
MW
60
32
Log Kow > 4
Chemicals
Benzo-a-anthracene
Benzo-a-pyrene
Benzo-b-fluoranthene
Chrysene
DDT
Dibenzo(a,h)anthracene
Indeno( 1 ,2,3 -c,d)pyrene
PCB -chlorobiphenyl
PCB-hexachlorobiphenyl
Phenanthrene
Pentachlorophenol
TCDD
Tris(2,3-dibromopropyl) phosphate
Log Kow
5.66
6.10
6.12
5.66
6.36
6.84
6.58
6.50
6.72
4.46
5.86
6.80
4.98
MW
228
250
252
228
355
278
276.3
292
361
178.2
266
322
697.6
'Range was approximated from properties of the chemicals identified by the EPD analysis, but do not define the
EPD.
A-6
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A.1.2 CALCULATION OF OTHER PARAMETERS IN DAevent
The two-compartment model used to represent the skin (recommended in DBA) is unchanged in RAGS
Part E, although all equations used in the evaluation of the dermal absorbed dose (DAevent) are updated, according
to the latest literature [Cleek and Bunge (1993) and Bunge and Cleek (1995)]. At short exposure durations,
Equation 3.2 specifies that the DAevent is proportional to the stratum corneum permeability coefficient (Kp) and
the contribution of the permeability of the viable epidermis is not included. Significantly, B (the ratio of the
permeability coefficient of a compound through the stratum corneum relative to its permeability coefficient
across the viable epidermis) does not appear in the equation for short exposure duration [Eq 3.2] because the
absorbing chemical has not had enough time to travel across the stratum corneum. Consequently, for short
exposure durations, the amount of chemical absorbed depends only on the permeability coefficient (Kp) of the
stratum corneum (SC), the outermost skin layer. For longer exposure durations, Equation 3.3 specifies that the
DAevent is restricted by the permeability of the viable epidermis and the stratum corneum, and thus B, the ratio of
the permeability of the stratum corneum to that of the epidermis, appears in Equation 3.3.
The following presentation and Equations A. 1 to A.8 summarize and update the equations from those in
the DEA, Chapters 4 and 5, for estimating all parameters needed to evaluate DAevent. For a detailed explanation
and derivation of the equations, please refer to DEA, Chapters 4 and 5, and Cleek and Bunge (1993) and Bunge
and Cleek (1995).
The dimensionless parameter B expresses the relative contribution of the permeability coefficient of the
compound in the stratum corneum (Kp, estimated from Equation 3.8) and its permeability coefficient in the viable
epidermis. Bunge and Cleek (1995) discussed four different methods to estimate B, and recommended the use of
Equation A. 1, as adopted in this document.
The complete derivation of Equation A.I is presented in Bunge and Cleek (1995). As defined, B is a
function of the permeability coefficient (Kp), which is a function of molecular weight (MW) and the partition
coefficient (log Kow) given by Equation 3.8. Exhibit A-3 shows how B changes with MW and log Kow.
A-7
-------
B =
K
K
p,ve
/MW
2.6
(as an approximation)
(A.I)
where:
Parameter
B
Kp,ve
MW
De
L.
Definition (units)
Dimensionless ratio of the permeability
coefficient of a compound through the stratum
corneum relative to its permeability coefficient
across the viable epidermis (ve)
Steady-state permeability coefficient through
the viable epidermis (ve) (cm/hr)
Dermal permeability coefficient in water
(cm/hr)
Molecular weight (g/mole)
Equilibrium partition coefficient between the
epidermis and water for the absorbing
chemical (dimensionless)
Effective diffusivity of the absorbing chemical
in the epidermis (cmVhr)
Effective thickness of the epidermis (cm)
Default Value
Kp ve = KewDe/Le, Kew = 1 assuming
epidermis behaves essentially as water; Le
= 10'2 cm,
De = 7. lx!0'6/MW cm2/s assuming De=10"
6 cnf/s when MW = 50 (Bunge and
Cleek, 1995)
Equation 3.8
Chemical-specific
Chemical-specific
Chemical-specific
io-2
A-8
-------
EXHIBIT A-3
EFFECTS OF MW AND LOG Kow ON B
8
7-
6-
5-
4-
3-
2-
1
i i i i
0 100 200 300 400 500
MW
A-9
-------
Using the same approach as in DBA, Equations 5.13, A.2 and A.3 are derived to estimate Dsc/lsc (cm/hr).
or:
where:
Parameter
Dsc
lsc
MW
D /A 9^
log _i£ = -2.80 - 0.0056 MW (A'Z)
lsc
sc _ 1 n(-2.80 - 0.0056 MW) (A. 3)
J. \J
Definition (units) Default Value
Effective diffusion coefficient for chemical Chemical-specific
transfer through the stratum corneum (cnf/hr)
Apparent thickness of stratum corneum (cm) 10"3 cm
Molecular weight (g/mole) Chemical-specific
Assuming lsc = 10"3 cm as a default value for the thickness of the stratum corneum, tevent can be evaluated using
Equation A.4:
= 0.105
where:
Parameter
ievent
Dsc
lsc
MW
Definition (units)
Lag time per event (hr/event)
Effective diffusion coefficient for chemical
transfer through the stratum corneum (cmVhr)
Apparent thickness of stratum corneum (cm)
Molecular weight (g/mole)
Default Value
Chemical-specific
Chemical-specific
10"3
Chemical-specific
(A.4)
A-10
-------
Calculate t*:
where:
Parameter
B
^ event
Dsc
lsc
b, c
IfB < 0.6, then t* = 2.4 x
IfB> 0.6, then t* = 6 xevent (b - Jb2 - c2}
(A.5)
(A.6)
b =
_ 2 (1 + B)2
- c
71
C =
I + 3B + 3B2
3(1 + B)
(A.7)
(A.8)
Definition (units)
Dimensionless ratio of the permeability
coefficient of a compound through the stratum
corneum relative to its permeability coefficient
across the viable epidermis (ve)
(dimensionless).
Time to reach steady-state (hr)
Lag time per event (hr/event)
Effective diffusion coefficient for chemical
transfer through the stratum corneum (cmVhr)
Apparent thickness of stratum corneum (cm)
Correlation coefficients which have been fitted
to the Flynn's data to give Equation 3.8
Default Value
Chemical-specific
Chemical-specific
Chemical-specific
Chemical-specific
io-3
All the above calculations are performed for over 200 chemicals for a defined default scenario (adults
showering once a day for 35 minutes) with the results tabulated in Appendix B. These calculations are also
provided in two MS Excel spreadsheets: one for organics (ORG04_01.XLS), and one for inorganics
A-ll
-------
(INORG04_01.XLS), which will be available at the RAGS E website: http://www.epa.gov/superfund/programs/
risk/ragse/index.htm or http://www.epa.gov/oswer/riskassessment/.
A.1.3. MODEL ADJUSTMENT FOR LIPOPHILIC COMPOUNDS OUTSIDE EPD
The above model assumes that all chemicals absorbed into the skin during the exposure event (tevent)
would eventually be absorbed into the systemic circulation, with the stratum corneum being the main barrier for
most chemicals. For highly lipophilic chemicals, the viable epidermis can be a significant barrier for chemical
transfer from the stratum corneum to the systemic circulation. When this occurs, the relative rate of desquama-
tion of the stratum corneum and cell proliferation rate at the base of the viable epidermis contribute to a net
decrease in the total amount of absorbed chemical. For similar reasons, stratum corneum desquamation can
reduce the amount of absorption for chemicals that are not highly lipophilic but large enough (high MW) that
penetration through the stratum corneum is slow (i.e., lag times are long).
A mathematical model was developed by Reddy et al. (2000) to account for the loss of chemical avail-
able for systemic absorption due to the desquamation of the outer layer of the stratum corneum. This model
accounts for the relative rates of epidermal turnover and percutaneous penetration. Using the assumptions that
the average turnover time of the stratum corneum is 14 days (tjc ~ 14 days or 336 hours), while that of the viable
epidermis is 28 days (twice the time for the stratum corneum to turnover) in normal skin, Reddy et al. (2000)
solved a set of partial differental mass balances for the stratum corneum and viable epidermis. After solving
these equations, they calculated the fraction of the chemical that is ultimately absorbed (FA), allowing for losses
by stratum corneum desquamation. Reddy et al. (2000) showed that FA is almost independent of tevent. However,
FA depends strongly on the chemical's lipophilic characteristic and molecular weight as expressed in the B
parameter and the lag time (Tevent), as illustrated in Exhibit A-4. A large number of the chemicals outside the EPD
fall into this category, as well as a few chemicals within the EPD, especially those with high molecular weight.
Given B and Tevent, FA values can be obtained from Exhibit A-5. FAs are included in Exhibit B-3 and in the
spreadsheet ORG04_01.XLS. There are only a small number of chemicals that have a FA value < 0.5, but since
most of those are highly lipophilic molecules that are often found in Superfund sites, the Dermal Workgroup is
recommending that FA should be included in the calculation of DAD when applicable.
A-12
-------
A. 1.4 MODEL VALIDATION
Two papers in the literature have offered an attempt to validate the dermal absorption model (from now
on referred to as the DBA model) presented in Section 3.1 for organics: McKone (1993) and Pirot et al. (1997).
McKone (1993) used experimentally measured and previously reported (Jo et al., 1990) ratios of
chloroform concentrations in inhaled air to tap-water concentration to evaluate the exposure model predictions.
Particular attention was given to the implied dermal uptake measured by these experiments and to whether this is
consistent with the recommended value for skin uptake of chloroform calculated by the DBA model. The
Workgroup finds that the Kp implied by the Jo et al. (1990) shower data is 2.4 times higher than the value
predicted by McKone and Howd (1992) and 6.7 times higher than the value predicted by the DBA model; and
that the DAevent implied by the Jo et al., (1990) shower data is 2.6 times higher than the value predicted by
McKone and Howd (1992) and 5 times higher than the value predicted by the DBA model. Also found was that
both predictive models appear to have lag time estimates higher than is consistent with the Jo et al. (1990)
shower data.
The Workgroup concludes that these results do not likely indicate any inherent flaws in the two predic-
tive models, but instead reveal that models are only as reliable as the data they employ, and that a more formal
process to assess sources of uncertainty is needed. For example, McKone and Howd (1992) have shown that the
estimation error in their prediction of Kp has a geometric standard deviation (GSD) of three and they have
estimated the GSD in the DBA model prediction of Kp as 3.8, confirmed as given by the 95% confidence level
(95% CL) in Exhibit B-2. If this estimation error is applied to the measurement errors in the Jo et al. (1990a)
experiments, the predicted and experimentally implied skin uptake parameters could reasonably differ from each
other by factors of 3 to 7.
More recently, Pirot et al. (1997) have used attenuated total reflectance Fourier Transform infrared
spectroscopy to quantify in vivo the uptake of 4-hydroxybenzonitrile by human stratum corneum. Results of this
analysis were used to construct a time profile of the cumulative amount of 4-hydroxybenzonitrile permeating the
skin as a function of time. The authors show that the calculated permeability coefficient (Kp ~ 3.6 x 10~3 cm/hr)
based on an assumed value of lsc = 1.5 x 10~2 cm, agrees well with that predicted by Equation 3.8, which yields a
Kp = 6.8 xlO-3 cm/hr.
A-13
-------
EXHIBIT A-4
FRACTION ABSORBED (FA) AS A FUNCTION OF SPECIFIC
COMBINATIONS OF B AND Tevent/tsc
340-
u
C/3
34 -
3.4 -
0.34
I I I I I I III I I I I 11 III
FA = 0.2
t I I I I III I I I I I I III
1.000
-0.100
U
r 0.010
0.001
0.01 0.1 1 10
B
A-14
-------
EXHIBIT A-5
EFFECT OF STRATUM CORNEUM TURNOVER ON FRACTION ABSORBED
(WATER) AS A FUNCTION OF B
340
<
[in
1
Tevent (hr) for tsc= 14 d
34 3.4
10
100
1000
tsc/^event
no ve: No viable epidermis-A model solution obtained assuming that the stratum corneum is the
only barrier to dermal absorption
A-15
-------
A.2 DERMAL ABSORPTION OF INORGANIC AND IONIZED ORGANIC
COMPOUNDS
As discussed in Chapter 3, Equation 3.4 should be used in evaluating dermal absorbed dose for
inorganics or highly ionized organic chemicals. As a consequence of and in keeping with recommendations in
DBA (Chapter 5), using actual measured values of Kp is recommended for the inorganics. If no value is avail-
able, the permeability coefficient of 1 x 10~3 cm/hr is recommended as a default value (DBA) for all inorganics.
Organometallics (e.g., tetraethyl lead) probably behave more like organic chemicals than inorganic chemicals and
should be treated with the procedure outlined for organics.
Dermal Absorbed Dose Per Event for Inorganic Compounds - Water Contact
DAevent (mg/cm2-event) is calculated for inorganics or highly ionized organic chemicals as follows:
where:
Parameter
We
DA = K x r x t
event p ^w event
Definition (units)
Absorbed dose per event (mg/cm2-event)
Dermal permeability coefficient of compound
in water (cm/hr)
Chemical concentration in water (mg/cm3)
Event duration (hr/event)
(3.4)
Default Value
Chemical-specific, see Exhibit A-6 and
Appendix B
Site-specific
See Exhibit 3-2
Exhibit A-6 shows a more detailed compilation of the apparent permeability coefficients in humans for
most of these inorganic chemicals at different concentrations (Hostynek et al., 1998). The data in this table may
be used to give a better estimate of the apparent permeability coefficients of the corresponding inorganic
chemicals when the specific species is known. This table may also be useful in evaluating high exposure
concentrations that approach those in several cited experimental studies.
A-16
-------
EXHIBIT A-6
APPARENT PERMEABILITY COEFFICIENTS OF INORGANICS
Metal
Cadmium
Chromium
Chromium
Chromium
Chromium
Chromium
Chromium
Chromium
Chromium
Chromium
Chromium
Chromium
Chromium
Mercury
Mercury
Mercury
Potassium
Potassium
Nickel
Nickel
Compound
CdCl2
Na2CrO4
Na2CrO4
CrCl3
Na2CrO4
K2Cr2O7
K2Cr2O7
CrO4
Cr04
Cr(III)
Cr(III)
CrCl3
Cr(N03)3
HgCl2
HgCl2
Hg vapor
KC1
KC1
NiSO4
NiSO4
Concentration
0.239M
0.01-0.2 M
0.017-0.398 M
0.017-0.398 M
0.034 M
0.03-0.25% Cr
(0.006-0.081 M)
0.034 M Cr
0.005 M
2.1
0.006 M
1.2 M
0.034 M
0.034 M
0.005 M
0.080-0.239 M
0.88-2.7 ng/m3
0.155 M
0.155 M
0.001-0.1 M
0.001 M
Apparent Permeability
Coefficient
Kp (cm/hr)
l.lxlO'3
1.0-2.1xlO-3
0.9-1.5 xlO-3
1.0-1.4 xlO'3
0.02-0.3 IxlO'3
0.01-1.0 xlO-3
0.43 x 10-3
2.7 x 10-3
0.23 x 10-3
0.4 x 10-3
0.013 xlO-3
0.041 x 10-3
0.030 xlO'3
0.02-0.88 x 10-3
0.10-0.93 xlO-3
61.0-240.0 xlO'3
2.0 xlO'3
2.0 xlO-3
0.003-0.01 x 10-3
<0.002-0.27 x 10-3
Species and
Experimental
conditions
guinea pig, in vivo3
human, in vivo
human, in vitro
human, in vitro
human in vitrob
human, in vitro
human, in vitro
human, in vitro0
human, in vitro0
human, in vitro0
human, in vitro0
human, in vitro
human, in vitro
human, in vitrob
human, in vitrob
human, in vivo
rabbit, in vitrod
pig, in vitro6
human, in vitro
human, in vitrof
A-17
-------
EXHIBIT A-6
APPARENT PERMEABILITY COEFFICIENTS OF INORGANICS (continued)
Metal
Nickel
Nickel
Nickel
Lead
Lead
Sodium
Sodium
Sodium
Compound
NiCl2, NiSO4
NiCl2
NiCl2
Pb(CH3CO2)2
Pb(NO3)2
NaCl
NaCl
NaCl
Concentration
1.32mgNi/ml
0.62-5%NiCl2
5%NiCl2
6 mM, 9 mmol/kg
0.5 M
0.155 M
0.156M
0.015-1.59 M
Apparent Permeability
Coefficient
Kp (cm/hr)
0.003-0.23 x 10-3
<0.0026-0.022 x 10'3
0.05 x 10-3
0.0005 x 10-3
0.13 xlO-3
0.06 x 10-3
0.028 x 10-3, fresh
0.050 x 1Q-3, frozen
(medians)
0.006-1. 19 xlO'3 (range)
Species and
Experimental
conditions
human, in vitro
human, in vitro
human, in vitro
human, in vivo
human, in vitro
human, in vivo
human, in vitro
human, in vitro
taken from Hostynek, et al, 1998
aln guinea pigs; there are no published data on human skin.
bDepends upon the time interval; larger values are for the first few hours.
Through epidermis.
dln rabbits; there are no published data with human skin.
eln pigs.
^rom various vehicles and for various durations.
A-18
-------
Recently, Vecchia (1997) collected permeability coefficients from the literature for in vitro penetration
of human skin by several ionized chemicals, including cations, anions and zwitterions. Like permeability
coefficients for inorganic chemicals, these Kp values are 10~3 cm/hour or lower. Thus, 10~3 cm/hour is recom-
mended as a conservative estimate for ionized organic chemicals.
Calculations of DAD and screening levels for inorganics using default exposure assumptions are
presented in Exhibit B-4 for all inorganics with a given experimental GI Absorption value (ABSGI from
Exhibit 4-1).
A.3 UNCERTAINTY ANALYSIS
Sources of uncertainty in the above calculations compared with actual human exposure conditions
include uncertainty in the model assumption, its formulation, and default values of the parameters used in
models. Uncertainty discussion is provided below for the assumptions made in the development of the dermal
absorption model, the modified Pott and Guy's Kp correlation, and the concentration of the chemicals in water.
As mentioned above, the skin is assumed to be a two-compartment model, with the two layers: stratum
corneum and viable epidermis. Although exact solutions to this two-compartment model have been derived
(Cleek and Bunge, 1993), these exact solutions are simplified in the recommended exposure assessment proce-
dure for easy application for the regional risk assessors. Several assumptions are made with the application of
these solutions, including the thickness of the stratum corneum (lsc = 10~3 cm) and the use of part of Equation 3.8
in Equations A.2 and A.3 to estimate Dsc/lsc.
For the permeability coefficient, the modified Flynn database is obtained from in vitro human diffusion
studies, where the Kp was estimated. Vecchia (1997), in reexamining a more comprehensive database of Kp
(twice the size of the Flynn database), found one to two orders of magnitude difference in replicated measure-
ments. The correlation coefficient (r2 = 0.67) resulting from the modified Potts and Guy correlation shows that
67% of the experimentally observed variance in Kp is explained by this regression equation. The remaining 33%
can be explained by inherent experimental errors and laboratory variabilities, and by the errors inherent in the
choice of the Kow value, whether it is measured or predicted. The residual error analysis provides the average
residual error between the measured log Kp (Kp.msd) and the log Kp that is predicted (Kp_pred) using the regression.
The residual error or standard error of the estimator (SEE) is calculated in Equation A.9 as:
A-19
-------
where:
Parameter
N
SEEofloSKp=
Definition (units)
Number of chemical samples used in the
estimation protocol
Dermal permeability coefficient of compound
in water (cm/hr)
Measured Kp
Predicted Kp
N
£
(log
p-msd &
N-2
p -pred*
(A.9)
Default Value
Site-specific
Chemical-specific, see Exhibit A-6 and
Appendix B
Chemical-specific
Chemical-specific
where N is the number of chemical samples used in the estimation protocol, and log Kp_msd - log Kp_pred is the
difference between logarithms of measured (Kp_msd) and predicted values of Kp (Kp_pred). For the Potts and Guy
correlation, the SEE is calculated to be 0.69. Exhibit A-7 shows that there might be a wedge pattern to the
residuals, which indicates the true value could be almost anything (i.e., large scatter between predicted and
experimental value) when the predicted value is small. However, when the predicted Kp is large, the value is
likely to be quite close to the true value. This result is consistent with experimental uncertainties, some of which
are probably not chemically dependent (e.g., penetration through appendages or damaged regions of the skin).
Consequently, these sources of variability contribute less significantly when the measured value is larger.
A-20
-------
EXHIBIT A-7
STUDENTIZED RESIDUALS OF PREDICTED Kp VALUES
RSTUDENT BYPREDICTEDS
W
_l
<
D
Q
w
LU
£
Q
LU
N
h
Z
1U
Q
D
W
2 -
O -
-2 -
-4
-6
0
°o o
-4 -2
Predicted logKp
O
A-21
-------
The equations used for the estimation of the 95% confidence interval (lower and upper limits) are given
in Equation A. 10 as follows:
95% upper and lower confidence level of K = K ± t,_2_-[ l_a/2) JVar(K ) (A.10)
where:
Kp = Predicted Kp from Equation 3.8
Var (Kp) = Variance of Kp (see Draper and Smith, 1998 for definition of
variance for linear regression with two independent variables)
(KP) = Standard error of the predicted Kp This standard error is
smaller for compounds in the Flynn data set, which results only
from errors in the correlation coefficients. For new
compounds, this standard error is much larger because it
includes both the errors from the correlation coefficients and
the residual error of the model.
= Student's t distribution for two independent variables with a
sample size of n and a two-sided confidence interval of 100 (1-
a) = 95%
Wischut et al. (1995) provides an analysis of the reliability of five mathematical models used for
simulating the permeability coefficient of substances through human skin. A database containing 123 measure-
ments for 99 different chemicals was used in the analysis. Reliability of the models was evaluated by testing
variation of regression coefficients and the residual variance for subsets of data, randomly selected from the
complete database. This study found that a revised Potts and Guy model using these data had a lower residual
variance than the McKone and Howd (1992) model, but that the McKone and Howd model and a revised
unpublished model by Robinson (Proctor and Gamble) could provide better prediction of the permeability
coefficient of highly lipophilic compounds. The Robinson model for Kp is based on a theoretical basis of a
maximum permeability coefficient to account for the limiting transport properties of the epidermis. The current
approach in this document, using the Potts and Guy model in combination with the parameter B in the dermal
absorption model to account for the effect of permeation in the epidermis, provides the same theoretical basis as
the Robinson model for Kp alone. Among all the models discussed by Wischut et al. (1995), the revised
Robinson model had the lowest residual variance, which is the SEE squared.
