SHEDS-HT Supplemental Material

A. SHEDS-HT Code..................................................................................................................................1

B. Input Files.............................................................................................................................................2

C. Output Files.........................................................................................................................................10

D. Running the SHEDS-HT Case Study for the U.S. Population............................................................10

E. SHEDS-HT Equations........................................................................................................................12

a. Residential Media Concentrations: Reduced SHEDS-Fugacity Model..........................................12

b. Direct Pathway Exposure Methods.................................................................................................18

c. Indirect Pathway Methods: Indirect Exposure Equations...............................................................19

d. Dietary Exposure Methods..............................................................................................................20

e. Total Chemical Exposures by Route...............................................................................................21

f. Dermal Removal Processes.............................................................................................................21

g. Absorption Rates: Intake Dose Estimates.......................................................................................23

F. References...........................................................................................................................................23

G. Attachments ........................................................................................................................................23

A. SHEDS-HT Code

The SHEDS-HT Code is written in R, and is included as an attachment. The following packages, with 

their dependencies, must be downloaded and installed:

 data.table (http://cran.r-project.org/web/packages/data.table/index.html)

 gdata (http://cran.r-project.org/web/packages/gdata/index.html)

 plyr (http://cran.r-project.org/web/packages/plyr/index.html)

 ggplot2 (http://cran.r-project.org/web/packages/ggplot2/index.html

The code subroutines are included in 6 source files:

 ShedsHT.R: setup and main exposure routines

 Readdata.R: subroutines for reading SHEDS-HT input files

 Distributions.R: subroutines for generating random samples from various probability distributions

 Summarize.R: output file generation

 RunScenarios.R: subroutines for running SHEDS-HT from the batch scenarios file or for a single 

chemical

 Fugacity.R: subroutines for generating residential media concentrations using a reduced fugacitybased source-to-concentration module. 

The SHEDS-HT file structure is as follows (where ... is the installation directory):

 .../R/ SHEDS-HT code R files

 .../Inputs/ SHEDS-HT Input files

 .../Output/ Location where output exposure files are written
B. Input Files

The SHEDS-HT Input files and their contents are as follows. All SHEDS-HT default and case study input 

files are included in the attachments. 

 Physiological Parameters File (.../Inputs/bwsa.csv) Contains regression data for body weight, 

height, and basal metabolic rate as functions of age and gender. This file has been used with 

other SHEDS models including SHEDS-Multimedia.

 Diaries File (.../Inputs/diaries.csv) Contains a summary of the activity diaries from the 

Consolidated Human Activity Database (CHAD). Each record represents one 24-hour personday of data, with indicator variables for the age, gender, season, and weekday. The times (in 

minutes) in each of the SHEDS-HT microenvironments is given, along with the mean metabolic 

equivalent (METS, a multiple of basal metabolic rate) value in each microenvironment, based on 

the CHAD activity codes. The “bath” column indicates the time spent in a bath or shower, if this 

was recorded.

 Diet Diaries File (.../Inputs/diet_diaries.csv) Summary of food consumption data from the 

NHANES-What We Eat In America Study (1999-2006). Food consumption in g is given for each 

of the SHEDS-HT default food groups (Table S3) for each person in the study.

 Microenvironments File (.../Inputs/micros.csv) This small file contains a list of the 

microenvironments in SHEDS-HT, along with short descriptions of each. There is no reason to 

change this file, unless the user wanted to define new microenvironments. That would have 

several consequences. In particular, the Diaries file would need to be compatible with the new 

microenvironments by indicating the time spent in each.

 Media File (.../Inputs/media.csv) Contains contact probabilities for media (e.g. air, surfaces, 

and pet) in each microenvironment. The contact probability (contact.p) is the fraction of time 

spent in that micro in contact with that medium, and must be between zero and one, inclusive.

 Population File (.../Inputs/pop2000.csv) This file contains counts of males and females of each 

year of age from 0 to 99, from the 2000 U.S. census. These are used to generate probabilities for 

each age-gender combination. If the user is modeling a distinctive population subgroup, then this 

file should be altered or replaced with the appropriate modifications.

 Exposure Factors File (.../Inputs/ ExpFactors.csv) Contains default SHEDS-HT exposure 

factor distributions. Data sources and variables are provided in the main Exposure SAP White 

Paper.

 Fugacity Inputs File (.../Inputs/Fugacity.csv) Contains input parameter distributions for the 

SHEDS-HT fugacity module. Default values are given in Table S1. 

 Chemicals File (.../Inputs/chemprops.csv) EPI-Suite derived chemical properties for over 

144000 environmental chemicals.
 Scenarios file (.../Inputs/Scenarios.csv) Can be thought of as the main SHEDS-HT input file, 

that allows the model to generate HT aggregate exposure estimates. This file contains a 

structured listing of all exposure scenarios to be modeled, by chemical, and the input parameters 

required to parameterize the corresponding exposure equations (given in Section E). The 

scenarios are parameterized by consumer product category or food/eater group as appropriate. 

Default SHEDS-HT consumer product categories are given in Table S2; default food groups are 

given in Table S3. Consumer product use parameters for the initial SHEDS-HT case study (the 

included scenarios.csv) were determined from available data sources (including default values 

used by other screening-level models) or assumed using best judgment. The chemical 

composition data used in the case study was obtained from two existing databases of chemical 

ingredients in consumer products. The first database was EPA’s Consumer Product Chemical 

Profile Database (CPCPdb, Goldsmith et al. 2014). This database contains information on 1797 

chemicals found in 8921 consumer products derived from retailer-provided material safety data 

sheets (MSDS). The second database was the National Library of Medicine’s Household Products 

Database (NLM) which is also based on collated MSDS data. Food and water residue 

distributions were derived from the Pesticide Data Program Databases for 1997-2011 (USDA). 

The currently available exposure scenarios and a summary of their required input parameter 

distributions are:

o DIRDERM: Direct dermal (parameterized by chemical and consumer product category)

 Composition (chemical mass percent)

 Frequency of use (1/year)

 Fraction of population using product

 Mass of product used (g)

 Duration of product use (min)

 Fraction of mass in contact with skin

 Fraction of residual mass retained on skin after use

o DIRINHVAP: Direct dermal inhalation of vapor (parameterized by chemical and 

consumer product category)

 Composition (chemical mass percent)

 Frequency of use (1/year)

 Fraction of population using product

 Mass of product used (g)

 Duration of product use (min)

o DIRINHAER: Direct dermal inhalation of aerosol mass(parameterized by chemical and 

consumer product category)

 Composition (chemical mass percent)

 Frequency of use (1/year)

 Fraction of population using product

 Mass of product used (g)

 Duration of product use (min)

o DIRINGEST: Direct incidental ingestion (parameterized by chemical and consumer 

product category)
 Composition (chemical mass percent)

 Frequency of use (1/year)

 Fraction of population using product

 Mass of product used (g)

 Duration of product use (min)

 Fraction of mass used that is ingested

o INDIRECT: Post-application indirect exposure via inhaling contaminated air or 

touching contaminated surfaces (parameterized by chemical and consumer product 

category) 

 Composition (chemical mass percent)

 Frequency of use (1/year)

 Fraction of population using product

 Mass of product used (g)

o DIETARY: Ingestion via residue in food or drinking water (parameterized by chemical 

and food/water group) 

 Number of zero and non-zero measurements for food groups 

 Residue (concentration, μg /g) distribution for group

Table S1. Input variables for the fugacity module of SHEDS-HT.

