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

variety of plant produced by selective breeding) but was not related to genotype. Twenty
cultivars were tested from three genotypes. The differences in Pb concentrations among
cultivars were smallest when comparing concentrations in the grains at the ripening stage.
This study also found that toxicity varied by cultivar; at 800 mg Pb/kg soil, some cultivars
were greatly inhibited, some were significantly improved, and others showed no change.
Dearth et al. (2004) compared the response of Fisher 344 (F344) rats and Sprague-Dawley
(SD) rats to exposure via gavage to 12 mg Pb/mL as Pb-acetate. Blood Pb levels in the F344
dams were higher than those of the SD dams. Lead delayed the timing of puberty and
suppressed hormone levels in F344 offspring. These effects were not observed in the offspring
of SD rats, even when the dose was doubled. The authors conclude that F344 rats are more
sensitive to Pb (Dearth et al., 2004).
Biological Factors
Several biological factors may influence Pb uptake and organism response, including
organism age, sex, species, feeding guild, and, for plants, the presence of mycorrhizal fungi.
Monogastric animals are more sensitive to Pb than ruminants (Humphreys, 1991).
Younger organisms may be more susceptible to Pb toxicity (Eisler, 1988; Humphreys,
1991). Nestlings are more sensitive to the effects of Pb than older birds, and young altricial birds
(species unable to self-regulate body heat at birth, such as songbirds), are considered more
sensitive than precocial birds (species that have a high degree of independence at birth, such as
quail, ducks, and poultry) (Scheuhammer, 1991).
Gender can also have an effect on the accumulation of Pb by wildlife (Eisler, 1988).
Female birds accumulate more Pb than males (Scheuhammer, 1987; Tejedor and Gonzalez,
1992). These and other authors have related this to the increased requirement for calcium in
laying females.
Different types of invertebrates accumulate different amounts of Pb from the environment
(U.S. Environmental Protection Agency, 1986a). There may be species- and sex-specific
differences in accumulation of Pb into invertebrates, specifically arthropods. This has been
shown by Wilczek et al. (2004) who studied two species of spider, the web-building
A. labyrinthica and the active hunter wolf spider P. lugubris. The body burdens of Pb in the
wolf spider were higher than in the web-building spider, and this may be due to the more
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