Air Quality Criteria for Lead Volume II of II - (NEPIS)(EPA) - US ...

Protection Agency, 2005b). Very little research has been done to expand the knowledge of the
toxicity of Pb to mammalian wildlife, since the Eco-SSL work was done. Most studies
conducted on mammals use laboratory animals to study potential adverse effects of concern for
humans, and such studies are summarized in other sections of this document.
Of the 2,429 papers identified in the literature search for Eco-SSL development, 219 met
the minimum criteria for further consideration for mammalian Eco-SSL development (U.S.
Environmental Protection Agency, 2005b). The 343 ecotoxicological endpoints for mammals
that were further evaluated included biochemical, behavioral, physiological, pathological,
reproductive, growth, and survival effects. Growth and reproduction data were used to derive
the Eco-SSL (Table AX7-1.3.4, Figure AX7-1.3.2). The geometric mean of the NOAELs was
calculated as 40.7 mg/kg-day, which was higher than the lowest bounded LOAEL for survival,
growth, or reproduction. Therefore, the highest bounded NOAEL that was lower than the lowest
bounded LOAEL for survival, growth, or reproduction (4.7 mg Pb/kg bw-day) was used as the
TRV (U.S. Environmental Protection Agency, 2005b). The TRV was used to back-calculate the
Eco-SSL of 56 mg/kg soil (U.S. Environmental Protection Agency, 2005b). For more
information on the rationale for selecting TRVs, please refer to U.S. Environmental Protection
Agency (2003).
A review of the data presented in the Eco-SSL document (U.S. Environmental Protection
Agency, 2005b) reveals that effects on survival generally are observed at Pb doses much greater
than those reported in the 1986 Lead AQCD, where it was concluded that most animals would
die when consuming a regular dose of 2 to 8 mg Pb/kg bw-day (U.S. Environmental Protection
Agency, 1986a). However, the data presented in the Eco-SSL document (U.S. Environmental
Protection Agency, 2005b) generally do not support this. While five studies reported decreased
survival at these levels, 34 other studies reported no mortality or a LOAEL for mortality at
significantly higher doses (U.S. Environmental Protection Agency, 2005b). The five studies that
supported this low toxic level were conducted on three species (mouse, rat, and cow) and used
either gavage or drinking water as the exposure method. The 34 other studies included data on
these three species as well as five other species (rabbit, dog, pig, hamster, and shrew) and
included gavage and drinking water as well as food ingestion exposure methods. The NOAELs
for survival ranged from 3.5 to 3200 mg/kg-day (U.S. Environmental Protection Agency,
2005b). Therefore, the review of data in the Eco-SSL document suggests effects on survival of
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