Variable 

Name Description Units Value in SHEDS

AERo

air exchange rate for rooms with 

outdoors 1/d Lognormal(11.9, 1.7)

MAsf chemical mass applied to surfaces at t=0 g/m2Determined from category-specific use patterns

MAa chemical mass applied to air at t=0 μg/m3Assumed to be 0 for indirect pathways

H height of walls m Uniform(2.44,3) Assumed

Aftotal floor area of the house m

2

Lognormal(130, 1.8)

Cout chemical concentration in outdoor air μg/m3Assumed to be 0 as default

CI,a prior chemical concentration in air μg/m3Assumed to be 0 as default

CI,sf prior chemical concentration on surfaces μg/cm2Assumed to be 0 as default

CSa

chemical emission rate (source strength) 

in air

μg/m3/d

ay User supplied; not used in current case study

CSsf

chemical emission rate (source strength) 

in surfaces

μg/m2/d

ay User supplied; not used in current case study

Da chemical decay rate constant in air 1/d Determined from EPI Suite

Dsf chemical decay rate constant on surfaces 1/d

Determined from EPI Suite half-lives as described in 

main manuscript 

DCa diffusion coefficient in air m

2

/d Determined from EPI Suite

Kow octanol-water partition coefficient - Determined from EPI Suite

VP vapor pressure Pa Determined from EPI Suite

Sol solubility mol/ m

3

Determined from EPI Suite

MW molecular weight g/mol Determined from EPI Suite

CFs

organic carbon fraction for small 

particles - Normal (0.3,0.03) 

CFl organic carbon fraction for large particles - Normal (0.15,0.01) 

CLa,s

cleaning removal rate for small particles 

in air 1/d Uniform (0.018,0.22) 

CLa,l cleaning removal rate for large particles 1/d Uniform (0.03,0.5) 
Variable 

Name Description Units Value in SHEDS

in air

CLsf,s

cleaning removal rate for small particles 

on surfaces 1/d Uniform (0.035, 0.45) 

CLsf,l

cleaning removal rate for large particles 

on surfaces 1/d Uniform (0.035, 0.045) 

PDa,s air-to-floor small particle deposition rate m/d Normal (11,1) 

PDa,l air-to-floor large particle deposition rate m/d Normal (387,20) 

T indoor temperature K Normal (296,2) 

THb boundary layer thickness over surfaces m Uniform (0.025,0.0275)

THsf effective thickness of surfaces m Normal (0.0098,0.002)

Rsf,s

surface-to-air small particle resuspension 

rate 1/d Normal (0.00072, 0.00082) 

Rsf,l

surface-to-air large particle resuspension 

rate 1/d Normal (0.0015, 0.0017) 

La,s loading of small particles in air μg/m3Uniform (15, 25) 

La,l loading of large particles in air μg/m3Uniform (2.2, 2.5) 

Lsf,s loading of small particles on surfaces μg/cm2Uniform (6, 14.5) 

Lsf,l loading of large particles on surfaces μg/cm2Uniform (11.5, 28) 

Table S2. SHEDS-HT Default Consumer Product Categories.

