Definitions
A
brief
description
of
the
terms
used
in
the
PBT
Profiler
is
provided
below
Persistence
Persistence
is
the
ability
of
a
chemical
substance
to
remain
in
an
environment
in
an
unchanged
form.
The
longer
a
chemical
persists,
the
higher
is
the
potential
for
human
or
environmental
exposure
to
it.
The
individual
environmental
media
for
which
a
chemical's
persistence
is
usually
measured
or
estimated
are
air,
water,
soil,
and
sediment.

It
is
important
to
distinguish
between
persistence
in
a
single
medium
and
overall
environmental
persistence.
Persistence
in
an
individual
medium
is
controlled
by
transport
of
the
substance
to
other
media,
as
well
as
transformation
to
other
molecular
species.
Persistence
in
the
environment
as
a
whole
is
a
distinct
concept.
It
is
based
on
the
observations
that
the
environment
behaves
as
a
set
of
interconnected
media,
and
that
a
chemical
substance
released
to
the
environment
will
become
distributed
in
these
media
in
accordance
with
its
intrinsic
(physical/
chemical)
properties
and
reactivity.
Multimedia
mass
balance
models
offer
the
most
convenient
means
to
estimate
overall
environmental
persistence
from
information
on
sources
and
loadings,
chemical
properties
and
transformation
processes,
and
intermedia
partitioning.

When
reviewing
chemicals
for
pollution
prevention
opportunities,
the
medium­
specific
persistence
and
amount
of
the
chemical
expected
to
be
found
in
each
medium
need
to
be
considered
relative
to
its
potential
releases
to
the
environment
from
manufacture,
use,
transport
and
disposal.
The
longer
a
chemical
persists
in
the
environment,
the
higher
its
potential
for
harm
to
health
and
the
environment.

The
PBT
Profiler
expresses
persistence
in
individual
media
half­
lives
in
air,
water,
soil,
and
sediment
measured
in
days.
These
half­
lives
are
for
reactivity­
based
persistence
only.
The
EPA
has
established
a
series
of
proposed
thresholds
for
persistence
based
on
the
efforts
of
scientists,
regulators,
and
other
interested
parties
worldwide
in
helping
to
identify
and
regulate
chemicals
that
may
present
the
greatest
health
and
environmental
risks.
The
PBT
Profiler
compares
the
individual­
medium
half­
lives
it
estimates
for
air,
water,
soil,
and
sediment
to
the
cutoffs
proposed
by
the
EPA.
If
the
estimated
half­
lives
are
greater
than
those
proposed
by
the
EPA,
the
PBT
Profiler
highlights
these
values
automatically
by
changing
the
font
color
for
the
estimated
value
from
green
to
orange
or
red,
depending
on
which
cutoff
is
exceeded.
In
the
black­
and­
white
version,
underlines
and
italics
are
used
to
indicate
if
the
criteria
are
exceeded.
The
PBT
Profiler
currently
uses
the
following
cutoff
values
for
persistence
in
individual
media:
Half­
Life
(days)

Environmental
Compartment
Not
Persistent
Persistent
Water
<2
months
>=
2
months
>6
months
Soil
<2
months
>=
2
months
>6
months
Air
<=
2
days
>
2
days
Sediment
<2
months
>=
2
months
>6
months
In
the
black­
and­
white
version,
these
appear
as
follows:

Half­
Life
(days)

Environmental
Compartment
Not
Persistent
Persistent
Water
<2
months
>=
2
months
>6
months
Soil
<2
months
>=
2
months
>6
months
Air
<=
2
days
>
2
days
Sediment
<2
months
>=
2
months
>6
months
More
information
on
the
persistence
cutoffs
can
be
found
on
the
PBT
Profiler's
PBT
Criteria
Page.

To
determine
the
persistence
portion
of
the
PBT
estimate
(the
persistence
ranking),
the
PBT
Profiler
considers
water,
soil,
and
sediment
but
not
air.
This
is
because
bioaccumulation
is
commonly
considered
only
for
these
environmental
compartments.
To
determine
the
Persistence
ranking,
the
PBT
Profiler
first
determines
the
media
(environmental
compartment)
a
chemical
is
most
likely
to
be
found
in.
It
then
determines
if
the
chemical's
persistence
in
this
media
exceeds
the
criteria
discussed
above.
If
it
does,
then
the
persistence
portion
of
the
PBT
estimate
is
shaded
orange
or
red.
A
chemical's
persistence
in
air
is
also
important
in
determining
its
potential
to
travel
long
distances
from
its
original
point
of
release.
The
is
discussed
in
more
detail
under
the
long
range
transport
section
of
this
page.
Information
on
the
techniques
that
the
PBT
profiler
uses
to
estimate
a
chemical's
persistence
in
the
environment
is
available
in
the
PBT
profiler
methodology
section.
Definitions
of
chemical
persistence
in
air,
water,
soil,
and
sediment
are
briefly
described
on
this
page.
A
detailed
discussion
on
the
persistence
of
a
chemical
in
the
environment
is
contained
in
EPA's
final
TRI
rule
on
PBT
chemicals.

