Dames & Moore, 1999 - USDA Forest Service

Lupinus bicolor, and Trijolium prafem) were also significantly more tolerant of copper than plants not
growing on mine soils.
The information provided above indicates that phytotoxic conditions do not currently esist at several areas
at the Holden site. Therefore, it was desirable to develop a tier I1 set of toxicity benchmarks by which to
judge the potential toxicity of the Holden soils to plants. Beyer et al. (1985) reported that a number of plants
were able to survive and grow at a site contaminated with cadmium, copper, lead, and zinc (Table 7.2.3-3B).
These values were used as TRVs for plants.
Aquatic and Terrestrial Birds and Mammals
Oak Ridge National Laboratory (Sample et al. (1996) has compiled a series of toxicological benchmarks
for birds and mammals. However, for certain mammalian species, these benchmarks were supplemented
andlor replaced with peer-reviewed pubIished toxicological data. Tables 7.2.3-4A and 7.2.3-48 list the
selected ROCs, PCOCs, and benchmark values. If PCOCs were not toxic to plants or earthworms, it was
assumed they would not be toxic to birds or mammals. .
- Birds
Sample et al. (1996) recommended that the TRV for site-specific avian species should be the same as the
NOAEL for the surrogate species used. This decision was based upon data developed by Mineau et al.
(1996) which showed that scaling factors for body mass in birds were not significantly different From unity.
This conclusion is supported by Hancock (1997). Since there is no evidence that scaling is appropriate for
birds exposed to metals, no scaling for body size was used in the present document. This was considered a
conservative approach since most of the birds used in bioassays are larger than the potentially most exposed
ROCs, the American Dipper and the American Robin, and scaled sensitivity increases with decreasing body
mass.
Where only LOAEL data were available, ORNL estimated the NOAEL by dividing the LOAEL by 10. In
the present study, where the ORNL no effect concentration (NOEC) and the lowest effect concentrations
(LOEC) were close, the ORNL NOAEL was accepted without change. However, where there are large
gaps between the NOEC and the LOEC, there is a risk that the real NOEC much higher than the lowest
concentration tested. Therefore, where the NOEC and the LOEC were separated by a factor of 10-fold or
more, the NOAEL was estimated from the LOAEL by dividing by 5. This is justified because Lewis et al.
(1990) showed that a factor of 5 is adequate to account for the LOAEL to NOAEL conversion in 96 percent
of the 52 species where both LOAEL and NOAEL data were available. Dourson and ~tara also found that a
factor of 5 or less was sufficient to account for the conversion of LOAELs to NOAELs in 96 percent of
chemicals tested (EPA, 1997). Therefore, for this risk assessment, NOAELs were estimated From LOAELs
by dividing by 5. The TRVs for birds are shown in Table 7.2.3-4A.
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17693-005-019Uuly 27.1999;5:16 PMDRMT FINAL RI REPORT