Product Category

ARTS AND CRAFTS; ARTS AND CRAFTS FINISH

ARTS AND CRAFTS; ARTS AND CRAFTS FINISH, SPRAY

ARTS AND CRAFTS; ARTS AND CRAFTS FRAGRANCES

ARTS AND CRAFTS; ARTS AND CRAFTS PAINT

ARTS AND CRAFTS; ARTS AND CRAFTS PAINT THINNER

ARTS AND CRAFTS; ARTS AND CRAFTS PAINT, EXTERIOR

ARTS AND CRAFTS; ARTS AND CRAFTS PAINT, SPRAY

ARTS AND CRAFTS; ARTS AND CRAFTS SEALANT

ARTS AND CRAFTS; BIKE TIRE SEALER

ARTS AND CRAFTS; BODY PAINT

ARTS AND CRAFTS; CANDLE-MAKING

ARTS AND CRAFTS; CERAMICS

ARTS AND CRAFTS; DYE

ARTS AND CRAFTS; FABRIC PAINTS AND SEALERS

ARTS AND CRAFTS; FINGER PAINT

ARTS AND CRAFTS; FIXATIVE

ARTS AND CRAFTS; FLOCKING

ARTS AND CRAFTS; FOGGER

ARTS AND CRAFTS; GESSO

ARTS AND CRAFTS; GLASS ETCHING/POLISHING

ARTS AND CRAFTS; GLAZE

ARTS AND CRAFTS; MODEL ENGINE FUEL

ARTS AND CRAFTS; MODEL PAINT

ARTS AND CRAFTS; OIL PAINT

ARTS AND CRAFTS; PENS AND MARKERS

ARTS AND CRAFTS; SOAP-MAKING

AUTO PRODUCTS; ANTIFREEZE

AUTO PRODUCTS; AUTO AIR FRESHENER

AUTO PRODUCTS; AUTO DEGREASER

AUTO PRODUCTS; AUTO FLUIDS AND ADDITIVES

AUTO PRODUCTS; AUTO LUBRICANT

AUTO PRODUCTS; AUTO PAINT

AUTO PRODUCTS; AUTO REFRIGERANT
Product Category

AUTO PRODUCTS; BOAT CLEANER

AUTO PRODUCTS; BOAT ENGINE FLUIDS

AUTO PRODUCTS; BOAT PAINT

AUTO PRODUCTS; BODY REPAIR

AUTO PRODUCTS; BODY WASH OR WAX

AUTO PRODUCTS; DETAILING

AUTO PRODUCTS; MOTOR OIL

AUTO PRODUCTS; TIRE REPAIR

AUTO PRODUCTS; WHEELS

AUTO PRODUCTS; WINDOWS/WINDSHIELD

HOME MAINTENANCE; ADHESIVE

HOME MAINTENANCE; ADHESIVE REMOVER

HOME MAINTENANCE; ADHESIVE, EXTERIOR

HOME MAINTENANCE; BLEACHING OIL

HOME MAINTENANCE; CAULK REMOVER

HOME MAINTENANCE; CAULK/SEALANT

HOME MAINTENANCE; CAULK/SEALANT, EXTERIOR

HOME MAINTENANCE; CONCRETE

HOME MAINTENANCE; CONCRETE ADDITIVE

HOME MAINTENANCE; CORROSION PROTECTION

HOME MAINTENANCE; DEGREASER

HOME MAINTENANCE; DRYWALL RETARDER

HOME MAINTENANCE; ELECTRONICS LUBRICANT

HOME MAINTENANCE; FINISH

HOME MAINTENANCE; FINISH GLAZE

HOME MAINTENANCE; FINISH HARDENER

HOME MAINTENANCE; FINISH, SPRAY

HOME MAINTENANCE; FINISH, EXTERIOR

HOME MAINTENANCE; GLAZING

HOME MAINTENANCE; GROUT ADDITIVE

HOME MAINTENANCE; GROUT HAZE REMOVER

HOME MAINTENANCE; GROUT SEALER

HOME MAINTENANCE; HOME MAINTENANCE CLEANER

HOME MAINTENANCE; JOINT COMPOUND

HOME MAINTENANCE; LACQUER

HOME MAINTENANCE; LOCK DEICER

HOME MAINTENANCE; LUBRICANT

HOME MAINTENANCE; MORTAR OR GROUT

HOME MAINTENANCE; MULTIPURPOSE ADHESIVE

HOME MAINTENANCE; PAINT

HOME MAINTENANCE; PAINT ADDITIVE

HOME MAINTENANCE; PAINT CLEANER

HOME MAINTENANCE; PAINT TEXTURE

HOME MAINTENANCE; PAINT THINNER

HOME MAINTENANCE; PAINT, EXTERIOR

HOME MAINTENANCE; PAINT, INTERIOR

HOME MAINTENANCE; PAINT, SPRAY

HOME MAINTENANCE; PATCH AND REPAIR

HOME MAINTENANCE; PLASTER

HOME MAINTENANCE; PLUMBING

HOME MAINTENANCE; PORCELAIN

HOME MAINTENANCE; PRESTAIN PRODUCTS

HOME MAINTENANCE; PRIMER

HOME MAINTENANCE; PRIMER, EXTERIOR

HOME MAINTENANCE; PRIMER, INTERIOR

HOME MAINTENANCE; PRIMER, SPRAY

HOME MAINTENANCE; PUTTY OR FILLER

HOME MAINTENANCE; REFRIGERANT

HOME MAINTENANCE; ROOF

HOME MAINTENANCE; SEALANT

HOME MAINTENANCE; SOLDER
Product Category

HOME MAINTENANCE; SPRAY FOAM

HOME MAINTENANCE; STAIN

HOME MAINTENANCE; STAIN, EXTERIOR

HOME MAINTENANCE; STAIN, SPRAY

HOME MAINTENANCE; STRIPPER

HOME MAINTENANCE; STRIPPER, EXTERIOR

HOME MAINTENANCE; STUCCO REPAIR

HOME MAINTENANCE; SUPER GLUE

HOME MAINTENANCE; SURFACE SEALER

HOME MAINTENANCE; SURFACE SEALER, EXTERIOR

HOME MAINTENANCE; WELDING

HOME MAINTENANCE; WOOD ADHESIVE

HOME MAINTENANCE; WOOD PRESERVATIVE

HOME OFFICE; PRINTER INK/TONER

HOME OFFICE; WHITE OUT

INSIDE THE HOME; AIR FRESHENER

INSIDE THE HOME; ANTI-STATIC SPRAY

INSIDE THE HOME; AUTOMATIC DISHWASHING

INSIDE THE HOME; AUTOMATIC DISHWASHING ADDITIVE

INSIDE THE HOME; AUTOMATIC DISHWASHING DETERGENT

INSIDE THE HOME; BATHROOM CLEANER

INSIDE THE HOME; BLEACH

INSIDE THE HOME; CARPET CLEANER

INSIDE THE HOME; CARPET DEODORIZER

INSIDE THE HOME; CLEANER

INSIDE THE HOME; DISH SOAP

INSIDE THE HOME; DISINFECTANT

INSIDE THE HOME; DISINFECTANT, SPRAY

INSIDE THE HOME; DRAIN

INSIDE THE HOME; DRY CLEANER

INSIDE THE HOME; ELECTRONICS CLEANER

INSIDE THE HOME; FABRIC DEODORIZER

INSIDE THE HOME; FABRIC PROTECTANT

INSIDE THE HOME; FABRIC SOFTENER

INSIDE THE HOME; FIREPLACE

INSIDE THE HOME; FLOOR CLEANER

INSIDE THE HOME; FLOOR POLISH

INSIDE THE HOME; FLOOR SEALER

INSIDE THE HOME; FURNITURE WAX

INSIDE THE HOME; GARBAGE DISPOSAL DEODORIZER

INSIDE THE HOME; GLASS CLEANER

INSIDE THE HOME; GROUT CLEANER

INSIDE THE HOME; GUM REMOVER

INSIDE THE HOME; HAND CLEANER

INSIDE THE HOME; HOUSEPLANT CARE

INSIDE THE HOME; LAMP OIL/LIGHTER FLUID

INSIDE THE HOME; LAUNDRY DETERGENT

INSIDE THE HOME; LAUNDRY STAIN REMOVER

INSIDE THE HOME; LAUNDRY STARCH

INSIDE THE HOME; LEATHER CLEANER

INSIDE THE HOME; LIME REMOVER

INSIDE THE HOME; METAL POLISH

INSIDE THE HOME; OVEN CLEANER

INSIDE THE HOME; PRODUCE CLEANER

INSIDE THE HOME; SHOE POLISH OR PROTECTANT

INSIDE THE HOME; SILVER CLEANER

INSIDE THE HOME; STARCH

INSIDE THE HOME; SURFACE CLEANER

INSIDE THE HOME; UPHOLSTERY CLEANER

INSIDE THE HOME; WASHING MACHINE CLEANER

INSIDE THE HOME; WAX REMOVER
Product Category

INSIDE THE HOME; WOOD POLISH

LANDSCAPE/YARD; BUBBLE SOLUTION

LANDSCAPE/YARD; CLEANER, EXTERIOR

LANDSCAPE/YARD; COMPOST

LANDSCAPE/YARD; COMPOST TREATMENTS

LANDSCAPE/YARD; FERTILIZER

LANDSCAPE/YARD; GARDEN CARE, OTHER

LANDSCAPE/YARD; GARDEN FERTILIZER

LANDSCAPE/YARD; GRILL/CAMPING FUEL

LANDSCAPE/YARD; HERBICIDE

LANDSCAPE/YARD; HOT TUB/SPA CHEMICALS

LANDSCAPE/YARD; HUMUS

LANDSCAPE/YARD; LAWN CARE, OTHER

LANDSCAPE/YARD; LAWN FERTILIZER

LANDSCAPE/YARD; LAWN FUNGICIDE

LANDSCAPE/YARD; LAWN SEED

LANDSCAPE/YARD; LAWNMOWER FLUIDS

LANDSCAPE/YARD; MULCH

