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

TRV. The toxicity data that were reviewed to develop the TRV are presented in the following
subsections.
Representative avian and mammalian wildlife species were selected for modeling Pb
exposures to wildlife with different diets and calculating the Eco-SSL. The avian species
selected were dove (herbivore), woodcock (insectivore), and hawk (carnivore). The mammalian
species selected were vole (herbivore), shrew (insectivore), and weasel (carnivore). The lowest
of the three back-calculated soil concentrations, which resulted in an HQ = 1, was selected as the
Eco-SSL. For Pb, the lowest values were for the insectivorous species of bird and mammal.
Avian Consumers
Effects on birds observed in studies conducted since the 1986 Lead AQCD (U.S.
Environmental Protection Agency, 1986a) are similar to those reported previously: mortality,
changes in juvenile growth rate and weight gain, effects on various reproductive measures, and
changes in behavior (U.S. Environmental Protection Agency, 2005b). Reproductive effects
following Pb exposure included declines in clutch size, number of young hatched, and number of
young fledged as well as decreased fertility or eggshell thickness. Few significant reproductive
effects have been reported in birds at Pb concentrations below 100 mg/kg in the diet
(Scheuhammer, 1987).
The literature search completed for Eco-SSL development identified 2,429 papers for
detailed review for either avian or mammalian species, of which 54 met the minimum criteria for
further consideration for avian Eco-SSL development (U.S. Environmental Protection Agency,
2005b). The 106 toxicological data points for birds 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 AX7-1.3.3;
Figure AX7-1.3.1). The geometric mean of the NOAELs was calculated as 10.9 mg/kg-day,
which was higher than the lowest bounded LOAEL (the term “bounded” means that both a
NOAEL and LOAEL were obtained from the same study). Therefore, the highest bounded
NOAEL that was lower than the lowest bounded LOAEL for survival, growth, or reproduction
(1.63 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 11 mg/kg soil for avian species (U.S.
AX7-65