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

other organs, have been reported (Brar et al., 1997a,b). Lead also may cause lipid peroxidation
(Mateo and Hoffman, 2001), which may be alleviated by vitamin E, although Pb poisoning may
still result (Mateo et al., 2003b). Changes in fatty acid production have been reported, which
may influence immune response and bone formation (Mateo et al., 2003a).
Response Modification
Genetics, biological factors, physical/environmental factors, nutritional factors, and other
pollutants can modify terrestrial organism response to Pb. Fisher 344 rats were found to be more
sensitive to Pb than Sprague-Dawley rats (Dearth et al., 2004). Younger animals are more
sensitive than older animals (Eisler, 1988; Scheuhammer, 1991), and females generally are more
sensitive than males (Scheuhammer, 1987; Tejedor and Gonzalez, 1992; Snoeijs et al., 2005).
Monogastric animals are more sensitive than ruminants (Humphreys, 1991). Insectivorous
mammals may be more exposed to Pb than herbivores (Beyer et al., 1985; Sample et al., 1998),
and higher tropic-level consumers may be less exposed than lower trophic-level organisms
(Henny et al., 1991). Diets deficient in nutrients (including calcium) result in increased uptake
of Pb (Snoeijs et al., 2005) and greater toxicity (Douglas-Stroebel et al., 2005) in birds, relative
to diets containing adequate nutrient levels.
Mycorrhizal fungi may ameliorate Pb toxicity until a threshold is surpassed (Malcova and
Gryndler, 2003), which may explain why some studies show increased uptake into plants (Lin
et al., 2004) while others show no difference or less uptake (Dixon, 1988). Uptake of Pb into
plants and soil invertebrates increases with a decrease in soil pH. However, calcium content,
organic matter content, and cation exchange capacity of soils also have had a significant
influence on uptake of Pb into plants and invertebrates (Beyer et al., 1987; Morgan and Morgan,
1988).
Interactions of Pb with other metals are inconsistent, depending on the endpoint
measured, the tissue analyzed, the animal species, and the metal combination (Phillips et al.,
2003; An et al., 2004; He et al., 2004; Garcia and Corredor, 2004; Perottoni et al., 2005).
AX7.1.3 Exposure-Response of Terrestrial Species
Section AX7.1.3 summarized the most important factors related to uptake of Pb by
terrestrial organisms, the physiological effects of Pb, and the factors that modify terrestrial
AX7-57