LANDSCAPE/YARD; POND TREATMENTS

LANDSCAPE/YARD; POOL CHEMICALS

LANDSCAPE/YARD; POTTING SOIL

LANDSCAPE/YARD; SKUNK ODOR REMOVER

LANDSCAPE/YARD; SURFACE DEICER

LANDSCAPE/YARD; TOOL LUBRICANT

LANDSCAPE/YARD; TOPSOIL

LANDSCAPE/YARD; TREES

PERSONAL CARE; AFTERSHAVE

PERSONAL CARE; BABY CONDITIONER

PERSONAL CARE; BABY LOTION

PERSONAL CARE; BABY OIL

PERSONAL CARE; BABY POWDER

PERSONAL CARE; BABY SHAMPOO

PERSONAL CARE; BABY WASH

PERSONAL CARE; BABY WIPES

PERSONAL CARE; BAR SOAP

PERSONAL CARE; BATH OIL/SALTS

PERSONAL CARE; BODY HAIR BLEACH

PERSONAL CARE; BODY LOTION

PERSONAL CARE; BODY MAKEUP

PERSONAL CARE; BODY POWDER

PERSONAL CARE; BODY WASH

PERSONAL CARE; BODY WIPES

PERSONAL CARE; BUBBLE BATH

PERSONAL CARE; CLIPPER LUBRICANT

PERSONAL CARE; CONDITIONER

PERSONAL CARE; CONTACT CARE

PERSONAL CARE; DENTURE PRODUCTS

PERSONAL CARE; DEODORANT

PERSONAL CARE; DEPILATORY

PERSONAL CARE; DIAPER CREAM

PERSONAL CARE; EYE MAKEUP

PERSONAL CARE; EYE PRODUCTS, OTHER

PERSONAL CARE; FACE CREAM

PERSONAL CARE; FACE MAKEUP

PERSONAL CARE; FACE WASH

PERSONAL CARE; FOOT CARE

PERSONAL CARE; FRAGRANCES

PERSONAL CARE; HAIR COLOR

PERSONAL CARE; HAIR RELAXER

PERSONAL CARE; HAIR SPRAY

PERSONAL CARE; HAIR STYLING
Product Category

PERSONAL CARE; HAND LOTION

PERSONAL CARE; HAND SANITIZER

PERSONAL CARE; HAND SOAP

PERSONAL CARE; JEWELRY CLEANER

PERSONAL CARE; KID'S FRAGRANCE

PERSONAL CARE; LICE SHAMPOO

PERSONAL CARE; LINIMENT

PERSONAL CARE; LIPS

PERSONAL CARE; MOUTHWASH

PERSONAL CARE; NAIL ADHESIVE

PERSONAL CARE; NAIL POLISH

PERSONAL CARE; NAIL POLISH REMOVER

PERSONAL CARE; SCALP TREATMENTS

PERSONAL CARE; SELF TANNER

PERSONAL CARE; SEXUAL WELLNESS

PERSONAL CARE; SHAMPOO

PERSONAL CARE; SHAVING CREAM

PERSONAL CARE; SUNSCREEN

PERSONAL CARE; TEETH WHITENER

PERSONAL CARE; TONER

PERSONAL CARE; TOOTHPASTE

PESTICIDES; ANIMAL REPELLENT

PESTICIDES; FUNGICIDE

PESTICIDES; INSECT REPELLENT

PESTICIDES; INSECT REPELLENT, EXTERIOR

PESTICIDES; INSECT REPELLENT, SKIN

PESTICIDES; INSECTICIDE

PESTICIDES; INSECTICIDE, EXTERIOR

PESTICIDES; INSECTICIDE, INTERIOR

PESTICIDES; RODENTICIDE

PET CARE; AQUARIUM

PET CARE; CAT LITTER

PET CARE; OTHER PET TREATMENTS

PET CARE; PESTICIDE, PET

PET CARE; PET SHAMPOO

PET CARE; SPOT CLEANER

Table S3. SHEDS-HT default food groups (crop groups).

Crop Group Label in SHEDS Crop Group Description

AS Asparagus

BA Banana

BF Beef

BR Brassica (Cole) Leafy Vegetables

BS Berry and Small Fruit

BV Bulb Vegetables

CF Citrus Fruits

CG Cereal Grains

CH Chicken

CV Cucurbit Vegetables

DP Dairy Products

DW Drinking Water (Direct, Indirect)

EF Edible Fungi

EG Egg

FI Fish

FV Fruiting Vegetables (except cucurbits)

GO Goat

HM Human milk
Crop Group Label in SHEDS Crop Group Description

HO Honey

HS Herbs and Spices

LE Leafy Vegetables (except Brassica vegetables)

LR Leaves of Root and Tuber Vegetables

LV Legume Vegetables (Succulent or dried)

MA Mango

MG Meat, game

NA Nongrass Animal Feeds (Forage, Fodder, Straw and Hay)*

OS Oilseeds

OT Other

PA Papaya

PE Peanut

PF Pome Fruits

PI Pineapple

PO Poultry, Other

PR Pork

RA Rabbit

RS Raisins

RT Root and Tuber Vegetables

SF Stone Fruits

SH Sheep

TN Tree Nuts

TU Turkey

*Alfalfa is only food commodity in this group

C. Output Files

The SHEDS-HT output files contain aggregate exposure percentiles (and mean/standard deviations), by 

route, for each chemical in the model run (each chemical is written to its own file). The variables included 

in the file are:

 exp.dermal: Total dermal exposure via direct and indirect scenarios (μg/day)

 exp.ingest: Total ingestion exposure via direct and dietary scenarios (μg/day)

 exp.inhal: Total inhalation exposure via direct and indirect scenarios (μg/m3)

 dose.intake: Intake dose via inhalation, dermal, and ingestion pathways (mg/kg/day)

 abs.dermal.ug: Dermally absorbed dose (μg)

 abs.inhal.ug: Inhaled absorbed dose (μg)

 abs.ingest.ug: Ingested absorbed dose (μg)

 abs.tot.ug: Total absorbed dose (μg)

 abs.tot.mgkg: Total absorbed dose (mg/kg/day)

D. Running the SHEDS-HT Case Study for the U.S. Population

Included as attachments are the SHEDS-HT input files required to run a case study of over 2500 

chemicals found in consumer products and foods. This section contains a brief descriptions of the steps 

required to run this case study for the US Population (all ages and genders).

1) Install R (and RStudio, if desired). Download and install the required R packages and 

dependencies. This is done easily by running the install.packages command from R, for example, 

install.packages(“plyr”) .
2) Download the SHEDS-HT directories (R, Inputs, and Out as described in Section A) to a local 

directory. The local directory can have any name, but for convenience will be called 

SHEDSHome here.

3) Open the main SHEDS-HT module, SHEDSHT.R. Edit the argument of the “setup” to designate 

the location of the working directory to be the path of SHEDSHome. Note that the slashes must 

be forward slashes. 

4) Source SHEDSHT.R (In RStudio, Code->Source, or use the “Source” button).

5) Run setup (In RStudio, by typing “setup()”at the prompt. This loads the required packages for the 

current R session and sources all the SHEDS-HT R code.

6) Run SHEDS-HT for all exposure scenarios in the case study scenarios file by typing 

runScenarios(size=N, runName=”Name”) where N is the number of individuals to simulate and 

“Name” is an identifier that will be appended to each output file. For example, to run a 10,000-

individual run called Base, type runScenarios(size=10000, runName=”Base”) (note run name 

must be in quotes).

The output results included in the attachment (runName “test”) are for a relatively small run of the case 

study for 1000 individuals.