In
addition
to
reactivity­
based
persistence
in
the
individual
media,
the
PBT
profiler
estimates
an
overall
environmental
persistence
for
a
standardized
set
of
environmental
conditions
in
which
net
advection
and
sediment
burial
have
been
removed,
using
a
level
III
mult
imedia
fate
model.
The
purpose
of
this
is
to
provide
to
the
user
a
measure
of
overall
environmental
persistence
based
on
reactivity
only.
This
may
be
useful
in
making
pollution
prevention
decisions
since
ultimately,
on
a
global
scale,
there
is
no
advective
removal.
If
advective
loss
is
included
the
residence
time
is
reduced
and
can
give
a
misleading
impression
of
a
short
persistence.
Advective
losses
merely
relocate
the
chemical;
they
do
not
destroy
it.

Bioaccumulation
Bioaccumulation
is
a
general
term
that
is
used
to
describe
the
process
by
which
organisms
may
accumulate
chemical
substances
in
their
bodies.
Bioaccumulation
generally
refers
to
uptake
of
a
chemical
through
all
environmental
sources
including
the
food
chain.
A
similar
term,
bioconcentration,
refers
to
the
potential
for
a
chemical
in
water
to
concentrate
in
fish
and
aquatic
organisms.
In
general,
chemicals
that
have
the
potential
to
bioconcentrate
also
have
the
potential
to
bioaccumulate.

Bioconcentration
in
fish
can
be
readily
measured
in
the
laboratory
and
is
frequently
used
to
predict
the
importance
of
bioaccumulation,
which
is
much
more
complicated
to
determine.
The
potentialforbioconcentration
in
fish
isexpressed
asitsbioconcentration
factor,
or
BCF.
There
are
many
reliable
techniques
for
measuring
or
estimating
a
chemical's
BCF.
The
PBT
profiler
estimates
a
BCF
based
on
a
chemical's
physical
and
chemical
properties.
This
technique
is
described
more
fully
in
the
methodology
section.
A
detailed
discussion
of
bioaccumulation,
bioconcentration,
and
BCFs
can
be
found
in
EPA's
final
TRI
rule
on
PBT
chemicals.

The
EPA
has
established
a
series
of
proposed
thresholds
for
bioaccumulative
chemicals
to
help
identify
and
regulate
chemicals
that
may
present
the
greatest
health
and
environmental
risks.
The
PBT
Profiler
compares
the
bioconcentration
factors
(BCFs)
it
estimates
to
the
cutoffs
proposed
by
the
EPA.
The
BCFWIN
model
used
to
estimate
BCF
does
not
explicitly
address
a
variety
of
factors
that
may
influence
bioaccumulation
under
field
conditions,
such
as
possible
metabolism
of
the
chemical
in
exposed
organisms,
which
could
lead
to
actual
bioaccumulation
being
lower
than
predicted.
The
user
therefore
needs
to
exercise
due
caution
when
interpreting
BCFWIN
results.
If
the
estimated
BCF
is
greater
than
those
proposed
by
the
EPA,
the
PBT
Profiler
highlights
the
values
automatically
by
changing
the
font
color
for
the
estimated
value
from
green
to
orange
or
red,
depending
on
which
cutoff
is
exceeded.
The
output
of
the
PBT
profiler
uses
these
colors
so
that
the
user
can
quickly
identify
which
chemicals
have
the
highest
potential
to
bioaccumulate
in
fish
and
aquatic
organisms.
The
PBT
Profiler
currently
uses
the
following
cutoff
values
for
bioaccumulation:

Bioconcentration
Factor
Not
Bioaccumulative
Bioaccumulative
<
1,
000
>=
1,
000
>=
5,
000
In
the
black­
and­
white
version,
the
BCF
criteria
appear
as:

Bioconcentration
Factor
Not
Bioaccumulative
Bioaccumulative
<
1,
000
>=
1,
000
>=
5,
000
More
information
on
the
bioaccumulation
cutoffs
can
be
found
on
the
PBT
Profiler's
PBT
Criteria
Page.

