IC-BODYWT--The average body weight of individuals for the current exposure location Units: kilograms
Range: between 1 and 100
Enter the average body weight for the current exposure location. The MEPAS
user interface will prompt the user to enter the data for each location for the
current transport type. The default value for this parameter is 70 kg
representing the standard man calculation (EPA 1991). To
simulate exposure of a child, this parameter can be set to a smaller value, such
as 10 kg. If younger age groups are to be simulated, care must be taken to also
adjust other age dependent parameters, including inhalation rate, exposure
duration and food, water, and soil ingestion rates.
IC-EXPDUR--Exposure duration for individuals at the current usage location Units: years
Range: between 1 and 100
Enter the exposure duration for individuals being described for the current
usage location. As an example of the use of the two parameters defined in this screen,
consider the estimation of risk from soil ingestion to a young child for the
period of 1 to 6 years of age (inclusive) for measured soil concentrations. The
exposure duration is 6 years and the average weight for this age is 15 kg. The
parameters are set as follows:
IC-BODYWT = 15 kg, IC-EXPDUR = 6 yrs
A soil ingestion rate of 200 mg/d or 0.2 g/d is recommended by EPA for this
age group. The soil ingestion rate is set in the 'Customize' screen on the
'soil' tab, parameter 'soil ingestion rate'. Use of these parameter values will
provide an estimate of risk to young children for soil ingestion of
chemicals. Note that the International Commission on Radiological
Protection (ICRP) dose factors and EPA slope factors are primarily based on
exposure to adults and thus can not be used to estimate risk to young children
from exposure to radionuclides.
IC-DERM--Water dermal absorption model
This pull-down menu box allows selection of the method to estimate intake by
dermal absorption. Two methods are available: the EPA dermal absorption
model or the linear model. The EPA dermal absorption model may be used
for organic chemicals that have a value defined for octanol-water partition
coefficient. If no value is available for octanol-water partition
coefficient, then the linear model is used. The linear model is also used
for all inorganic chemicals and radionuclides, no matter which option is
selected here.
IG-UDWGW--Drinking water ingestion rate of ground water Units: liters per day (L/d)
Range: 0.0 to 10.0
Default Value: 1.4
The daily water ingestion by the exposed individual represents the water
intake from all used of domestic water. The intake includes drinking
water, use of water in cooking, and use of water to prepare beverages (coffee,
tea, reconstituted juices, etc.). The default value is based on
recommendations of the (EPA 1997 (Vol.1)).
IW-UDWSW--Drinking water ingestion rate of surface water Units: liters per day (L/d)
Range: 0.0 to 10.0
Default Value: 1.4
The daily water ingestion by the exposed individual represents the water
intake from all uses of domestic water. The intake includes drinking
water, use of water in cooking, and use of water to prepare beverages (coffee,
tea, reconstituted juices, etc.). The default value is based on
recommendations of the (EPA 1997 (Vol.1)).
IC-TAGE1--Age of receptor at start of exposure Units: yr
Range: 0.0 to 100
Default Value: 0 (EPA 1991)
The parameters TAGE1 and TAGE2 are used to specify the age range of the
exposed individual. TAGE1 being the lower age range limit and TAGE2 being
the upper age range limit. This is useful if an assessment is being
performed to address the impacts to a specific age group. For example, if
an industrial usage scenario is being modeled, the user may want to specify
that only 25 to 55 year olds will be exposed. In this case, TAGE1 would
be 25 and TAGE2 would be 55.
IC-TAGE2--Age of receptor at end of exposure Units: yr
Range: TAGE1 + 1 to 100
Default Value: 70 (EPA 1991)
The parameters TAGE1 and TAGE2 are used to specify the age range of the
exposed individual. TAGE1 being the lower age range limit and TAGE2 being
the upper age range limit. This is useful if an assessment is being
performed to address the impacts to a specific age group. For example, if
an industrial usage scenario is being modeled, the user may want to specify
that only 25 to 55 year olds will be exposed. In this case, TAGE1 would
be 25 and TAGE2 would be 55.
HE-INHAL--Selection Index for Inhalation Impact Analysis Units: none
Range: "average daily intake" or "air concentration"
Default Value: "air concentration"
The parameter INHAL is used to select the method for evaluation of human
impacts from inhalation exposure pathways. There are two options: average
daily intake or air concentration. When average daily intake is selected
the health impacts are to be based on the average daily intake rate (mg/kg/day)
and either the inhalation slope factor for carcinogenic chemicals or the
inhalation reference dose for other chemicals. When "air
concentration" is selected, the health impacts are to be based on the air
concentration (mg/m^3) at the exposure location and either the inhalation unit
risk factor or the inhalation reference concentration. Use of this
parameter must be coordinated with the model selected under the health impacts
component. When the MEPAS components are used for both the receptor and
impacts analysis, non-zero results for chemicals will only be obtained for
inhalation if the selection flags agree (i.e., both "average daily
intake" or both "air concentration".
INTAKE MODULE CUSTOMIZATION
The parameters available under this option allow modification of additional
intake parameters that are normally represented by default values.
