1
Date:
June
12,
2004
To:
Lynn
Zipf,
EPA
From:
Ian
Cadillac
and
Maureen
F.
Kaplan,
ERG
Subject:
Toxic
Weighting
Factors
(
TWFs)
Database:
Preliminary
Working
Version
Introduction
EPA
estimates
the
hazard
of
pollutants
discharged
in
industrial
wastewaters
by
calculating
hazard
scores
using
pollutant­
specific
toxic
weighting
factors
(
TWFs).
Where
data
is
available
these
TWFs
reflect
both
aquatic
life
and
human
health
effects.
Multiplying
the
pounds
of
pollutants
discharged
by
their
TWFs
results
in
an
estimate
of
toxic­
weighted
pound
equivalents
(
TWPE).
Currently,
EPA
uses
a
spreadsheet
with
one
worksheet
to
identify
all
the
input
data
used
in
calculating
TWFs.
This
spreadsheet
does
not
present
the
equations
used
in
calculating
TWFs.
EPA
used
the
TWFs
in
this
existing
spreadsheet
to
calculate
TWPEs
for
the
industrial
sectors
reviewed
in
the
2004
effluent
guidelines
plan
(
see
DCN
01198
in
Section
2.1.1
and
DCN
01199
in
Section
2.1.2
for
a
table
of
these
TWFs).

EPA
is
developing
a
new
database
format
for
documenting
both
the
input
data
and
the
equations
used
in
calculating
TWFs.
The
new
database
will
provide
better
transparency
regarding
the
calculation
of
TWFs.
When
complete,
EPA
will
use
this
new
database
format
for
future
effluent
guidelines
reviews.
The
draft
database
format
attached
to
this
memorandum
is
a
Microsoft
Excel
spreadsheet
with
multiple
worksheets
and
is
named
"
TWF_
DRAFT_
v1.
xls."
The
purpose
of
this
memorandum
is
to
provide
an
overview
of
the
draft
database
format.

1.
Draft
Database
Format
Overview
In
order
to
work
with
the
draft
database
format,
the
user
should:


Double­
click
on
the
file
("
TWF_
DRAFT_
v1.
xls")
to
open
it.
Click
the
button
"
Enable
Macros."


Go
to
sheet
"
READ
FIRST"
and
follow
instructions.

Data
Dictionary.
This
the
preliminary
format
for
the
data
element
dictionary.
Notes
will
be
added,
e.
g.,
see
entry
for
Q1*.

2.
Sheets
with
calculations
TWFs.
This
is
the
summary
sheet
for
the
draft
database
format.
At
the
moment,
the
equation
in
the
"
preferred"
columns
is
"
Select
EPA
`
organism
only'
if
it
is
available,
else
use
EPA
`
water
and
organism'."

HHCALC.
This
sheet
shows
the
values
used
to
calculate
a
human
health
criterion
and
calculates
four
versions
of
the
criterion
based
on
whether
it
is
a
carcinogen
or
not
(
q1*
or
RFD
basis)
and
the
1980
or
2
2000
methodology.
We
have
left
columns
for
variables
used
in
the
2000
methodology
such
as,
relative
source
contribution
(
RSC),
point
of
departure
(
POD),
and
uncertainty
factor
(
UF).
This
sheet
pulls
in
each
variable
(
e.
g.,
q1*,
RFD,
etc.)
from
other
sheets.
In
this
sheet,
"
NA"
indicates
a
blank
in
the
existing
EPA
TWF
spreadsheet.

3.
Data
Sheets
WQ_
WO_
EPA
and
WQ_
ORG_
EPA.
These
sheets
are
for
human
health
criteria
published
by
EPA
and
correspond
to
the
HHWO
and
HHOO
columns
in
the
existing
EPA
TWF
spreadsheet.
We
have
inserted
the
description
for
human
health
type
and
source
where
codes
were
given
in
the
existing
EPA
TWF
spreadsheet.
An
"
NA"
entry
indicates
a
blank
in
the
existing
EPA
TWF
spreadsheet.
We
assume
these
sheets
would
be
updated
whenever
EPA
publishes
criteria
or
if
the
values
come
from
another
EPA
publication.

AQ_
FRESH_
ACUTE,
AQ_
FRESH_
CHRONIC,
AQ_
SALT_
ACUTE,
and
AQ_
SALT_
CHRONIC.
These
four
sheets
form
the
documentation
for
aquatic
life
criteria
for
fresh/
salt
water
and
acute/
chronic
exposure.
An
"#
NA"
entry
means
that
there
was
a
code
listed
in
the
existing
EPA
TWF
spreadsheet.

BCF,
Cancer
Potency
Factor,
and
Reference
Dose.
These
three
sheets
list
the
values
and
sources
used
for
bioconcentration
factors,
q1*,
and
RFDs.
We
assume
these
sheets
would
be
updated
if
EPA
had
to
develop/
revise
a
criterion
for
a
pollutant.

Constants,
Notes,
and
Abbreviations.
These
sheets
are
still
under
development.

Versar
Codes
and
Versar
Refs.
These
form
the
lookup
tables
and
are
taken
from
EPA
TWF
documentation.

Ranges.
This
sheet
is
required
in
order
to
have
the
DGET
functions
work
properly.
It
is
an
artifact
of
working
in
Excel.
We
have
protected
this
sheet
accordingly.