Toxicity
Toxicity
is
a
relative
property
of
a
chemical
that
refers
to
its
potential
to
have
a
harmful
effect
on
a
living
organism.
It
is
a
function
of
the
concentration
of
the
chemical
and
the
duration
of
exposure.
Because
persistent
and
bioaccumulative
chemicals
are
long­
lasting
substances
that
can
build
up
in
the
food
chain
to
high
levels,
they
have
a
higher
potential
to
express
toxicity
and
be
harmful
to
humans
and
the
ecosystem.

The
PBT
profiler
uses
a
chronic
(long­
term)
toxicity
value
called
a
ChV
to
estimate
a
chemical's
relative
toxicity.
The
PBT
Profiler
currently
uses
the
following
cutoff
values
for
toxicit
y:

Fish
ChV
(mg/
l)

Not
Toxic
Toxic
>
10
mg/
l
or
no
effects
at
saturation
<
10
mg/
l
<0.
1mg/
l
In
the
black­
and­
white
version,
the
toxicity
criteria
are:

Fish
ChV
(mg/
l)

Not
Toxic
Toxic
>
10
mg/
l
or
no
effects
at
saturation
<
10
mg/
l
<0.
1mg/
l
For
more
information
on
how
the
PBT
Profiler
estimates
toxicity,
see
the
PBT
Profiler
methodology
section.
More
information
on
the
toxicity
cutoffs
can
be
found
on
the
PBT
Profiler's
PBT
Criteria
Page.

Media
These
are
the
four
environmental
compartments
a
chemical
may
be
found
in;
air,
water,
soil,
and
sediment.
Air
is
also
commonly
referred
to
as
the
atmosphere
or
atmospheric
compartment.
The
atmospheric
compartmentincludesthe
area
closesttothe
Earth's
surface
(troposphere)
and
the
stratosphere.
Water
refers
to
surface
water,
and
includes
oceans,
rivers,
lakes,
and
ponds.
As
defined,
this
medium
does
not
include
aquifers
found
below
the
Earth's
surface
(groundwater).
The
PBT
Profiler
does
not
explicitly
consider
groundwater.

Soil
refers
to
the
topmost
layer
(the
first
few
inches)
of
the
Earth's
surface
that
is
not
covered
by
water.
Soil
includes
the
horizons
near
the
surface
that
differ
from
the
underlying
rock
material.
Sediment
is
the
particulate
matter
found
under
surface
water.
For
the
purposes
of
the
estimation
methods
used
by
the
PBT
Profiler,
soil
is
considered
aerobic
(oxygenated)
and
sediment
is
consider
anaerobic
(free
of
oxygen).

PBT
strategies
typically
consider
the
persistence
of
a
chemical
in
water,
soil,
and
sediment
but
not
air.
This
strategy
is
also
used
by
the
PBT
Profiler.
Nevertheless,
the
persistence
of
a
chemical
in
air
is
important
in
identifying
P2
opportunities
because
once
in
the
atmosphere,
it
may
travel
a
long
distance
from
its
original
point
of
release.
Therefore,
the
potential
for
harm
to
health
or
the
environment
may
occur
far
away
from
the
area
where
it
was
originally
released.
To
help
determine
what
chemicals
have
the
potential
to
travel
long
distances
from
their
original
point
of
release,
the
PBT
Profiler
provides
an
indication
of
a
chemical's
long
range
transport
by
providing
its
estimated
Characteristic
Travel
Distance
(CTD).
The
CTD
is
discussed
in
more
detail
in
the
longrange
transport
definition.

Half­
Life
Half­
life
is
the
length
of
time
it
takes
for
the
concentration
of
a
substance
to
be
reduced
by
one­
half
relative
to
its
starting
level,
assuming
first­
order
decay
kinetics.
Generally,
it
is
useful
to
consider
"complete
removal"
as
taking
approximately
six
half­
lives.
The
PBT
profiler
estimates
the
half­
life
of
a
chemical
in
each
environmental
medium
(air,
water,
soil,
and
sediment).
These
half­
lives
are
for
reactivity
and
do
not
take
into
consideration
partitioning
into
or
out
of
the
medium,
or
physical
transport
(i.
e.,
advection).
See
the
discussion
on
the
PBT
Profiler
methodology
for
additional
details
on
how
the
half­
life
is
estimated.