AIR EXPOSURE TAB
IC-UBR--Inhalation rate for general exposure to contaminated air Units: cubic meters per day (m3/d)
Range: 0.0 to 50.0 m3/d
Default Value: 15.2 m3/d
The inhalation rate is the daily average rate of air intake and is used to
estimate inhalation intake of pollutants from the air inhalation exposure
pathway. The default value is recommended by (EPA (1997) Vol.1).
IC-UBRES--Inhalation rate for resuspension pathway Units: cubic meters per day (m3/d)
Range: 0.0 to 50.0 m3/d
Default Value: 15.2 m3/d
The individuals exposed to airborne resuspended contamination are exposed
when they inhale particulate materials. The inhalation rate gives the
daily average intake rate for exposure to this pathway. The default value
represents the average daily inhalation rate recommended by (EPA
(1997) Vol.1).
IC-FREQINH--Annual frequency factor for air inhalation Units: dimensionless
Range: 0.0 to 1.0
Default Value: 1.0
The exposure pathway annual factors represent the fraction of days in a year
that exposure occurs to each exposure pathway. For example, if a person
is present at the exposure location 350 days in a year (EPA
1991), the annual factor would be calculated as 350/365.25 = 0.9582.
The default value is set to 1 (exposure every day during a year).
IC-FREQSL--Annual frequency factor for soil resuspension inhalation Units: dimensionless
Range: 0.0 to 1.0
Default Value: 1.0
The exposure pathway annual factors represent the fraction of days in a year
that exposure occurs to each exposure pathway. For example, if a person
is present at the exposure location and inhales resuspended soil 180 days in a
year, the annual factor would be calculated as 180/365.25 = 0.4928. The
default values are set to 1 (exposure every day during a year).
IC-FREQEXT--Annual frequency factor for air external exposure Units: dimensionless
Range: 0.0 to 1.0
Default Value: 1.0
The exposure pathway annual factors represent the fraction of days in a year
that exposure occurs to each exposure pathway. For example, if a person
is present and subject to air exposure 350 days in a year (EPA
1991), the annual factor would be calculated as 350/365.25 = 0.9582.
The default values are set to 1 (exposure every day during a year).
EXTERNAL GROUND DOSE TAB
The shielding factors and time fractions for indoor and outdoor activities
are used to estimate the external dose from ground contamination. This
allows the user to apply appropriate shielding corrections for the type of
dwelling under consideration. The shielding factor is multiplied by the
unshielded dose rate to obtain the dose rate for the activity (indoors or
outdoors). The time fractions indicate the relative amount of time the
individual spends indoors and outdoors. The default value for shielding
factor outdoors (1.0) represents no reduction in dose rate.
IC-FTI--Fraction of time spent indoors Units: none
Range: 0.0 to 1.0
Default Value: 0.875
Limitation: IC-FTI + IC-FTO <= 1.0
This parameter is the fraction of time that the exposed individual spends
indoors on a daily average (EPA 1997 (Vol.3)).
IC-SHI--Shielding factor for indoor exposure Units: none
Range: 0.0 to 1.0
Default Value: 0.33
This parameter is the shielding factor for external contamination to ground
for time spent indoors (Kennedy and Strenge, 1992).
IC-FTO--Fraction of time spent outdoors Units: none
Range: 0.0 to 1.0
Default Value: 0.125
Limitation: IC-FTI + IC-FTO <= 1.0
This parameter is the fraction of time that the exposed individual spends
outdoors on a daily average (EPA 1997 (Vol.3)).
IC-SHO--Shielding factor for outdoors Units: none
Range: 0.0 to 1.0
Default Value: 1.0
This parameter is the shielding factor for external contamination to ground
for time spent outdoors (Kennedy and Strenge, 1992).
IC-UEXT--Daily exposure time to external radiation for atmospheric and measured soil pathways Units: hours per day (hr/d)
Range: 0.0 to 24.0
Default Value: 24.0
This parameter gives the hours per day that the individual is subject to
exposure to radiation from an airborne plume and from contamination in
soils. The default value represents continuous exposure.
IC-FREQSLEXT--Annual frequency factor for soil external exposure Units: dimensionless
Range: 0.0 to 1.0
Default Value: 1.0
The exposure pathway annual factors represent the fraction of days in a year
that exposure occurs to each exposure pathway. For example, if a person
is present at the exposure location 180 days in a year, the annual factor would
be calculated as 180/365.25 = 0.4982. The default values are set to 1
(exposure every day during a year).
TERRESTRIAL FOOD TAB
IC-UAGLEAF--Ingestion rate of leafy vegetables Units: kilograms per day (kg/d)
Range: 0.0 to 5.0 kg/d
Default Value: 0.125 kg/d
The ingestion rate of farm products is the annual average rate at which the
exposed individual consumes contaminated foods of each type. Default
values for ingestion rates are taken as 25% of the values recommended by
(EPA 1997 (Vol.2)). The
reduction (25%) is applied to account for only a fourth of the individual's
intake coming from the contaminated source. The remainder is purchased
from markets and is assumed to be uncontaminated.
IC-UAGVEG--Ingestion rate of other vegetables Units: kilograms per day (kg/d)
Range: 0.0 to 5.0 kg/d
Default Value: 0.157 kg/d
The ingestion rate of farm products is the annual average rate at which the
exposed individual consumes contaminated foods of each type. Default
values for ingestion rates are taken as 25% of the values recommended by
(EPA 1997 (Vol.2)). The
reduction (25%) is applied to account for only a fourth of the individuals
intake coming from the contaminated source. The remainder is purchases
from markets and is assumed to be uncontaminated.