The first several minutes of the run will be set time, wherein data files are read, and simulated people are 

created. Then, SHEDS-HT will begin to march through the scenarios file, calculating population

aggregate exposures for each chemical (they are index by CASRN) and writing the resulting summary 

statistics to output files. Progress is written to the R Console. The Output files are written to the 

SHEDSHome/Out directory. Each output file is named output_CASRN_Name where “Name” is the 

runName given in the runScenarios call.

SHEDS-HT does not currently contain tools for loading data for all chemicals and performing 

visualizations or analyses; this must be done by the user outside of the program.

The SHEDS-HT case study can be run with other settings (e.g. different age/gender groups) by updating 

the settings in the getScenSpecs subroutine in ReadData.R, sourcing that file, and calling runScenarios 

again. Future versions of the code will have the ability to update these parameters in a more convenient 

manner. Some key settings that can be changed are:

 runSeed This is a number from 1 to 2147483647, used as the initial random number seed for the 

run. If output from two model runs for the same chemical is to be combined into a single data set, 

the runSeeds for the two runs should be different.

 minAge The smallest age to simulate. Must be an integer. Age=0 refers to all children under 12 

months.

 maxAge The maximum age to simulate. Must be an integer and cannot exceed 99. Centenarians 

are considered to remain age 99 indefinitely.

 Genders One of “F”, “M”, or c(“F”,”M”), for females, males, or both, respectively. The quotes 

are required. The c() function forms a list of strings.

 seasonsThe seasons are “W” (winter: Dec, Jan, Feb), “P” (spring: Mar, Apr, May), “S” (summer: 

Jun, Jul, Aug), and “F” (fall: Sep, Oct, Nov). If two or more seasons are to be modeled, combine 

them with the c() function. For example, seasons=c(“P”,”S”) for spring and summer, or 

seasons=c(“W”,”P”,”S”,”F”) for all.

 ageMatchPct This is the maximum percentage mismatch allowed in age when choosing an 

activity diary. For example, if the simulated person is age 50 and ageMatchPct=10, then activity 

diaries from persons age 45 to 55 (inclusive) may potentially be selected. The window is rounded 
to the nearest integer at both ends. The greatest difficulty is in matching the oldest persons. To 

always have suitable diaries available for all seasons, day types, and genders, using the default 

diary database, the minimum value is ageMatchPct=11. The default value is 15. For runs 

restricted to young people, there are many suitable diaries of the correct age, and is it possible to 

set ageMatchPct=0 to force an exact match.

E. SHEDS-HT Equations

a. Residential Media Concentrations: Reduced SHEDS-Fugacity Model 

The simplified, screening-level, version of the SHEDS-Fugacity model incorporated in SHEDS-HT has 

just two compartments: air and floor. Subscripts for the two model compartments are “a” (air) and “sf” 

(surfaces). Subscripts for large and small particles are given as “l” and “s.” Variable names and 

definitions for the required inputs are given in in Section B. The equations are given below.

Particle Masses and Cleaning Rates

Volume of air compartment (m3):

		 Va= Af ×	H (1)

Small and large particle masses in air (μg):

MPa,s		= Va ×	La,s (2)

MPa,l		= Va ×	La,l (3)

Small and large particle masses on surfaces (μg); 1E4 factor is for units conversion (cm2to m2):

MPsf,s		= Af ×	1E4	×	Lsf,s (4)

MPsf,l =		Af ×	1E4	×	Lsf,l (5)

Cleaning rates from surfaces for large and small particles (1/day). These are sampled from the input 

distributions, but then constrained to force particle mass balance as below:

CLsf,s		 ≥ PDa,s ×	La,s /	(1E4	×	Lsf,s) – Rsf,s (6)

CLsf,l		 ≥ PDa,l ×	La,l /	(1E4	×	Lsf,l) – Rsf,l (7)

Cleaning rates from air for large and small particles (1/day). These are sampled from the input 

distributions, but then constrained to force particle mass balance as below:

CL,a,s		 ≥ (Rsf,s × MPsf,s - PDa,s	× La,s ×	Af)/	MPa,s		 (8)

						 CL,a,l		 ≥ (Rsf,l × MPsf,l - PDa,l	× La,l ×	Af)/	MPa,l (9)
Partition Coefficients

Conversion factor between μg and moles (μg/mol):

ugmol	 =1E6	× MW (10)

Air/surface partition coefficient (derived from the mean of the expressions for vinyl and carpet from 

Bennett and Furtaw, 2004):

Ka_sf=	82500	×	VP-0.65 (11)

Air/particle partition coeffcient for small and large particles (m3/μg), where the gas constant Rgas=8.314 

Pa-m

3

/(mol-K):

Kp,s =

1.6625E−12×Kow×Rgas×T×CFs

VP

(12)

Kp,l=

1.6625E−12×Kow×Rgas×T×CF

VP

(13)

Fugacity Capacities and Fugacity to Mass Ratios

Fugacity capacity of air ([mol/(Pa m3)]:

Za,b=		



×

(14)

Fugacity capacity of bulk surface compartment ([mol/(Pa m3)]:

Zsf,b= Ka_sf ×	Za,b (15)

Ratio of mass to fugacity (ZV, in μg/Pa) for bulk (vapor phase) air:

ZVa =		Za,b ×	Va×	ugmol (16)

Ratio of mass to fugacity (ZV, in μg/Pa) for surfaces:

ZVsf,b		=		Zsf,b ×	Af ×	THsf ×	ugmol (17)

Ratio of mass to fugacity (ZV, in μg/Pa) for small and large particles in the air compartment:

ZVa,s		=	ZVa,b		×	Kp,s ×	La,s (18)

ZVa,l		=	ZVa,b		×	Kp,l	×	La,l (19)

Unit capacities of large and small particles (fugacity capacity per unit mass, in 1/Pa): 

CPs		=	Za ×	Kp,s ×	ugmol	=	1.6625E−6×MW×Kow×CFs×Sol

VP

(20)
CPl		=	Za ×	Kp,l	×	ugmol	=	1.6625E−6×MW×Kow×CFl×Sol

VP

(21)

Ratio of mass to fugacity (ZV, in μg/Pa) for small and large particles in the surface compartment:

ZVsf,s =	CPs ×	MPs,s		 (22)

ZVsf,l=	CPl ×	MPs,l		 (23)

Ratio of mass to fugacity (ZV, in μg/Pa) and fugacity to mass (iZV, Pa/ μg) for entire air compartment 

(sum of phase-specific ZV):

ZVa=	ZVa,b	+	ZVa,s+ZVa,l (24)

iZVa=	(ZVa,b	+	ZVa,s+ZVa,l)

-1 (25)

Ratio of mass to fugacity (ZV, in μg/Pa) and fugacity to mass (iZV, Pa/ μg) for entire surface 

compartment (sum of phase-specific ZV):

ZVsf=	ZVs,b	+	ZVs,s+ZVs,l (26)

iZVsf =	(ZVsf,b	+	ZVsf,s+ZVsf,l)

-1 (27)

Chemical Flows

Given the chemical mass in the air compartment Ma and the surface compartment Msf, chemical flow via 

small and large particles (μg/day) from the air compartment due to any process X, either deposition (PD) 

or cleaning (CL):

