Superfund Research Program
Wildlife Applications to Remediation Decision-Making
Project Leader: Michael J. Hooper (Texas Tech University)
Grant Number: P42ES004696
Funding Period: 1995 - 2006
Final Progress Reports
Year: 2005 1999
Studies during the last year have focused on finishing investigations of small mammal metal exposure and effects, performing analysis of oxidative stress endpoints and assessing metal uptake in hibernating toads. Two large studies were performed to complete the project’s assessments of metal uptake from Anaconda Smelter Site soils in laboratory-reared deer mice. The first was performed in adult mice (50-day-old) dosed with 3% soil in their diet and exposed for 48 days. Soil metal concentrations encompassed low, medium and high levels as described in earlier updates. Arsenic, lead and cadmium accumulated in a dose-dependent fashion in all tissues analyzed while copper and zinc levels did not vary, as anticipated for these well regulated essential metals. Most importantly, blood lead levels that increased through the three doses were effective at inhibiting ALAD (delta-aminolevulinic acid dehydratase) activity in only the low and medium soils while the mice fed high metals soils had ALAD activities at control levels. The lack of ALAD inhibition in the presence of blood lead levels that should have severely inhibited the enzyme is consistent with findings from field studies on these sites performed earlier in this study, indicating that the feeding model project researchers have developed has strong potential for implementation as a bioassay for superfund soils. The actual mechanism for this finding is likely reactivation of the ALAD activity by transient increases in blood Zn levels during feeding bouts. A similar study is now being completed where deer mice were dosed from birth (lactationally from Anaconda soil-dosed dams for the first 21 post-natal days, 3% soil in the diet thereafter) through 100 days of age to evaluate the effects of life-long exposure in comparison to adult only exposure. Project researchers have characterized and implemented glutathione, gamma-glutamyl cystein ligase and TBARS (thiobarbituric acid reactive substances) assays for application to study tissues to assess their utility as oxidative stress biomarkers that might function better than ALAD for mixed-metal soils. Finally, a preliminary study that evaluated metal uptake in Bufo cognatus, the Great Plains toad, led to development of hibernation protocols for a more complete hibernation experiment that encompasses the typical eight month hibernation period for the focal toad species. This definitive study is under way and encompasses 12 different treatments that will examine uptake and a suite of sub-lethal endpoints, such as metabolism, water balance, morphometrics, and ALAD inhibition. These treatments represent a range of doses including: cadmium at three levels (30-400 ug/g soil), lead at three levels (10-1000 ug/g), elevated lead combined with copper at two levels, elevated lead combined with zinc at two levels, and elevated lead combined with both copper and zinc at the higher levels.