^\ ^The Dermal Chronic RfD, Dermal Subchronic RfD, and Dermal Slope
Factor are all derived values. These values were calculated using the
method provided in the *Risk Assessment Guidance for Superfund: Volume
1, Human Health Evaluation Manual, Part A *(EPA/540/1-89/002).

^\ ^Doses were derived from inhalation reference concentrations
(mg/m^3^) from IRIS and HEAST by multiplying a conversion factor of 20
m^3^/day per 70 kg by the reference concentrations.

\* EPA Region 4 has adopted the following default oral absorption
efficiencies when chemical-specific values are not available: 80% for
VOCs; 50% for SVOCs; 20% for inorganic chemicals. *RAGS: Region 4
Bulletins, Human Health Risk Assessment* (Interim Guidance) (November
1995).

a Source: Integrated Risk Information System (IRIS)

b Source: Health Effects and Environmental Affects Summary Table (HEAST)
1995

c These subchronic and chronic non-cancer toxicity values are found in
Agency documents, but were calculated by alternative methods that are
not currently practiced by the RfD/RfC Work Group. These values are
considered to be adequate provisional values for risk assessment
purposes at Superfund and RCRA sites, but are subject to be reviewed by
the RfD/RfC Work Group and revised when necessary to reflect current
work group practices.

d Lead Alkyls - See IRIS cover sheet for further explanation

e Contact the Superfund Health Risk Technical Support Center:
(513)569-7300

f HEAST concluded that toxicity data were inadequate for calculation of
oral RfDs for copper and substituted the current drinking water standard
(MCLG) of 1.3 mg/L.

g Listed as \"Dinitrotoluene mixture, 2,4-/2,6-\" in IRIS. The value is
based on a study using technical grade DNT.

h Value expressed as fibers/L.

i (pg/m^3^)^-1^

j The oral toxicity values for 'Cadmium (Diet)' are to be used for soil
and food uses while the oral toxicity values for 'Cadmium (Water)' are
to be used for water uses only.

k This chemical is a criteria pollutant regulated by National Ambient
Air Quality Standards under the Clean Air Act. The NAAQS are not
included in the table because they represent different levels of review
and different methods of calculation and must be interpreted and used
differently. A list of NAAQS is appended to the table.

L Agency for Toxic Substances and Disease Registry (ATSDR).
*Toxicological Profile for Carbon Disulfide. *1992. ATSDR/TP-91/09.

m IRIS no longer separates manganese values for chronic oral RfDs into
water and diet RfDs. The chronic oral RfD for the total oral intake of
manganese is 1.40E-01. However, when assessing exposure to manganese
from drinking water or soil, IRIS recommends using a modifying factor of
3, thereby lowering the RfD to 4.67E-02, which has been rounded to
4.6E-02. Rounding to 4.7E-02 is more accurate, but makes the value less
conservative. HEAST values remain separated into water and diet
subchronic RfDs.

n The cancer potency of PCB mixtures is determined using a three tiered
approach that depends on the information available. Criteria for use of
the High Risk and Persistence Tier include: food chain exposure;
sediment or soil ingestion; dust or aerosol inhalation; dermal exposure
if an absorption factor has been applied; any early-life exposure; and
the presence of dioxin-like, tumor-promoting, or persistent congeners.
This value, 2.00e+00 per (mg/kg)/day, is the upper-bound slope factor
for the High Risk and Persistence Tier. The central-estimate slope
factor for this tier is 1.00+00 per (mg/kg)/day.

o Criteria for use of the Low Risk and Persistence Tier includes:
ingestion of water-soluble congeners; inhalation of evaporated
congeners; and dermal exposure if no absorption factor has been applied.
The value of 4.00E-01 per (mg/kg/day) is the upper-bound Oral Slope
Factor for the Low Risk and Persistence Tier. The central-estimate Oral
Slope Factor for the Low Risk and Persistence Tier is 3.00E-01 per
(mg/kg/day). For ingestion of water-soluble congeners, the middle tier
upper-bound slope factor can be converted to a unit risk of 1.00E-05 per
(ug/L/day).

p This value is the upper-bound Oral Slope Factor for the Lowest Risk
and Persistence Tier. Criteria for use of this tier include situations
in which congener or isomer analyses verify that congeners with more
than 4 chlorines comprise less than 0.5% of the total PCBs. The
central-estimate Oral Slope Factor for the Lowest Risk and Persistence
Tier is 4.00E-02 per (mg/kg/day).

q For inhalation of evaporated congeners, the middle tier (Low Risk and
Persistence Tier) slope factor can be converted to a unit risk estimate.
The value 4.00E-01 per (mg/kg/day) is the upper-bound Inhalation Slope
Factor for the Low Risk and Persistence Tier. The value 1.00E-04 per
(ug/m^3^/day) is the upper-bound Inhalation Unit Risk. For inhalation of
an aerosol or dust contaminated with PCBs, the slope factor for the High
Risk and persistence Tier should be used.