IC-UAGMT--Ingestion rate of meat Units: kilograms per day (kg/d)
Range: 0.0 to 5.0 kg/d
Default Value: 0.147 kg/d
The ingestion rate of farm products is the annual average rate at which the
exposed individual consumes contaminated foods of each type. Default
value is from (EPA 1997 (Vol.2)).
IC-UAGMK--Ingestion rate of milk Units: liters per day (L/d)
Range: 0.0 to 4.0 L/d
Default Value: 0.560L/d
The ingestion rate of farm products is the annual average rate at which the
exposed individual consumes contaminated foods of each type. Default
value is from (EPA 1997 (Vol.2)).
IC-FREQLEAF--Annual frequency factor for ingestion of leafy vegetables Units: dimensionless
Range: 0.0 to 1.0
Default Value: 1.0
The exposure pathway annual factors represent the fraction of days in a year
that exposure occurs to each exposure pathway. For example, if a person
consumes leafy vegetables at the average rate 350 days in a year, the annual
factor would be calculated as 350/365.25 = 0.9582. The default values are
set to 1 (exposure every day during a year).
IC-FREQVEG--Annual frequency factor for ingestion of other vegetables Units: dimensionless
Range: 0.0 to 1.0
Default Value: 1.0
The exposure pathway annual factors represent the fraction of days in a year
that exposure occurs to each exposure pathway. For example, if a person
consumes other vegetables at the average rate for 350 days in a year, the
annual factor would be calculated as 350/365.25 = 0.9582. The default
values are set to 1 (exposure every day during a year).
IC-FREQMT--Annual frequency factor for ingestion of meat Units: dimensionless
Range: 0.0 to 1.0
Default Value: 1.0
The exposure pathway annual factors represent the fraction of days in a year
that exposure occurs to each exposure pathway. For example, if a person
consumes meat at the average rate for 350 days in a year, the annual factor
would be calculated as 350/365.25 = 0.9582. The default values are set to
1 (exposure every day during a year).
IC-FREQMK--Annual frequency factor for ingestion of milk Units: dimensionless
Range: 0.0 to 1.0
Default Value: 1.0
The exposure pathway annual factors represent the fraction of days in a year
that exposure occurs to each exposure pathway. For example, if a person
milk at the average rate for 350 days in a year, the annual factor would be
calculated as 350/365.25 = 0.9582. The default values are set to 1
(exposure every day during a year).
DOMESTIC USE TAB
This screen allow the user to modify several parameter related to domestic
water use.
IC-TESHWR--Duration of one shower event Units: hours per shower (hr/shower)
Range: 0.0 to 1.0
Default Value: 0.167
The shower dermal contact, shower inadvertent ingestion, and MEPAS shower
inhalation model require the duration of each shower. The default shower
exposure duration is set to 0.167 hours (10 minutes) based on recommendations
of (EPA 1997 (Vol.3)).
IC-EVSHWR--Frequency of showering Units: showers per day (showers/d)
Range: 0.0 to 5.0
Default Value: 1.0
The shower frequency is the number of shower exposure events assumed to
occur each day for the exposed individual. The default value is set to
one shower per day based on recommendations of (EPA 1997 (Vol.3)).
The product of shower frequency and shower duration must not be greater than 24 hours.
IC-UBRSH--Inhalation rate while showering Units: cubic meters per day (m3/d)
Range: 0.0 to 50.0
Default Value: 15.2
The inhalation rate while showering is used to estimate inhalation intake
from volatile pollutants released from domestic water. The inhalation
rate represents the rate of inhalation during a shower (when the MEPAS shower
inhalation model is selected) or the daily intake of indoor air (when the
EPA/Andelman model is selected). The default value of
20 m3/d is appropriate when the MEPAS shower model is selected
representing an average inhalation rate for a day (EPA 1991).
The inhalation only occurs during the time the individual is in the
shower. When the EPA indoor air model is selected, a value of 15 m3/d
is recommended by (EPA (1997) Vol.1) for use.
IC-UBW--Water ingestion while showing Units: liters per hour (L/hr)
Range: 0.0 to 1.0
While showering an individual may inadvertently ingest some water. The
intake rate represents a nominal rate of inadvertent ingestion.
IC-ASKINDM--Area of skin exposed while showering Units: square centimeters (cm2)
Range: 0.0 to 40,000.0
Default Value: 20,000.0
The area of the skin exposed is required for several exposure
pathways. The area exposed while showering and swimming usually is
defined to represent the entire area of the body. The area for exposure
to soil usually represent the area of the hands and arms. Default values
for these parameters are based on suggested values from (EPA
1997 (Vol.1)).
IC-FREQING--Annual frequency factor for drinking water ingestion Units: dimensionless
Range: 0.0 to 1.0
Default Value: 1.0
The exposure pathway annual factors represent the fraction of days in a year
that exposure occurs to each exposure pathway. For example, if a person
drinks water at the exposure location 350 days in a year, the annual factor
would be calculated as 350/365.25 = 0.9582. The default values are set to
1 (exposure every day during a year).