Percentage
in
Each
Medium
Once
a
chemical
is
released
to
the
environment,
it
may
move
from
one
environmental
compartment
to
another.
The
expected
distribution
of
a
chemical
in
air,
water,
soil,
and
sediment
is
expressed
as
the
estimated
percentage
in
each
medium
relative
to
the
total
amount
in
the
environment.
The
PBT
profiler
determines
the
amount
in
each
medium
using
a
fugacity
model
that
is
based
on
a
chemical's
physical/
chemical
properties
and
reactivity.
The
method
the
fugacity
model
uses
to
estimate
the
percentage
in
each
medium
is
discussed
in
detail
in
the
PBT
Profiler
methodology
section.

Bioconcentration
Factor
The
bioconcentration
factor
(BCF)
is
a
measure
of
the
ability
a
water­
borne
chemical
substance
to
concentrate
in
fatty
tissue
of
fish
and
aquatic
organisms
relative
to
its
surroundings.
EPA
defines
bioconcentration
as
the
net
accumulation
of
a
substance
by
an
aquatic
organism
as
a
result
of
uptake
directly
from
the
ambient
water
through
gill
membranes
or
other
external
body
surfaces
(60
FR
15366).
In
general,
chemicals
that
have
the
potential
to
bioconcentrate
also
have
the
potential
to
bioaccumulate.
Because
BCF
values
are
much
easier
to
measure
(and
estimate),
the
BCF
is
frequently
used
to
determine
the
potential
for
a
chemical
to
bioaccumulate.

The
PBT
profiler
estimates
a
bioconcentration
factor
from
a
chemical's
physical
and
chemical
properties.
More
information
on
how
a
BCF
is
estimated
can
be
found
in
the
PBT
Profiler
methodology
section.

Fish
ChV
Fish
chronic
toxicity
value.
This
is
the
same
as
a
chronic
no­
effect­
concentration
(NEC)
and
the
geometric
mean
of
the
maximum
allowable
toxicant
concentration
(MATC).
The
MATC
is
the
range
of
concentrations
between
the
lowest­
observed­
effect
concentration
(LOEC)
and
the
no­
observed­
effect
concentration
(NOEC).

No
Effects
at
Saturation
"No
effects
at
saturation"
is
the
phrase
used
to
describe
the
situation
which
occurs
when
that
the
estimated
Fish
ChV
(in
mg/
L)
is
greater
than
a
chemicals'
water
solubility
(also
in
mg/
L).
This
indicates
that
a
saturated
aqueous
solution
of
the
chemical
(one
where
the
maximum
water
solubility
has
been
reached)
does
not
have
a
concentration
high
enough
to
allow
potential
toxic
effects
to
be
expressed.

Long­
Range
Transport/
Characteristic
Travel
Distance
Long­
Range
Transport
(LRT)
potential
refers
to
the
ability
of
a
chemical
substance
to
be
transported
long
distances
in
the
atmosphere,
potentially
resulting
in
widespread
distribution
and
deposition
in
regions
far
from
where
the
chemical
was
produced
or
used.
LRT
potential
is
linked
to
overall
environmental
persistence,
but
no
simple
relationship
between
the
two
exists
because
the
medium
or
media
of
transport
(usually
air;
sometimes
water)
may
not
be
the
media
in
which
persistence
is
longest.
The
method
used
to
estimate
LRT
potential
is
discussed
in
the
PBT
Profiler
methodology
section.
That
method
calculates
the
chemical's
Characteristic
Travel
Distance
(CTD)
as
the
expression
of
LRT
potential.
CTD
does
not
imply
the
existence
of
an
environmental
threat,
only
the
potential
for
transport
and
resultant
exposures
at
remote
locations,
and
thus
a
need
for
further
investigat
ion.

The
PBT
Profiler
currently
uses
the
following
cutoff
values
for
CTD
in
air:

High
Moderate
Low
CTD
>
2,
000
Km
>=
700
and
<=
2,
000
Km
<
700
Km
In
the
black­
and­
white
version,
those
values
that
exceed
the
high
cutoff
are
underlined
(e.
g.,
2,
100)
and
those
that
exceed
the
medium
cutoff
are
italicized
(e.
g.,
1,
100).
These
criteria
have
been
published
[Beyer
A.,
Mackay,
D.,
Matthies,
M.,
Wania,
F.
and
Webster,
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range
Transport
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34:
699­
703
(2000)],
and
are
described
in
more
detail
in
the
methodology
section
of
the
PBT
Profiler.

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