user's guide and background technical document for the nevada ...

information summarized in USEPA (1986). The NDEP has chosen to utilize the more recent
methodology for assessing ARR proposed in Berman and Crump (2003) and fully described in
the guidance document.
Cadmium
Because IRIS provides different oral RfDs for cadmium in water and in foods, the BCL for
cadmium in water is based on the oral RfD for water, and the BCL for soil ingestion is based on
the RfD for food.
4,4-Dichlorobenzil
In the absence of 4,4-dichlorobenzil toxicity criteria from standard hierarchy of sources, NDEP
has provided interim guidance on this chemical (NDEP, 2009b). This guidance may be found at
http://ndep.nv.gov/bmi/docs/090115_dichlorobenzil.pdf and provides an interim RfD for
dichlorobenzil of 3.0 x 10 -4 mg/kg-d.
Hexachlorocyclohexane (HCH)
The NDEP has adopted a threshold dose value for alpha-, beta-, and gamma-HCH for use in
quantifying potential human health risks at the BMI Complex (Integral 2011a, b, and c). The
criteria documents supporting this decision are provided on the NDEP BMI Complex website
(http://ndep.nv.gov/bmi/technical.htm). These toxicity values have been incorporated into the
BCLs for these compounds.
Essential Nutrients; Specifically Calcium, Potassium, and Sodium
Calcium, potassium, and sodium are essentially nutrients and are on the Generally Recognized
As Safe (GRAS) list of the Food and Drug Administration (FDA, 2011).
“GRAS exemptions are granted for substances that are generally recognized, among
experts qualified by scientific training and experience to evaluate their safety, as having
been adequately shown through scientific procedures …to be safe under the conditions of
their intended use.” FDA, 2011
“There is no evidence in the available information on [substance] that demonstrates, or
suggests reasonable grounds to suspect, a hazard to the public when they are used at
levels that are now current or might reasonably be expected in the future.” FDA, 2011
Therefore, these three elements do not need to be included in a risk assessment for potential
human health impacts unless they are present in a compound that is a regulated chemical agent
and/or in compounds present at concentrations that may create a health hazard through
physical/chemical properties (e.g., extremely low or high pH having caustic potential).
Lead
The residential soil value for lead is based on the Integrated Exposure Uptake Biokinetic
(IEUBK) Model for lead in children developed using default parameters (USEPA, 1994). More
information on this model and other lead risk assessment guidance can be found at
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