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6.0 ECO-SSL FOR MAMMALIAN WILDLIFE
The derivation of the Eco-SSL for mammalian wildlife was completed as two parts. First, the
TRV was derived according to the Eco-SSL guidance (U.S. EPA, 2003; Attachment 4-5).
Second, the Eco-SSL (soil concentration) was back-calculated for each of three surrogate
species based on the wildlife exposure model and the TRV (U.S. EPA, 2003).
6.1 Mammalian TRV
The literature search was completed according to the Eco-SSL guidance (U.S. EPA, 2003;
Attachment 4-2) and identified 2,429 papers with possible toxicity data for lead for either avian
or mammalian species. Of these studies, 2,157 were rejected for use as described in Section 7.5.
Of the remaining papers, 219 contained data for mammalian test species. These papers were
reviewed and the data were extracted and scored according to the Eco-SSL guidance (U.S. EPA,
2003; Attachment 4-3). The results of the data extraction and review are summarized in Table
6.1. The complete results are provided in Appendix 6-1.
Within the 219 papers there were 343 results for biochemical (BIO), behavioral (BEH),
physiology (PHY), pathology (PTH), reproduction (REP), growth (GRO), and survival (MOR)
endpoints with a total Data Evaluation Score >65 that were used to derive the TRV (U.S. EPA,
2003; Attachment 4-4). These data are plotted in Figure 6.1 and correspond directly with the
data presented in Table 6.1. The NOAEL results for growth and reproduction are used to
calculate a geometric mean NOAEL. This mean NOAEL is examined in relationship to the
lowest bounded LOAEL for reproduction, growth, and survival to derive the TRV according to
procedures in the Eco-SSL guidance (U.S. EPA, 2003; Attachment 4-5).
A geometric mean of the NOAEL values for reproduction and growth was calculated at 40.7 mg
lead/kg bw/day. However, this value is higher than the lowest bounded LOAEL for
reproduction, growth or mortality results. Therefore, the TRV is equal to the highest bounded
NOAEL below the lowest bounded LOAEL for reproduction, growth, or survival and is equal to
4.70 mg lead/kg bw/day.
6.2 Estimation of Dose and Calculation of the Eco-SSL
Three separate Eco-SSL values are calculated for mammalian wildlife, one each for three
receptor groups representing different trophic levels. The mammalian Eco-SSLs derived for lead
are calculated according to the Eco-SSL guidance (U.S. EPA 2003) and are summarized in Table
6.2.
Eco-SSL for Lead 11
March 2005