To:
Cindy
Roberts
&
September
26,
2000
Joyce
Donahue
From:
Frank
Bell,
Enrollee,
NCBA,
EPA
Subject:
Report
on
Uncertainty
Factors
(
UF)
and
Relative
Source
Contributions
(
RSC)
for
"
Chemicals
in
the
Six
Year
Review"
REF:
UFRSCOO1
Per
instructions
I
have
completed
a
review
of
the
chemicals
in
the
six
year
review,
shown
in
Attachment
1.
The
information
desired
was
the
UFs
and
RSCs
for
each
chemical
that
had
an
MCLG
set
on
the
basis
of
"
non­
carcinogenic"
factors.
My
procedure
was
as
follows:
 
to
identify
those
chemicals
classified
as
carcinogens
 
A
or
B
and
those
Cs
that
have
been
assigned
a
0
MCLG,
since
these
would
not
require
UFs
or
RSCs
,
listed
in
Table
1.
 
Next
I
examined
the
Health
Advisories
(
HA),
where
they
existed,
and
compared
the
Lifetime
Health
Advisories
(
LHA)
with
tabulated
MCLGs
for
the
various
chemicals.
Where
the
LHA
in
the
HA
is
identical
with
the
promulgated
MCLG,
I
took
the
UF
and
RSC
from
the
HA.
Where
there
was
a
change,
I
searched
the
various
Federal
Register
(
FR)
Notices
until
I
found
the
UF
and
RSC.
Table
2
provides
1)
Uncertainty
Factors
(
regular),
2)
Uncertainty
Factors
(
carcinogenic),
3)
Relative
Source
Contributions
and
4)
Source
References
for
applicable
chemicals.
It
should
be
noted
that
several
chemicals
 
barium,
copper,
fluoride,
nitrate,
nitrite
and
selenium
 
did
not
fit
the
normal
pattern
for
UFs
and
RSCs
because
their
MCLGs
were
based
on
direct
human
data,
not
animal
research.

In
an
overall
review,
I
noted
the
chemicals,
having
HAs
(
some
final)
where
the
LHA
had
been
changed
at
the
time
of
MCLG
promulgation.
Since
people
may
still
want
to
refer
to
a
HA
for
future
reference
and,
I
believe,
some
are
still
available
through
NTIS,
it
seems
proper
that
we
prepare
a
cover
sheet
update
to
go
with
each
Final
HA
where
a
change
in
LHA
computation
has
been
made,
to
explain
and
justify
the
change.
Otherwise
we
have
the
strange
situation
of
a
Final
HA
that
does
not
jibe
with
the
promulgated
MCLG.
The
other
option
would
be
to
create
an
entirely
new
HA
"
Final"
to
replace
the
old
outdated
"
Final".
Those
needing
this
attention
are
listed
in
Table
3.
Two
loose
ends
were
noted
in
consideration
of
Table3:
 
for
thallium,
a
discrepancy
between
the
LHA
in
the
HA
(
0.0004
mg/
l)
and
the
MCLG
(
0.0005
mg/
l),
caused
by
different
roundings
looks
strange
but
maybe
tolerable?
 
for
toluene
and
xylene,
the
Final
HAs
of
1987
have
been
upstaged
by
the
Draft
HAs
of
1993.
Shouldn't
the
latter
be
finalized
and
formally
replace
the
former?
P­
3,
UFRSC001
Table
1:
CHEMICALS
CLASSIFIED
AS
CARCINOGENS
(
A
or
B
and
C,
having
a
zero
MCLG
 
no
associated
UF
or
RSC)

arsenic
asbestos
acrylamide
benzene
alachlor
benzo(
a)
pyrene
carbon
tetrachloride
chlordane
1,2­
dibromo­
3­
chloropropane
1,2­
dichloroethane
dichloromethane
1,2­
dichloropropane
di(
2­
ethylhexyl)
phthalate
dioxin
epichlorohydrin
ethylene
dibromide
heptachlor
heptachlor
epoxide
hexachlorobenzene
lead
PCB's
pentachlorophenol
toxaphene
trichloroethylene
tetrachloroethylene
vinyl
chloride
P­
4,
UFRSC001
TABLE
2,
UNCERTAINTY
FACTORS
AND
RELATIVE
SOURCE
CONTRIBUTIONS
FOR
CHEMICALS,
ANALYSIS
PRIMARILY
BASED
ON
NON­
CARCINOGENIC
FACTORS,
SIX­
YEAR
REVIEW
Chemical,
Source
Uncertainty
Factors
Relative
Source
Reference
#
Regular
Carcinogenic
Contribution
(%)

antimony,
1
1000
 
40
atrazine,
2
100
10
20
barium,
3
3
 
NA
berillium,
1
100
10
20
cadmium,
4
10
 
25
carbofuran,
6
100
 
20
chromium,
7
100(
5)
 
71
chlorobenzene,
6
1000
 
20
copper,
5
2
 
NA
cyanide,
8
100(
5)
 
20
2,4­
D,
9
100
 
20
dalapon,
10
100(
3)
 
20
p­
dichlorobenzene,
11
1000
10
20
o­
dichlorobenzene,
11
1000
 
20
di(
2­
ethylhexyl)
adipate,
15
100(
3)
10
20
1,1­
dichloroethylene,
12
1000
10
20
cis­
1,2­
dichloroethylene,
13
3000
 
