2.
Response
to
Comment
2.4
Master
Responses
to
Comments
residential
uses
than
for
commercial/industrial
uses,
human
health
risks
for
residential
uses
are
greater
and
remediation
standards
are
more
stringent
than
for
commercial
industrial
uses.
Determinations
as
to
the
human
health
risks
associated
with
any
particular
contaminated
site
are
analyzed
in
a
“human
health
risk
assessment.”
Human
health
risk
assessments
are
used
to
evaluate
the
potential
adverse
health
impacts
receptor
populations
may
experience
if
exposed
to
a
dose
of
a
constituent
or
chemical
in
soil,
water,
air,
or
food
via
exposure
pathways
such
as
ingestion,
inhalation,
and
dermal
contact.
Receptor
populations
usually
are
site-specific
and
may
include,
but
are
not
limited
to,
construction
workers,
residential
populations,
commercial
office
or
industrial
workers,
and
landscape
maintenance
workers.
The
constituents
or
chemicals
present
on
a
site
are
assessed
based
on
their
toxicity,
whether
it
is
carcinogenic,
the
exposure
pathway(s)
by
which
the
receptor
population
is
exposed,
and
the
dose
to
which
the
receptor
population
is
exposed.
Based
on
the
most
recent
DTSC
guidance,
the
following
exposure
parameters
are
used
in
human
health
risk
assessments
6
:
Body
weight
(adult,
child)
Averaging
time
of
exposure
in
days
(carcinogens,
non-carcinogens)
Exposure
duration
in
hears
(adult,
child)
Exposure
frequency
(days/year)
Exposure
duration
(hours/day)
Inhalation
rate
(adult,
child)
Drinking
water
ingestion
(adult,
child)
Soil
ingestion
(adult,
child)
Particulate
emission
factor
Skin
surface
area
for
soil
contact
(adult,
child)
Soil
adherence
factor
(adult,
child)
Dermal
absorption
rate
(chemical
specific)
Dermal
permeability
coefficient
from
water
(chemical
specific)
Showering/bathing
scenario
(skin
surface
area,
exposure
time,
and
exposure
frequency
for
both
adults
and
children)
Human
health
risk
assessments
are
prepared
following
federal
(USEPA)
and
State
(DTSC)
guidance,
and
are
reviewed
and
approved
by
the
regulatory
agency
or
agencies
responsible
for
remediation
of
a
particular
site
(see
for
discussion
regarding
the
timing
of
human
health
risk
assessments
in
the
remediation
review
and
approval
process).
The
objectives
of
human
health
risk
assessments
are
to
ensure
that
sufficient
analyses
have
been
completed
to
properly
evaluate
human
health
risks
based
on
a
property’s
future
intended
use,
and
to
develop
risk-based
cleanup
goals
to
protect
the
health
of
future
site
users.
6
DTSC
guidance
provides
default
exposure
parameters
for
use
in
risk
assessment
at
California
hazardous
waste
sites.
For
example
the
default
parameter
for
adult
body
weight
is
80
kg
(176
pounds)
and
15
kg
for
children
(33
pounds).
Brisbane
Baylands
Final
EIR
2.4-43
May
2015