r Region 4 has adopted a Toxicity Equivalency Factor (TEF) methodology
for carcinogenic polycyclic aromatic hydrocarbons (PAHs) and dioxins and
furans on the Target Compound List as described in Supplemental Guidance
from *RAGS:Region 4 Bulletins, Human Health Risk Assessment *(Interim
Guidance) (November 1995). These TEFs are based on the potency of each
compound relative to that of benzo(a)pyrene (BaP) and 2,3,7,8-TCDD. The
following TEFs were used to convert each PAH concentration to an
equivalent concentration of BaP: (1) benzo(a)pyrene, TEF=1.0; (2)
benz(a)anthracene, TEF=0.1; (3) benzo(b)fluoranthene, TEF=0.1; (4)
benzo(k)fluoranthene, TEF=0.01; (5) chrysene, TEF=0.001; (6)
dibenz(a,h)anthracene, TEF=1.0; (7) indeno(1,2,3-cd)pyrene, TEF=0.1. The
following TEFs were used to convert each dioxin and furan concentration
to an equivalent concentration of TCDD: (1) 2,3,7,8-TCDD, TEF=1.0; (2)
2,3,7,8-PeCDD, TEF=0.5; (3) 2,3,7,8-HxCdd, TEF=0.1; (4) 2,3,7,8-HpCdd,
TEF=0.01; (5) OCDD, TEF=0.001; (6) 2,3,7,8-TCDF, TEF=0.1; (7)
1,2,3,7,8-PeCDF, TEF=0.5; (8) 2,3,4,7,8-PeCDF, TEF=0.05; (9)
2,3,7,8-HxCDF, TEF=0.1; (10) 2,3,7,8-HpCDF, TEF=0.01; and (11) OCDF,
TEF=0.001.

s The chemical name \'Mercury (inorganic)\' was replaced with the name
\'Mercury (elemental)\' in 9/95; both have the same CAS number as
\'Mercury (elemental)\' and a GIABS of 0.01%. Note: because 'Mercuric
Chloride' was used in the studies from which the toxicity values for
'Mercury (inorganic)' were derived and because 'Mercuric Chloride' is a
specific inorganic form/compound of 'Mercury (inorganic)', the oral RfD
values have been assigned to 'Mercuric Chloride'. However, the RAP may
also use these values for 'Mercury (inorganic)' or 'Mercury Inorganic
Salts', but they do [not]{.underline} apply to 'Mercury (elemental).

t This entry was formerly listed as Nickel (metallic) with the CAS
number 7440-02-0. The chemical name was changed so that it more
accurately indicates the chemicals used in the studies from which the
values were derived. Several different nickel salts were used, so the
listing of one CAS number is not appropriate and has been replaced with
the work VARIOUS. The values remain unchanged. Risk Assessment Program
assigns these values to Nickel (metallic), although they are no longer
listed with that chemical name.

u The Inhalation Slope Factor was calculated from inhalation unit risk
as described in Supplemental Guidance from *RAGS: Region 4 Bulletins,
Human Health Risk Assessment* (Interim Guidance) (November 1995).

v The Risk Assessment Program has contacted Superfund and been given
provisional values which should be used for DOE-ORR projects. This value
should be clearly documented as provisional. For other projects,
Superfund Health Risk Technical Support Center should be contacted
directly (513)569-7300.

w This value was withdrawn from IRIS or HEAST. If this chemical is
identified as a risk driver, the risk assessor should consult Region 4
Office of Health Assessment personnel. All withdrawn values should be
clearly documented when used in any risk assessment activity.

x Provisional inhalation toxicity values have been developed by the
National Center for Environmental Assessment (NCEA). *RAGS: Region 4
Bulletins, Human Health Risk Assessment* (Interim Guidance) (November
1995).

y The value of 34 mg/L is a concentration in drinking water given to
both chronic and subchronic RfDs. Specifically related to organoleptic
threshold. Safe concentration may be higher, but data are inadequate to
assess.

z An unverified oral chronic RfD of 0.04 mg/kg-d was developed for
Mercuric Sulfide by the Chemical Hazard Evaluation group of the Health
and Environmental Risk Analysis section of the ORNL Life Sciences
Division in March of 1993, based on the study by *N.W. Revis, G.
Holdsworth, G. Bingham, A. King, J. Elmore. 1989, An assessment of
health risk associated with Mercury in soil and sediment from East Fork
Poplar Creek, Oak Ridge, Tennessee, Oak Ridge Research Institute, Final
Report, pages 1-58*. Until this RfD is EPA-approved, use of the value by
the RAP should be documented and footnoted, and the uncertainties
associated with this RfD discussed in the risk assessment. The UF is 300
and the MF is 1; the confidence in the RfD study=medium, database=low,
and RfD=low. The dermal chronic RfD associated with this unverified oral
chronic RfD is 1.2E-05 mg/kg-d; use of this dermal toxicity value should
also be documented, footnoted, and discussed in the risk assessment.

aa An EPA-approved oral chronic RfD for elemental Mercury is currently
not available (refer to footnote s). However, because of the low
bioavailability similar to that of Mercuric Sulfide, the RAP may use the
unverified oral chronic RfD for Mercuric Sulfide (0.04 mg/kg-d) as a
proxy/surrogate with appropriate documentation, explanation, footnotes,
and uncertainty discussions (refer to footnote z). The dermal chronic
RfD associated with this unverified oral chronic RfD for elemental
Mercury is 4.0E-06 mg/kg-d; use of this dermal toxicity value should
also be documented, footnoted, and discussed in the risk assessment.

ab United States Environmental Protection Agency (EPA). 1992. *Dermal
Exposure Assessment: Principles and Applications. *Interim Report.
EPA/600/8-91/011B.

ac Where chemical-specific information is not available, dermal
absorption factors of 1.0% for organics and 0.1% for inorganics should
be used as defaults in determining the uptake associated with dermal
exposure to contaminated soils. *RAGS: Region 4 Bulletins, Human Health
Risk Assessment* (Interim Guidance) (November 1995).

ad The Inhalation Unit Risk was calculated from inhalation slope factor
as described in Supplemental Guidance from RAGS: Region 4 Bulletins,
Human Health Risk Assessment (Interim Guidance) (November 1995).