Several other physico-chemical characteristics can also be added to improve the above correlation, e.g.,
molar volume (Potts and Guy, 1992). Alternatively, the data could be grouped into smaller subsets of more
homogeneous chemical classes, which could yield much better correlations, as reviewed and summarized in
-------
DBA, Table 5.6. This selection of the Potts and Guy approach is based on the universal availability of the MW
and the Kow, which allow for the easy extrapolation of this correlation to other organic chemicals. However, the
large uncertainty resulting from these assumptions gives a 95% confidence interval of one to three orders of
magnitude for the Kp estimated by this correlation, as shown in Exhibits B-l and B-2. Because of this uncer-
tainty, suggestions have been made to simplify the skin two-compartment diffusion model to the standard Picks'
first law, which would provide a more conservative apparent Kp. This approach is retained to balance application
of more defined, available modeling to limited empirical data correlation. This approach might not improve the
uncertainty much for chemicals with small lag time, reflected by using the simplified Picks' first law equation
for the inorganics. However, for those chemicals with long lag time, the two-compartment approach, together
with the empirically predicted Kp, provides a much better description of the dermal absorption processes.
A note of caution is added here regarding the use of Equation 3.8 to estimate Kp for halogenated and
other chemicals with large MW relative to their molar volume. Notably, the list of 200 pollutants in Appendix B
includes several halogenated chemicals. Specifically, correlations like Equation 3.8 would be expected to under-
estimate Kp. The Flynn data set, from which Equation 3.8 was derived, consists almost entirely of hydrocarbons
with a relatively constant ratio of molar volume to MW. As a consequence, for this database, there is almost no
statistical difference in a regression of the Kp data, using MW to represent molecular size compared with a
regression using molar volume (the quantity which is expected to control permeability) to represent molecular
size. Because halogenated chemicals have a lower ratio of molar volume relative to their MW than hydrocarbons
(due to the relatively weighty halogen atom), the Kp correlation based on MW of hydrocarbons will tend to
underestimate permeability coefficients for halogentated organic chemicals. Unfortunately, Kp data are only
available for a small number of halogenated organic chemicals [only seven in the Vecchia (1997) database, which
is larger than the Flynn data set]. Vecchia (1997) found that Kp values for six of seven halogenated compounds
were underestimated by a correlation of similar form to Equation 3.8. To address this problem, a new Kp correla-
tion based on molar volume and log Kow will be explored.
The EPD for the modified Potts and Guy correlation, an evaluation based on Mandel's approach, depends
entirely upon the database used to generate both the correlation and the EPD. Sources of uncertainty in this
Flynn database include actual chemicals used for the correlation, as well as values of K^ associated with those
chemicals, values which would contribute to the predictability of the correlation, as well as to the range defined
by the EPD. For compounds with long lag time, where the adjustment of the fraction absorbed (FA) takes into
consideration the desquamation of the skin, another uncertainty of about 10-20% arises from the assumption of
steady-state and the approximation of these values from Exhibit A-5.
A-23
-------
For highly lipophilic molecules, which are often found on Superfund sites, there are uncertainties in
several steps of this approach. The permeability coefficients (Kp) of most of these compounds are outside of the
predictive domain, and the large uncertainty of these values is reflected in the large range of the 95% confidence
interval limit. For most of these chemicals, a value of FA < 1 is due to the effects of desquamation. However,
estimation of the Dermal/Oral contribution using standard default assumptions in Exhibit B-3 for these
compounds reveals that even using the lower 95% confidence limit of the Kp, a few compounds would yield a
ratio Dermal/Oral > 10%, which is the criterion used for inclusion of these chemicals in the site risk assessment
quantitative analysis. These results are shown in Exhibit A-8.
The recommendations from the Dermal Workgroup for these chemicals include: 1) conducting experi-
mental studies to obtain their Kp values, for at least in vitro exposure conditions under saturation concentration,
and 2) including these chemicals in the quantitative analysis and characterizing the uncertainty of the risk
assessment results clearly.
For the concentrations of chemicals in water (Cw) in Equations 3.2 through 3.4, values used for Cw should
reflect the available concentration of the chemicals in water for dermal absorption, and might be potentially
different from the measured field values. This difference would result from the conditions of the samples and the
type of chemicals to be analyzed. For the sample conditions, higher concentration of chemicals of interest might
be found in unfiltered groundwater samples as compared to filtered samples, due to the existence of particulate
matter and undissolved chemicals. However, to be consistent with existing RAGS guidance (U.S. EPA, 1989), it
is recommended that unfiltered samples be used as the basis for estimating the chemical concentration (Cw) for
calculating the dermal dose.
A-24
-------
EXHIBIT A-8
EVALUATION OF DERMAL/ORAL CONTRIBUTION FOR LIPOPHILIC COMPOUNDS
* 19
* 20
* 21
* 49
* 56
* 62
* 126
* 170
* 171
* 173
*176
* 186
* 203
CHEMICAL
Benzo-a-anthracene
Benzo-a-pyrene
Benzo-b-fluoranthene
Chrysene
DDT
Dibenzo(a,h)anthracene
Indeno( 1 ,2,3-CD)pyrene
PCB-chlorobiphenyl, 4-
PCB-hexachlorobiphenyl
Pentachlorophenol
Phenanthrene
TCDD
Tris(2 , 3 -dibromopropy 1)
phosphate
CAS No.
56553
50328
205992
218019
50293
53703
193395
2051629
26601649
87865
85018
1746016
126727
MWT
228.3
250.0
252.3
228.3
355.0
278.4
276.3
292.0
361.0
266.4
178.2
322.0
697.6
log
K-ow
5.66
6.10
6.12
5.66
6.36
6.84
6.58
6.50
6.72
5.86
4.46
6.80
4.98
KP
95%
LCL
1.7E-02
2.4E-02
2.4E-02
1.7E-02
9.2E-03
4.9E-02
3.5E-02
2.5E-02
1.4E-02
1.4E-02
5.5E-03
2.7E-02
1.3E-05
KP
(cm/hr)
predicted
4.7E-01
7.0E-01
7.0E-01
4.7E-01
2.7E-01
1.5E+00
l.OE+00
7.5E-01
4.3E-01
3.9E-01
1.4E-01
8.1E-01
3.9E-04
KP
95%UCL
1.3E+01
2.0E+01
2.0E+01
1.3E+01
7.8E+00
4.7E+01
3.1E+01
2.2E+01
1.3E+01
1.1E+01
3.8E+00
2.5E+01
1.1E-02
FA
1
1
1
1
0.7
0.6
0.6
0.6
0.5
0.9
1
0.5
1
Derm/
Oral
95%
LCLK,,
45%
75%
76%
45%
40%
110%
77%
62%
46%
43%
11%
66%
1%
Derm/
Oral
average
Kp
1283%
2186%
2221%
1283%
1156%
3388%
2307%
1844%
1376%
1226%
283%
2003%
22%
Derm/
Oral
95%
UCLK,,
36172%
63553%
64633%
36172%
33682%
104681%
69550%
54977%
41414%
34780%
7446%
61044%
642%
Note: All the above calculations are done using the same assumptions as those in Exhibit B-3
The types of chemicals in the samples would also influence the available concentration of the chemicals
for dermal absorption, due to their ionization status in the samples. This discussion is detailed in Bunge and
McDougal (1998). For organic chemicals in which Kp is calculated using Equation 3.8, Cw should be the concen-
tration of only the non-ionized fraction of the chemical, Cu, to be consistent. If the organic chemical is not ioniz-
able, Cw is equal to the total concentration of chemical in the aqueous solution, Ctot. For organic acids with one
dominant acid-base reaction of pKa, Cu is calculated using Equations A. 11 or A. 12.
A-25
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For organic
For organic
where:
Parameter
cu
acids with one dominant acid-base reaction of pKa, Cu is:
(-< _ tot
11 fY-P ~ Pa)
bases with one dominant acid-base reaction:
(^ _ tot
11 fY-P a ~ P *)
Definition (units) Default Value
Concentration of non-ionized species (mg/1) Site-specific
Total concentration (mg/1) Site-specific
Log of the ionization equilibrium constant of the Chemical-specific
chemical in the aqueous solution
(A. 11)
(A. 12)
For organic chemicals with more than one ionizable group, in general, pK,, values should be known for
all ionizing reactions, and the concentration of the non-ionized species, Cu, should be calculated by combining
expressions for species mass balances, electroneutrality, and reaction equilibrium.
For organic chemicals, both ionized and non-ionized species at conditions of the aqueous solution,
calculate DAevent as the sum of the DAevent for the non-ionized species (using Equations 3.2 and 3.3 and the
concentration of the non-ionized species, Cw = Cu, with the Kp of the non-ionized species) and the DAevent for the
ionized species (using Equations 3.2 and 3.3 and the concentration of the ionized form of the chemical, Cw = Ctot -
C^ with the Kp of the ionized species). For inorganic chemicals, Cw = Ctot. If the Kp of the ionized species is
always smaller than the Kp of the non-ionized species, using Cw as a default total concentration would always
yield a conservative estimate of the dermal absorbed dose.
A.4 SCREENING PROCEDURE FOR CHEMICALS IN WATER
For purposes of scoping and planning an exposure and risk assessment, it is useful to know when it is
important to consider dermal exposure pathways. Assessors must decide what level (from cursory to detailed) of
analysis is needed to make this decision. The following screening procedure addresses this issue primarily by
A-26
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analyzing when the dermal exposure route is likely to be significant when compared to the other routes of
exposure. This discussion is based on methodology presented in Chapter 9 of the DBA using the parameters
provided in this current guidance, and provides the basis for the current Chapter 2 on Hazard Identification.
Readers are encouraged to consult the DBA document for more details.
The first step is to identify the chemicals of interest. The next step is to make a preliminary analysis of
the chemical's environmental fate and the population behavior to judge whether dermal contact may occur. The
third step is to review the dermal toxicity of the compound and determine if it can cause acute effects. The scope
of this screening procedure has been limited to dermal exposure assessments in support of risk assessments for
systemic chronic health effects. However, consideration of other types of health effects can be a critical factor in
determining the overall importance of the dermal exposure route. Even if the amount of a compound contacting
the skin is small compared to the amount ingested or inhaled, the dermal route can still be very important to
consider for compounds that are acutely toxic to the skin.
The remainder of this procedure evaluates the importance of dermal contact by comparing it to other
exposure routes that are likely to occur concurrently. For example, the importance of dermal contact with water
is evaluated by assuming that the same water is used for drinking purposes as for swimming or bathing and
comparing these two pathways. However, the underlying assumption that concurrent exposure routes will occur
is not valid in all situations. For example, the water in a contaminated quarry may not be used as a domestic
water supply but may be used for occasional recreational swimming. Even where concurrent exposure routes
occur, the contaminant concentrations may differ. For example, in a situation involving a contaminated river
used as a domestic water supply, swimmers may be exposed to a higher concentration in the river than occurs
during ingestion of tap water due to treatment. Thus, the assessor should confirm the assumptions that concur-
rent exposures occur and that the same contaminant levels apply. Where these assumptions are not valid, dermal
exposure should be evaluated independently.
Where the same water supply is used for drinking and bathing, the importance of dermal contact with
water can be evaluated by comparing the possible absorbed dose occurring during bathing relative to that
occurring as a result of ingestion, represented by the standard default of drinking 2 liters of water per day per
person. Assuming a 35 min (0.58 hr) showering (RME value from Exhibit 3-2), for all the 200 pollutants
included in Exhibit B-3, the following ratio of the dermal absorbed dose relative to ingestion is presented in
Equations A.13 to A.16 for organics and Equation A.13 for inorganics.
A-27
-------
Dermal Dose
DAevent(SA}(EV)
(A. 13)
Ingestion Dose (CJ(/K)(1000cm 3/L)(ABSGI)
For short exposure (t event
-------
where:
Parameter
Kp
T :
L event
FA
Dermal Dose
Ingested Dose
(A.15)
Definition (units)
Default Value
Dermal permeability coefficient of compound in Chemical-specific, see Appendix B
water (cm/hour)
Lag time per event (hr/event)
Fraction absorbed (dimensionless)
Chemical-specific, see Appendix B
Chemical-specific, see Appendix B
Using the screening criteria of 10% dermal to ingestion, the dermal dose exceeds 10% of the ingested dose as
presented in Equation A.15 when:
For organics:
i -
> 10% when (FA) (K ) Ji; > 0.005
Ingestion p v
(A. 16)
It should be noted that this screening procedure for exposure to water-borne chemicals is limited to the
ingestion and showering pathways (using RME value for showering duration) for adults, and does not include
consideration of swimming exposures, and therefore should not be used for screening chemicals in surface water
where exposure may be through swimming activity. This procedure has also been evaluated to be more conserva-
tive than the scenario of children bathing for one hour (RME value for children bathing). In addition, site-
specific scenarios and exposure conditions should always be used when available.
The screening criterion of 10% dermal exposure to ingestion exposure was selected to ensure that this
screening procedure does not eliminate compounds of potential concern. This criterion introduces a safety factor
of 10. For compounds with low GI absorption (e.g., < 50%), this screening procedure should not be used, and the
actual GI absorption fraction should be used to adjust for the toxicity effect (see Section 3.2 on Dermal Absorp-
tion from Soil for methodology).
A-29
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Exhibit B-3 in Appendix B lists more than 200 common organic pollutants and their permeability
coefficients. The compounds are listed in alphabetical order. Assessors can check this list to see if the
compound of interest is on the list. Chemicals which are considered appropriate to evaluate for the dermal
pathway are indicated in Exhibit B-3 with a "Y" in the "Chemicals To Be Assessed" column. Exhibit B-4
provides the same information for all inorganics with a GI absorption fraction provided in Exhibit 4-1.
For inorganics, using the same procedure, the screening equation results in Equation A. 17.
Dermal
For inorganics: > 10% when K > ABSGI (A 17)
Ingestion p
A.5 PROCEDURES FOR CALCULATING DERMAL DOSE
This section presents the steps required to identify appropriate values for the exposure and absorption
parameters, and notes how to combine these values to estimate the dermally absorbed dose of a compound in an
aqueous medium.
Step 1: Select Values for Exposure Parameters
Site-specific measurement or modeling is required to identify values for the concentration of the
contaminant(s) of interest in water. Concentration values should be used that are representative of the location
and time period where exposure occurs. Lacking site-specific data to the contrary, the default values presented in
Exhibit A-9 are recommended for the parameters characterizing water contact during bathing.
Background information and the rationales supporting default recommendations are obtained from the
Exposure Factors Handbook (U.S. EPA, 1997a), and are briefly summarized here. The exposed skin area is
based on the assumption that people are entirely immersed during bathing or swimming; the corresponding body
areas were presented in the Exposure Factors Handbook. The bathing frequency of 350 days/year is based on
information that most people bathe once per day (1 event/day). The bathing event time is based on the range
given in the Exposure Factors Handbook to be representative of baths as well as showers and considering that
some water residue remains on the skin for a brief period after bathing. The exposure duration of 9 to 30 years
A-30
-------
represents the likely time that a person spends in one residence, with 9 years used for central tendency residential
exposure duration, and 30 years used for high end residential exposure duration.
EXHIBIT A-9
DEFAULT VALUES FOR WATER CONTACT EXPOSURE PARAMETERS
Parameter Bathing Default Parameters
Adult Skin Area (cm2) 18,000
Event Time and Frequency 35 min/event, 1 event/day
and 350 days/yr
Exposure Duration (years) 9-30
Step 2: Select Normalizing Parameters Used in Dose Equations
Dose estimates are normalized over body weight and time to express them in a manner that is consistent
with dose-response relationships. An average body weight [70 kg for adults, see U.S. EPA, 1989 for age-specific
values for children] is used for this purpose. For cancer risk assessments, an averaging time equal to a mean
lifetime (70 yr) is used. For noncancer risk assessments, an averaging time equal to the exposure duration is
used. (For more details regarding these parameters, see U.S. EPA, 1989.)
A-31
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Step 3: Estimate DAevent
These equations were given in Chapter 3 and Appendix A. Section A.I gives the equations for the
organics; Section A.2 gives the equations and values for inorganics. For organics:
Dermal Absorbed Dose per event for Organic Compounds - Water Contact
DAevent (mg/cm2-event) is calculated for oganic compounds as follows :
* t\ then: DAevent = 2 FA - K x Cw
1ft > t*
J event '
DAevent = FA x Kp x CM
where:
Parameter
DAevent =
FA
Cw
fr
L event
^event
t*
B
Definition (units)
Absorbed dose per event (mg/cm2-event)
Fraction absorbed (dimensionless)
Dermal permeability coefficient of compound
in water (cm/hr)
Chemical concentration in water (mg/cm3)
Lag time per event (hr/event)
Event duration (hr/event)
Time to reach steady-state (hr) = 2.4 ievent
Dimensionless ratio of the permeability
coefficient of a compound through the stratum
corneum relative to its permeability
coefficient across the viable epidermis (ve)
(dimensionless).
t
1 + B
+ 2 T
6 T X t
event event
71
1 + 3 B + 3 B:
Default Value
Chemical-specific, See Appendix B
Chemical-specific, See Appendix B
Site-specific
Chemical-specific, See Appendix B
See Exhibit 3-2
Chemical-specific, See Eq. A.5 to A.:
Chemical-specific, See Eq. A. 1
(3.2)
(3.3)
A-32
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Equations A. 1 to A.8 update those in the DBA for estimating all parameters needed to evaluate DAevent:
n KP v ^ . . t. .
B = ~ A J (as an approximation) (A.I)
K 2.6
p,ve
where:
Parameter Definition (units) Default Value
B = Dimensionless ratio of the permeability
coefficient of a compound through the
stratum corneum relative to its permeability
coefficient across the viable epidermis (ve)
Kpve = Steady-state permeability coefficient through Kpve = KewDe/Le, Kew =1 assuming EPI
the viable epidermis (ve) (cm/hr) behaves essentially as water; Le = 10"2 cm,
De =7.1xlO-6/MW cmVs assuming De=10'6
cnf/s when MW = 50 (Bunge and Cleek,
1995)
Kp = Dermal permeability coefficient in water Equation 3.8
(cm/hr)
MW = Molecular weight (g/mole) Chemical-specific
Using the same approach as in DBA, Equation 5.13, A.2 and A.3 estimate Dsc/lsc (cm/hr).
or:
where:
Parameter
Dsc
lsc
MW
D
1nrt SC _ 0 or.
sc
- 0.0056
MW
sc _ 1 n(-2.80 - 0.0056 MW)
1K
Definition (units)
Effective diffusion coefficient for chemical
transfer through the stratum corneum (cmVhr)
Apparent thickness of stratum corneum (cm)
Molecular weight (g/mole)
Default Value
Chemical-specific
io-3
Chemical-specific
(A.2)
(A.3)
A-33
-------
Assuming lsc = 10"3 cm as a default value, tevent can be evaluated using Equation A.4:
6 D
= 0.105 X ltf.O.OO*6MW)
(A.4)
where:
Parameter
fr -
L event
Dsc
lsc
MW
Definition (units)
Lag time per event (hr/event)
Effective diffusion coefficient for chemical
transfer through the stratum corneum (cmVhr)
Apparent thickness of stratum corneum (cm)
Molecular weight (g/mole)
Default Value
Chemical-specific
Chemical-specific
io-3
Chemical-specific
A-34
-------
Calculate t*
IfB < 0.6, then t* = 2.4 x^
(A.5)
IfB > 0.6, then t* = (b - Jb2 - c2)
(A.6)
where:
b _ 2(1+ B)2 _
(A.7)
C =
1 + 3B + 3B
3(1 + B)
2
(A.8)
where:
Parameter Definition (units)
B = Dimensionless ratio of the permeability
coefficient of a compound through the stratum
corneum relative to its permeability coefficient
across the viable epidermis (ve)
(dimensionless).
t* = Time to reach steady-state (hr)
ievent = Lag time per event (hr/event)
Dsc = Effective diffusion coefficient for chemical
transfer through the stratum corneum (cmVhr)
lsc = Apparent thickness of stratum corneum (cm)
b, c = Correlation coefficients which have been fitted
to the Flynn's data to give Equation 3.8
Default Value
Chemical-specific
Chemical-specific
Chemical-specific
Chemical-specific
io-3
Chemical-specific
A-35
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For Inorganics:
DAevent (mg/cm2-event) is calculated for inorganics or highly ionized organic chemicals as follows:
Dermal Absorbed Dose Per Event for Inorganic Compounds - Water Contact
DA = K x r x t
event p w event
where:
Parameter
DAevent =
KP
Cw
Definition (units)
Absorbed dose per event (mg/cm2-event)
Dermal permeability coefficient of compound
in water (cm/hr)
Chemical concentration in water (mg/cm3)
Event duration (hr/event)
Default Value
Chemical-specific, see Exhibit A-6 and
Appendix B
Site-specific, non ionized fraction, see
Appendix A for more discussion
See Exhibit 3-2
(3.4)
Step 4: Integrate Information to Determine Dermal Dose
Finally, the dermal dose is calculated by collecting the information from the earlier steps and
substituting into Equation 3.1.
A-36
-------
where:
Parameter
DAD
DA =
-"-'"-event
SA
EV
EF
ED
BW
AT
ZX4D =
Dermal Absorbed Dose - Water Contact
DA x EV x ED x EF
Definition (units)
Dermally Absorbed Dose (mg/kg-day)
Absorbed dose per event (mg/cm2-event)
Skin surface area available for contact (cm2)
Event frequency (events/day)
Exposure frequency (days/year)
Exposure duration (years)
Body weight (kg)
Averaging time (days)
(3.1)
Default Value
Chemical-specific, see Eq. 3.2 and 3.3
See Exhibit 3-2
See Exhibit 3-2
See Exhibit 3-2
See Exhibit 3-2
70kg
noncarcinogenic effects AT = ED x 365 d/yr
carcinogenic effects AT = 70 yr x 365 d/yr
Step 5: Further Refinement of Dose Estimate
Where dose estimates are desired for children during specific age ranges, a summation approach is
needed to reflect changes in skin surface area and body weight. Assuming all other exposure factors remain
constant over time, Equation 3.1 is modified to Equation A. 18; where m and n represent the age range of interest.
The skin surface areas for the ages of interest can be obtained from Exhibit C-3 (Appendix C) and body weights
from the Exposure Factors Handbook (U.S. EPA, 1997a).
A-37
-------
where:
Parameter
DAD
Daevent =
SA
EV
EF
ED
BW
AT
Dermal Absorbed Dose - Water Contact
Surface Area/Body Weight Adjustment
DAD =
DA
EV EF
AT
SAj ED,
BW.