QX,a,s	=	Ma ×	MPa,s ×	iZVa ×	CPs ×	Xa,s	 (28)

QX,a,l	=	Ma× MPa,l ×	iZVa ×	CPl ×	Xa,l (29)

Chemical flow (μg /day) to the air from the surface compartment is given by the following, where the 

process X is either resuspension (R) or cleaning (CL):

QX,a,s	=	Msf ×MPsf,s ×	iZVsf ×	CPs ×	Xsf,s (30)

QX,a,l	=	Msf ×MPsf,s×	iZVsf ×	CPl ×	Xsf,l (31)

Chemical flow (μg/day) due to bulk air movement is given by the following equations. Flow from air to 

outdoors:

Qa_o,b			=		Ma ×	AERo (32)

Flow from outdoors to indoor air:

Qo_a,b			=		Cout ×	AERo ×	Va (33)
Transfer factors between air and surface (see Bennett and Furtaw, 2004) and diffusive flows from air to 

surfaces and surfaces to air:

Ya_sf		=		min	[DCa ×	Za /	THb,	0.0135 ×	(VP)-0.32] (34)

Qa_sf,df						=		Ma ×	Af ×	iZVa ×	ugmol	×	Ya_sf (35)

Qsf_a,df						=		Msf ×	Af ×	iZVsf ×	ugmol	×	Ya_sf (36)

Summary of Chemical Flows

Table S4 summarizes all the chemical flows in the system that are proportional to the chemical mass in 

the “from” compartment (source terms are handled below). 

Table S4. Summary of chemical flows in the fugacity module of SHEDS-HT

To From Mechanism Chemical Flow Rate 

(per unit chemical mass in 

'from' compartment)

surfaces air small particles-deposition Af	 ×	La,s	× iZVa × CPs × PDa,s

surfaces air large particles-deposition Af	 ×	La,l × iZVa ×		CPl × PDa,l

surfaces air diffusion Af ×	iZVa × ugmol	× Ya_sf		

outdoors air bulk flow AERO

loss air small particles-cleaning MPa,s ×	iZVa × CPs × CLa,s

loss air large particles-cleaning MPa,l ×	iZVa × CPl × CLa,l

loss air degradation Da

Air surfaces small particlesresuspension

MPsf,s ×	iZVsf ×	CPs ×	Rsf,s

Air surfaces large particlesresuspension

MPsf,l ×	iZVsf ×	CPl ×	Rsf,l

Air surfaces diffusion iZVsf × Af × ugmol	× Ya_sf		

loss surfaces small particles-cleaning MPsf,s ×	iZVsf x	CPs ×	CLsf,s

loss surfaces large particles-cleaning MPsf,l ×	iZVsf x	CPl ×	CLsf,l

loss surfaces degradation Dsf

Construction of Jacobian Matrix

Define the following composite expressions to simplify the construction of the equations in the Jacobian 

matrix for solution of the system:

CLa =	iZVa	×	(MPa,s×CPs×CLa,s+	MPa,l×CPl×CLa,l) (37)

CLsf =	iZVsf×	(MPsf,s×CPs×CLsf,s+	MPsf,l×CPl×CLsf,l) (38)

Dep =	iZVa	×	Af ×	(La,s×CPs×DPa,s+	La,l×CPl×DPa,l) (39)

Res =	iZVsf	×	Af×	(MPsf,s ×CPs×Rsf,s+	MPsf,l ×CPl×Rsf,l) (40)

Diffsf =	iZVsf	×	ugmol×Af× Ya_sf		 (41)
Diffa =	iZVa ×	ugmol×Af× Ya_sf		 (42)

The Jacobian elements are then given by:

J1,1 =	AERo+	Da +	CLa +	Dep +	Diffa (43)

J	1,2 =	−(Res+Diffsf) (44)

J	2,1 =	−(Dep+Diffa) (45)

J	2,2 =Dsf +	CLsf +	Res+	Diffsf (46)

In addition, there may be chemical source terms in each compartment. These are chemical inflows that are 

constant in time and do not depend on the amount of chemical in any compartment. There are only three 

such terms - two corresponding to the air compartment and one to surfaces. The air compartment may 

have inflow from outdoor air, or an in-home source, or both. The floor compartment may have a single 

source term. All source terms have units of [μg /d]:

S1=	Cout ×	AERo ×	Va +	CSa×	Va (47)

S2=CSa×Af (48)

Solution of the Model

The equation for the system of masses in each compartment is

d()

dt

= −J M(t)+S (49)

Separating the chemical mass vector M(t) into a time-dependent part MT(t) and a constant part MC :

M(t)	=	MT(t)+ MC (50)

Then

()

 = − J (t) (51)

and 

J MC=	S (52)

The mass vectors M(t), MT(t), and MC , along with the source vector S, are 2x1 vectors with the first 

component representing the air compartment and the second representing the floor compartment. The 

Jacobian matrix J is 2x2. These equations are simple enough that the solutions may be given explicitly. 

Let the initial masses in the air and floor compartments be m0,a and m0,sf, respectively, in units of 

micrograms. In summary, let

r = (J)

 + 4 (JJ) − 2 (JJ) + (J) (53)
mc = (J × S − J × S) / (J × J − J × J) (54)

mc = (−J × S + J × S) / (J × J − J × J) (55)

mt, = m, – mc(56)

mt0,f = m0,f – mcf(57)

The eigenvalues and eigenvectors of the Jacobian matrix are

λ = (J + J + r) ⁄ 2 (58)

λ = (J + J − r) ⁄ 2 (59)

 = 





 = 

 + J − J

2 J

 (60)

 = 





 = 

 − J + J

−2 J

 (61)

The determinant of the eigenvalue matrix is  =  −  = −4 J .

In general, the initial state is a mix of the two eigenstates with amounts given by the constants 

, , , and . Each eigenstate decays exponentially at a rate that depends on its eigenvalue:



() = k e

  + k e 

(62)



() = k e

  + k e 

(63)

After some algebra, these constants are found to be

k =





mt, −





mt,(64)

k = −





mt, +





mt,(65)

k =





mt, −





mt,(66)

k = −





mt, +





mt,(67)

These equations determine the time-dependent mass MT(t). The total chemical mass in each compartment 

is then MT(t)+MC:

ma(t) = mc + k e

  + k e 

(68)

mf(t) = mc + k e

  + k e 

(69)

For each person in the simulation, for each indirect scenario, the time t is determined by sampling a 

uniform distribution from t=0 to 

t=356/FR (70)
where FR is the frequency of use of the product containing the chemical. Corresponding air and surface 

concentrations for the selected time point are then calculated, and exposures via the indirect pathway are 

calculated as described in Section c below.

b. Direct Pathway Exposure Methods

For each simulated individual, exposure via the direct pathway (dermal route) is calculated as 

E, = U × prob 



 × M × F × F × F × 1E6 (71)

ED,derm is the effective dermal exposure in μg on the simulated day. Fcomp is the mass fraction of chemical 

in the applied product, Fcont is the fraction of the mass of the product used that comes in contact with the 

skin, and Fret is the fraction of product retained on the skin after the direct use event (i.e. not washed off). 