IC-FREQSRDER--Annual frequency factor for shower dermal contact Units: dimensionless
Range: 0.0 to 1.0
Default Value: 1.0
The exposure pathway annual factors represent the fraction of days in a year
that exposure occurs to each exposure pathway. For example, if a person
showers 350 days in a year, the annual factor would be calculated as 350/365.25
= 0.9582. The use of these factors must be coordinated with the specific
pathway frequency parameters (e.g. EVSHWR and shower exposure frequency).
The specific pathway frequency parameters are generally used to represent the
number exposure events during a day in which exposure occurs. For example
if an individual showers 2 times in each of the 350 days of exposure, the
shower frequency factor (EVSHWR) would be set to 2. Note, however, that
the default values are set to 1 (exposure every day during a year) and the
specific pathway frequency parameters are set to the fraction of days the
exposure occurs. Which ever representation is used for the two sets of
parameters, the user must be careful to coordinate their use so double
accounting does not occur.
IC-FREQSRING--Annual frequency factor for shower water ingestion Units: dimensionless
Range: 0.0 to 1.0
Default Value: 1.0
The exposure pathway annual factors represent the fraction of days in a year
that exposure occurs to each exposure pathway. For example, if a person
showers 350 days in a year, the annual factor would be calculated as 350/365.25
= 0.9582. The use of these factors must be coordinated with the specific
pathway frequency parameters (e.g. EVSHWR and shower exposure frequency).
The specific pathway frequency parameters are generally used to represent the
number exposure events during a day in which exposure occurs. For example
if an individual showers 2 times in each of the 350 days of exposure, the
shower frequency factor (EVSHWR) would be set to 2. Note, however, that
the default values are set to 1 (exposure every day during a year) and the
specific pathway frequency parameters are set to the fraction of days the exposure
occurs. Which ever representation is used for the two sets of parameters,
the user must be careful to coordinate their use so double accounting does not
occur.
IC-FREQSRINH--Annual frequency factor for shower or indoor air inhalation Units: dimensionless
Range: 0.0 to 1.0
Default Value: 1.0
The exposure pathway annual factors represent the fraction of days in a year
that exposure occurs to each exposure pathway. For example, if a person
showers 350 days in a year, the annual factor would be calculated as 350/365.25
= 0.9582. The use of these factors must be coordinated with the specific
pathway frequency parameters (e.g. EVSHWR and shower exposure frequency).
The specific pathway frequency parameters are generally used to represent the
number exposure events during a day in which exposure occurs. For example
if an individual showers 2 times in each of the 350 days of exposure, the
shower frequency factor (EVSHWR) would be set to 2. Note, however, that
the default values are set to 1 (exposure every day during a year) and the
specific pathway frequency parameters are set to the fraction of days the
exposure occurs. Which ever representation is used for the two sets of
parameters, the user must be careful to coordinate their use so double
accounting does not occur.
SWIMMING TAB
This screen allows the user to modify parameters related to swimming
exposure pathways (water ingestion, dermal contact, and external exposure).
IC-USW--Water ingestion rate while swimming Units: liters per hour (L/hr)
Range: 0.0 to 1.0
Individuals swimming are subject to inadvertently ingest small amounts of
water. The ingestion is defined as the amount ingested per hour of
swimming activity. The total intake (per swimming event) is calculated by
MEPAS as the product of the ingestion rate and the swimming exposure duration.
IC-TESWIM--Duration of a swimming event Units: hours per event (hr/event)
Range: 0.0 to 24.0
Default Value: 1.0
Individuals involved in swimming are potentially exposed from dermal contact
with the water, inadvertent ingestion of water while swimming, and by external
exposure to radionuclides in the water. These pathway require an estimate
of the duration of contact with the water. The default value, when
multiplied by the annual average default swimming frequency gives a daily
average exposure time of 0.033 hr. This value is equivalent to the
recommended annual average exposure time of 12 hours (EPA
1997 (Vol.3)).
IC-EVSWIM--Frequency of swimming Units: events per day (events/d)
Range: 0.0 to 5.0
Default Value: 0.033
The swimming frequency gives the number of swimming events per day for the
exposed individual. The value used for this parameter must be coordinated
with the value use for the annual factor. The default value is set to
0.066 to give an annual average exposure time of 12 hours as recommended by (EPA 1997 (Vol.3)). If the annual factor is used to indicate
the fraction of days in which swimming occurs, the swimming frequency should be
set to 1. The product of frequency of swimming and swimming event
duration must not be greater than 24 hours.
IC-ASKINSW--Area of skin exposed while swimming Units: square centimeters (cm2)
Range: 0.0 to 40,000.0
Default Value: 20,000.0
The area of the skin exposed is required for the dermal contact while
swimming exposure pathways. The area exposed while swimming usually is
defined to represent the entire area of the body. Default values for
these parameters are based on suggested values from (EPA
1997 (Vol.1)).