Definition (units)
Dermal Absorbed Dose (mg/kg-day)
Absorbed dose per event (mg/cm2-event)
Skin surface area available for contact (cm2)
Event frequency (events/day)
Exposure frequency (days/year)
Exposure duration (years)
Body weight (kg)
Averaging time (days)
(A. 18)
Default Value
Chemical-specific, see Equation 3.12
See Appendix C and Equations 3.13-3.16
See Exhibit 3-5
See Exhibit 3-5
See Exhibit 3-5
EFH (U.S. EPA, 1997a)
noncarcinogenic effects AT = ED x 365 d/yr
carcinogenic effects AT = 70 yr x 365 d/yr
Step 6: Screening
where:
Parameter
DA =
-"-'"-event
cw
SA
EV
IR
ABSGI =
Dermal Dose
(A.13)
Ingestion Dose (CJ(IK)( 1000cm 3/L)(ABSGI)
Definition (units)
Absorbed dose per event (mg/cm2-event)
Chemical concentration in water (mg/cm3)
Skin surface area available for contact (cm2)
Event frequency (events/day)
Water ingestion rate (L/day)
Fraction of contaminant absorbed in the gastrointestional tract (dimensionless)
- For Organics: ABSGI is assumed to be 1 (or 100% absorption)
- For Inorganics: ABSGI is chemical specific, given by Exhibit 4-1
Default Value
Chemical-specific, see Equation 3.12
Site-specific, non ionized fraction, see Appendix
A for more discussion
See Appendix C and Equations 3.13-3.16
See Exhibit 3-5
A-38
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Step 7: Evaluate Uncertainty
As explained in Chapter 4 and Section A.4, the procedures for estimating the dermal dose from water
contact are very new and should be approached with caution. One "reality check" that assessors should make for
bathing scenarios is to compare the total amount of contaminant in the bathing water to the dose. The amount of
contaminant in the water is easily computed by multiplying the contaminant concentration by the volume of
water used (showers typically use 5 to 15 gal/min). Obviously, the dose cannot exceed the amount of contami-
nant in the water. In fact, it seems unlikely that a high percentage of the contaminant in the water could be
dermally absorbed. As a preliminary guide, if the dermal dose estimate exceeds 50% of the contaminant in the
water, the assessor should reexamine the assumptions and sources of data. Volatile compounds have been shown
to volatilize significantly during showering. Andelman (1988) found that about 90% of TCE volatilized during
showering. This would suggest that the effective concentration of volatile contaminants in water, and thus the
resulting dermal dose for volatiles, may be reduced. So for volatile compounds, assessors may want to assume a
reduced contaminant concentration in water contacting the skin as part of a sensitivity analysis.
The dermal permeability estimates are probably the most uncertain of the parameters in the dermal dose
equation. As discussed in Section A.4, the measured values probably have an uncertainty of plus or minus a half
order of magnitude. In addition, FA is obtained graphically to the nearest one significant figure, and therefore
contributes somewhat to the uncertainty of the final calculation. Accordingly, the final dose and risk estimates
should be considered highly uncertain. Some idea of the range of possible values can be obtained by first using
average or typical values for each parameter to get a typical dose estimate. Setting two or three of the most
variable parameters to their upper values and the others to their average values will also yield some idea of the
possible upper-dose estimate.
A.5.1 STEPWISE PROCEDURE FOR CALCULATING DERMAL DOSE USING SPREADSHEETS
Revised spreadsheets have been set up on Microsoft Excel to support the calculations for the dermally
absorbed dose described in Chapter 3 and this Appendix for the organics (ORG04_01.XLS) and the inorganics
(INORG04_01.XLS). These spreadsheets replace the previous LOTUS 123 files sent to the Regions with the
1992 document. Electronic versions of the spreadsheets are provided on the Internet (http://www.epa.gov/
superfund/programs/risk/ragse/index.htm). The spreadsheets provide data for 209 organics and 19 inorganic
chemicals, with all equations included. Calculations are also given for these chemicals, using either default or
assumed values for the purpose of illustration.
A-39
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Results from the spreadsheets for the organics are tabulated in Appendix B, Exhibits B-l to B-3. For
the organics, Equations A. 1 to A.8 and 3.1 to 3.8 are set up for over 200 compounds in the spreadsheet. Given
the log Kow and MW of chemicals, Kp is estimated using Equation 3.8. Depending on the exposure duration
(teventX either Equation 3.2 or 3.3 should be selected to be used in Equation 3.1. All other default exposure factors
in Equation 3.1 are obtained from Chapter 3 and Appendix A.
Compounds from Exhibits B-2 and B-3 marked with an * are the highly lipophilic compounds which are
listed in Exhibit A-2. Compounds from the organics list marked with an ** are the halogenated compounds.
For each new site risk assessment, the following procedures need to be followed:
Step 1: Input parameter values common to all chemicals at the top of the spreadsheet, i.e. SA, tevent, EV, EF, ED,
BW, AT. Default values for all these parameters can be found in Chapter 3 and in Appendix A.
Step 2: Compile the list of chemicals on the site and their concentrations.
Step 3: Find the chemicals on the spreadsheet provided. If not listed, find their Molecular Weight and Log Kow
and enter data for the new chemicals at the bottom of the spreadsheet. Copy the respective formulas for
all the calculations to these new chemicals. Numerical values corresponding to the conditions on the
site will be calculated automatically. Delete the ones not found on the site to obtain your own
spreadsheet for the site.
Step 4: Enter the actual concentration of each chemical found on the site in the column marked "Cone".
Step 5: Check in the Column "Chemicals to be assessed" to find out whether or not you need to include that
chemical in your Risk Assessment.
Step 6: Check on all Print setup for your particular printer. You can rearrange the columns to print only the
values of interest by copying your spreadsheet to a new spreadsheet, pasting the values only, and not the
formulas. This new spreadsheet can be formatted freely, as well as imported into a wordprocessing
software as tables. Note that any changes in calculations still need to be done in the original
spreadsheet with the embedded equations.
A-40
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APPENDIX B
SCREENING TABLES AND REFERENCE VALUES
FOR THE WATER PATHWAY
Note: The following exhibits are provided using Kow values from the DEA (U.S. EPA, 1992a). EPA is currently
revising criteria for selecting Kow values, and these exhibits will be updated with appropriate Kow values, as well
as expanded to include more chemicals. The new changes may also affect Equation 3.8 and all other related
evaluations.
B-l
-------
EXHIBIT B-l
FLYNN DATA SET
Notes:
1. The predicted Kp was calculated using Equation 3.8 and the Lotus spreadsheet software, and is the average
value of the regression correlation equation.
2. 95% LCL (lower confidence level) and UCL (upper confidence level) of Kp are calculated using the statisti-
cal software package STATA (STATA Corporation, 702 University Drive East, College Station, Texas
77840, USA).
3. Compounds in italics are common to both the Flynn data set and the organic data set. For these compounds,
the 95% LCL and UCL are obtained from Exhibit B-l and are common to both Exhibits B-l and B-2.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Flynn's in vitro experimental data
Aldosterone
Amobarbital
Atropine
Barbital
Benzyl alcohol
4-Bromophenol
2,3-Butanediol
Butanoic acid (butyric acid)
n-Butanol
2-Butanone
Butobarbital
4-Chlorocresol
2-Chlorophenol
4-Chlorophenol
Chloroxylenol
Codeine
Cortexolone
(11 -desoxy- 1 7-hydroxycorticosterone)
Cortexone (deoxycorticosterone)
Corticosterone
Cortisone
o-Cresol
m-Cresol
p-Cresol
n-Decanol
MW
360.4
226.3
289.4
184.2
108.1
173
90.12
88.1
74.12
72.1
212.2
142.6
128.6
128.6
156.6
299.3
346.4
330.4
346.4
360.5
108.1
108.1
108.1
158.3
Log Kow
1.08
1.96
1.81
0.65
1.10
2.59
-0.92
0.79
0.88
0.28
1.65
3.10
2.15
2.39
3.39
0.89
2.52
2.88
1.94
1.42
7.95
1.96
1.95
4.57
KP
95%
LCL
4.4E-05
1.2E-03
4.1E-04
2.4E-04
1.3E-03
5.8E-03
5.2E-05
9.9E-04
1.3E-03
5.1E-04
8.8E-04
1.7E-02
5.2E-03
7.3E-03
2.1E-02
7.6E-05
5.6E-04
1.2E-03
2.2E-04
7.7E-05
4.8E-03
4.9E-03
4.8E-03
9.5E-02
KP
Predicted
(cm/hr)
7.8E-05
1.7E-03
5.9E-04
3.9E-04
2.1E-03
8.8E-03
1.2E-04
1.7E-03
2.3E-03
9.5E-04
1.3E-03
2.9E-02
8.0E-03
1.2E-02
3.7E-02
1.3E-04
8.4E-04
1.8E-03
3.5E-04
1.3E-04
7.7E-03
7.8E-03
7.7E-03
2.2E-01
KP
Measured
(in vitro
data)
cm/hr
3.0E-06
2.3E-03
8.5E-06
1.1E-04
6.0E-03
3.6E-02
4.0E-05
l.OE-03
2.5E-03
4.5E-03
1.9E-04
5.5E-02
3.3E-02
3.6E-02
5.2E-02
4.9E-05
7.4E-05
4.5E-04
6.0E-05
l.OE-05
1.6E-02
1.5E-02
1.8E-02
7.9E-02
KP
95%
UCL
1.4E-04
2.4E-03
8.6E-04
6.4E-04
3.4E-03
1.3E-02
2.8E-04
2.9E-03
4.0E-03
1.8E-03
1.8E-03
4.9E-02
1.2E-02
1.8E-02
6.6E-02
2.2E-04
1.3E-03
2.7E-03
5.4E-04
2.2E-04
1.2E-02
1.2E-02
1.2E-02
5.1E-01
B-2
-------
EXHIBIT B-l
FLYNN DATA SET (continued)
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Flynn's in vitro experimental data
2,4-Dichlorophenol
Digitoxin
Ephedrine
B-estradiol
B-estradiol (2)
Estriol
Estrone
Ethanol
2-Ethoxy ethanol (Cellosolve)
Ethyl ether
4-Ethylphenol
Etorphine
Fentanyl
Fentanyl (2)
Fluocinonide
Heptanoic acid (enanthic acid)
n-Heptanol
Hexanoic acid (caproic acid)
n-Hexanol
Hydrocortisone
Hydrocortisone (2)
[Hydrocortisone-21-yl]-N,N dimethyl
succinamate
[Hydrocortisone-2 1 -yl] -hemipimelate
[Hydrocortisone-2 1 -hemisuccinate
[Hydrocortisone-2 1 -yl] -hexanoate
[Hydrocortisone-2 1 -yl] -6-hydroxy
hexanoate
[Hydrocortisone-2 1 -yl] -octanoate
[Hydrocortisone-2 1 -yl] -pimelamate
[Hydrocortisone-2 1 -yl] -proprionate
[Hydrocortisone-2 1 -yl] -succinamate
Hydromorphone
Hydroxypregnenolone
1 7a-Hydroxyprogesterone
Isoquinoline
Meperidine
Methanol
MW
163
764.9
165.2
272.4
272.4
288.4
270.4
46.07
90.12
74.12
122.2
411.5
336.5
336.5
494.6
130.2
116.2
116.2
102.2
362.5
362.5
489.6
504.6
462.5
460.6
476.6
488.7
503.6
418.5
461.6
285.3
330.4
330.4
129.2
247
32.04
Log Kow
3.06
1.86
1.03
2.69
2.69
2.47
2.76
-0.31
-0.32
0.89
2.58
1.86
4.37
4.37
3.19
2.50
2.62
1.90
2.03
1.53
1.53
2.03
3.26
2.11
4.48
2.79
5.49
2.31
3.00
1.43
1.25
3.00
2.74
2.03
2.72
-0.77
KP
95%
LCL
1.2E-02
3.5E-07
5.8E-04
2.0E-03
2.0E-03
1.2E-03
2.2E-03
2.6E-04
1.5E-04
1.4E-03
l.OE-02
7.6E-05
8.4E-03
8.4E-03
1.8E-04
8.4E-03
1.2E-02
4.1E-03
5.8E-03
9.0E-05
9.0E-05
3.1E-05
1.7E-04
5.3E-05
1.8E-03
1.3E-04
4.8E-03
3.9E-05
4.1E-04
1.8E-05
1.7E-04
1.4E-03
9.7E-04
4.3E-03
2.8E-03
1.4E-04
KP
Predicted
(cm/hr)
2.1E-02
1.4E-06
9.0E-04
2.8E-03
2.8E-03
1.7E-03
3.3E-03
5.4E-04
3.0E-04
2.3E-03
1.7E-02
1.3E-04
1.6E-02
1.6E-02
3.5E-04
1.3E-02
1.9E-02
6.4E-03
9.3E-03
1.5E-04
1.5E-04
6.3E-05
3.4E-04
l.OE-04
3.9E-03
2.4E-04
1.3E-02
8.0E-05
6.9E-04
3.6E-05
2.7E-04
2.2E-03
1.5E-03
6.6E-03
4.1E-03
3.2E-04
KP
Measured
(in vitro
data)
cm/hr
6.0E-02
1.3E-05
6.0E-03
3.0E-04
5.2E-03
4.0E-05
3.6E-03
7.9E-04
2.5E-04
1.6E-02
3.5E-02
3.6E-03
5.6E-03
l.OE-02
1.7E-03
2.0E-02
3.2E-02
1.4E-02
1.3E-02
3.0E-06
1.2E-04
6.8E-05
1.8E-03
6.3E-04
1.8E-02
9.1E-04
6.2E-02
8.9E-04
3.4E-03
2.6E-05
1.5E-05
6.0E-04
6.0E-04
1.7E-02
3.7E-03
5.0E-04
KP
95%
UCL
3.4E-02
5.4E-06
1.4E-03
4.1E-03
4.1E-03
2.4E-03
4.7E-03
1.1E-03
6.1E-04
4.0E-03
2.7E-02
2.3E-04
3.2E-02
3.2E-02
6.8E-04
2.1E-02
3.2E-02
l.OE-02
1.5E-02
2.5E-04
2.5E-04
1.3E-04
6.8E-04
1.9E-04
8.2E-03
4.5E-04
3.3E-02
1.6E-04
1.2E-03
7.3E-05
4.1E-04
3.3E-03
2.2E-03
l.OE-02
6.0E-03
7.3E-04
B-3
-------
EXHIBIT B-l
FLYNN DATA SET (continued)
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
SO
87
82
83
84
85
86
87
88
89
90
Flynn's in vitro experimental data
Methyl-[hydrocortisone-21-yl]-succinate
Methyl-[hydrocortisone-21-yl]-pimelate
Methyl-4-hydroxy benzoate
Morphine
2-Naphthol
Naproxen
Nicotine
Nitroglycerine
3-Nitrophenol
4-Nitrophenol
n-Nonanol
Octanoic acid (caprylic acid)
n-Octanol
Pentanoic acid (valeric acid)
n-Pentanol
Phenobarbital
Phenol
Pregnenolone
Progesterone
n-Propanol
Resorcinol
Salcylic acid
Scopolamine
Sucrose
Sufentanyl
Testosterone
Thymol
2,4,6-Trichlorophenol
Water
3,4-Xylenol
MW
476.6
518.6
152.1
285.3
144.2
230.3
162.2
227.1
139.1
139.1
144.3
144.2
130.2
102.1
88.15
232.2
94.11
316.5
314.4
60.1
110.1
138.1
303.4
342.3
387.5
288.4
150.2
197.4
18.01
122.2
Log Kow
2.58
3.70
1.96
0.62
2.84
3.18
1.17
2.00
2.00
1.91
3.77
3.00
2.97
1.30
1.56
1.47
1.46
3.13
3.77
0.25
0.80
2.26
1.24
-2.25
4.59
3.31
3.34
3.69
-1.38
2.35
KP
95%
LCL
9.1E-05
2.6E-04
3.0E-03
5.8E-05
1.1E-02
6.6E-03
7.6E-04
1.3E-03
3.7E-03
3.2E-03
4.0E-02
1.4E-02
1.6E-02
1.9E-03
3.4E-03
5.1E-04
2.7E-03
2.0E-03
5.0E-03
5.6E-04
7.7E-04
5.4E-03
1.3E-04
1.6E-07
5.7E-03
3.8E-03
2.1E-02
1.9E-02
5.8E-05
7.4E-03
KP
Predicted
(cm/hr)
1.7E-04
5.5E-04
4.4E-03
l.OE-04
1.9E-02
l.OE-02
1.2E-03
1.8E-03
5.5E-03
4.8E-03
7.8E-02
2.4E-02
2.7£-02
3.1E-03
5.5E-03
7.4E-04
4.3E-03
3.2E-03
8.6E-03
1.1E-03
1.3E-03
8.4E-03
2.1E-04
6.0E-07
1.2E-02
6.0E-03
3.7E-02
3.5E-02
1.5E-04
1.2E-02
KP
Measured
(in vitro
data)
cm/hr
2.1E-04
5.4E-03
9.1E-03
9.3E-06
2.8E-02
4.0E-04
1.9E-02
1.1E-02
5.6E-03
5.6E-03
6.0E-02
2.5E-02
5.2£-02
2.0E-03
6.0E-03
4.6E-04
8.1E-03
1.5E-03
1.5E-03
1.4E-03
2.4E-04
6.3E-03
5.0E-05
5.2E-06
1.2E-02
4.0E-04
5.2£-02
5.9£-02
5.0E-04
3.6E-02
KP
95%
UCL
3.3E-04
1.2E-03
6.5E-03
1.8E-04
3.1E-02
1.6E-02
1.8E-03
2.5E-03
8.4E-03
7.3E-03
1.5E-01
4.0E-02
4.7E-02
4.9E-03
8.9E-03
1.1E-03
7.0E-03
4.9E-03
1.5E-02
2.0E-03
2.1E-03
1.3E-02
3.3E-04
2.3E-06
2.4E-02
9.4E-03
6.6E-02
6.2E-02
3.9E-04
1.9E-02
B-4
-------
EXHIBIT B-2
PREDICTED KP FOR ORGANIC CONTAMINANTS IN WATER
Notes:
1. Chemicals with an asterisk (*) preceding them have been identified to be outside the effective prediction
domain (EPD). EPD determination is calculated using the software package MLAB (Civilized Software,
Inc., 8120 Woodmont Avenue, #250, Bethesda, MD 20814, USA).
2. Chemicals with two asterisks (**) are halogenated compounds. Because halogenated chemicals have a lower
ratio of molar volume relative to their molecular weight than hydrocarbons (due to the relatively weighty
halogen atom), the Kp correlation based on molecular weight of hydrocarbons will tend to underestimate
permeability coefficients for halogenated organic chemicals. To address this problem, a new Kp correlation
based on molar volume and log Kow will be explored. In selecting the halogenated compounds, the focus was
on trihalomethanes, the halogenated acids, and the halogenated aliphatics with halogenated molecules
contributing to a large percentage of the molecular weight.
3. Kp is obtained from the modified Potts and Guy's equation (Equation 3.8). Values in the exhibit are obtained
from the organic spreadsheet (ORG04_01.XLS) where the coefficients of Equation 3.8 carry more significant
figures than shown in Chapter 3 and Appendix A.
4. 95% LCL and UCL are calculated using the statistical software package STATA (STATA Corporation, 702
University Drive East, College Station, Texas 77840, USA). Compounds in italics are common to both the
Flynn data set and the organic data set. For these compounds, the 95% LCL and UCL are obtained from
Exhibit B-l and common to both Exhibits B-l and B-2.
5. All calculations were performed using the Lotus spreadsheet software, except where noted.
1
2
3
4
5
6
7
** g
9
10
11
12
13
14
15
CHEMICAL
Acetaldehyde
Acetamide
Acetylaminofluorene, 2-
Acrolein
Acrylamide
Acrylonitrile
Aldrin
Allyl chloride
Amino-2-methylanthraquinone, 1-
Aminoanthraquinone, 2-
Aminoazobenzene, p-
Aminoazotoluene, o-
Aminobiphenyl, 4-
Aniline
Anisidine, o-
CAS No.
75070
60355
53963
107028
79061
107131
309002
107051
82280
117793
60093
97563
92671
62533
90040
MW
44.1
59
223
56.1
71
53.1
365
76.5
237.3
223
197
225.3
169.2
93.1
145
log Kow
-0.22
-1.26
3.24
-0.10
-0.67
0.25
3.01
1.45
2.80
2.15
2.62
3.92
2.80
0.90
1.18
KP
95%
LCL
2.4E-05
3.9E-06
5.0E-04
2.5E-05
8.5E-06
4.5E-05
5.7E-05
2.2E-04
2.2E-04
9.7E-05
2.8E-04
1.4E-03
5.2E-04
7.5E-05
5.9E-05
KP
(cm/hr)
predicted
6.3E-04
1.1E-04
1.2E-02
6.5E-04
2.2E-04
1.2E-03
1.4E-03
5.4E-03
5.3E-03
2.4E-03
6.8E-03
3.4E-02
1.3E-02
1.9E-03
1.5E-03
KP
(cm/hr)
measured
KP
95% UCL
1.6E-02
2.9E-03
3.1E-01
1.7E-02
5.9E-03
2.9E-02
3.5E-02
1.3E-01
1.3E-01
5.7E-02
1.7E-01
8.7E-01
3.2E-01
4.7E-02
3.6E-02
B-5
-------
EXHIBIT B-2
PREDICTED KP FOR ORGANIC CONTAMINANTS IN WATER (continued)
16
17
18
* 19
* 20
* 21
22
23
24
25
** 26
** 27
** 28
29
30
31
32
33
34
35
** 36
37
38
39
40
41
** 42
** 43
** 44
** 45
46
47
48
* 49
50
51
52
53
* 54
* 55
CHEMICAL
Auramine
Benzene
Benzidine
Benzo-a-anthracene
Benzo-a-pyrene
Benzo-b-fluoranthene
Benzoic acid
Benzotrichloride
Benzyl chloride
Bis(2-chloroethyl)ether
Bromodichloromethane
Bromoform
Bromomethane
Bromophenol, p-
Butadiene, 1,3-
2,3-Butanediol
n-Butanol
Butoxyethanol, 2-
Captan
Carbon disulfide
Carbon tetrachloride
Chlordane
Chlordane (cis)
Chlordane (trans)
Chlorobenzene
4-Chlorocresol
Chlorodibromomethane
Chloroethane
Chloroform
Chloromethane
2-Chlorophenol
4-Chlorophenol
Chlorothalonil
Chrysene
Cresidine, p-
m-Cresol
o-Cresol
p-Cresol
ODD
DDE
CAS No.
