Effects of Inorganic and Organic Nanomaterials in Aquatic Systems.
Metal oxide nanomaterials are widely used components of our daily lives, but relatively little has been done to evaluate their toxicity to developing organisms. This is in large part due to their low acute toxicity. Chronic studies of developing Xenopus laevis exposed to CuO and ZnO in water indicate that these materials are more toxic than a similar concentration of their respective divalent cations. As has been noted with several toxicants, a sharp increase in toxicity is observed for CuO and ZnO after 4 days of exposure. The magnitude of this increase is greater than with the respective divalent cations. There are also marginal improvements in survival and growth at very low concentrations on ZnO and CuO. These data provide clear directions for future research needs into the effects of these types of compounds.
Bioaccumulation and bioavailability are critical aspects of understanding nanomaterial behavior and potential risk. C60 has been chosen as a model compound for study by the USEPA and by many other federal agencies. This prompted our evaluation of C60 bioaccumulation with the standard test organism Lumbriculus variegatus. C60 accumulation was dependent on the size of nC60 agglomerates and proceeded minimal extent in all cases. Comparisons to pyrene bioaccumulation indicated that the nC60 bioaccumulated to a lesser extent than would be predicted by Kow. Conversely, nC60 elevated the oxidative stress indicator, peroxidase, to a greater extent than did pyrene. These data indicate a need to evaluate biological endpoints rather than simple uptake in the case of nC60 and related compounds.
George P. Cobb
Professor and Chair
Department of Environmental Science
Waco, TX 76798