IC-FREQSWING--Annual frequency factor for swimming ingestion Units: dimensionless
Range: 0.0 to 1.0
Default Value: 1.0
The exposure pathway annual factors represent the fraction of days in a year
that exposure occurs to each exposure pathway. For example, if a person
swims during 7 days in a year, the annual factor would be calculated as
7/365.25 = 0.0192. The use of these factors must be coordinated with the
specific pathway frequency parameters (e.g. EVSWIM, swimming exposure
frequency). The specific pathway frequency parameters are generally used
to represent the number exposure events during a day in which exposure
occurs. For example if an individual swims 2 times in each of the 7 days
of exposure, the swimming frequency factor (EVSWIM) would be set to 2.
Note, however, that the default values are set to 1 (exposure every day during
a year) and the specific pathway frequency parameters are set to the fraction
of days the exposure occurs. Which ever representation is used for the
two sets of parameters, the user must be careful to coordinate their use so
double accounting does not occur.
IC-FREQSWDER--Annual frequency factor for swimming dermal contact Units: dimensionless
Range: 0.0 to 1.0
Default Value: 1.0
The exposure pathway annual factors represent the fraction of days in a year
that exposure occurs to each exposure pathway. For example, if a person
swims during 7 days in a year, the annual factor would be calculated as
7/365.25 = 0.0192. The use of these factors must be coordinated with the
specific pathway frequency parameters (e.g. EVSWIM, swimming exposure frequency).
The specific pathway frequency parameters are generally used to represent the
number exposure events during a day in which exposure occurs. For example
if an individual swims 2 times in each of the 7 days of exposure, the swimming
frequency factor (EVSWIM) would be set to 2. Note, however, that the
default values are set to 1 (exposure every day during a year) and the specific
pathway frequency parameters are set to the fraction of days the exposure
occurs. Which ever representation is used for the two sets of parameters,
the user must be careful to coordinate their use so double accounting does not
occur.
IC-FREQSWEXT--Annual frequency factor for swimming external exposure Units: dimensionless
Range: 0.0 to 1.0
Default Value: 1.0
The exposure pathway annual factors represent the fraction of days in a year
that exposure occurs to each exposure pathway. For example, if a person
swims during 7 days in a year, the annual factor would be calculated as
7/365.25 = 0.0192. The use of these factors must be coordinated with the
specific pathway frequency parameters (e.g. EVSWIM, swimming exposure
frequency). The specific pathway frequency parameters are generally used
to represent the number exposure events during a day in which exposure occurs.
For example if an individual swims 2 times in each of the 7 days of exposure,
the swimming frequency factor (EVSWIM) would be set to 2. Note, however,
that the default values are set to 1 (exposure every day during a year) and the
specific pathway frequency parameters are set to the fraction of days the
exposure occurs. Whichever representation is used for the two sets of
parameters, the user must be careful to coordinate their use so double
accounting does not occur.
BOATING TAB
This screen allows the user to modify parameters associated with external
exposure while boating.
IC-TEBOAT--Time spent in one boating event Units: hours per event (hr/event)
Range: 0.0 to 24.0
Default Value: 0.5
The time spent boating is used to estimate the external radiation dose
received while boating on contaminated surface waters. The time
represents the average time spent on the water per boating event, and usually
is set to the total time during a day in which boating occurs. The default
time of 0.5 hours, when multiplied by the default boating frequency gives an
average annual daily exposure time of 0.0033 hours/day (12 hours/year)
consistent with recommendations of the Nuclear Regulatory Commission (Strenge, Peloquin, and Whelan (1986)).
IC-EVBOAT--Frequency of boating event Units: events per day (events/d)
Range: 0.0 to 5.0
Default Value: 0.066
The boating frequency is the number of events per day in which the
individual is involved in boating events. The definition of this
parameter must be coordinated with the annual frequency for boating. The
default boating frequency is set to give a total annual boating exposure time
of 12 hours (see the help screen for TEBOAT) as recommended by the Nuclear
Regulatory Commission (Strenge, Peloquin, and Whelan
(1986)). Also, the number of boating events per day multiplied by the
time spent boating (per event) must not be greater than 24 hours.
IC-SBRF--Boating geometry factor for external exposure Units: dimensionless
Range: 0.0 to 1.0
Default Value: 0.5
Individual boating are exposed to penetrating radiation from contamination
in the water. The dose is estimated using water immersion external dose
conversion factors. Because the individuals in a boat are above the
water, and not in the water, the dose received will be approximately half of
that estimated using the immersion factors. The default value of 0.5 is
as recommended by (NRC 1977), (Strenge,
Peloquin, and Whelan (1986)), and (Napier et al.
(1988)).
IC-FREQBOAT--Annual frequency factor for boating external exposure Units: dimensionless
Range: 0.0 to 1.0
Default Value: 1.0
The exposure pathway annual factors represent the fraction of days in a year
that exposure occurs to each exposure pathway. For example, if a person
boats during 7 days in a year, the annual factor would be calculated as
7/365.25 = 0.0192. The use of these factors must be coordinated with the
specific pathway frequency parameters (e.g. EVBOAT, boating exposure
frequency). The specific pathway frequency parameters are generally used
to represent the number exposure events during a day in which exposure
occurs. For example if an individual boats 2 times in each of the 7 days
of exposure, the boating frequency factor (EVBOAT) would be set to 2.
Note, however, that the default values are set to 1 (exposure every day during
a year) and the specific pathway frequency parameters are set to the fraction
of days the exposure occurs. Which ever representation is used for the
two sets of parameters, the user must be careful to coordinate their use so
double accounting does not occur.