20
trans­
1,2­
dichloroethylene,
14
1000
 
20
dinoseb,
16
1000
 
20
diquat,
1
100
 
20
endrin,
19
100
 
20
ethylbenzene,
17
1000
 
20
endothall,
1
100
 
20
fluoride,
29
NA
 
NA
glyphosate,
1
100
 
20
hexachlorocyclopentadiene,
1
1000
 
20
lindane,
18
1000
10
20
nitrate,
6
NA
 
NA
nitrite,
6
NA
 
NA
methoxychlor,
6
&
20
1000(
10)
 
20
mercury,
21
1000
 
20
oxamyl,
19
100
 
20
picloram,
19
100
 
20
selenium,
6
NA
 
NA
simazine,
22
1000
10
20
P­
5,
UFRSC001
styrene,
23
1000
10
20
2,4,5­
TP,
24
100
 
20
thallium,
19
1000(
3)
 
20
toluene,
25
1000
 
20
1,2,4­
trichlorobenzene,
1
1000
 
20
1,1,2­
trichloroethane,
27
1000
10
20
1,1,1­
trichloroethane,
26
1000
 
20
xylenes,
28
100
 
20
NA:
means
Not
Appropriate,
usually
for
UFs
and
/
or
RSCs
with
respect
to
MCLGs
and
LHAs
set
on
the
basis
of
human
data,
not
animal
research
data.

SOURCE
REFERENCES
1.
FR
57
(
138),
July
17,
1992.
2.
Atrazine
Health
Advisory,
August,
1988.
3.
FR
56
(
126),
July
1,
1991.
4.
Cadmium
Health
Advisory,
March
31,
1987.
5.
FR
56
(
110),
June
7,
1991.
6.
FR
56
(
20),
January
30,
1991.
7.
Chromium
Health
Advisory,
March
31,
1987.
8.
Cyanide
Health
Advisory,
March
31,
1987.
9.
2,4­
dichlorophenoxyacetic
acid
(
2,4­
D)
Health
Advisory,
March
31,
1987.
10.
Dalapon
Health
Advisory,
February,
1989.
11.
Ortho­,
meta­
and
para­
dichlorobenzenes
Health
Advisory,
March
31,
1987.
12.
1,1­
dichloroethylene
Health
Advisory,
March
31,
1987.
13.
Cis­
1,2­
dichloroethylene
Health
Advisory,
August
1990.
14.
FR
54(
97),
May
22,
1989.
15.
Di(
2­
ethylhexyl)
adipate
Drinking
Water
Criteria
Document,
January,
1992.
16.
Dinoseb
Health
Advisory,
August,
1988.
17.
Ethylbenzene
Health
Advisory,
March
31,
1987.
18.
Lindane
Health
Advisory,
March
31,
1987.
19.
FR
55(
143),
July
25,
1990.
20.
Methoxychlor
Health
Advisory,
March
31,
1987
(
for
the
RSC).
21.
FR
54(
97),
May
22,
1989.
22.
Simazine
Health
Advisory,
August,
1988.
23.
Styrene
Health
Advisory,
March
31,
1987.
24.
Silvex
(
2,4,5­
TP)
Health
Advisory,
1988.
25.
Toluene
(
Draft)
Health
Advisory,
October,
1993.
26.
1,1,1­
trichloroethane
Health
Advisory,
March
31,
1987.
27.
1,1,2­
trichloroethane
Health
Advisory,
September
1,
1989.
28.
Xylenes
Health
Advisory
(
Draft),
September,
1993.
29.
FR50(
93),
May
14,
1985.
P­
6,
UFRSC001
Table
3
CHEMICALS
WITH
HEALTH
ADVISORIES
THAT
REQUIRE
UPDATING
CHEMICAL,
DECIDING
REFERENCE
HEALTH
ADVISORY
STATUS
1.
Antimony,
1
F(
92)
2.
Barium,
3
D(
93)
3.
Carbofuran,
6
F(
87)
4.
Chlorobenzene
(
monochlorobenzene),
6
F(
87)
5.
Trans­
1,2­
dichloroethylene,
14
F(
87)
6.
Endrin,
19
F(
87)
7.
Endothall,
1
F(
88)
8.
Glyphosate,
1
F(
88)
9.
Nitrate,
6
D(
93)
10.
Nitrite,
6
D(
93)
11.
Methoxychlor,
6
&
20
F(
87)
12.
Mercury,
21
F(
87)
13.
Oxamyl,
19
F(
87)
14.
Picloram,
19
F(
88)
15.
Thallium,
19***
F(
92)***
16.
Toluene,
25*
F(
87)*
17.
1,2,4­
trichlorobenzene,
1
F(
89)
18.
Xylenes,
28**
F(
87)**

*
Final
HA
of
1987
needs
to
be
upgraded
or
replaced
by
the
Draft
of
1993
or?
**
Final
HA
of
1987
needs
to
be
upgraded
or
replaced
by
the
Draft
of
1993
or?
***
The
rounding
of
the
Lifetime
HA
for
thallium
was
done
differently
in
the
92
HA
(.
0004
mg/
l)
than
in
FR
55(
143),
July
25,
1990
(.
0005
mg/
l).
Does
this
need
to
be
resolved?
