Browsing by Subject "Water -- Pollution -- Toxicology."
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Item Assessing interactions between nutrients and toxicity : influences of nitrogen and phosphorus on triclosan toxicity to the aquatic macrophyte "lemna gibba".(2009-07-01T17:00:58Z) Fulton, Barry A.; Brooks, Bryan W.; Environmental Science.; Baylor University. Dept. of Environmental Science.In the present study, influences of nutrient availability on triclosan toxicity to a model aquatic macrophyte Lemna gibba were explored. Triclosan effective concentrations varied by up to 6.5-fold depending on nutrient treatment and standardized endpoint. Mesocosm results validated these laboratory findings by also indicating greater triclosan-inhibition under higher P-availability. Ecologically relevant endpoints such as elemental stoichiometry and uptake were also differentially affected according to nutrient – triclosan treatments. In particular, tissue-N inhibition was more pronounced that tissue-P leading to N:P dose-response trends, which were most sensitive in P-limited exposure media. These stoichiometric endpoints were generally less sensitive compared to standardized growth endpoints, except under a P-limited scenario. Interactions between nutrients and contaminants were further highlighted by variable triclosan toxicity to N-uptake kinetics determined over an N-gradient. Significant inhibition to N-uptake kinetics was determined for plants co-exposed at high N concentrations while lower N-availability did not result in significant N-uptake inhibition.Item Chemical toxicity distributions in aquatic toxicology : relative sensitivities of estrogenicity assays and ecotoxicity of parabens in model freshwater organisms.(2008-12) Dobbins, Laura L.; Brooks, Bryan W.; Biology.; Baylor University. Dept. of Biology.A probabilistic ecological hazard assessment technique, chemical toxicity distributions, was used to examine the relative sensitivities of in vitro and in vivo assays for detecting estrogenicity, and to assess the hazards associated with parabens to model aquatic organisms, Pimephales promelas and Daphnia magna. Parabens represent a class of understudied personal care products with estrogenic activity that have been detected in surface waters. MCF-7 and rainbow trout vitellogenin induction were found to be the most sensitive in vitro and in vivo assays of estrogenicity, respectively. Parabens were determined to not pose a hazard to aquatic organisms at levels that are environmentally relevant, based on the bioassay endpoints evaluated. A screening level assessment further identified estrogenic activity of select parabens to adult male P. promelas. This thesis demonstrated the utility of chemical toxicity distributions for determining sensitivities among toxicological models and for assessing those compounds for which environmental exposure data are limited.