492808
71432
92875
56553
50328
205992
65850
98077
100447
111444
75274
75252
74839
106412
106990
513859
71363
111762
133062
75150
56235
57749
5103719
5103742
108907
59507
124481
75003
67663
74873
95578
106489
1897456
218019
120718
108394
95487
106445
72548
72559
MW
267.4
78.1
184.2
228.3
250
252.3
122
195
127
143
163.8
252.8
95
173
54
90.12
74.12
118
300
80
153.8
409.8
410
410
112.6
142.6
208.3
64.5
119.4
50.5
128.6
128.6
265.9
228.3
137.2
108.1
108.1
108.1
320
318
log Kow
3.54
2.13
1.34
5.66
6.10
6.12
1.87
2.92
2.30
1.29
2.09
2.37
1.19
2.59
1.99
-0.92
0.88
0.83
2.35
2.24
2.83
5.54
5.47
5.47
2.84
3.10
2.23
1.43
1.97
0.91
2.15
2.39
3.86
5.66
1.67
1.96
1.95
1.95
5.80
5.69
KP
95%
LCL
4.5E-04
5.9E-04
4.6E-05
1.7E-02
2.4E-02
2.4E-02
2.3E-04
4.5E-04
4.1E-04
7.2E-05
1.9E-04
9.2E-05
1.1E-04
5.8E-03
6.5E-04
5.2£-05
1.3E-03
4.9E-05
4.8E-05
6.9E-04
6.6E-04
1.4E-03
1.2E-03
1.2E-03
1.1E-03
1.7E-02
1.3E-04
2.4E-04
2.8E-04
1.3E-04
5.2E-03
7.3E-03
7.4E-04
1.7E-02
1.4E-04
4.9E-03
4.8E-03
4.8E-03
6.4E-03
5.6E-03
KP
(cm/hr)
predicted
1.1E-02
1.5E-02
1.1E-03
4.7E-01
7.0E-01
7.0E-01
5.7E-03
1.1E-02
l.OE-02
1.8E-03
4.6E-03
2.2E-03
2.8E-03
8.8E-03
1.6E-02
1.2E-04
2.3E-03
1.2E-03
1.2E-03
1.7E-02
1.6E-02
3.8E-02
3.4E-02
3.4E-02
2.8E-02
2.9E-02
3.2E-03
6.1E-03
6.8E-03
3.3E-03
8.0E-03
1.2E-02
1.9E-02
4.7E-01
3.4E-03
7.8E-03
7.7E-03
7.7E-03
1.8E-01
1.6E-01
KP
(cm/hr)
measured
4.0E-05
2.5E-03
5.5E-02
3.3E-02
3.6E-02
1.5E-02
1.6E-02
1.8E-02
KP
95% UCL
2.8E-01
3.7E-01
2.8E-02
1.3E+01
2.0E+01
2.0E+01
1.4E-01
2.7E-01
2.5E-01
4.4E-02
1.1E-01
5.5E-02
7.0E-02
1.3E-02
4.1E-01
2.8E-04
4.0E-03
3.0E-02
2.9E-02
4.3E-01
4.0E-01
l.OE+00
9.2E-01
9.2E-01
7.1E-01
4.9E-02
7.9E-02
1.5E-01
1.7E-01
8.3E-02
1.2E-02
1.8E-02
4.7E-01
1.3E+01
8.4E-02
1.2E-02
1.2E-02
1.2E-02
5.0E+00
4.3E+00
B-6
-------
EXHIBIT B-2
PREDICTED KP FOR ORGANIC CONTAMINANTS IN WATER (continued)
* 56
* 57
58
59
60
61
* 62
63
64
65
66
67
** 68
** 69
** 70
** 71
** 72
73
** 74
** 75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
CHEMICAL
DDT
n-Decanol
Di-2-ethylhexyl phthalate
Diaminoanisole, 2,4-
Diaminotoluene
Diaminotoluene, 2,4-
Dibenzo(a,h)anthracene
Dibutyl phthalate
Dichlorobenzene, 1,2-
Dichlorobenzene, 1,3-
Dichlorobenzene, 1,4-
Dichlorobenzidine, 3,3'
Dichlorodifluoromethane
Dichloroethane, 1,1-
Dichloroethane, 1,2-
Dichloroethylene, 1,1-
Dichloroethylene, 1,2- (trans)
2,4-Dichlorophenol
Dichloropropane, 1,2-
Dichloropropene, 1,3-
Dichlorvos
Dieldrin
Diepoxybutane
Diethyl phthalate
Diethyl sulfate
Dimethoxybenzidine, 3,3'-
Dimethyl phthalate
Dimethyl sulfate
Dimethylamine, n-nitroso-
Dimethylaminoazobenzene, 4-
Dimethylbenzidine, 3,3'-
Dimethylcarbamyl chloride
Dimethylhydrazine, 1,1-
Dimethylphenol, 2,4-
Dimethylphenol, 3,4-
Dinitrophenol, 2,4-
Dinitrotoluene, 2,4-
Dinitrotoluene, 2,6-
Dioxane, 1,4-
Diphenylamine, n-nitroso-
CAS No.
50293
112301
117817
615054
95807
101804
53703
84742
95501
541731
106467
91941
75718
75343
107062
75354
540590
120832
78875
542756
62737
60571
1464535
84662
64675
119904
131113
77781
62759
60117
119937
79447
57147
105679
95658
51285
121142
606202
123911
86306
MW
355
158.3
391
138.2
122
200
278.4
278
147
147
147
253.1
120.9
99
99
96.9
96.9
163
113
111
221
381
86.1
222
154
254.4
194
126
74.1
225
212.3
107.5
60
122.2
122
184.1
182.1
182.1
88.1
198.2
log Kow
6.36
4.57
5.11
-0.12
0.34
2.06
6.84
4.13
3.38
3.60
3.39
3.51
2.16
1.79
1.48
2.13
1.86
3.06
2.00
1.60
1.47
4.56
-1.84
2.47
1.14
1.81
1.56
1.16
-0.57
4.58
2.34
0.00
-1.50
2.30
2.23
1.54
1.98
1.72
-0.27
3.13
KP
95%
LCL
9.2E-03
9.5E-02
9.4E-04
8.5E-06
2.2E-05
1.1E-04
4.9E-02
9.4E-04
1.6E-03
2.3E-03
1.7E-03
5.1E-04
3.6E-04
2.7E-04
1.7E-04
4.7E-04
3.1E-04
1.2E-02
3.1E-04
1.7E-04
3.5E-05
4.7E-04
1.1E-06
1.6E-04
5.0E-05
3.8E-05
5.7E-05
7.3E-05
9.6E-06
3.6E-03
1.5E-04
4.9E-06
2.6E-06
4.4E-04
4.0E-04
6.3E-05
1.3E-04
8.5E-05
1.3E-05
5.9E-04
KP
(cm/hr)
predicted
2.7E-01
2.2E-01
2.5E-02
2.2E-04
5.4E-04
2.8E-03
1.5E+00
2.4E-02
4.1E-02
5.8E-02
4.2E-02
1.3E-02
9.0E-03
6.7E-03
4.2E-03
1.2E-02
7.7E-03
2.1E-02
7.8E-03
4.3E-03
8.5E-04
1.2E-02
3.1E-05
3.9E-03
1.2E-03
9.3E-04
1.4E-03
1.8E-03
2.5E-04
9.5E-02
3.6E-03
3.9E-04
7.3E-05
1.1E-02
9.8E-03
1.5E-03
3.1E-03
2.1E-03
3.3E-04
1.5E-02
KP
(cm/hr)
measured
7.9E-02
6.0E-02
KP
95% UCL
7.8E+00
5.1E-01
6.6E-01
5.6E-03
1.4E-02
6.7E-02
4.7E+01
6.1E-01
l.OE+00
1.5E+00
1.1E+00
3.2E-01
2.2E-01
1.7E-01
l.OE-01
2.9E-01
1.9E-01
3.4E-02
1.9E-01
1.1E-01
2.1E-02
3.2E-01
8.7E-04
9.5E-02
3.0E-02
2.3E-02
3.4E-02
4.5E-02
6.6E-03
2.5E+00
8.8E-02
3.4E-03
2.0E-03
2.7E-01
2.4E-01
3.7E-02
7.5E-02
5.1E-02
8.6E-03
3.6E-01
B-7
-------
EXHIBIT B-2
PREDICTED KP FOR ORGANIC CONTAMINANTS IN WATER (continued)
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
** 111
112
113
114
* 115
116
111
118
119
* 120
** 121
** 122
123
124
* 125
* 126
127
128
129
130
131
132
133
134
** 135
CHEMICAL
Diphenylhydrazine, 1,2-
Dipropylamine, n-nitroso-
Endrin
Epichlorohydrin
Ethanol
Ethanol, 2-(2-butoxyethoxy)-
Ethanol, 2-(2-ethoxyethoxy)-
Ethanol, 2-(2-methoxyethoxy)-
2-Ethoxy ethanol (Cellosolve)
Ethoxyethyl acetate, 2-
Ethyl acrylate
Ethyl carbamate
Ethyl ether
Ethylbenzene
Ethylene oxide
Ethylenedibromide
Ethyleneimine
Ethylenethiourea
4-Ethylphenol
Fluoranthene
Formaldehyde
Glycerol
Heptachlor
n-Heptanol
Hexachlorobenzene
Hexachlorobutadiene
Hexachloroethane
Hexamethylphosphoramide
n-Hexanol
Hydrazine/Hydrazine sulfate
Indeno( 1,2,3 -CD)pyrene
Isophorone
Lindane
Mechlorethamine
Methanol
Methoxyethanol, 2-
Methoxypropan-2-ol, 1-
Methyl ethyl ketone
Methyl-4-hydroxy benzoate
Methyl iodide
CAS No.
122667
621647
72208
106898
64175
112345
111900
111773
110805
111159
140885
51796
60297
100414
75218
106934
151564
96457
123079
206440
50000
56815
76448
111706
118741
87683
67721
680319
111273
302012
193395
78591
58899
51752
67561
109864
107982
78933
99763
74884
MW
184.2
130.2
381
92
46.07
162
134
120
90.12
132
100
89
74.12
106.2
44.1
188
43
96
722.2
202.3
30
92.1
373.5
116.2
284.8
260.8
236.7
179
102.2
32
276.3
138.2
291
156
32.04
76
90
72
152.1
142
log Kow
2.94
1.36
4.56
-0.21
-0.31
-0.92
-0.08
-0.42
-0.32
0.65
1.32
-0.15
0.89
3.15
-0.30
1.96
-1.12
-0.66
2.58
4.95
0.35
-1.76
4.27
2.62
5.31
4.78
3.93
0.03
2.03
-2.07
6.58
1.67
3.72
1.07
-0.77
-0.77
-0.18
0.29
7.96
1.51
KP
95%
LCL
5.3E-04
9.5E-05
4.7E-04
1.3E-05
2.6E-04
1.8E-06
9.6E-06
6.7E-06
1.5E-04
3.1E-05
1.3E-04
1.5E-05
1.4E-03
1.9E-03
2.2E-05
1.1E-04
6.0E-06
6.3E-06
l.OE-02
8.3E-03
7.1E-05
1.1E-06
3.4E-04
1.2E-02
4.9E-03
3.1E-03
1.2E-03
6.4E-06
5.8E-03
1.5E-06
3.5E-02
1.4E-04
4.3E-04
4.4E-05
1.4E-04
6.8E-06
1.4E-05
3.8E-05
3.0E-03
l.OE-04
KP
(cm/hr)
predicted
1.3E-02
2.3E-03
1.2E-02
3.5E-04
5.4E-04
4.7E-05
2.5E-04
1.7E-04
3.0E-04
7.7E-04
3.2E-03
3.9E-04
2.3E-03
4.9E-02
5.6E-04
2.8E-03
1.6E-04
1.7E-04
1.7E-02
2.2E-01
1.8E-03
3.2E-05
8.6E-03
1.9E-02
1.3E-01
8.1E-02
3.0E-02
1.6E-04
9.3£-03
4.4E-05
l.OE+00
3.4E-03
1.1E-02
1.1E-03
3.2E-04
1.8E-04
3.7E-04
9.6E-04
4.4E-03
2.5E-03
KP
(cm/hr)
measured
7.9E-04
1.6E-02
3.5E-02
3.2E-02
1.3E-02
5.0E-04
9.1E-03
KP
95% UCL
3.2E-01
5.8E-02
3.2E-01
8.9E-03
1.1E-03
1.3E-03
6.3E-03
4.5E-03
6.1E-04
1.9E-02
8.0E-02
l.OE-02
4.0E-03
1.2E+00
1.5E-02
6.8E-02
4.4E-03
4.3E-03
2.7£-02
6.0E+00
4.6E-02
9.1E-04
2.2E-01
3.2£-02
3.6E+00
2.1E+00
7.6E-01
4.1E-03
1.5E-02
1.3E-03
3.1E+01
8.3E-02
2.7E-01
2.6E-02
7.3E-04
4.8E-03
9.6E-03
2.4E-02
6.5E-03
6.2E-02
B-8
-------
EXHIBIT B-2
PREDICTED KP FOR ORGANIC CONTAMINANTS IN WATER (continued)
136
137
138
** 139
140
141
** 142
143
144
145
146
147
148
149
* 150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
* 170
* 171
** 172
* 173
CHEMICAL
Methylaziridine, 2-
Methylene bis(2-chloroaniline),
4,4'-
Methylene
bis(N,N'-dimethyl)aniline, 4,4'-
Methylene chloride
Methylenedianiline, 4,4'-
Michler's ketone
Mustard Gas
Naphthalene
2-Naphthol
Naphthylamine, 1-
Naphthylamine, 2-
Nitrilotriacetic acid
Nitro-o-anisidine, 5-
Nitrobiphenyl, 4-
Nitrofen
Nitrophenol, 2-
Nitrophenol, 2-amino-4-
3-Nitrophenol
4-Nitrophenol
Nitrophenol, 4-amino-2-
Nitropropane, 2-
Nitroso-di-n-butylamine, n-
Nitroso-N-ethylurea, n-
Nitroso-N-methylurea, n-
Nitrosodiethanolamine, n-
Nitrosodiethylamine, n-
Nitrosodiphenylamine, p-
Nitrosomethylvinylamine, n-
Nitrosomorpholine, n-
Nitrosonornicotine, n-
Nitrosopiperidine, n-
n-Nonanol
n-Octanol
Parathion
PCB-chlorobiphenyl, 4-
PCB -hexachlorobiphenyl
Pentachloronitrobenzene
Pentachlorophenol
CAS No.
75558
101144
101611
75092
101779
90948
505602
91203
135193
134327
91598
139139
99592
92933
1836755
88755
99570
554847
100027
119346
79469
924163
759739
684935
1116547
55185
156105
4549400
59892
16543558
100754
143088
111875
56382
2051629
26601649
82688
87865
MW
57
267.2
254
84.9
198
268.4
159.1
128.2
144.2
143.2
143.2
191
152.7
199.2
284.1
139.1
154.1
139.1
139.1
154.1
110
158.2
117.1
103.1
134
88
198.2
86.1
116.1
177.2
350.3
144.3
130.2
291
292
361
295.3
266.4
log Kow
-0.60
3.94
4.75
1.25
1.59
4.07
2.03
3.30
2.84
2.25
2.28
-0.18
1.47
3.77
5.53
1.79
1.36
2.00
1.91
0.96
0.55
1.92
0.23
-0.03
-1.58
0.48
3.50
0.00
-0.44
0.03
0.36
3.77
2.97
3.83
6.50
6.72
4.64
5.86
KP
95%
LCL
1.1E-05
8.2E-04
3.2E-03
1.4E-04
5.7E-05
9.8E-04
1.8E-04
1.8E-03
1.1E-02
3.1E-04
3.3E-04
3.9E-06
8.4E-05
1.5E-03
6.8E-03
1.6E-04
7.0E-05
3.7E-03
3.2E-03
3.8E-05
3.5E-05
1.6E-04
1.9E-05
1.5E-05
8.9E-07
4.2E-05
l.OE-03
2.0E-05
6.9E-06
6.5E-06
1.1E-06
4.0E-02
1.6E-02
5.1E-04
2.5E-02
1.4E-02
1.6E-03
1.4E-02
KP
(cm/hr)
predicted
3.0E-04
2.1E-02
8.4E-02
3.5E-03
1.4E-03
2.5E-02
4.5E-03
4.7E-02
1.9E-02
7.7E-03
8.1E-03
l.OE-04
2.1E-03
3.8E-02
1.9E-01
4.0E-03
1.7E-03
5.5E-03
4.8E-03
9.3E-04
8.8E-04
3.8E-03
4.9E-04
3.9E-04
2.5E-05
l.OE-03
2.6E-02
5.1E-04
1.8E-04
1.7E-04
2.9E-05
7.8E-02
2.7E-02
1.3E-02
7.5E-01
4.3E-01
4.2E-02
3.9E-01
KP
(cm/hr)
measured
2.8E-02
5.6E-03
5.6E-03
6.0E-02
5.2E-02
KP
95% UCL
7.9E-03
5.2E-01
2.2E+00
8.8E-02
3.4E-02
6.3E-01
1.1E-01
1.2E+00
3.1E-02
1.9E-01
2.0E-01
2.6E-03
5.1E-02
9.7E-01
5.2E+00
9.9E-02
4.2E-02
8.4E-03
7.3E-03
2.3E-02
2.2E-02
9.4E-02
1.2E-02
l.OE-02
6.9E-04
2.6E-02
6.4E-01
1.3E-02
4.6E-03
4.2E-03
7.6E-04
1.5E-01
4.7E-02
3.2E-01
2.2E+01
1.3E+01
1.1E+00
1.1E+01
B-9
-------
EXHIBIT B-2
PREDICTED KP FOR ORGANIC CONTAMINANTS IN WATER (continued)
174
175
* 176
177
178
779
180
181
182
183
184
185
* 186
** 187
** 188
189
190
191
792
193
194
195
196
197
** 198
** \Q()
** 200
** 201
202
* 203
204
* 205
** 206
** 207
* 208
209
CHEMICAL
n-Pentanol
Pentanone, 4-methyl-2-
Phenanthrene
Phenol
Phenol, 4,6-dinitro-2-methyl-
n-Propanol
Propiolactone, beta-
Propylene oxide
Resorcinol
Safrole
Styrene
Styrene oxide
TCDD
Tetrachlorethylene
Tetrachloroethane, 1,1,2,2-
Thioacetamide
Thiodianiline, 4,4'-
Thiourea
Thymol
Toluene
Toluidine hydrochloride, o-
Toluidine, o-
Toxaphene
Trichlorobenzene, 1,2,4-
Trichloroethane, 1,1,1-
Trichloroethane, 1,1,2-
Trichloroethylene
Trichlorofluoromethane
2,4,6-Trichlorophenol
Tris(2,3-dibromopropyl)phosphate
Tris(aziridinyl)-para-benzoquinone
Urea
Vinyl bromide
Vinyl chloride
Water
Xylene, m-
CAS No.
71410
108101
85018
108952
534521
71238
57578
75569
108463
94597
100425
96093
1746016
127184
79345
62555
139651
62566
89838
108883
636215
95534
8001352
120821
71556
79005
79016
75694
88062
126727
68768
57136
593602
75014
7732185
108383
MW
88.15
100
178.2
94.11
198.1
60.1
72
58.1
110.1
162.2
104.1
120
322
165.8
167.9
75
216
76
150.2
92.1
143.2
107
414
181.5
133.4
133.4
131.4
137.4
197.4
697.6
231.3
60
107
62.5
18.01
106.2
log Kow
1.56
1.19
4.46
1.46
2.12
0.25
-0.46
0.03
0.80
2.66
2.95
1.61
6.80
3.40
2.39
0.71
2.03
-0.95
3.34
2.73
1.29
1.32
4.82
3.98
2.49
2.05
2.42
2.53
3.69
4.98
-1.34
-2.11
1.57
1.36
-1.38
3.20
KP
95%
LCL
3.4E-03
1.1E-04
5.5E-03
2.7E-03
1.3E-04
5.6E-04
1.2E-05
3.0E-05
7.7E-04
4.6E-04
1.5E-03
1.6E-04
2.7E-02
1.3E-03
2.8E-04
7.0E-05
8.8E-05
5.1E-06
2.1E-02
1.2E-03
7.2E-05
1.2E-04
4.5E-04
2.6E-03
5.1E-04
2.6E-04
4.7E-04
5.1E-04
1.9E-02
1.3E-05
3.7E-07
9.9E-07
1.8E-04
2.2E-04
5.8E-05
2.1E-03
KP
(cm/hr)
predicted
5.5E-03
2.7E-03
1.4E-01
4.3E-03
3.1E-03
1.1E-03
3.1E-04
7.7E-04
1.3E-03
1.1E-02
3.7E-02
3.9E-03
8.1E-01
3.3E-02
6.9E-03
1.8E-03
2.1E-03
1.4E-04
3.7E-02
3.1E-02
1.8E-03
3.0E-03
1.2E-02
6.6E-02
1.3E-02
6.4E-03
1.2E-02
1.3E-02
3.5E-02
3.9E-04
l.OE-05
2.9E-05
4.3E-03
5.6E-03
1.5E-04
5.3E-02
KP
(cm/hr)
measured
6.0E-03
8.1E-03
1.4E-03
2.4E-04
5.2E-02
5.9E-02
5.0E-04
KP
95% UCL
8.9E-03
6.6E-02
3.8E+00
7.0E-03
7.6E-02
2.0E-03
8.0E-03
2.0E-02
2.1E-03
2.8E-01
9.4E-01
9.6E-02
2.5E+01
8.4E-01
1.7E-01
4.4E-02
5.2E-02
3.7E-03
6.6E-02
7.8E-01
4.4E-02
7.3E-02
3.1E-01
1.7E+00
3.1E-01
1.6E-01
2.9E-01
3.2E-01
6.2E-02
1.1E-02
2.8E-04
8.3E-04
1.1E-01
1.4E-01
3.9E-04
1.4E+00
B-10
-------
EXHIBIT B-3
CALCULATION OF DERMAL ABSORBED DOSE FOR
ORGANIC CHEMICALS IN WATER
Note: The following default exposure conditions are used to calculate exposure to chemicals in water through
showering, assuming carcinogenic effects. Site-specific exposure conditions should be used in the spreadsheet
ORG04_01.XLS for appropriate health effects (cancer or noncancer).