Fcont and Fret are product category dependent. U is either zero or one, based on a Bernoulli (binomial)

sample using the usage prevalence (PR), which is the fraction of the population using the product. FR is 

the usage frequency, expressed as the average number of uses per year, for users. M is the mass of the 

given product applied on a usage day [g]; 1E6 converts g to μg. The prob function (which stands for 

probabilistic rounding) takes one or more real arguments and randomly selects one of the integers on 

either side of the value, using the distance to the integers as weights. For example, if the argument is 0.7, 

then prob(0.7) returns a value of one 70% of the time, and a value of zero the other 30% of the time. Thus 

the prob function determines the number of product usage events on the modeled day.

Exposure for the ingestion route of the direct pathway (ED,ing, μg) is:

E, = U × prob 



 × M × F × F × 1E6 (72)

The only difference between this equation and the above dermal equation is the replacement of Fret by 

Fing, the fraction of the applied product mass that is ingested. 

For the inhalation of vapor scenario, SHEDS-HT calculates an estimate of the evaporation amount from 

standard chemical properties. It is assumed that the evaporation rate is proportional to the vapor pressure, 

a refinement of an instantaneous release assumption. A standard is set for this by assuming that a 

chemical with a vapor pressure (VP) equal to total atmospheric pressure would fully evaporate in one 

minute (if there was enough air to avoid saturation). The air concentration in μg /m3is given by

C, = M × F ×





× D ×





× 1E6 (73)

The Paterm is atmospheric pressure, D is duration of use in minutes, and Vevap is the volume into which 

the evaporation occurs, which is assumed to be room volume of 5 m3in SHEDS. The calculated CA value

is compared to the saturation air concentration which may not be exceeded, no matter how much chemical 

is present. The daily inhalation exposure (ED,vap, μg) is: 

E, = U × prob 



 × C, ×





× BVA × PAI (74)

D is the duration of the direct use in minutes; dividing by 1440 gives fraction of the day. The parameter 

BVA is the basal alveolar ventilation rate in cubic meters of air per day, which is a function of the 

person’s age, gender, and body weight. The physical activity index (PAI) is the duration-weighted 

average breathing rate expressed as a unitless multiple of the basal rate. The PAI for each person for each 

micro is supplied by the activity diary summary file, and was determined from the metabolic equivalent 
(METS) values associated with each CHAD activity. PAI and BVA are determined for each person from 

the CHAD diary using methods that have been previously described (Glen et al., 2012). 

The other direct inhalation scenario is the inhalation of aerosols or sprays. This is generally similar to 

vapor inhalation, except that the airborne concentration depends on the formation and release of droplets, 

rather than on vapor pressure. Air concentration (μg /m3) in this case is given by: 

C, =

××



× 1E6 (75)

The default values for cloud volume Vcloud and airborne fraction Fairb are equivalent to those used in 

ConsExpo exposure model (Delmaar et al. 2005). The corresponding inhalation exposure ED,aer is then 

given by an equation analogous to eq. 74.

c. Indirect Pathway Methods: Indirect Exposure Equations

Exposure to an indirect source results when a person encounters the specified chemical in the residence 

after its direct use, or “post-application”. SHEDS-HT uses a set of generic microenvironments (hereafter 

called “micros”) to determine the simulated person’s surroundings and the amount of chemical present. 

The model uses summaries of CHAD activity diaries to determine the amount of time spent in each micro 

by the simulated person. Exposure occurs as individuals contact different media within the 

microenvironment. These media can be user-defined but are typically air, surfaces (including floors), and 

pets. In this case study, only surfaces and air media are used; any products used on pets are assumed to be 

applied to surfaces as no distinction was made in these runs between transfer rates or contact probabilities 

for pets versus surfaces. Exposure is proportional to both the contact time and the concentration

(calculated from the fugacity module), and also depends on behavioral factors such as a transfer 

coefficient or chemical factors (such as the availability for potential transfer). The indirect pathway 

exposures in SHEDS-HT are daily totals over all the micros, and are expressed as four specific routes: 

dermal, inhalation, hand-to-mouth (non-dietary) ingestion, and object-to-mouth (non-dietary) ingestion.

Inhalation exposure via the indirect pathway is given by 

E, =

,×



× BVA × PAI (76)

where CA,I is the average daily air concentration in the residence due to indirect sources (μg /m3), D is the 

duration of time spent in the residence (min) and BVA x PAI is the daily volume of inhaled air (m3) as 

described above. 

The indirect dermal route refers to chemical getting on the skin by touching contaminated surfaces. The 

dermal exposure in SHEDS-HT is the amount of chemical transferred onto the skin (per day), regardless 

of what happens to that chemical later. The dermal dose is the amount of chemical that enters the body by 

being absorbed through the skin. Typically, only a few percent of the dermal exposure becomes dermal 

dose. The remainder can be washed off, ingested (by hand-to-mouth contact), or removed without 

washing by dermal brush-off. The dermal dose and hand-to-mouth exposure both depend on the dermal 

exposure and on the size of the competing removal terms. Dermal exposure via the indirect route (μg/day) 

due to contact with surface media is given by:

E, = C × D × F ×





(77)
The available fraction Favail gives the fraction of the chemical present on surfaces that can be removed by 

touching. The transfer coefficient TCderm quantifies the rate of transfer of chemical (cm2/hr). The 

parameter Dcis the contact duration with surfaces (min/day), and 60 is a min/hr conversion factor. 

Contact durations are calculated as the product of the contact probability for the media and the time spent 

in the microenvironment by that person.

Exposure via the object-to-mouth route is given by 

E = E × F (78)

This equation allows the object-to-mouth exposure pathway to be parameterized in terms of the indirect 

dermal exposure plus one route-specific fraction (FOM). An appropriate distribution of FOM was 

determined from SHEDS-Multimedia, which uses a more complex equation on a more finely resolved 

time-step to model the object-to-mouth pathway. 

The hand-to-mouth and object-to-mouth exposures are combined to give non-dietary (indirect) 

ingestion exposure:

E, = E + E (79)

Hand-to-mouth exposure EHM is considered a chemical removal process in SHEDS-HT and is described 

below.

d. Dietary Exposure Methods

Dietary exposures in SHEDS-HT are calculated by determining the total mass of a chemical present in the 

food eaten by a simulated person within a day. SHEDS-Multimedia considers on the order of 450 

different food commodities that may contain chemical, and requires a distribution of chemical residues 

for each. SHEDS-HT has simplified this approach by considering larger food groups, specifically a set of 

41 crop groups and drinking water. The list of crop groups is given in Table S3. These default groups 

allows the user to input fewer chemical residue distributions while still maintaining variability in residues 

across food types due to differences in agricultural treatments or packaging. 