SHORELINE TAB
This screen allows the user to modify parameters related to shoreline
exposure pathways (sediment ingestion, dermal contact with sediment, and
external exposure to sediment).
IC-TESHOR--Duration of a shoreline exposure event Units: hours per event (hr/event)
Range: 0.0 to 24.0
Default Value: 2.0
Individuals involved in shoreline activities are potentially exposed from
dermal contact with the sediment, inadvertent ingestion of sediment, and by
external exposure to radionuclides in the sediment. These pathways
require an estimate of the time spent on the shoreline. The default
value, when multiplied by the annual average default shoreline frequency gives
a daily average exposure time of 0.033 hr. This value is equivalent to
the recommended annual average exposure time of 12 hours (NRC
1977).
IC-EVSHOR--Frequency of a shoreline exposure event Units: events per day (events/d)
Range: 0.0 to 10.0
Default Value: 0.017
The shoreline frequency gives the number of shoreline events per day for the
exposed individual. The value used for this parameter must be coordinated
with the value use for the annual factor. The default value is set to
0.017 to give an annual average exposure time of 12 hours as recommended by (NRC 1977). If the annual factor is used to indicate
the fraction of days in which shoreline use occurs, the shoreline frequency
should be set to 1. The product of shoreline frequency and event duration
must not be greater than 24 hours.
IC-USED--Shoreline sediment ingestion rate Units: grams per hour (g/hr)
Range: 0.0 to 10.0
Individuals who participate in shoreline recreational activities may
inadvertently ingest shoreline sediments. The sediment ingestion rate
gives the hourly rate at which sediments are ingested.
IC-SWF--Shore width factor for shoreline external exposure Units: dimensionless
Range: 0.0 to 1.0
Default Value: 0.2
The shore width factor is used as an adjustment to the external dose factors
for ground contamination by radioactive materials. The external dose
factors represent exposure to large areas of contamination (essentially
infinite in extent considering the range of penetrating radiation in
air). The shoreline geometry represents a situation that is less than
infinite. The correction factor is intended to account for this
difference in geometry. The default value is suggested by the Nuclear
Regulatory Commission (NRC 1977).
IC-ASKINSL--Area of skin exposed during shoreline sediment contact Units: square centimeters (cm2)
Range: 0.0 to 40,000.0
Default Value: 5,000.0
The dermal contact exposure pathway for shoreline sediments requires an
estimate of area of skin that comes in contact with sediments. The
default value represents approximately half of the total surface area of the
skin (EPA 1997 (Vol.1)).
IC-ADHSED--Sediment adherence factor for sediment contact events Units: milligrams per square centimeter (mg/cm2)
Range: 0.0 to 10.0
Default Value: 1.0
The estimate of pollutant absorption resulting from contact with sediment
requires an estimate of the average mass of sediment on the skin (for the area of
skin that has been in contact with sediment). The default value is based on
recommendation of (EPA 1992).
IC-FREQSHDER--Annual frequency factor for shoreline dermal contact Units: dimensionless
Range: 0.0 to 1.0
Default Value: 1.0
The exposure pathway annual factors represent the fraction of days in a year
that exposure occurs to each exposure pathway. For example, if a person
is involved with shoreline activities during 7 days in a year, the annual
factor would be calculated as 7/365.25 = 0.0192. The use of these factors
must be coordinated with the specific pathway frequency parameters (e.g.
EVSHOR, shoreline exposure frequency). The specific pathway frequency
parameters are generally used to represent the number exposure events during a
day in which exposure occurs. For example if an individual visits the
shoreline 2 times in each of the 7 days of exposure, the shoreline frequency
factor (EVSHOR) would be set to 2. Note, however, that the default values
are set to 1 (exposure every day during a year) and the specific pathway
frequency parameters are set to the fraction of days the exposure occurs.
Which ever representation is used for the two sets of parameters, the user must
be careful to coordinate their use so double accounting does not occur.
IC-FREQSHING--Annual frequency factor for shoreline sediment ingestion Units: dimensionless
Range: 0.0 to 1.0
Default Value: 1.0
The exposure pathway annual factors represent the fraction of days in a year
that exposure occurs to each exposure pathway. For example, if a person
is involved with shoreline activities during 7 days in a year, the annual
factor would be calculated as 7/365.25 = 0.0192. The use of these factors
must be coordinated with the specific pathway frequency parameters (e.g.
EVSHOR, shoreline exposure frequency). The specific pathway frequency
parameters are generally used to represent the number exposure events during a
day in which exposure occurs. For example if an individual visits the
shoreline 2 times in each of the 7 days of exposure, the shoreline frequency
factor (EVSHOR) would be set to 2. Note, however, that the default values
are set to 1 (exposure every day during a year) and the specific pathway
frequency parameters are set to the fraction of days the exposure occurs.
Which ever representation is used for the two sets of parameters, the user must
be careful to coordinate their use so double accounting does not occur.
IC-FREQSHEXT--Annual frequency factor for shoreline external exposure Units: dimensionless
Range: 0.0 to 1.0
Default Value: 1.0
The exposure pathway annual factors represent the fraction of days in a year
that exposure occurs to each exposure pathway. For example, if a person
is involved with shoreline activities during 7 days in a year, the annual
factor would be calculated as 7/365.25 = 0.0192. The use of these factors
must be coordinated with the specific pathway frequency parameters (e.g.