Concentration in ppb (1 ppb = 1 ,ug/L x mg/1000 /j,g x L/1000 cm3):
Cone = 1 ppm = 1000 ppb = 1000 ,ug/L = 1 mg/L = 10"3mg/cm3 (default value for purpose of illustration)
(site-specific concentration should be used in actual calculations)
Surface area exposed (cm2): SA = 18000 cm2
Event time (hr/event): tevent = 0.58 hr/event (35 minutes/event)
Event frequency (events/day): EV =1.0 event/day
Exposure frequency (days/year): EF = 350.0 days/yr
Exposure duration (years): ED = 30.0 years
Body weight (kg): BW = 70.0 kg
Averaging time (days): AT = 25550 days
for carcinogenic effects, AT = 70 years (25550 days)
for noncarcinogenic effects, AT = ED (in days)
Skin thickness (assumed to be 10 pan): lsc = 10"3 cm
Time to reach steady-state (hr): t* is chemical-specific
Fraction absorbed (FA, from Exhibit A-5, to the nearest one significant figure)
Kp used in the calculation of DAevent is the Kp predicted for all chemicals
Default conditions for screening purposes: Compare Dermal adults (showering for 35 minutes per day) to Oral
adults (drinking 2 liters of water per day)
DAD (mg/day) = DAevent x SA x EV
Oral Dose (mg/day) = Cone x IR x ABSGI
IR: Ingestion rate of drinking water = 2000 (cmVday = L/day x 1000 cmVL)
ABSGI: Absorption fraction in GI tract =1.0 (assuming 100% GI absorption)
The actual ratio Dermal/Oral is given in the column labeled "Derm/Oral", the next column "Chem Assess" gives
the result of the comparison of these two routes of exposure as "Y" when Dermal Exposure exceeds 10% of
Drinking Water (ratio of DAD from Dermal to Oral). The Oral route is represented by drinking 2 liters of water
per day.
The spreadsheet (ORG04_01.XLS) also provides the calculation of the ratio of the dermal dose absorbed to the
total dose available from a showering scenario, assuming 5 gallons/minute as a flow rate. Refer to Chapter 3 and
Appendix A for equations to evaluate DAevent and DAD.
All calculations were performed using the Lotus spreadsheet software, except otherwise noted.
For chemicals noted with "*" or "**", see Notes on Exhibit B-2.
B-ll
-------
EXHIBIT B-3
CALCULATION OF DERMAL ABSORBED DOSE FOR
ORGANIC CHEMICALS IN WATER (continued)
1
2
3
4
5
6
7
** g
9
10
11
12
13
14
15
16
17
18
* 19
* 20
* 21
22
23
24
25
** 26
** 27
** 28
29
30
31
32
33
34
35
** 36
37
38
CHEMICAL
Acetaldehyde
Acetamide
Acetylaminofluorene, 2-
Acrolein
Acrylamide
Acrylonitrile
Aldrin
Allyl chloride
Amino-2-methylanthraq
uinone, 1-
Aminoanthraquinone, 2-
Aminoazobenzene, p-
Aminoazotoluene, o-
Aminobiphenyl, 4-
Aniline
Anisidine, o-
Auramine
Benzene
Benzidine
Benzo-a-anthracene
Benzo-a-pyrene
Benzo-b-fluoranthene
Benzoic acid
Benzotrichloride
Benzyl chloride
Bis(2-chloroethyl)ether
Bromodichloromethane
Bromoform
Bromomethane
Bromophenol, p-
Butadiene, 1,3-
2,3-Butanediol
n-Butanol
Butoxyethanol, 2-
Captan
Carbon disulfide
Carbon tetrachloride
Chlordane
Chlordane (cis)
CAS
No.
75070
60355
53963
107028
79061
107131
309002
107051
82280
117793
60093
97563
92671
62533
90040
492808
71432
92875
56553
50328
205992
65850
98077
100447
111444
75274
75252
74839
106412
106990
513859
71363
111762
133062
75150
56235
57749
5103719
KP
(cm/hr)
6.3E-04
1.1E-04
1.2E-02
6.5E-04
2.2E-04
1.2E-03
1.4E-03
5.4E-03
5.3E-03
2.4E-03
6.8E-03
3.4E-02
1.3E-02
1.9E-03
1.5E-03
1.1E-02
1.5E-02
1.1E-03
4.7E-01
7.0E-01
7.0E-01
5.7E-03
1.1E-02
l.OE-02
1.8E-03
4.6E-03
2.2E-03
2.8E-03
8.8E-03
1.6E-02
1.2E-04
2.3E-03
1.2E-03
1.2E-03
1.7E-02
1.6E-02
3.8E-02
3.4E-02
B
0.0
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.2
0.1
0.0
0.0
0.1
0.1
0.0
2.8
4.3
4.3
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.1
0.3
0.3
T
(hr)
0.19
0.23
1.90
0.22
0.27
0.21
11.89
0.29
2.28
1.90
1.36
1.96
0.95
0.35
0.69
3.37
0.29
1.15
2.03
2.69
2.77
0.51
1.32
0.55
0.68
0.88
2.79
0.36
0.99
0.21
0.34
0.28
0.49
5.13
0.30
0.78
21.21
21.27
t*
(hr)
0.45
0.55
4.56
0.53
0.64
0.51
28.54
0.69
5.48
4.56
3.26
4.69
2.27
0.85
1.66
8.09
0.70
2.76
8.53
11.67
12.03
1.24
3.17
1.32
1.62
2.12
6.70
0.87
2.39
0.51
0.82
0.67
1.17
12.32
0.72
1.86
50.91
51.05
FA
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.9
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.7
0.7
r» A
lV/ievent
(mg/cm2
-event)
6.1E-07
1.1E-07
3.6E-05
6.7E-07
2.4E-07
1.2E-06
l.OE-05
6.1E-06
1.7E-05
6.9E-06
1.7E-05
l.OE-04
2.6E-05
2.3E-06
2.6E-06
3.9E-05
1.7E-05
2.6E-06
1.4E-03
2.4E-03
2.5E-03
8.6E-06
2.7E-05
1.6E-05
3.1E-06
9.2E-06
7.9E-06
3.6E-06
1.9E-05
1.6E-05
1.5E-07
2.6E-06
1.8E-06
5.7E-06
2.0E-05
3.0E-05
2.6E-04
2.3E-04
DAD
(mg/kg
-dav)
6.4E-05
1.2E-05
3.8E-03
7.0E-05
2.6E-05
1.2E-04
1.1E-03
6.4E-04
1.8E-03
7.2E-04
1.8E-03
1.1E-02
2.8E-03
2.5E-04
2.7E-04
4.1E-03
1.8E-03
2.7E-04
1.5E-01
2.6E-01
2.6E-01
9.1E-04
2.8E-03
1.7E-03
3.3E-04
9.7E-04
8.4E-04
3.8E-04
2.0E-03
1.7E-03
1.6E-05
2.7E-04
1.9E-04
6.0E-04
2.1E-03
3.2E-03
2.7E-02
2.4E-02
Derm/
Oral
(%)
1%
0%
33%
1%
0%
1%
9%
5%
15%
6%
15%
91%
24%
2%
2%
35%
15%
2%
1283%
2186%
2221%
8%
24%
14%
3%
8%
7%
3%
17%
15%
0%
2%
2%
5%
18%
27%
231%
208%
Chem
Assess
N
N
Y
N
N
N
N
N
Y
N
Y
Y
Y
N
N
Y
Y
N
Y
Y
Y
N
Y
Y
N
N
N
N
Y
Y
N
N
N
N
Y
Y
Y
Y
B-12
-------
EXHIBIT B-3
CALCULATION OF DERMAL ABSORBED DOSE FOR
ORGANIC CHEMICALS IN WATER (continued)
39
40
41
** 42
** 43
** 44
** 45
46
47
48
* 49
50
51
52
53
* 54
* 55
* 56
* 57
58
59
60
61
* 62
63
64
65
66
67
** 68
** 69
** 70
** 71
** 72
73
** 74
CHEMICAL
Chlordane (trans)
Chlorobenzene
4-Chlorocresol
Chlorodibromomethane
Chloroethane
Chloroform
Chloromethane
2-Chlorophenol
4-Chlorophenol
Chlorothalonil
Chrysene
Cresidine, p-
m-Cresol
o-Cresol
p-Cresol
ODD
DDE
DDT
n-Decanol
Di-2-ethylhexyl
phthalate
Diaminoanisole, 2,4-
Diaminotoluene
Diaminotoluene, 2,4-
Dibenzo(a,h)anthracene
Dibutyl phthalate
Dichlorobenzene, 1,2-
Dichlorobenzene, 1,3-
Dichlorobenzene, 1,4-
Dichlorobenzidine, 3,3'
Dichlorodifluoromethan
e
Dichloroethane, 1,1-
Dichloroethane, 1,2-
Dichloroethylene, 1,1-
Dichloroethylene, 1,2-
(trans)
2,4-Dichlorophenol
Dichloropropane, 1,2-
CAS
No.
5103742
108907
59507
124481
75003
67663
74873
95578
106489
1897456
218019
120718
108394
95487
106445
72548
72559
50293
112301
117817
615054
95807
101804
53703
84742
95501
541731
106467
91941
75718
75343
107062
75354
540590
120832
78875
KP
(cm/hr)
3.4E-02
2.8E-02
2.9E-02
3.2E-03
6.1E-03
6.8E-03
3.3E-03
8.0E-03
1.2E-02
1.9E-02
4.7E-01
3.4E-03
7.8E-03
7.7E-03
7.7E-03
1.8E-01
1.6E-01
2.7E-01
2.2E-01
2.5E-02
2.2E-04
5.4E-04
2.8E-03
1.5E+00
2.4E-02
4.1E-02
5.8E-02
4.2E-02
1.3E-02
9.0E-03
6.7E-03
4.2E-03
1.2E-02
7.7E-03
2.1E-02
7.8E-03
B
0.3
0.1
0.1
0.0
0.0
0.0
0.0
0.0
0.1
0.1
2.8
0.0
0.0
0.0
0.0
1.2
1.1
1.9
1.1
0.2
0.0
0.0
0.0
9.7
0.2
0.2
0.3
0.2
0.1
0.0
0.0
0.0
0.0
0.0
0.1
0.0
T
(hr)
21.27
0.46
0.67
1.57
0.24
0.50
0.20
0.56
0.56
3.30
2.03
0.63
0.43
0.43
0.43
6.65
6.48
10.45
0.82
16.64
0.63
0.51
1.41
3.88
3.86
0.71
0.71
0.71
2.80
0.51
0.38
0.38
0.37
0.37
0.87
0.46
t*
(hr)
51.05
1.09
1.61
3.77
0.59
1.19
0.49
1.34
1.34
7.93
8.53
1.50
1.03
1.03
1.03
25.99
25.08
42.51
3.18
39.93
1.52
1.24
3.38
17.57
9.27
1.71
1.71
1.71
6.72
1.22
0.92
0.92
0.89
0.89
2.10
1.10
FA
0.7
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.9
1.0
1.0
1.0
1.0
1.0
0.8
0.8
0.7
1.0
0.8
1.0
1.0
1.0
0.6
0.9
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
r» A
lV/ievent
(mg/cm2
-event)
2.3E-04
4.0E-05
4.9E-05
8.5E-06
6.3E-06
l.OE-05
3.3E-06
1.3E-05
1.8E-05
6.4E-05
1.4E-03
5.7E-06
1.1E-05
1.1E-05
1.1E-05
7.8E-04
6.7E-04
1.3E-03
4.2E-04
1.7E-04
3.7E-07
8.3E-07
6.9E-06
3.8E-03
9.0E-05
7.4E-05
l.OE-04
7.5E-05
4.5E-05
1.3E-05
8.8E-06
5.5E-06
1.5E-05
9.9E-06
4.1E-05
1.1E-05
DAD
(mg/kg
-dav)
2.4E-02
4.2E-03
5.2E-03
9.0E-04
6.7E-04
1.1E-03
3.4E-04
1.3E-03
1.9E-03
6.8E-03
1.5E-01
6.0E-04
1.1E-03
1.1E-03
1.1E-03
8.3E-02
7.1E-02
1.4E-01
4.5E-02
1.8E-02
3.9E-05
8.7E-05
7.3E-04
4.0E-01
9.5E-03
7.8E-03
1.1E-02
7.9E-03
4.8E-03
1.4E-03
9.3E-04
5.8E-04
1.6E-03
l.OE-03
4.3E-03
1.2E-03
Derm/
Oral
(%)
208%
36%
44%
8%
6%
9%
3%
11%
16%
58%
1283%
5%
10%
10%
10%
703%
602%
1156%
380%
155%
0%
1%
6%
3388%
81%
66%
93%
67%
41%
12%
8%
5%
14%
9%
37%
10%
Chem
Assess
Y
Y
Y
N
N
N
N
Y
Y
Y
Y
N
N
N
N
Y
Y
Y
Y
Y
N
N
N
Y
Y
Y
Y
Y
Y
Y
N
N
Y
N
Y
N
B-13
-------
EXHIBIT B-3
CALCULATION OF DERMAL ABSORBED DOSE FOR
ORGANIC CHEMICALS IN WATER (continued)
** 75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
CHEMICAL
Dichloropropene, 1,3-
Dichlorvos
Dieldrin
Diepoxybutane
Diethyl phthalate
Diethyl sulfate
Dimethoxybenzidine,
3,3'-
Dimethyl phthalate
Dimethyl sulfate
Dimethylamine,
n-nitroso-
Dimethylaminoazobenze
ne, 4-
Dimethylbenzidine, 3,3'-
Dimethylcarbamyl
chloride
Dimethylhydrazine, 1,1-
Dimethylphenol, 2,4-
Dimethylphenol, 3,4-
Dinitrophenol, 2,4-
Dinitrotoluene, 2,4-
Dinitrotoluene, 2,6-
Dioxane, 1,4-
Diphenylamine,
n-nitroso-
Diphenylhydrazine, 1,2-
Dipropylamine,
n-nitroso-
Endrin
Epichlorohydrin
Ethanol
Ethanol,
2-(2-butoxyethoxy)-
Ethanol,
2-(2-ethoxyethoxy)-
Ethanol,
2-(2-methoxyethoxy)-
2-Ethoxy ethanol
(Cellosolve)
Ethoxyethyl acetate, 2-
CAS
No.
542756
62737
60571
1464535
84662
64675
119904
131113
77781
62759
60117
119937
79447
57147
105679
95658
51285
121142
606202
123911
86306
122667
621647
72208
106898
64175
112345
111900
111773
110805
111159
KP
(cm/hr)
4.3E-03
8.5E-04
1.2E-02
3.1E-05
3.9E-03
1.2E-03
9.3E-04
1.4E-03
1.8E-03
2.5E-04
9.5E-02
3.6E-03
3.9E-04
7.3E-05
1.1E-02
9.8E-03
1.5E-03
3.1E-03
2.1E-03
3.3E-04
1.5E-02
1.3E-02
2.3E-03
1.2E-02
3.5E-04
5.4E-04
4.7E-05
2.5E-04
1.7E-04
3.0E-04
7.7E-04
B
0.0
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.5
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.1
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
T
(hr)
0.45
1.85
14.62
0.32
1.87
0.78
2.85
1.30
0.54
0.28
1.95
1.65
0.43
0.23
0.52
0.51
1.15
1.12
1.12
0.33
1.38
1.15
0.57
14.62
0.35
0.19
0.86
0.60
0.50
0.34
0.59
t*
(hr)
1.07
4.44
35.09
0.78
4.50
1.87
6.84
3.13
1.30
0.67
4.67
3.97
1.02
0.55
1.24
1.24
2.76
2.69
2.69
0.80
3.31
2.76
1.37
35.09
0.84
0.46
2.07
1.44
1.20
0.82
1.41
FA
1.0
1.0
0.8
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.8
1.0
1.0
1.0
1.0
1.0
1.0
1.0
r» A
lV/ievent
(mg/cm2
-event)
6.1E-06
2.5E-06
7.9E-05
3.7E-08
1.1E-05
2.3E-06
3.3E-06
3.4E-06
2.8E-06
2.8E-07
2.8E-04
9.8E-06
5.4E-07
7.6E-08
1.7E-05
1.5E-05
3.5E-06
6.9E-06
4.6E-06
4.0E-07
3.6E-05
3.0E-05
3.7E-06
7.9E-05
4.3E-07
5.2E-07
9.3E-08
4.0E-07
2.6E-07
3.7E-07
1.2E-06
DAD
(mg/kg
-dav)
6.4E-04
2.6E-04
8.3E-03
3.9E-06
1.2E-03
2.4E-04
3.5E-04
3.5E-04
3.0E-04
3.0E-05
2.9E-02
l.OE-03
5.7E-05
8.0E-06
1.7E-03
1.6E-03
3.7E-04
7.3E-04
4.9E-04
4.3E-05
3.8E-03
3.1E-03
3.9E-04
8.3E-03
4.6E-05
5.5E-05
9.8E-06
4.2E-05
2.8E-05
3.9E-05
1.3E-04
Derm/
Oral
(%)
5%
2%
71%
0%
10%
2%
3%
3%
3%
0%
251%
9%
0%
0%
15%
13%
3%
6%
4%
0%
32%
27%
3%
71%
0%
0%
0%
0%
0%
0%
1%
Chem
Assess
N
N
Y
N
Y
N
N
N
N
N
Y
N
N
N
Y
Y
N
N
N
N
Y
Y
N
Y
N
N
N
N
N
N
N
B-14
-------
EXHIBIT B-3
CALCULATION OF DERMAL ABSORBED DOSE FOR
ORGANIC CHEMICALS IN WATER (continued)
106
107
108
109
110
**111
112
113
114
*115
116
117
118
119
*120
**121
**122
123
124
*125
*126
127
128
129
130
131
132
133
134
**135
136
137
138
CHEMICAL
Ethyl acrylate
Ethyl carbamate
Ethyl ether
Ethylbenzene
Ethylene oxide
Ethylenedibromide
Ethyleneimine
Ethylenethiourea
4-Ethylphenol
Fluoranthene
Formaldehyde
Glycerol
Heptachlor
n-Heptanol
Hexachlorobenzene
Hexachlorobutadiene
Hexachloroethane
Hexamethylphosphoram
ide
n-Hexanol
Hydrazine/Hydrazine
sulfate
Indeno( 1,2,3 -CD)pyrene
Isophorone
Lindane
Mechlorethamine
Methanol
Methoxyethanol, 2-
Methoxypropan-2-ol, 1-
Methyl ethyl ketone
Methyl-4-hydroxy
benzoate
Methyl iodide
Methylaziridine, 2-
Methylene
bis(2-chloroaniline),
4,4'-
Methylene
bis(N,N'-dimethyl)anilin
e, 4,4'-
CAS
No.
140885
51796
60297
100414
75218
106934
151564
96457
123079
206440
50000
56815
76448
111706
118741
87683
67721
680319
111273
302012
193395
78591
58899
51752
67561
109864
107982
78933
99763
74884
75558
101144
101611
KP
(cm/hr)
3.2E-03
3.9E-04
2.3E-03
4.9E-02
5.6E-04
2.8E-03
1.6E-04
1.7E-04
1.7E-02
2.2E-01
1.8E-03
3.2E-05
8.6E-03
1.9E-02
1.3E-01
8.1E-02
3.0E-02
1.6E-04
9.3E-03
4.4E-05
l.OE+00
3.4E-03
1.1E-02
1.1E-03
3.2E-04
1.8E-04
3.7E-04
9.6E-04
4.4E-03
2.5E-03
3.0E-04
2.1E-02
8.4E-02
B
0.0
0.0
0.0
0.2
0.0
0.0
0.0
0.0
0.1
1.2
0.0
0.0
0.1
0.1
0.9
0.5
0.2
0.0
0.0
0.0
6.7
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.5
T
(hr)
0.39
0.34
0.28
0.42
0.19
1.21
0.19
0.37
0.52
1.45
0.16
0.35
13.27
0.48
4.22
3.09
2.27
1.08
0.40
0.16
3.78
0.63
4.57
0.80
0.16
0.28
0.34
0.27
0.76
0.67
0.22
3.36
2.83
t*
(hr)
0.93
0.81
0.67
1.01
0.45
2.90
0.45
0.88
1.24
5.68
0.38
0.84
31.85
1.15
16.21
7.42
5.44
2.58
0.96
0.39
16.83
1.52
10.97
1.92
0.39
0.68
0.82
0.65
1.82
1.60
0.53
8.06
6.80
FA
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.8
1.0
0.9
0.9
1.0
1.0
1.0
1.0
0.6
1.0
0.9
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.9
1.0
r» A
lV/ievent
(mg/cm2
-event)
4.3E-06
4.8E-07
2.6E-06
6.7E-05
5.4E-07
6.4E-06
1.5E-07
2.1E-07
2.5E-05
5.7E-04
1.6E-06
4.0E-08
5.3E-05
2.8E-05
5.2E-04
2.7E-04
9.6E-05
3.6E-07
1.2E-05
3.9E-08
2.6E-03
5.7E-06
4.4E-05
2.0E-06
2.9E-07
2.0E-07
4.6E-07
1.1E-06
8.1E-06
4.3E-06
3.1E-07
7.2E-05
3.0E-04
DAD
(mg/kg
-dav)
4.5E-04
5.1E-05
2.8E-04
7.1E-03
5.7E-05
6.8E-04
1.6E-05
2.2E-05
2.7E-03
6.0E-02
1.7E-04
4.3E-06
5.6E-03
3.0E-03
5.5E-02
2.9E-02
l.OE-02
3.8E-05
1.3E-03
4.2E-06
2.7E-01
6.0E-04
4.6E-03
2.1E-04
3.0E-05
2.1E-05
4.8E-05
1.1E-04
8.6E-04
4.6E-04
3.3E-05
7.6E-03
3.2E-02
Derm/
Oral
(%)
4%
0%
2%
61%
0%
6%
0%
0%
23%
512%
1%
0%
48%
25%
469%
243%
86%
0%
11%
0%
2307%
5%
40%
2%
0%
0%
0%
1%
7%
4%
0%
65%
270%
Chem
Assess
N
N
N
Y
N
N
N
N
Y
Y
N
N
Y
Y
Y
Y
Y
N
Y
N
Y
N
Y
N
N
N
N
N
N
N
N
Y
Y
B-15
-------
EXHIBIT B-3
CALCULATION OF DERMAL ABSORBED DOSE FOR
ORGANIC CHEMICALS IN WATER (continued)
**139
140
141
**142
143
144
145
146
147
148
149
*150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
*170
CHEMICAL
Methylene chloride
Methylenedianiline, 4,4'-
Michler's ketone
Mustard Gas
Naphthalene
2-Naphthol
Naphthylamine, 1-
Naphthylamine, 2-
Nitrilotriacetic acid
Nitro-o-anisidine, 5-
Nitrobiphenyl, 4-
Nitrofen
Nitrophenol, 2-
Nitrophenol, 2-amino-4-
3 -Nitrophenol
4-Nitrophenol
Nitrophenol, 4-amino-2-
Nitropropane, 2-
Nitroso-di-n-butylamine,
n-
Nitroso-N-ethylurea, n-
Nitroso-N-methylurea,
n-
Nitrosodiethanolamine,
n-
Nitrosodiethylamine, n-
Nitrosodiphenylamine,
P-
Nitrosomethylvinylamin
e, n-
Nitrosomorpholine, n-
Nitrosonornicotine, n-
Nitrosopiperidine, n-
n-Nonanol
n-Octanol
Parathion
PCB-chlorobiphenyl, 4-
CAS
No.
