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

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

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moved toward Pb at 6255 µg/L (p < 0.05). It is thought that attraction to Pb at certain elevated<br />

concentrations is related to Pb neuron-stimulating properties (Lefcort et al., 2004). These results<br />

are consistent with those from similar studies. Control snails from reference sites, and first and<br />

second-generation snails from contaminated sites were capable <strong>of</strong> detecting and avoiding heavy<br />

metals, although the first generation was better than the second generation, and the second was<br />

better than the controls at doing so. This suggests that detection and avoidance <strong>of</strong> Pb is both<br />

genetic and environmentally based <strong>for</strong> P. columbiana. Lefcort et al. (2004) observed heightened<br />

sensitivity to, and avoidance <strong>of</strong>, heavy metals by the snails when metals where present in<br />

combination.<br />

Aquatic Vertebrates<br />

Steele et al. (1989) studied the preference-avoidance response <strong>of</strong> bullfrog (Rana<br />

catesbeiana) to plumes <strong>of</strong> Pb-contaminated water following 144-h exposure to 0 to 1000 µg<br />

Pb/L. In this laboratory experiment, tadpoles were exposed to an influx <strong>of</strong> 1000 µg Pb/L at five<br />

different infusion rates (i.e., volumes per unit time into the test system). Experiments were<br />

videotaped and location data from the tank were used to assess response. No significant<br />

differences were seen in preference-avoidance responses to Pb in either nonexposed or<br />

previously exposed animals. In a similar subsequent study, Steele et al. (1991) studied<br />

preference-avoidance response to Pb in American toad (Bufo americanus) using the same<br />

exposure range (0 to 1000 µg Pb/L). B. americanus did not significantly avoid Pb, and<br />

behavioral stress responses were not observed. The results do not indicate whether the tadpoles<br />

were capable <strong>of</strong> perceiving the contaminant. Lack <strong>of</strong> avoidance may indicate insufficient<br />

perception or the lack <strong>of</strong> physiological stress (Steele et al., 1991).<br />

The olfactory system in fish is involved in their <strong>for</strong>ming avoidance response to heavy<br />

metals (Brown et al., 1982; Svecevičius, 1991). It is generally thought that behavioral avoidance<br />

<strong>of</strong> contaminants may be a cause <strong>of</strong> reduced fish populations in some water bodies, because <strong>of</strong><br />

disturbances in migration and distribution patterns (Svecevičius, 2001). Un<strong>for</strong>tunately,<br />

avoidance <strong>of</strong> Pb by fish has not been studied as extensively as <strong>for</strong> other heavy metals<br />

(Woodward et al., 1995).<br />

Woodward et al. (1995) studied metal mixture avoidance response in brown trout<br />

(Salmo trutta), as well as the added effects <strong>of</strong> acidification. A 1-fold (1Η) mixture contained<br />

AX7-157

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