F.
Risk
Assessment
for
Co­
Residential
Area
Sources
As
discussed
in
section
III.
J,
we
are
proposing
to
prohibit
PCE
emissions
from
new
coresidential
drycleaning
machines,
and
we
are
seeking
comments
on
approaches
beyond
those
otherwise
proposed
for
area
sources
for
addressing
risks
from
existing
co­
residential
sources.
This
decision
is
based
on
cancer
risk
estimates
for
these
co­
residential
facilities
of
between
4,000­
in­
1
million
to
31,000­
in­
1
million.
The
data,
methods
and
assumptions
used
to
develop
these
estimates
are
detailed
in
the
Risk
Characterization
Memo
in
the
public
docket.
We
solicit
comments
on
our
risk
characterization
approach,
specifically
on
the
data
used,
methods
for
estimating
risks,
and
assumptions
made
in
effort
to
identify
areas
of
this
assessment
that
may
be
overly
conservative,
and
therefore,
might
overstate
risks.
We
recognize
that
developing
residual
risk
standards
for
area
sources
subject
to
GACT
standards
is
discretionary
under
section
112(
f)(
5)
the
CAA,
and
that
some
further
level
of
emission
reductions
can
be
achieved
through
technologybased
standards
adopted
pursuant
to
CAA
section
112(
d)(
6)
that
could
be
more
stringent
than
either
the
currently
applicable
GACT
standards
or
the
standards
proposed
today
for
area
sources
in
general.
In
the
event
additional
information
becomes
available,
(
for
example,
data
showing
that
the
risks
are
substantially
less
than
the
risk
we
have
estimated),
we
also
solicit
comment
on
the
appropriateness
of
regulating
co­
residential
and/
or
other
area
sources
only
under
section
112(
d)(
6)
and
not
exercising
our
discretion
to
regulate
under
the
112(
f)
residual
risk
authority.
Under
this
approach,
for
example,
we
would
consider
adoption
of
the
New
York
level
of
regulatory
control
and
other
control
options
discussed
in
this
proposal.