75092
101779
90948
505602
91203
135193
134327
91598
139139
99592
92933
1836755
88755
99570
554847
100027
119346
79469
924163
759739
684935
1116547
55185
156105
4549400
59892
1654355
8
100754
143088
111875
56382
2051629
KP
(cm/hr)
3.5E-03
1.4E-03
2.5E-02
4.5E-03
4.7E-02
1.9E-02
7.7E-03
8.1E-03
l.OE-04
2.1E-03
3.8E-02
1.9E-01
4.0E-03
1.7E-03
5.5E-03
4.8E-03
9.3E-04
8.8E-04
3.8E-03
4.9E-04
3.9E-04
2.5E-05
l.OE-03
2.6E-02
5.1E-04
1.8E-04
1.7E-04
2.9E-05
7.8E-02
2.7E-02
1.3E-02
7.5E-01
B
0.0
0.0
0.2
0.0
0.2
0.1
0.0
0.0
0.0
0.0
0.2
1.2
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.0
0.0
0.0
0.4
0.1
0.1
4.9
T
(hr)
0.32
1.37
3.41
0.83
0.56
0.69
0.68
0.68
1.26
0.77
1.40
4.18
0.64
0.78
0.64
0.64
0.78
0.44
0.82
0.48
0.40
0.60
0.33
1.38
0.32
0.48
1.05
9.83
0.69
0.57
4.57
4.63
t*
(hr)
0.76
3.30
8.19
2.00
1.34
1.64
1.62
1.62
3.01
1.84
3.35
16.33
1.54
1.87
1.54
1.54
1.87
1.06
1.97
1.16
0.97
1.44
0.80
3.31
0.78
1.14
2.52
23.60
1.65
1.37
10.97
20.27
FA
1.0
1.0
0.9
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.9
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.9
0.6
r» A
^^event
(mg/cm2
-event)
4.2E-06
3.4E-06
8.7E-05
8.6E-06
7.4E-05
3.3E-05
1.3E-05
1.4E-05
2.4E-07
3.8E-06
9.5E-05
7.3E-04
6.8E-06
3.2E-06
9.4E-06
8.2E-06
1.7E-06
1.2E-06
7.3E-06
7.2E-07
5.3E-07
4.0E-08
1.3E-06
6.4E-05
6.2E-07
2.6E-07
3.6E-07
1.9E-07
1.4E-04
4.4E-05
5.2E-05
2.0E-03
DAD
(mg/kg
-dav)
4.5E-04
3.6E-04
9.2E-03
9.1E-04
7.8E-03
3.5E-03
1.4E-03
1.5E-03
2.5E-05
4.0E-04
l.OE-02
7.7E-02
7.2E-04
3.4E-04
9.9E-04
8.6E-04
1.8E-04
1.3E-04
7.7E-04
7.6E-05
5.6E-05
4.3E-06
1.3E-04
6.7E-03
6.5E-05
2.7E-05
3.8E-05
2.1E-05
1.4E-02
4.6E-03
5.5E-03
2.2E-01
Derm/
Oral
(%)
4%
3%
78%
8%
66%
30%
12%
13%
0%
3%
86%
660%
6%
3%
8%
7%
2%
1%
7%
1%
0%
0%
1%
57%
1%
0%
0%
0%
122%
39%
47%
1844%
Chem
Assess
N
N
Y
N
Y
Y
Y
Y
N
N
Y
Y
N
N
N
N
N
N
N
N
N
N
N
Y
N
N
N
N
Y
Y
Y
Y
B-16
-------
EXHIBIT B-3
CALCULATION OF DERMAL ABSORBED DOSE FOR
ORGANIC CHEMICALS IN WATER (continued)
*171
**172
*173
174
175
*176
177
178
179
180
181
182
183
184
185
*186
**187
**188
189
190
191
192
193
194
195
196
197
**198
**199
**200
**201
202
*203
CHEMICAL
PCB -hexachlorobipheny
1
Pentachloronitrobenzene
Pentachlorophenol
n-Pentanol
Pentanone, 4-methyl-2-
Phenanthrene
Phenol
Phenol,
4,6-dinitro-2-methyl-
n-Propanol
Propiolactone, beta-
Propylene oxide
Resorcinol
Safrole
Styrene
Styrene oxide
TCDD
Tetrachlorethylene
Tetrachloroethane,
1,1,2,2-
Thioacetamide
Thiodianiline, 4,4'-
Thiourea
Thymol
Toluene
Toluidine hydrochloride,
o-
Toluidine, o-
Toxaphene
Trichlorobenzene, 1,2,4-
Trichloroethane, 1,1,1-
Trichloroethane, 1,1,2-
Trichloroethylene
Trichlorofluoromethane
2,4,6-Trichlorophenol
Tris(2,3-dibromopropyl)
phosphate
CAS
No.
2660164
9
82688
87865
71410
108101
85018
108952
534521
71238
57578
75569
108463
94597
100425
96093
1746016
127184
79345
62555
139651
62566
89838
108883
636215
95534
8001352
120821
71556
79005
79016
75694
88062
126727
KP
(cm/hr)
4.3E-01
4.2E-02
3.9E-01
5.5E-03
2.7E-03
1.4E-01
4.3E-03
3.1E-03
1.1E-03
3.1E-04
7.7E-04
1.3E-03
1.1E-02
3.7E-02
3.9E-03
8.1E-01
3.3E-02
6.9E-03
1.8E-03
2.1E-03
1.4E-04
3.7E-02
3.1E-02
1.8E-03
3.0E-03
1.2E-02
6.6E-02
1.3E-02
6.4E-03
1.2E-02
1.3E-02
3.5E-02
3.9E-04
B
3.2
0.3
2.5
0.0
0.0
0.7
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.1
0.0
5.6
0.2
0.0
0.0
0.0
0.0
0.2
0.1
0.0
0.0
0.1
0.3
0.1
0.0
0.1
0.1
0.2
0.0
T
(hr)
11.29
4.83
3.33
0.33
0.39
1.06
0.36
1.38
0.23
0.27
0.23
0.44
0.87
0.41
0.50
6.82
0.91
0.93
0.28
1.73
0.28
0.74
0.35
0.68
0.42
22.40
1.11
0.60
0.60
0.58
0.63
1.36
874.39
t*
(hr)
47.90
11.60
13.82
0.80
0.93
4.11
0.86
3.30
0.56
0.65
0.54
1.06
2.08
0.98
1.20
30.09
2.18
2.24
0.67
4.16
0.68
1.78
0.84
1.62
1.02
53.75
2.66
1.43
1.43
1.39
1.51
3.27
2098.53
FA
0.5
0.9
0.9
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.5
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.8
1.0
1.0
1.0
1.0
1.0
1.0
1.0
r» A
^^event
(mg/cm2
-event)
1.5E-03
1.7E-04
1.4E-03
6.6E-06
3.5E-06
3.1E-04
5.5E-06
7.7E-06
1.1E-06
3.4E-07
8.0E-07
1.8E-06
2.2E-05
5.0E-05
5.8E-06
2.2E-03
6.7E-05
1.4E-05
2.0E-06
6.0E-06
1.5E-07
6.8E-05
3.9E-05
3.1E-06
4.1E-06
9.5E-05
1.5E-04
2.1E-05
l.OE-05
1.9E-05
2.1E-05
8.5E-05
2.4E-05
DAD
(mg/kg
-dav)
1.6E-01
1.8E-02
1.4E-01
7.0E-04
3.7E-04
3.3E-02
5.8E-04
8.1E-04
1.2E-04
3.5E-05
8.5E-05
1.9E-04
2.3E-03
5.3E-03
6.2E-04
2.4E-01
7.1E-03
1.5E-03
2.1E-04
6.3E-04
1.6E-05
7.2E-03
4.1E-03
3.3E-04
4.3E-04
l.OE-02
1.6E-02
2.2E-03
1.1E-03
2.0E-03
2.3E-03
9.0E-03
2.6E-03
Derm/
Oral
(%)
1378%
157%
1226%
6%
3%
283%
5%
7%
1%
0%
1%
2%
20%
45%
5%
2003%
60%
13%
2%
5%
0%
61%
35%
3%
4%
85%
133%
19%
9%
17%
19%
77%
22%
Chem
Assess
Y
Y
Y
N
N
Y
N
N
N
N
N
N
Y
Y
N
Y
Y
Y
N
N
N
Y
Y
N
N
Y
Y
Y
N
Y
Y
Y
Y
B-17
-------
EXHIBIT B-3
CALCULATION OF DERMAL ABSORBED DOSE FOR
ORGANIC CHEMICALS IN WATER (continued)
204
*205
**206
**207
*208
209
CHEMICAL
Tris(aziridinyl)-para-ben
zoquinone
Urea
Vinyl bromide
Vinyl chloride
Water
Xylene, m-
CAS
No.
68768
57136
593602
75014
7732185
108383
KP
(cm/hr)
l.OE-05
2.9E-05
4.3E-03
5.6E-03
1.5E-04
5.3E-02
B
0.0
0.0
0.0
0.0
0.0
0.2
T
(hr)
2.11
0.23
0.42
0.24
0.13
0.42
t*
(hr)
5.07
0.55
1.02
0.57
0.32
1.01
FA
1.0
1.0
1.0
1.0
1.0
1.0
r» A
^^event
(mg/cm2
-event)
3.1E-08
3.0E-08
6.0E-06
5.9E-06
1.3E-07
7.3E-05
DAD
(mg/kg
-dav)
3.3E-06
3.2E-06
6.3E-04
6.3E-04
1.4E-05
7.7E-03
Derm/
Oral
(%)
0%
0%
5%
5%
0%
65%
Chem
Assess
N
N
N
N
N
Y
B-18
-------
EXHIBIT B-4
CALCULATION OF DERMAL ABSORBED DOSE FOR
INORGANIC CHEMICALS IN WATER
Note: the following default exposure conditions are used to calculate exposure to chemicals in water through
showering, assuming carcinogenic effects.
Given below are default values from Exhibit 3-2. For site-specific conditions, change default values to site-
specific values.
Cone = 1 ppm = 0.001 mg/cm3 (default value for purpose of illustration)
SA= 18000cm2
tevent = 0.58 hr/event (35 minutes/event selected to be RME, due to high uncertainty in the value)
EV = 1 event/day
EF = 350 days/yr
ED = 30 years
BW = 70 kg
AT = 25550 days
Default conditions for screening purposes:
Compare Dermal adults (showering for 35 minutes per day) (RME value for showering) to Oral adults drinking
2 liters of water per day
DAD (mg/day) = DAevent x SA x EV
Oral Dose (mg/day) = Cone x IR x ABSGI
where:
IR: Ingestion rate of drinking water = 2000 (cmVday = L/day x 1000 cmVL)
ABSGI: Absorption fraction in GI tract (chemical specific, from Exhibit 4-1)
Condition for screening: "Y" when dermal exposure exceeds 10% of oral dose value.
Refer to Appendix A for equations to evaluate DAevent and DAD.
The spreadsheet (INORG04_01.XLS) also provides the calculation of the ratio of the dermal dose absorbed to
the total dose available from a showering scenario, assuming 5 gallons per minute as a flow rate.
All calculations were performed using the Lotus spreadsheet software, except where noted.
B-19
-------
EXHIBIT B-4
CALCULATION OF DERMAL ABSORBED DOSE FOR
INORGANIC CHEMICALS IN WATER (continued)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
CHEMICAL
Antimony
Arsenic (arsenite)
Barium
Beryllium
Cadmium
Cadmium
Chromium (III)
Chromium (VI)
Copper
Cyanate
Manganese
Mercuric chloride
(other soluble salts)
Insoluble or metallic
mercury
Nickel
Selenium
Silver
Thallium
Vanadium
Zinc
KP
(cm/hr)
l.OE-03
l.OE-03
l.OE-03
l.OE-03
l.OE-03
l.OE-03
l.OE-03
2.0E-03
l.OE-03
l.OE-03
l.OE-03
l.OE-03
l.OE-03
2.0E-04
l.OE-03
6.0E-04
l.OE-03
l.OE-03
6.0E-04
Source of
Kp (exp or
default)
default
default
default
default
experimental
experimental
experimental
experimental
default
default
default
experimental
experimental
experimental
default
experimental
default
default
experimental
r» A
lV/ievent
(mg/cm2-
event)
5.8E-07
5.8E-07
5.8E-07
5.8E-07
5.8E-07
5.8E-07
5.8E-07
1.2E-06
5.8E-07
5.8E-07
5.8E-07
5.8E-07
5.8E-07
1.2E-07
5.8E-07
3.5E-07
5.8E-07
5.8E-07
3.5E-07
DAD
(mg/kg
-dav)
6.2E-05
6.2E-05
6.2E-05
6.2E-05
6.2E-05
6.2E-05
6.2E-05
1.2E-04
6.2E-05
6.2E-05
6.2E-05
6.2E-05
6.2E-05
1.2E-05
6.2E-05
3.7E-05
6.2E-05
6.2E-05
3.7E-05
ABSGI
(chemical
specific)
15
95
7
0.7
2.5
5
1.3
2.5
57
47
6
7
7
4
30
4
100
2.6
Derm/
Oral
(%)
3.50
0.55
7.50
75.00
21.00
10.50
40.38
42.00
0.92
1.12
8.75
7.50
7.50
2.62
1.75
7.88
0.52
20.19
Chemical to be
assessed
N
N
N
Y
Y
Y
Y
Y
N
N
N
N
N
N
N
N
N
Y
highly variable
B-20
-------
APPENDIX C
SOIL PATHWAY
This appendix describes the methods used to derive the activity specific body-weighted soil adherence factors
and is divided into four sections: (1) Background; (2) Body Part-Specific Surface Areas and Activity-Specific Soil
Adherence Factors; (3) Overall Weighted Soil Adherence Factors; and (4) soil loading at the hypothetical mono-layer
for the Soil Conservation Service standard soil classifications.
Background
Recent data from Kissel et al. [Kissel et al. (1996a), Kissel et al. (1996b), Kissel et al.(1998), and Holmes et
al. (1999)] provide evidence to demonstrate that:
Soil properties influence adherence;
Soil adherence varies considerably across different parts of the body; and
Soil adherence varies with activity.
Given these results, the EPA now recommends that an activity which best represents all soils, body parts, and
activities be selected (U.S. EPA, 1997a). Body-part-weighted AFs can then be calculated and used in estimating
exposure via dermal contact with soil based on assumed exposed body parts. Data on body-part-specific AFs for
specific activities are summarized in Exhibit C-2 and were taken from Exposure Factors Handbook (U.S. EPA,
1997a), Table 6-12 and from Holmes et al. (1999). The raw data are available electronically at
http://depts.washington.edu/jkspage as presented in Exhibit C-2. These body-part-specific adherence data are
then combined as a surface weighted average and 95th percentile for each activity using the exposed body parts
that are listed for each scenario. The surface area calculations are presented in Exhibit C-l and the overall
values in Exhibit C-3 and Exhibit 3-3.
Body-Part-Specific Surface Areas
The surface area parameter (SA) describes the amount of skin exposed to the contaminated media. The
amount of skin exposed depends upon the exposure scenario. Clothing is expected to limit the extent of the
exposed surface area in cases of soil contact. All SA estimates used 50th percentile values to correlate with the
-------
EXHIBIT C-l
BODY PART-SPECIFIC SURFACE AREA CALCULATIONS
(CHILDREN)
CHILDREN
Age (y)
<15
1<2
2<3
3<4
4<5
5<66
6<7
7<86
8<96
9<10
10<116
11<126
12<13
13<14
14<156
15<166
16<17
17<18
<1 to<6
<7to<18
<1 to<6
<7 to<18
Fraction of Total SA (unitless)1
Head
0.182
0.165
0.142
0.136
0.138
0.131
0.131
0.12
0.12
0.12
0.0874
0.0874
0.0874
0.0997
0.0796
0.0796
0.0796
0.0758
Face3
0.0607
0.0550
0.0473
0.0453
0.0460
0.0437
0.0437
0.0400
0.0400
0.0400
0.0291
0.0291
0.0291
0.0332
0.0265
0.0265
0.0265
0.0253
Arms
0.137
0.13
0.118
0.144
0.14
0.131
0.131
0.123
0.123
0.123
0.137
0.137
0.137
0.121
0.131
0.131
0.131
0.175
Fraction of Total SA: Age-Weighted Body
0.149
0.097
Surface Area by
977
1276
0.050
0.032
Body Part (cm2)7
326
425
0.133
0.133
874
1749
Forearms4
0.0617
0.0585
0.0531
0.0648
0.0630
0.0590
0.0590
0.0554
0.0554
0.0554
0.0617
0.0617
0.0617
0.0545
0.0590
0.0590
0.0590
0.0788
Hands
0.053
0.0568
0.053
0.0607
0.057
0.0471
0.0471
0.053
0.053
0.053
0.0539
0.0539
0.0539
0.0511
0.0568
0.0568
0.0568
0.0513
Legs
0.206
0.231
0.232
0.268
0.278
0.271
0.271
0.287
0.287
0.287
0.305
0.305
0.305
0.32
0.336
0.336
0.336
0.308
Lower legs4
0.082
0.092
0.093
0.107
0.111
0.108
0.108
0.115
0.115
0.115
0.122
0.122
0.122
0.128
0.134
0.134
0.134
0.123
Feet
0.0654
0.0627
0.0707
0.0721
0.0729
0.069
0.069
0.0758
0.0758
0.0758
0.0703
0.0703
0.0703
0.0802
0.0693
0.0693
0.0693
0.0728
Part-Specific Average
0.060
0.060
393
787
0.055
0.053
358
700
0.248
0.307
1624
4026
0.099
0.123
650
1610
0.069
0.072
451
949
Total Body SA (m2 50th
Age (y)
<15
1<25
2<3
3<4
4<5
5<66
6<7
7<86
8<96
9<10
10<116
11<126
12<13
13<14
14<156
15<166
16<17
17<18
Total SA (
-------
EXHIBIT C-l
BODY PART-SPECIFIC SURFACE AREA CALCULATIONS
(ADULTS)
ADULT
Body Part
Total
Face3
Forearms4
Hands
Lower legs4
Feet
Surface Area of Adults
Male
19400
433
1310
990
2560
1310
(50th percentile8) (cm2)
Female
16900
370
1035
817
2180
1140
Average
18150
402
1173
904
2370
1225
1. Taken from Exposure Factors Handbook 1997, Table 6-8.
2. Taken from Exposure Factors Handbook 1991, Table 6-6 (male) and Table 6-7 (female).
3. Face SA was assumed to be 1/3 of head SA.
4. Assumed forearm-to-arm ratio (0.45) and lower leg-to-leg ratio (0.4) equivalent to an adult.
5. Due to lack of data for indicated ages, it was assumed that children <1 and 1<2 yr old had the same total SA as children 2<3 yr old.
6. Due to lack of data for indicated ages, it was assumed that body-part-specific fraction of total SA was equal to that of the next oldest age with data.
7. Body-part-weighted SA for children was calculated by multiplying body-part-specific fraction of total SA by total S A (avg. of male and female). Adult
body-part SA was taken from 50%tile body-part SA (avg. of Male/Female). All areas are reported to two significant digits.
8. Taken from Exposure Factors Handbook 1991, Tables 6-2 (male) and 6-3 (female).
C-3
-------
EXHIBIT C-2
ACTIVITY BODY PART-SPECIFIC SOIL ADHERENCE FACTORS
Activity
Children
Playing
(dry soil)
ID
CPGPol4
CPGPolS
CPGPol6
CPGPol?
CPGPolS
Age
Gender
M
M
F
M
F
Avg(ln x)
Stdev(ln x)
GeoMean
1 -tailed t-dist.
value
95th Percentile
Post-activity Loading (mg/cm2)
Hands
0.193
0.139
0.021
0.147
0.102
-2.337
0.881
0.097
2.132
0.632
Arms
0.015
0.010
0.002
0.018
0.095
-4.305
1.424
0.014
2.132
0.281
Legs
0.056
0.022
0.020
0.017
0.336
-3.163
1.250
0.042
2.132
0.608
Faces
0.002
0.004
0.002
0.002
0.022
-5.565
1.042
0.004
2.132
0.035
Feet
X
X
X
X
X
X
X
X
X
X
(face, forearms, hands, lowerlegs)
Daycare
Children
No. la
Daycare
Children
vfo. Ib
Daycare
Children
No. 3
Dial
Dla2
Dla3
Dla4
Dla5
Dla6
Dlbl
Dlb2
Dlb3
Dlb4
Dlb5
Dlb6
D3a
D3b
D3c
D3d
6.5
4
2
1.75
1
1
6.5
4
2
1.75
1
1
4.5
1.5
1.3
2
M
M
M
M
M
F
M
M
M
M
M
F
M
F
M
M
Avg(ln x)
Stdev(ln x)
GeoMean
1 -tailed t-dist.
value
95th Percentile
0.252
0.088
0.208
0.081
0.114
0.043
0.094
0.089
0.505
0.104
0.263
0.091
0.031
0.026
0.040
0.050
-2.375
0.823
0.093
1.753
0.394
0.027
0.044
0.043
0.027
0.029
0.008
0.018
0.024
0.037
0.035
0.084
0.017
0.015
0.010
0.011
0.010
-3.791
0.652
0.023
1.753
0.071
0.067
0.015
0.030
0.023
0.041
0.027
0.026
0.019
0.023
0.027
0.018
0.026
0.017
0.020
0.040
0.003
-3.787
0.652
0.023
1.753
0.071
x
x
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
0.205
0.087
0.024
0.110
0.031
0.171
0.210
0.117
0.126
0.111
0.082
0.204
0.015
0.008
0.013
0.000
-3.015
1.630
0.049
1.753
0.853
(forearms, hands, lowerlegs, feet)
Weighted AFs (mg/cm2)
Geometric
Mean
0.040
0.043
95th Percentile
0.431
0.324
C-4
-------
EXHIBIT C-2
ACTIVITY BODY PART-SPECIFIC SOIL ADHERENCE FACTORS (continued)
Activity
Children
Playing
(wet soil)
ID
CPGPol
CPGPo2
CPGPoS
CPGPo4
CPGPoS
CPGPo6
CPGPo?