EVSHOR, shoreline exposure frequency). The specific pathway frequency
parameters are generally used to represent the number exposure events during a
day in which exposure occurs. For example if an individual visits the
shoreline 2 times in each of the 7 days of exposure, the shoreline frequency
factor (EVSHOR) would be set to 2. Note, however, that the default values
are set to 1 (exposure every day during a year) and the specific pathway
frequency parameters are set to the fraction of days the exposure occurs.
Which ever representation is used for the two sets of parameters, the user must
be careful to coordinate their use so double accounting does not occur.
SOIL TAB
IC-SKINL--Thickness of skin layer, for dermal models Units: centimeters (cm)
Range: 0.0001 to 0.01 cm
Default Value: 0.001 cm
The thickness of the skin is used when the EPA dermal exposure model is used
(EPA 1992). A value should be provided if the
default value does not represent the skin of the exposed individual.
IC-ASKINSO--Area of skin exposed to soil Units: square centimeters (cm2)
Range: 0.0 to 40,000.0
Default Value: 5,000
The area of the skin exposed is required for several exposure
pathways. The area exposed while showering and swimming usually is
defined to represent the entire area of the body. The area for exposure
to soil usually represents the area of the hands and arms. Default values
for these parameters are based on suggested values from (EPA
1997 (Vol.1)).
IC-ADHFAC--Soil adherence factor for soil contact events Units: milligrams per square centimeter (mg/cm2)
Range: 0.0 to 10.0
Default Value: 1.0
The estimate of pollutant absorption resulting from contact with soil
requires an estimate of the average mass of soil on the skin (for the area of
skin that has been in contact with soil). The default value is based on
recommendation of (EPA 1992).
IC-EVSOIL--Frequency of soil dermal contact events Units: events per day (events/d)
Range: 0.0 to 10.0
Default Value: 1.0
The soil dermal exposure frequency represents the number of soil contact
events that occur on days in which contact occurs. The default value
represents one exposure per day. The default absorption fractions are
based on the soil remaining in contact with skin for about 12 hours. A
practical maximum for the soil dermal exposure frequency would be 2 per day.
IC-FREQSLDER--Annual frequency factor for soil dermal contact Units: dimensionless
Range: 0.0 to 1.0
Default Value: 1.0
The exposure pathway annual factors represent the fraction of days in a year
that exposure occurs to each exposure pathway. For example, if a person
comes in contact with soil during 180 days in a year, the annual factor would
be calculated as 180/365.25 = 0.4928. The use of these factors must be
coordinated with the specific pathway frequency parameters (e.g. EVSOIL, soil
exposure frequency). The specific pathway frequency parameters are
generally used to represent the number exposure events during a day in which
exposure occurs. For example if an individual has two soil contact events
in each of the 180 days of exposure, the soil frequency factor (EVSOIL) would
be set to 2. Note, however, that the default values are set to 1
(exposure every day during a year) and the specific pathway frequency
parameters are set to the fraction of days the exposure occurs. Which
ever representation is used for the two sets of parameters, the user must be
careful to coordinate their use so double accounting does not occur.
IC-USOIL--Soil ingestion rate Units: grams per day (g/d)
Range: 0.0 to 10.0
Default Value: 0.05
Individuals daily come in contact with soil and house dust and inadvertently
ingest some of the soil. The value provided here is used for all soil
ingestion calculations, unless a different value is provided for the specific
user location. The default soil intake is recommended for adults by EPA 1997 (Vol.1).
IC-FREQSLING--Annual frequency factor for soil ingestion Units: dimensionless
Range: 0.0 to 1.0
Default Value: 1.0
The exposure pathway annual factors represent the fraction of days in a year
that exposure occurs to each exposure pathway. For example, if a person
comes in contact with soil during 180 days in a year, the annual factor would
be calculated as 180/365.25 = 0.4928. The use of these factors must be
coordinated with the specific pathway frequency parameters (e.g. EVSOIL, soil
exposure frequency). The specific pathway frequency parameters are
generally used to represent the number exposure events during a day in which
exposure occurs. For example if an individual has two soil contact events
in each of the 180 days of exposure, the soil frequency factor (EVSOIL) would
be set to 2. Note, however, that the default values are set to 1
(exposure every day during a year) and the specific pathway frequency
parameters are set to the fraction of days the exposure occurs. Which
ever representation is used for the two sets of parameters, the user must be
careful to coordinate their use so double accounting does not occur.
IC-TMS--Thickness of measured soil contamination layer Units: meters (m)
Range: 0.0 to 5.0
The thickness of the measured soil layer is used to estimate the external
radiation dose from radionuclides in the soil. This parameter should
represent the thickness of the measured contamination layer.
IC-RHOMS--Density of measured soil contamination layer Units: grams per cubic centimeter (g/cm3)
Range: 0.0 to 4.0 g/cm3
The density of surface soils is used to estimate the external radiation dose
from radionuclides in the soil.
AQUATIC FOOD TAB
This screen allows the user to modify parameters for the fin fish and
shellfish ingestion exposure pathways.