Default food intake information in SHEDS-HT is also provided on a crop-group level. The SHEDS-HT 

intake diaries were developed from the National Health and Nutrition Examination Survey - What We Eat 

in America (NHANES-WWEIA) two-day food diaries. Each NHANES food diary was processed to 

calculate the mass of each crop group consumed. The diaries are stored in SHEDS-HT by age and gender, 

and are sampled for each simulated individual in a manner analogous to the CHAD activity diaries. When 

distributions of chemical residues in each crop group (CG) are also supplied as input, daily dietary 

exposures can be calculated as

E = M × C + ∑ M ×



 C (80)

where drinking water and crop group residue concentrations (Cw and Ccg, μg/g) are sampled once per 

person and the consumed mass of water and crop group (Mw and Mcg, g) are obtained from the sampled 

food diary for the individual.
e. Total Chemical Exposures by Route

The SHEDS-HT model is linear; total exposure for each route (inhalation, dermal, and ingestion) are 

summed over the available pathways. Total inhalation exposure for a given scenario is the sum of the 

exposures due to direct inhalation of aerosol, direct inhalation of vapor, and inhalation of chemical from 

indirect sources:

E = E, + E, + E, (81)

Total ingestion exposure is the sum of exposures due to incidental ingestion during direct use, dietary 

ingestion, and ingestion of chemical with indirect sources (via hand-to-mouth and object-to-mouth 

pathways): 

E = E, + E +E, (82)

Total dermal exposure is given by the sum of the dermal exposures due to direct and indirect sources:

E = E, + E, (83)

This dermal exposure can be thought of the as the total mass of new chemical that ends up on the skin 

over the simulated day. This chemical can subsequently be removed by the processes described below. 

Finally, the total route-specific exposures across all scenarios are summed to get total chemical exposure 

for each pathway:

E, = ∑ E





(84)

E, = ∑ E





(85)

E, = ∑ E





(86)

Here J is the number of scenarios present for the chemical. In the case of consumer products, multiple 

scenarios will exist for each type of product containing the chemical.

f. Dermal Removal Processes

There are five competing processes for removing chemical from the surface of the skin: 1) dermal 

absorption, 2) hand-to-mouth transfer, 3) bathing, 4) hand washing, and 5) brush-off. One of the 

distinctive features of all the SHEDS models is that more frequent hand washing and/or bathing will 

lower both the dermal dose and the hand-to-mouth exposure. Even though SHEDS-HT is a simpler model 

than the other SHEDS models, it was considered necessary to maintain these features. Chemical removal 

by each of these five processes is modeled as a fraction of the dermal exposure from all direct and indirect 

scenarios:

R = E, × F (87)

Where F = FHM (hand-to-mouth transfer), FA,derm (dermal absorption), FHW (hand washing), FBA

(bathing), or FBO (brush off). As noted earlier, the SHEDS-HT exposure module models one day per 

person, in a single time step. SHEDS-Multimedia included the potential of carryover of dermal loading of 

chemical from one event to the next, and from one day to the next. As part of the SHEDS-HT 
simplification, it is implicitly assumed that the modeled day in SHEDS-HT ends with the same carryover 

as it began. The total chemical removed from the skin equals the new exposure on the modeled day, thus, 

F + F, + F + F + F = 1 (88)

The means of the five F distributions sum to one. However, because the F values are randomly sampled, 

the five random samples will (almost) never sum to exactly one. Hence, the sampled values are 

interpreted as relative contributions to the removal. Each sample value is divided by the sum of the five, 

to force the standardized fractions to sum to unity. Each of the five removal processes is assigned an 

amount equal to its standardized fraction of the dermal exposure. 

For the hand-to-mouth pathway, the exposure is the amount of chemical entering the gastrointestinal (GI) 

tract after removal from the hands. Thus,

E = E, × F (89)

FHM is a function of the hand-to-mouth frequency (FreqHM) and the fraction of the hand area entering the 

mouth (AHM), both of which are SHEDS-HT inputs. The relationship between these input parameters and 

daily-level estimates of FHM were estimated from runs of SHEDS-MM (which operates on a more detailed 

event-level time scale). The fitted relationship is:

F = R × e

/ × A × Freq (90)

where RHW is the fraction of chemical removed in a single handwash (an input) and NHW is the sampled 

number of handwashes per day for the simulated person (based on the input parameter FreqHW, the 

frequency of handwashing). The daily removal fraction due to handwashing (FHW) was fit in a similar 

manner using SHEDS-MM results. The resulting relationship is

F = R × 1 − e

/.

 (91)

The dermal dose is the amount of chemical absorbed into or through the skin. Thus,

D = E, × F, (92)

FBA and FBO are inputs to the model; FBO is > 0 on every simulated person-day, and FBA is > 0 if a bath 

occurs on the simulated person-day. A bath/shower (on days when it occurs) will remove 70% of that 

day’s dermal exposure, on average. In reality, the amount removed would depend on whether the 

exposure occurs primarily before or after the bath or shower. However, SHEDS-HT considers a whole 

day to be a single modeling time step, and there is no explicit sequence to the contact and removal 

processes. SHEDS-HT implicitly accounts for such effects in the variability distribution for the removal

terms.

Since a bath removes 70% on average, the other four removal processes total only 30% on bath days (on 

average), but they total 100% on non-bath days. Therefore, on average the absorbed dermal dose and the 

hand-to-mouth transfer are substantially higher on non-bath days. Similarly, the fraction removed by hand 

washing has a higher mean on days when the number of hand washings is higher. Again, the dermal dose 

and the hand-to-mouth transfer are substantially higher on days with little or no hand washing.
g. Absorption Rates: Intake Dose Estimates

SHEDS-HT uses simple fractions to track the fate of chemical once it has entered the body. Dermal 

absorption is one of the competing removal processes discussed above (eq. 92). For inhalation, the 

amount absorbed is given by:

D = E, × F, (93)

Similarly, for ingestion the absorbed dose is given by:

D = E, × F, (94)

The total absorbed (intake) dose is the sum over the inhalation, ingestion, and dermal pathways:

D = D + D + D (95)

All of the variables above have units [μg/day]. The current approach of assigning a distribution of 

absorption rates will be retained while chemical-property-related (QSAR-based) approaches are 

investigated for these pathways.

F. References

1. Goldsmith, M.R., et al., Development of a consumer product ingredient database for chemical 

exposure screening and prioritization. Food Chem Toxicol, 2014. 65: p. 269-79.

2. NLM. The Household Products Database-National Library of Medicine. 2013; Available from: 

http://householdproducts.nlm.nih.gov/.

3. USDA. Pesticide Data Program. 2013; Available from: http://www.ams.usda.gov/AMSv1.0/pdp.

4. Glen G, Zartarian V, Smith L, and Xue J. The Stochastic Human Exposure and Dose Simulation 

Model for Multimedia, Multipathway, Chemicals (SHEDS-Multimedia): Residential Module. 

SHEDS-Residential version 4. Technical Manual. Office of Research and Development, US EPA. 

2012. Available at: http://www.epa.gov/heasd/research/sheds/user_information.html.

5. Delmaar, J., M. Park, and J. van Engelen, ConsExpo 4.0 Consumer Exposure and Uptake Models 

Program Manual. RIVM report 320104004/2005. 2005, National Institute for Public Health and the 

Environment.

G. Attachments

SHEDS-HT Code, Input Files, and Case Study Results for a population of 1000 individuals.