CPGPoS
CPGPo9
CPGPo 10
CPGPo 11
CPGPo 12
CPGPo 13
Age
Gender
M
F
M
M
M
F
F
M
F
M
M
F
M
Avg(ln x)
Stdev(ln x)
GeoMean
1 -tailed t-dist.
value
95th Percentile
Post-activity Loading (mg/cm2)
Hands
1.398
0.290
0.127
0.928
0.036
0.565
0.681
0.163
4.743
4.969
0.274
1.384
4.326
-0.421
1.509
0.656
1.782
9.660
Arms
0.026
0.005
0.009
0.069
0.008
0.011
0.015
0.006
0.101
0.064
0.003
0.005
0.034
-4.185
1.134
0.015
1.782
0.115
Legs
1.320
0.184
0.037
0.669
0.004
0.010
0.131
0.072
0.778
0.001
0.000
0.001
0.002
-3.634
2.732
0.026
1.782
3.439
Faces
0.013
0.010
0.012
0.009
0.005
0.002
0.006
0.004
0.006
0.002
0.001
0.001
0.006
-5.409
0.870
0.004
1.782
0.021
Feet
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
(face, forearms, hands, lowerlegs)
Indoor Children
No. 1
Indoor Children
No. 2
Daycare
Children
No. 2
IKla
IKlb
IKlc
IKld
IK2a
IK2b
IK2c
IK2d
IK2e
IK2f
D2a
D2b
D2c
D2d
D2e
13
11.5
10
6.5
13
11.5
10
6.5
7
3
4
1
1
2
2
F
M
M
M
F
M
M
M
M
F
M
F
M
M
M
Avg(ln x)
Stdev(ln x)
GeoMean
1 -tailed t-dist.
value
95th Percentile
0.003
0.008
0.014
0.009
0.022
0.011
0.015
0.010
0.025
0.009
0.042
0.064
0.070
0.070
0.159
-3.889
1.076
0.020
1.761
0.136
0.004
0.003
0.011
0.002
0.005
0.003
0.010
0.001
0.004
0.005
0.015
0.020
0.020
0.032
0.033
-4.912
0.994
0.007
1.761
0.042
0.004
0.003
0.011
0.002
0.002
0.002
0.005
0.002
0.004
0.004
0.018
0.012
0.007
0.009
0.011
-5.282
0.743
0.005
1.761
0.019
x
x
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
0.011
0.010
0.020
0.011
0.004
0.007
0.015
0.007
0.014
0.015
0.063
0.056
0.035
0.034
0.041
-4.089
0.823
0.017
1.761
0.071
(forearms, hands, lowerlegs, feet)
Weighted AFs (mg/cm2)
Geometric
Mean
0.011
95th Percentile
3.327
0.059
C-5
-------
EXHIBIT C-2
ACTIVITY BODY PART-SPECIFIC SOIL ADHERENCE FACTORS (continued)
Activity
Children-in-Mud
No. 1
Children-in-Mud
No. 2
ID
Kla
Klb
Klc
Kid
Kle
Klf
K2a
K2b
K2c
K2d
K2e
K2f
Age
11
11
10
14
9
9
11
11
10
14
9
9
Gender
M
M
F
M
M
M
M
M
F
M
M
M
Avg(ln x)
Stdev(ln x)
GeoMean
1 -tailed t-dist.
value
95th Percentile
Post-activity Loading (mg/cm2)
Hands
74.283
42.074
18.669
108.669
13.222
22.203
145.065
99.781
31.991
103.279
16.018
49.127
3.808
0.836
45.059
1.796
202.293
Arms
5.863
2.672
0.931
58.217
23.164
91.537
54.855
2.353
13.949
46.281
3.568
5.104
2.386
1.515
10.873
1.796
165.249
Legs
36.130
15.022
18.440
86.589
38.571
68.453
15.457
11.983
2.042
20.643
12.798
7.145
2.919
1.012
18.525
1.796
113.959
Faces
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
Feet
51.528
19.960
36.569
104.444
2.377
20.507
22.738
9.923
0.051
43.810
4.975
35.152
2.539
2.022
12.663
1.796
478.270
(forearms, hands, lowerlegs, feet)
Weighted AFs (mg/cm2)
Geometric
Mean
20.601
95th Percentile
230.663
C-6
-------
EXHIBIT C-2
ACTIVITY BODY PART-SPECIFIC SOIL ADHERENCE FACTORS (continued)
Activity
Grounds keepers
No. 1
Grounds keepers
No. 2
Grounds keepers
No. 3
Grounds keepers
No. 4
Grounds keepers
No. 5
ID
Gla
Gib
G2a
G2b
G2c
G2d
G2e
G3a
G3b
G3c
G3d
G3e
G3f
G3g
G4a
G4b
G4c
G4d
G4e
G4f
G4g
G5a
G5b
G5c
G5d
G5e
G5f
G5g
G5h
Age
52
29
33
34
28
37
22
43
40
45
30
43
49
62
38
30
22
34
27
29
35
44
43
40
64
45
31
49
19
Gender
M
F
F
M
M
F
M
M
F
F
M
M
M
M
F
M
M
F
F
M
M
M
M
F
M
F
M
M
M
Avg(ln x)
Stdev(ln x)
GeoMean
1 -tailed t-dist.
value
95th Percentile
Post-activity Loading (mg/cm2)
Hands
0.444
0.053
0.037
0.195
0.171
0.056
0.133
0.026
0.006
0.058
0.029
0.034
0.029
0.086
0.067
0.030
0.128
0.050
0.017
0.034
0.053
0.052
0.014
0.016
0.033
0.042
0.056
0.033
0.037
-3.069
0.863
0.046
1.701
0.202
Arms
0.007
0.004
0.001
0.006
0.004
0.001
0.003
0.005
0.001
0.002
0.002
0.002
0.003
0.004
0.011
0.021
0.027
0.005
0.010
0.012
0.022
0.032
0.033
0.018
0.049
0.030
0.045
0.024
0.002
-4.983
1.278
0.007
1.701
0.060
Legs
x
x
0.001
0.001
0.002
0.001
0.001
0.003
0.000
x
0.002
0.001
0.001
0.001
0.000
0.001
0.001
0.002
x
0.000
0.001
0.001
0.001
0.001
0.001
0.001
0.002
0.001
0.001
-6.942
0.565
0.001
1.711
0.003
Faces
0.004
0.001
0.007
0.018
0.024
0.007
0.005
0.009
0.001
0.003
0.013
0.005
0.002
0.010
0.002
0.006
0.005
0.002
0.002
0.001
0.003
0.006
0.005
0.001
0.006
0.002
0.006
0.004
0.008
-5.468
0.819
0.004
1.701
0.017
Feet
0.024
0.013
x
x
X
X
X
X
X
0.004
X
X
X
X
X
X
X
X
0.018
X
X
X
X
X
X
X
X
X
X
-4.388
0.776
0.012
2.353
0.077
Residential Scenario (face, forearms, hands, lowerlegs)
Commercial/Industrial (face, forearms, hands)
Weighted AFs (mg/cm2)
Geometric
Mean
0.011
0.021
95th Percentile
0.055
0.105
C-7
-------
EXHIBIT C-2
ACTIVITY BODY PART-SPECIFIC SOIL ADHERENCE FACTORS (continued)
Activity
Landscaper/
Rockery
ID
LR1
LR2
LR3
LR4
Age
43
36
27
43
Gender
F
M
M
M
Avg(ln x)
Stdev(ln x)
GeoMean
1 -tailed t-dist.
value
95th Percentile
Post-activity Loading (mg/cm2)
Hands
0.067
0.159
0.091
0.028
-2.630
0.730
0.072
2.353
0.402
Arms
0.034
0.060
0.039
0.010
-3.507
0.755
0.030
2.353
0.177
Legs
x
x
x
x
x
x
x
x
x
Faces
0.010
0.007
0.007
0.002
-5.168
0.635
0.006
2.353
0.025
Feet
x
x
X
X
X
X
X
X
X
Residential Scenario (face, forearms, hands, lowerlegs)
Commercial/Industrial (face, forearms, hands)
Gardeners
No. 1
Gardeners
No. 2
GAla
GAlb
GAlc
GAld
GAle
GAlf
GAlg
GAlh
GA2a
GA2b
GA2c
GA2d
GA2e
GA2f
GA2g
16
21
22
35
22
27
23
31
43
32
34
32
33
52
26
F
F
F
F
F
M
F
F
F
M
M
F
F
F
F
Avg(ln x)
Stdev(ln x)
GeoMean
1 -tailed t-dist.
value
95th Percentile
0.515
0.262
0.094
0.071
0.177
0.310
0.257
0.194
0.155
0.173
0.262
0.083
2.057
0.116
0.043
-1.662
0.919
0.190
1.761
0.958
0.055
0.026
0.030
0.267
0.035
0.044
0.033
0.070
0.048
0.059
0.071
0.018
0.407
0.049
0.017
-2.961
0.872
0.052
1.761
0.240
0.065
x
X
X
X
0.080
x
X
0.053
x
X
0.013
x
0.028
0.013
-3.411
0.802
0.033
2.015
0.166
0.065
0.025
0.043
0.059
0.097
x
0.060
0.088
0.093
x
0.058
0.024
0.056
0.031
0.047
-2.949
0.463
0.052
1.782
0.119
X
X
X
0.066
X
0.440
x
X
X
0.263
x
X
X
X
X
-1.626
0.983
0.197
2.920
3.473
Residential Scenario (face, forearms, hands, lowerlegs)
Commercial/Industrial (face, forearms, hands)
Irrigation
Installers
IR1
IR2
IRS
IR4
IRS
IR6
41
35
20
23
28
23
M
M
M
M
M
M
Avg(ln x)
Stdev(ln x)
GeoMean
1 -tailed t-dist.
value
95th Percentile
0.281
0.279
0.110
0.132
0.129
0.300
-1.671
0.467
0.188
2.015
0.482
0.039
0.014
0.003
0.008
0.045
0.062
-4.007
1.170
0.018
2.015
0.192
0.007
0.004
0.004
0.003
0.015
0.007
-5.214
0.610
0.005
2.015
0.019
0.006
0.006
0.004
0.008
0.008
0.007
-5.064
0.289
0.006
2.015
0.011
x
x
X
X
X
X
X
X
X
X
X
(face, forearms.hands)
Weighted AFs (mg/cm2)
Geometric
Mean
0.041
0.041
0.068
0.102
0.078
95th Percentile
0.234
0.234
0.328
0.482
0.268
C-8
-------
EXHIBIT C-2
ACTIVITY BODY PART-SPECIFIC SOIL ADHERENCE FACTORS (continued)
Activity
Staged
Activity:
Pipe Layers
(dry soil)
ID
APDGPola
APDGPo2a
APDGPoSa
APDGPo4a
APDGPoSa
APDGPo6a
APDGPolb
APDGPo2b
APDGPoSb
APDGPo4b
APDGPoSb
APDGPo6b
APDGPolc
APDGPo2c
APDGPoSc
APDGPo4c
APDGPoSc
APDGPo6c
Age
Gender
M
M
M
F
F
F
M
M
M
F
F
F
M
M
M
F
F
F
Avg(ln x)
Stdev(ln x)
GeoMean
1 -tailed t-dist.
value
95th Percentile
Post-activity Loading (mg/cm2)
Hands
0.131
0.243
0.216
0.158
0.106
0.174
0.182
0.125
0.133
0.397
0.124
0.075
0.551
0.311
0.184
0.226
0.168
0.133
-1.721
0.484
0.179
1.740
0.416
Arms
0.003
0.036
0.010
0.009
0.008
0.008
0.005
0.007
0.108
0.011
0.015
0.004
0.005
0.022
0.088
0.019
0.010
0.012
-4.419
0.984
0.012
1.740
0.067
Legs
0.001
0.258
0.113
0.046
0.093
0.296
0.000
0.166
0.115
0.095
0.112
0.393
0.001
0.355
0.246
0.131
0.104
0.579
-2.713
2.214
0.066
1.740
3.122
Faces
0.003
0.006
0.020
0.003
0.003
0.003
0.001
0.007
0.004
0.004
0.008
0.007
0.002
0.006
0.004
0.006
0.012
0.008
-5.354
0.663
0.005
1.740
0.015
Feet
x
x
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
(face, forearms, hands)
Construction
Workers
CO1
CO2
COS
CO4
COS
CO6
CO7
COS
26
27
24
22
22
30
24
21
M
M
M
M
M
M
M
M
Avg(ln x)
Stdev(ln x)
GeoMean
1 -tailed t-dist.
value
95th Percentile
0.376
0.283
0.230
0.179
0.440
0.141
0.164
0.266
-1.418
0.401
0.242
1.895
0.518
0.132
0.044
0.129
0.061
0.128
0.102
0.132
0.105
-2.328
0.416
0.098
1.895
0.215
0.066
0.046
0.056
0.052
0.125
0.080
x
0.063
-2.716
0.334
0.066
1.943
0.127
0.033
0.013
0.045
0.023
0.035
0.026
0.058
0.021
-3.550
0.478
0.029
1.895
0.071
X
X
X
X
X
X
X
X
X
X
X
X
X
(face, forearms, hands)
Weighted AFs (mg/cm2)
Geometric
Mean
0.072
0.139
95th Percentile
0.186
0.302
C-9
-------
EXHIBIT C-2
ACTIVITY BODY PART-SPECIFIC SOIL ADHERENCE FACTORS (continued)
Activity
Heavy
Equipment
Operators
No. 1
Heavy
Equipment
Operators
No. 2
ID
Ela
Elb
Elc
Eld
E2a
E2b
E2c
E2d
Age
54
34
51
21
54
34
51
21
Gender
M
M
M
M
M
M
M
M
Avg(ln x)
Stdev(ln x)
GeoMean
1 -tailed t-dist.
value
95th Percentile
Post-activity Loading (mg/cm2)
Hands
0.115
0.281
0.155
0.940
0.206
0.430
0.227
0.500
-1.245
0.682
0.288
1.895
1.049
Arms
0.053
0.080
0.091
0.161
0.192
0.339
0.223
0.358
-1.867
0.692
0.155
1.895
0.573
Legs
x
x
x
x
x
x
x
x
x
x
x
x
x
Faces
0.064
0.104
0.152
0.109
0.146
0.194
0.499
0.200
-1.874
0.605
0.154
1.895
0.483
Feet
x
x
X
X
X
X
X
X
X
X
X
X
X
(face, forearms, hands)
Utility Workers
No. 1
Utility Workers
No. 2
Ula
Ulb
Ulc
Uld
Ule
U2a
U2b
U2c
U2d
U2e
U2f
45
27
24
35
24
23
28
24
34
24
36
M
M
M
M
M
M
M
M
M
M
M
Avg(ln x)
Stdev(ln x)
GeoMean
1 -tailed t-dist.
value
95th Percentile
0.149
0.243
0.561
0.364
0.437
0.269
0.906
0.187
0.109
0.221
0.390
-1.226
0.611
0.293
1.812
0.889
0.052
0.131
0.184
0.783
0.311
0.189
0.835
0.179
0.298
0.219
0.426
-1.385
0.793
0.250
1.812
1.053
x
x
x
x
x
x
x
X
X
X
X
X
X
X
X
X
0.095
0.079
0.084
0.215
0.082
0.062
0.197
0.074
0.113
0.092
0.119
-2.283
0.393
0.102
1.812
0.208
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
(face,forearms,hands)
Weighted AFs (mg/cm2)
Geometric
Mean
0.203
0.242
95th Percentile
0.732
0.856
C-10
-------
EXHIBIT C-2
ACTIVITY BODY PART-SPECIFIC SOIL ADHERENCE FACTORS (continued)
Activity
Staged
Activity:
Pipe
Layers
(wet soil)
ID
APWGPola
APWGPo2a
APWGPoSa
APWGPo4a
APWGPoSa
APWGPo6a
APWGPoTa
APWGPolb
APWGPo2b
APWGPoSb
APWGPo4b
APWGPoSb
APWGPo6b
APWGPoTb
APWGPolc
APWGPo2c
APWGPoSc
APWGPo4c
APWGPoSc
APWGPo6c
APWGPoTc
Age
Gender
M
M
M
M
F
F
F
M
M
M
M
F
F
F
M
M
M
M
F
F
F
Avg(ln x)
Stdev(ln x)
GeoMean
1 -tailed t-dist.
value
95th Percentile
Post-activity Loading (mg/cm2)
Hands
2.122
19.708
10.531
0.334
0.019
0.445
0.978
4.573
14.032
3.319
1.257
4.052
1.050
1.872
1.263
7.890
6.866
0.087
6.280
0.181
3.658
0.527
1.758
1.694
1.725
35.138
Arms
0.018
0.999
0.030
0.005
0.001
0.013
0.003
0.113
0.446
0.001
0.018
0.013
0.018
0.004
0.370
0.439
0.147
0.002
0.085
0.010
0.029
-3.741
2.058
0.024
1.725
0.826
Legs
1.410
3.730
0.000
0.001
0.169
0.001
0.012
3.411
1.856
0.001
0.005
0.905
0.002
0.001
2.005
2.485
2.124
0.001
1.662
0.003
0.087
-3.008
3.607
0.049
1.725
24.864
Faces
0.019
0.018
0.001
0.002
0.000
0.004
0.003
0.019
0.018
0.004
0.004
0.011
0.001
0.006
0.012
0.018
0.007
0.002
0.037
0.003
0.004
-5.325
1.320
0.005
1.725
0.047
Feet
x
x
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
(face, forearms, hands)
Soccer Players
No. 1
Sla
Sib
Sic
Sid
Sle
Slf
Slg
Slh
13
14
14
15
13
14
13
13
M
M
M
M
M
M
M
M
Avg(ln x)
Stdev(ln x)
GeoMean
1 -tailed t-dist.
value
95th Percentile
0.068
0.052
0.116
0.120
0.280
0.170
0.146
0.055
-2.224
0.589
0.108
1.895
0.330
0.019
0.021
0.005
0.006
0.026
0.004
0.015
0.007
-4.555
0.714
0.011
1.895
0.041
0.022
0.251
0.015
0.047
0.092
0.060
0.008
0.005
-3.481
1.322
0.031
1.895
0.377
0.012
0.020
0.012
0.011
0.009
0.009
0.020
0.006
-4.457
0.398
0.012
1.895
0.025
X
X
X
X
X
X
X
X
X
X
X
X
X
(face, forearms, hands, lowerlegs)
Weighted AFs (mg/cm2)
Geometric
Mean
0.630
0.039
95th Percentile
13.212
0.250
C-ll
-------
EXHIBIT C-2
ACTIVITY BODY PART-SPECIFIC SOIL ADHERENCE FACTORS (continued)
Activity
Soccer Players
No. 2
Soccer Players
No. 3
ID
S2a
S2b
S2c
S2d
S2e
S2f
S2g
S2h
S3a
S3b
S3c
S3d
S3e
S3f
S3g
Age
31
24
34
30
24
25
29
24
28
24
30
34
31
28
25
Gender
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
Avg(ln x)
Stdev(ln x)
GeoMean
1 -tailed t-dist.
value
95th Percentile
Post-activity Loading (mg/cm2)
Hands
0.042
0.075
0.063
0.043
0.049
0.055
0.075
0.001
0.012
0.014
0.039
0.020
0.013
0.026
0.021
-3.638
1.047
0.026
1.761
0.166
Arms
0.003
0.003
0.003
0.008
0.021
0.005
0.002
0.002
0.005
0.002
0.002
0.002
0.013
0.003
0.002
-5.632
0.780
0.004
1.761
0.014
Legs
0.004
0.003
0.007
0.033
0.042
0.379
0.007
0.004
0.010
0.008
0.004
0.010
0.012
0.005
0.013
-4.540
1.253
0.011
1.761
0.097
Faces
0.012
0.016
0.011
0.038
0.015
0.020
0.014
0.012
0.009
0.012
0.014
0.007
0.015
0.008
0.027
-4.274
0.439
0.014
1.761
0.030
Feet
x
x
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
(face, forearms, hands, lowerlegs)
Weighted AFs (mg/cm2)
Geometric
Mean
0.012
95th Percentile
0.084
C-12
-------
EXHIBIT C-2
ACTIVITY BODY PART-SPECIFIC SOIL ADHERENCE FACTORS (continued)
Activity
Farmers
No. 1
Farmers
No. 2
ID
Fla
Fib
Flc
Fid
F2a
F2b
F2c
F2d
F2e
F2f
Age
39
39
44
42
41
40
43
39
19
18
Gender
F
F
M
M
F
F
M
M
M
M
Avg(ln x)
Stdev(ln x)
GeoMean
1 -tailed t-dist.
value
95th Percentile
Post-activity Loading (mg/cm2)
Hands
0.380
0.326
0.794
0.301
0.245
0.622
0.571
0.538
0.584
0.407
-0.802
0.374
0.448
1.833
0.890
Arms
0.025
0.020
0.190
0.132
0.033
0.175
0.337
0.154
0.142
0.094
-2.376
0.966
0.093
1.833
0.546
Legs
0.002
0.003
0.015
0.012
0.033
0.224
0.170
0.008
0.014
0.018
-4.033
1.506
0.018
1.833
0.280
Faces
0.014
0.013
0.025
0.022
0.027
0.321
0.045
0.014
0.038
0.022
-3.524
0.932
0.029
1.833
0.163
Feet
x
x
X
X
X
X
X
X
X
X
X
X
X
X
X
(face, forearms, hands, lowerlegs)
Rugby Players
No. 1
Rugby Players
No. 2
Rugby Players
No. 3
Rla
Rib
Rlc
Rid
Rle
Rlf
Rig
Rlh
R2a
R2b
R2c
R2d
R2e
R2f
R2g
R2h
R3a
R3b
R3c
R3d
R3e
R3f
R3g
22
20
20
20
21
22
22
21
33
28
27
26
23
27
27
30
27
26
27
27
30
27
24
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
Avg(ln x)
Stdev(ln x)
GeoMean
1 -tailed t-dist.