IC-UAQFIN--Ingestion rate of fin fish Units: kilograms per day (kg/d)
Range: 0.0 to 5.0 kg/d
Default Value: 0.00407 kg/d
The aquatic food pathways require an estimate of the average daily ingestion
rate of fish and shellfish. The default value for fish (fin fish)
ingestion rate is based (EPA 1997 (Vol.1)).
IC-UAQSHL--Ingestion rate of shellfish Units: kilograms per day (kg/d)
Range: 0.0 to 5.0 kg/d
Default Value: 0.00251 kg/d
The aquatic food pathways require an estimate of the average daily ingestion
rate of fish and shellfish. The default shellfish ingestion
rate is based on recommendations of (EPA 1997 (Vol.1))
representing an age-averaged intake rate.
IC-FREQFIN--Annual frequency factor for finned fish ingestion Units: dimensionless
Range: 0.0 to 1.0
Default Value: 1.0
The exposure pathway annual factors represent the fraction of days in a year
that exposure occurs to each exposure pathway. For example, if a person
consumes finfish during 7 days in a year, the annual factor would be calculated
as 7/365.25 = 0.0192. The default value is set to 1 (exposure every day
during a year).
IC-FREQSHL--Annual frequency factor for shellfish ingestion Units: dimensionless
Range: 0.0 to 1.0
Default Value: 1.0
The exposure pathway annual factors represent the fraction of days in a year
that exposure occurs to each exposure pathway. For example, if a person
consumes shellfish during 7 days in a year, the annual factor would be calculated
as 7/365.25 = 0.0192. The default values are set to 1 (exposure every day
during a year).
MEPAS Receptor Intake Model Internal Default Values
Parameter
Description
Value
Range
Units
Reference
SBRF
Boating geometry correction factor
0.5
fixed
fraction
Strenge et al 1986
MEPAS Receptor Intake Model Undocumented Equations
Skin Permeability Constant Estimation
A positive value for skin permeability constant is always generated at run
time by the MEPAS Receptor Intake module.
The method used depends on the type of constituent. For organic chemicals, the correlation is
from the EPA handbook on Dermal Exposure Assessment: Principles and
Applications (1992). A constituent is
determined to be organic and use of the correlation method is considered
appropriate if input values for molecular weight and Kow are both
positive. If these conditions are met,
then the following correlation is used.
Pk = -2.72 + 0.71* Log10(Kow) - 0.0061 * MW
Where
Pk = skinpermeability constant (cm/hr)
Kow = octanol-water partition coefficient(dimensionless)
MW = molecularweight of the constituent.
If the constituent is not organic, and the above conditionson Kow and
molecular weight are not met, then the skin permeability is set to0.001 cm/hr
(EPA 1992).
Indoor Air Model Parameters
The EPA indoor air model used water to indoor air transferfactors for
volatile chemicals (ANDFC), radon (ANDFR), and all other chemicalsand
radionuclides (ANDFO). These
threeparameters are supplied by the user in the MEPAS Exposure user
interface. The values are applied using
the followingsteps.
Theindoor air factor for a constituent is set to zero.
If apositive value was supplied for ANDFO, then the indoor air factor is setto ANDFO.
If theconstituent is a chemical (KTYPE>1), and the Henry’s Law Constant(RHLC) is greater than
1.E-5 and the molecular weight (RWM) is less than200, then the indoor air
factor is set to the value provided for volatilechemicals (ANDFC).
If theconstituent is Rn222, set the indoor air factor to ANDFR.
EPA.1992. Dermal Exposure Assessment: Principles and
Applications.USEPA/600/8-91/011B.U.S.Environmental Protection Agency, Office of
Research and Development,Washington, D.C.
EPA 1997 (Vol.1).Exposure Factors Handbook Volume I: General
Factors.EPA/600/P-95/002Fa, August1997.U.S.Environmental Protection Agency,
Office of Research and Development,
EPA 1997 (Vol.2).Exposure Factors Handbook Volume II: Food
Ingestion Factors.EPA/600/P-95/002Fb, August1997.U.S.Environmental Protection Agency,
Office of Research and Development,
EPA 1997 (Vol.3).Exposure Factors Handbook Volume III: Activity
Factors.EPA/600/P-95/002Fc, August1997.U.S.Environmental Protection Agency,
Office of Research and Development,
Kennedy, W. E. and D.L. Strenge.1992.Residual
Radioactive Contamination From Decommissioning: Technical Basis for Translating
Contamination Levels to Annual Total Effective Dose Equivalent.Final
Report. NUREG/CR-5512.U.S. Nuclear Regulatory Commission, Washington,
Napier, B. A., R. A.Peloquin, D. L. Strenge, and J.
V. Ramsdell.1988.GENII - The
NRC.1977.Calculation of Annual Doses to Man from Routine
Releases of Reactor Effluents for the Purpose of Evaluating Compliance with 10
CFR Part 50, Appendix I.Regulatory Guide 1.109, U.S.Nuclear Regulatory
Commission, Washington,D.C.
Strenge, D.L., R. A.Peloquin, G. Whelan.1986.ALDTAP
II - Technical Reference and UserGuide.U. S.Nuclear Regulatory Commission.
NUREG/CR-4013.Washington, D.C.
