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

plasma levels of uric acid and creatinine and significant declines in the levels of total proteins,
albumin, glucose, and cholesterol. Brar et al. (1997a) suggested that increased uric acid and
creatinine levels could be due to an accelerated rate of protein catabolism and/or kidney damage.
They also suggested that the decline in plasma proteins and albumin levels may be caused by
diarrhea and liver dysfunction due to the Pb exposure. Brar et al. (1997b) also found that
significant changes in plasma enzymes may be causing damage to other organs.
Lead can cause an increase in tissue lipid peroxides and changes in glutathione
concentrations, which may be related to peroxidative damage of cell membranes (Mateo and
Hoffman, 2001). There are species-specific differences in resistance to oxidative stress (lipid
peroxidation), which may explain why Canada geese are more sensitive to Pb poisoning than
mallards (Mateo and Hoffman, 2001). Lead also caused an increase in the production of the fatty
acid arachidonic acid, which has been associated with changes in bone formation and immune
response (Mateo et al., 2003a). The effects observed by Mateo et al. (2003a,b) were associated
with very high concentrations of Pb in the diet (1840 mg Pb/kg diet), much higher than would be
found generally in the environment, and high enough that birds decreased their food intake.
Lead also induces lipid peroxidation in plants. Rice plants exposed to a highly toxic level
of Pb (1000 µM in nutrient solution) showed elevated levels of lipid peroxides, increased activity
of superoxide dismutase, guaiacol peroxidase, ascorbate peroxidase, and glutatione reductase
(Verma and Dubey, 2003). The elevated levels of these enzymes suggest the plants may have an
antioxidative defense mechanism against oxidative injury caused by Pb (Verma and Dubey,
2003).
AX7.1.2.6 Factors that Modify Organism Response
Research has demonstrated that Pb may affect survival, reproduction, growth,
metabolism, and development in a wide range of species. These effects may be modified by
chemical, biological, and physical factors. The factors that modify responses of organisms to Pb
are described in the following sections.
Genetics
Uptake and toxicity of Pb to plants are influenced strongly by the type of plant. Liu et al.
(2003) found that Pb uptake and translocation by rice plants differed by cultivar (a cultivated
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