value
95th Percentile
0.207
0.427
1.123
0.338
0.237
0.456
0.413
0.454
0.147
0.074
0.168
0.139
0.195
0.097
0.164
0.179
0.052
0.052
0.073
0.043
0.033
0.109
0.023
-1.919
0.968
0.147
1.717
0.774
0.163
0.279
0.451
0.152
0.156
0.418
0.345
0.399
0.093
0.095
0.141
0.102
0.178
0.058
0.229
0.071
0.028
0.040
0.023
0.025
0.034
0.042
0.028
-2.282
0.978
0.102
1.717
0.547
0.266
0.695
0.733
0.267
0.237
0.341
0.503
0.189
0.203
0.064
0.190
0.160
0.140
0.086
0.253
0.173
0.050
0.083
0.051
0.042
0.060
0.062
0.061
-1.896
0.858
0.150
1.717
0.655
0.072
0.119
0.094
0.008
0.066
0.197
0.032
0.059
0.066
0.038
0.044
0.055
0.043
0.029
0.070
0.039
0.021
0.015
0.015
0.022
0.015
0.045
0.020
-3.244
0.773
0.039
1.717
0.147
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
(face, forearms, hands, lowerlegs)
Weighted AFs (mg/cm2)
Geometric
Mean
0.117
0.129
95th Percentile
0.448
0.609
C-13
-------
EXHIBIT C-2
ACTIVITY BODY PART-SPECIFIC SOIL ADHERENCE FACTORS (continued)
Activity
Archeologists
ID
AR1
AR2
AR3
AR4
AR5
AR6
AR7
Age
16
21
22
35
22
27
23
Gender
F
F
F
F
M
M
M
Avg(ln x)
Stdev(ln x)
GeoMean
1 -tailed t-dist.
value
95th Percentile
Post-activity Loading (mg/cm2)
Hands
0.139
0.175
0.098
0.158
0.201
0.114
0.138
-1.950
0.248
0.142
1.943
0.230
Arms
0.060
0.066
0.019
0.083
0.064
0.018
0.025
-3.203
0.651
0.041
1.943
0.144
Legs
0.031
0.021
0.002
0.138
0.070
0.047
0.030
-3.567
1.400
0.028
1.943
0.429
Faces
0.103
0.062
0.037
0.102
0.047
0.030
0.023
-2.996
0.584
0.050
1.943
0.156
Feet
0.299
x
X
0.357
0.161
0.233
0.194
0.249
0.079
1.283
2.132
1.518
(face, forearms, hands, lowerlegs, feet)
Reed
Gatherers
RD1
RD2
RD3
RD4
67
50
42
45
F
F
F
F
Avg(ln x)
Stdev(ln x)
GeoMean
1 -tailed t-dist.
value
95th Percentile
0.733
0.583
1.392
0.315
-0.418
0.613
0.658
2.353
2.787
0.086
0.017
0.049
0.022
-3.336
0.742
0.036
2.353
0.204
0.333
0.006
0.391
0.820
-1.837
2.215
0.159
2.353
29.245
x
x
X
X
X
X
X
X
X
0.844
0.041
1.024
4.492
-0.457
1.965
0.633
2.353
64.598
(forearms, hands, lowerlegs, feet)
Tae Kwon Do
TK1
TK2
TK3
TK4
TK5
TK6
TK7
42
8
8
10
11
12
14
M
M
M
M
M
M
F
Avg(ln x)
Stdev(ln x)
GeoMean
1 -tailed t-dist.
value
95th Percentile
0.006
0.013
0.008
0.006
0.011
0.003
0.003
-5.081
0.581
0.006
1.943
0.019
0.002
0.001
0.000
0.011
0.005
0.001
0.005
-6.289
1.301
0.002
1.943
0.023
0.002
0.001
0.003
0.006
0.001
0.001
0.003
-6.230
0.599
0.002
1.943
0.006
x3
X
X
X
X
X
X
X
X
X
X
X
0.005
0.004
0.004
0.001
0.005
0.002
0.001
-6.014
0.743
0.002
1.943
0.010
(forearms, hands, lowerlegs ,feet)
Weighted AFs (mg/cm2)
Geometric
Mean
0.302
0.316
0.003
95th Percentile
0.546
26.662
0.012
Daycare Children No. 2 from 1997 Exposure Factors Handbook (U.S. EPA, 1997), Table 6-11, and Indoor Children Nos 1 & 2 were combined.
C-14
-------
average body weights used for all scenarios and pathways. This was done to prevent inconsistent parameter
combinations as body weight and SA are dependent variables. Body part-specific SAs were calculated as described
under Chapter 3 for adult (>18 years old), teenager (>6 to <18 years old), and child (<1 to <6 years old) receptors
and documented in Exhibit C-l.
Weighted Soil Adherence Factors
Given that soil adherence is dependent upon the body part, it is necessary to calculate an overall body part-
weighted AF for each activity. The assumed clothing scenario determines which body part-specific AFs are used in
calculating the 50th and 95th percentile weighted AFs. The weighted AFs are used in combination with the relative
absorption, exposure frequency and duration, exposed surface area, body weight, and averaging time to estimate the
dermally absorbed dose. Details on the methods used to calculate the overall weighted AFs are contained under
Chapter 3 of the document. The results from the supporting calculations are shown in Exhibit 3-3.
Mono-layer Soil Loading for SCS Soils.
The range of possible soil adherence factors (AF) was calculated using the Soil Conservation Service (SCS) textural
classes and the Duff and Kissel (1996) equation for a mono-layer, assuming spherical particles and face-centered
packing,
Tld 3
nd
= rp i = p
monlayer L particle 2 particle f
using the SCS arithmetic mean particle diameter and particle density, pparticie= 2.65 gm/cm3, from the Soil Screening
Guidance (U.S. EPA, 1996b).
These values can be used as bounding estimates as maximums for AF using site-specific soil properties. The AF
should not exceed these estimated values based on the mono-layer theory. To restate the recommendation of this
guidance, construct the RME exposure scenario with a site-specific upper-end activity pattern, mean AF from Exhibit
C-3, and upper-end exposure time. The uncertainty can be bounded by using these maximum estimated mono-layer
AF values.
C-15
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EXHIBIT C-3
OVERALL BODY PART-SPECIFIC WEIGHTED
SOIL ADHERENCE FACTORS
CHILDREN1
Indoor Children
Daycare Children (playing indoors and outdoors)
Children Playing (dry soil)
Children Playing (wet soil)
Children-in-Mud2
RESIDENTIAL ADULTS3
Grounds keepers
Landscaper/Rockery
Gardeners
COMMERCIAL/INDUSTRIAL ADULTS4
Grounds keepers
Landscaper/Rockery
Staged Activity: Pipe Layers (dry soil)
Irrigation Installers
Gardeners
Construction Workers
Age
(years)
1-13
1-6.5
8-12
8-12
9-14
>18
>18
>16
>18
>18
>15
>18
>16
>18
Weighted Soil Adherence Factor (mg/cm2)
Geometric Mean
0.01
0.04
0.04
0.2
21
0.01
0.04
0.07
0.02
0.04
0.07
0.08
0.1
0.1
95th Percentile
0.06
0.3
0.4
3.3
231
0.06
0.2
0.3
0.1
0.2
0.2
0.3
0.5
0.3
1 Weighted AF based on exposure to face, forearms, hands, lower legs, & feet.
2 Information on soil adherence values for the Children-in-Mud scenario is provided to illustrate the range of values for
this type of activity. However, the application of these data to the dermal dose equations in this guidance may result in a
significant overestimation of dermal risk. Therefore, it is recommended that the 95 percentile AF values not be used in
a quantitative dermal risk assessment. See Exhibit C-4 for bounding estimates.
3 Weighted AF based on exposure to face, forearms, hands, & lower legs.
4 Weighted AF based on exposure to face, forearms, & hands.
Note: this results in different weighted AFs for similar activities between residential
and commercial/industrial exposure scenarios.
C-16
-------
EXHIBIT C-3
OVERALL BODY PART-SPECIFIC WEIGHTED
SOIL ADHERENCE FACTORS (continued)
COMMERCIAL/INDUSTRIAL ADULTS4 (continued)
Utility Workers
Staged Activity: Pipe Layers (wet soil)
MISCELLANEOUS ACTIVITIES5
Soccer Players #2 (adults)
Soccer Players #1 (teens, moist conditions)
Farmers
Rugby Players
Archeologists
Reed Gatherers
Age
(years)
>18
>18
>15
>18
13-15
>20
>21
>19
>22
Weighted Soil Adherence Factor (mg/cm2)
Geometric Mean
0.2
0.2
0.6
0.01
0.04
0.1
0.1
0.3
0.3
95th Percentile
0.7
0.9
13
0.08
0.3
0.4
0.6
0.5
27
Weighted AF based on all body parts for which data were available
C- 17
-------
EXHIBIT C-4
ESTIMATION OF SOIL ADHERENCE FACTOR AT MONO-LAYER
FOR SOIL CONSERVATION SERVICE (SCS) SOIL CLASSIFICATIONS
SCS Textural Class
sand
loamy sand
sandy loam
sandy clay loam
sandy clay
loam
clay loam
silty loam
clay
silty clay loam
silt
silty clay
Diameter (cm)
0.044
0.040
0.030
0.029
0.025
0.020
0.016
0.011
0.0092
0.0056
0.0046
0.0039
AF at mono-layer (mg/cm2)
61
55
42
40
35
28
22
15
13
7.7
6.4
5.4
C-18
-------
APPENDIX D
SAMPLE SCREENING CALCULATIONS
D.I SAMPLE CANCER SCREENING CALCULATION FOR DERMAL
CONTAMINANTS IN WATER
The equations used in calculating the risk from dermal exposure for contaminants in water are summarized
in Exhibit D-l. This example illustrates the steps used to calculate the clean-up level from dermal exposure to
compounds in water given an acceptable risk of 10"6. The default scenarios used in the calculations are (1) the adult
30 year exposure, and (2) an age-adjusted 30 year exposure incorporating a child bathing for 1 hour/event (RME
value), once a day, 350 days/year for 6 years and an adult showering at 35 min/event (RME value), once a day, 350
days/year for 24 years. The general equations are presented for any compound, and the example gives the calculation
for one compound in water with a cancer risk of 10"6.
EXHIBIT D-l
SUMMARY OF DERMAL RISK ASSESSMENT PROCESS
Risk Assessment Process
Hazard ID
Exposure
Assessment
Child or Adult
Age-adjusted
Child/Adult
SFSADJ
Toxicity Assessment
Risk Characterization
Cancer Risk
Section 2
Water Dose
Section 3.1,
Equations 3.1-3.4
Appendix A
See Note
Soil Dose
Section 3.2,
Equations
3.11/3.12
Section 3.2.2.5
Equation 3.21
Section 4,
SFABS Equation 4.2
Section 5.1, Equation 5.1
DAD x SF^s
Hazard Index
Section 2
Water Dose
Section 3.1,
Equations
3.1-3.4
See Note
Soil Dose
Section 3.2,
Equations
3.11/3.12
Section 3.2.2.5,
Equation 3.21
Section 4,
RlD^s, Equation 4.3
Section 5.1, Equation 5.2
DAD/RfDABS
Uncertainty Analysis Section 5.2
Note: The calculations used in developing the screening tables in Appendix B (Exhibits B-3 and B-4) for the water pathway determined that the adult
receptor experiences the highest dermal dose. Therefore, the adult exposure scenario is recommended for screening purposes. However, if an age-
adjusted exposure scenario for the dermal route is selected to be consistent with methods for determining the risk of other routes of exposure (e.g.,
oral), sample calculations are provided as guidance.
D- 1
-------
Procedures: Given a cancer risk level at 10"6
1) For cancer risk, from Equation 5.1:
n/m _ Dermal cancer risk _ (Dermal cancer risk) x (ABSGI)
DAD ~ ~ (D 1)
ABS O
2) For hazard quotient, from Equation 5.2:
DAD = Dermal hazard quotient x RfDABS
(D.2)
= Dermal hazard quotient x RfDo x ABSGI
3) Evaluate DAevent from Equation 3.1
DAD x BW x AT
event EV x ED x EF x SA
4) Evaluate permissible water concentration Cw:
For organics, from Equations 3.2 and 3.3:
DA
< t », then: Cm = event (R4)
2 x FA x K
6 T X t
event event
DA ,
event
- (D.5)
FA x K
+ 2 T
1 + 3B +352
event
1 + B < I (1 + B)2
For inorganics, from Equation 3.4:
DA
C =
p X l event
D-2
-------
Parameter
TRL
BW
AT
cp
^rAES
ED
EV
EF
FA
tevent-RME
SA
KP
ABSGI
^event
SF
v>r0
t*
DAD
DADevent
Definition
Target Risk Level
(unitless)
Body Weight (kg)
Averaging Time (yr)
Absorbed Cancer Slope
Factor (mg/kg-day)
Exposure Duration (yr)
Event Frequency
(events/day)
Exposure Frequency
(days/yr)
Fraction Absorbed
(unitless)
Event Duration (hr)
Surface Area (cm2)
Permeability coefficient
(cm/hr)
Absorption Fraction
(unitless)
Lag time per event (hr)
Oral Cancer Slope
Factor (mg/kg-day)
Time to Reach Steady-
State (hr)
Dermal Absorbed Dose
(mg/kg-day)
Absorbed Dose per
Event (mg/cm2 -event)
Default - Child
io-6
15
70
chemical-
specific
6
1
350
chemical-
specific
1
(bathing)
6,600
chemical-
specific
chemical-
specific
chemical-
specific
chemical-
specific
chemical-
specific
site-specific
site-specific
Default -
Adult
io-6
70
70
chemical-
specific
30
1
350
chemical-
specific
0.58
(showering)
18,000
chemical-
specific
chemical-
specific
chemical-
specific
chemical-
specific
chemical-
specific
site-specific
site-specific
D-3
-------
Sample Calculations for Exposure to a Carcinogen in Water
Tetrachloroethylene (PCE)
SF0 = 5.2x10'2 (mg/kg-d)4
Kp = 0.033 cm/hr
ABSGI = 1
t* = 2.18hr
Tevent = 0.91hr
tevent = 0.58hr
FA= 1
Residential exposure scenarios
Using Equations D.I, D.3 and D.4 and default values presented:
Adult:
BW
DA , = DAD x AT[ ] m 3)
EVa x EDa x EFa x SAa ^^
DA , = (1.9xW~5mg/kg^day) (25550day)[ S ] = l.g x 10~7 mglcm2^event
I event/day x 30yr x 350day/yr x 18,000cm2
(D.4)
1.8x10 7 mg/cm2-event ~n in-6 ,
C = 6 = 2.7 x 10 mglcm-
i /i\ /r\ rvoo n \ 6 x 0.91 hr x 0.58 hr
2 (1) (0.033 cm/hr)
\ 71
C = 2.7 x 10 6mg/cm3 = 2.7 [ig/L = 2.7 ppb
D-4
-------
Age-Adjusted:
BWM1J BW^
DA , = DAD x AT [
EV X ED X EF X SA EV X ED X EF X SA
c c c c a a a a
Note: age-adjusted teTel]1 for 6 years as child and 24 years as adult.
_ (6 year x I hrlevent) + (24 years x 0.58 hrlevenf)
event
30 years
hrlevent
DA = (1.9xW-5mg/kg-day) (25550day)[
1 event/day 6yr 350day/yr 6,600cm2 1 event/day 24yr 350day/yr 18,000cm2
DAevent= 7.5 x 10 mg/cm -event
7.5 x 10 me/cm -event * * n-* , 3
Cw = ° = 1.1 x 0 mg/cm
o ^^ ^nmo n \ 6 X 0.91 /Zf X 0.66 ftr
2 (1) (0.033 cmlhr) \
1.1 x W^mg/cm6 = 11 ug/L = II ppb
D-5
-------
D.2 SAMPLE NON-CANCER SCREENING CALCULATION FOR
CONTAMINANTS IN RESIDENTIAL SOIL
The equations to be used in the determination of a dermal hazard index for residential soil contamination are
outlined in Exhibit 5-1. This example uses cadmium in soil and calculates a level of concern that is equal to a hazard
index of 1. Following the four steps of the risk assessment process.
Hazard ID: cadmium has both an oral reference dose and ABSd to allow for a quantitative evaluation.
Exposure Assessment: the scenario to be evaluated is residential soil. Equations 3.11 and 3.12 are combined and
solved for the soil concentration Csoil resulting in the following.
Example Dermal Calculations Using Child, Adult, and Age-Adjusted Scenarios:
Screening
Level Equation for Dermal Contact with Non- Carcinogenic Contaminants
in Residential Soil
Equation for use with age-adjusted parameters:
^ _ THQ xRfD x BW xAT x 365 dayslyr x 106 mg/kg
'-'soil
ED x EVx EF x SA xAF x ABSd
^ THQ x RfD x AT x 365 dayslyr x 106 mg/kg
^soil
Parameter
THQ
BW
EV x EF x SFSadj x ABSd
Definition Default -
Child
Target Hazard Quotient 1
(unitless)
Body Weight (kg) 15
Default - Adult Default - Age-
Adjusted
1 1
70
D-6
-------
Parameter
AT
RfD
ED
EV
EF
SA
AF
ABS
SFSadj
Definition
Averaging Time (yr)
Reference Dose (mg/kg-
day)
Exposure Duration (yr)
Event Frequency
(events/day)
Exposure Frequency
(days/yr)
Surface Area (cm2)
Adherence Factor
(mg/cm2-event)
Absorption Fraction
(unitless)
Age- Adjusted Dermal
Factor
(see equation below)
Default -
Child
6
chemical-
specific
6
1
350
2800
0.2
chemical-
specific
-
Default - Adult
30
chemical-
specific
30
1
350
5700
0.07
chemical-
specific
-
Default - Age-
Adjusted
30
chemical-specific
-
1
350
-
-
chemical-specific
360
D-7
-------
The age-adjusted, body-part weighted dermal factor is as presented in Section 3.2.2.5.
^ + (SA7_31) x (AF7_31) x (ED7_31)
(BW7_31)
sps = (2800cm2) x (0.2mg/cm2-event) x (6yr) + (5700cm2) x (0.07mg/cm2-event) x (24yr)
adi ~ (15kg) + (10kg)
SFSad- = 360 mg-yrsl'kg-event
The dermal absorption fraction for cadmium comes from Exhibit 3-4 and is 0.001.
Toxicity Assessment: In order to determine the dermal reference dose, data from Exhibit 4-1 suggests that the
gastrointestinal adjustment for cadmium is either 5% for water or, more applicable for this example, 2.5% from food.
Therefore, the dermal reference dose is 3E-5 (mg/kg-day) using Equation 4.3, the oral reference dose of 1E-3 from
food, and a GI absorption of 2.5%. Note: since the pharmacokinetic model used to derive the oral RfD is based on
human data and the differential absorption data between different media is taken into account, the dermal reference
dose would be the same via either media, food or water.
RfDABS = RfDo x ABSGI
(Ixl03mg/kg-day) x (0.025) = 2.5x10 5mg/kg-day
Risk Characterization: Incorporating all the previous data results in the following:
D-8
-------
Child:
Sample Calculations for Exposure to a Non-Carcinogen
Cadmium
c
sml
(I) x (0.000025 mg/kg-day) x (15 kg) x (6 yr) x (365 day sly f) x (106 mglkg)
(6 yr) x (1 event/day) x (350 day sly f) x (2800 cm2) x (0.2 mg/cm2 -event) x (0.001)
Csou = 70° mglkg = 700 ppm
Adult:
(1) x (0.000025 mg/kg-day) x (70 fcg) jc (30 yr) x (365 rfqy^/yr) jc (1
(30 yr) jc (1 event/day) x (350 days/yr) jc (5700 cm2) x (0.07 mg/cm2 -event) x (0.001)
= 4'600
Age-Adjusted:
(1) x (0.000025 mg/kg-day) x (30 yr) x (365 dayslyr) x (W6mg/kg)
(1 event/day) x (350 dayslyr) x (360 mg-yr/kg-event) x (0.001)
C =2 200
'"soil A^-UU
=2,200
D-9
-------
APPENDIX E
DISCUSSION ON EVALUATING/DEVELOPING SITE-SPECIFIC
DERMAL ABSORPTION DATA
In some situations, it may be worthwhile to develop site-specific dermal absorption data during remedial investi-
gations at Superfund sites. Such data would be most useful when dermal exposure contributes significantly to the
overall risk and when the default assumptions may not be applicable. In the future, EPA plans to develop detailed
laboratory protocols for how to conduct these experiments. To help in the interim, the discussion below offers
some general principles and information sources on designing experiments and evaluating the resulting data.
Part E makes numerous references to ORD's 1992 Dermal Exposure Assessment (DEA) and is considered an
extension of the principals and methods identified in DEA for Superfund sites. Section 5.1 of the DEA presents a
strategy for reviewing data on dermal absorption of chemicals from an aqueous medium. Chapter 6 of the DEA
discusses dermal absorption from soils. The literature in this area was and still is quite sparse. Therefore, much
less detail is provided on how to evaluate soil data. These portions of the DEA should be reviewed in detail
before planning dermal absorption experiments. However, some of the general principles are summarized below:
Test skin should be healthy and intact.
Experiments should be conducted in a manner that matches exposure conditions to the extent practical. For
water contact scenarios this means using an aqueous vehicle. For soil contact scenarios, this means using a
soil load on skin and particle size that matches exposure conditions. Generally, soil loading should not
exceed a monolayer. Procedures should be used to ensure that the soil maintains close contact with skin
throughout the experiment.
In vitro tests should use continuous flow and infinite dose procedures.
In vivo tests should allow periodic collection of data to demonstrate that steady state has been achieved.
Experiments should be conducted at ambient temperatures, and volatilization should not be prevented.
Other parts or programs of EPA have published guidance on how to conduct dermal absorption studies. While
these are generally specific to products rather than contaminated soils or water, they contain some potentially
useful information for Superfund assessments and could be consulted for further guidance:
OPPTS Harmonized Test Guidelines. Series 870 Health Effects Test Guidelines-Final Guidelines. 870.7600
Dermal penetration, August 1998,
http://www.epa.gov/opptsfrs/OPPTS_Harmonized/870_Health_Effects_Test_Guidelines/Series/
EPA's Office of Pollution Prevention and Toxic Substances: Federal Register / Vol. 64, No. 110 / page 31074.
June 9, 1999. Proposed Test Rule for In Vitro Dermal Absorption Rate Testing of Certain Chemicals of Interest
to Occupational Safety and Health Administration.
Similar guidance has also been developed at the international level by the Organization of Economic Cooperation
and Development (OECD) and could also be consulted:
OECD (2000a). OECD Guideline for the Testing of Chemicals. Draft Guideline 428: Skin absorption: in vitro
method (December 2000).
E-l
-------
OECD (2000b). OECD Guideline for the Testing of Chemicals. Draft Guideline 427: Skin absorption: in vivo
method (December 2000).
OECD (2000c). Draft guidance document for the conduct of skin absorption studies. OECD environmental
Health and Safety Publications Series on Testing and Assessment No. 28 (December 2000).
OECD (2000d) Test Guidelines Program. Percutaneous absorption testing: is there a way to consensus? OECD
document ENV/JM/TG(2000)5, April 2000, Paris, France.
E-2
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