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Estimates of the concentration of cadmium constituting a threat to aquatic ecosystems were derived from laboratory tests conducted at two levels of the biological hierarchy. A population level estimate was derived from single species toxicity tests and a community level estimate was derived from laboratory tests on microbial communities. Estimates were compared to each other and to an ecosystem level estimate derived from reports of ecological health and ambient cadmium levels in rivers, lakes, and streams. Estimates of permissible levels for short term exposures differed by an order of magnitude. Single species toxicity tests indicated that a level of 46.1 ug Cd/L would affect only 5% of taxa. The corresponding estimate from the community level test was 459.4 ug Cd/L. Similar estimates of permissible levels for chronic exposures were not significantly different (1.02 and 0.20 ug Cd/L, single species arid community level tests, respectively). Both of the laboratory derived estimates of permissible levels for chronic exposure fell within a rational range; the minimum level defined by median cadmium levels reported in healthy aquatic systems (0.05 ug Cd/L), and the maximum level defined by median cadmium levels reported in damaged aquatic systems (9.2 ug Cd/L). However, the community level estimate was obtained more efficiently, permitting an estimate of effects on diversity from a single test. Single species level tests, community level tests, and field studies each contributed unique information to hazard evaluation. Using information from all levels will strengthen predictions. / Master of Science

Thesis (M.A.)--University of Hawaii at Manoa, 2005. / Includes bibliographical references (leaves 146-156). / Also available by subscription via World Wide Web / xxi, 156 leaves, bound ill., maps 29 cm

There is relatively little known about the fate of human pharmaceuticals once they are released into the aquatic environment and what adverse impacts these compounds have on exposed aquatic organisms. Both of these factors are essential in defining the potential risk pharmaceuticals pose in the aquatic environment. For this project up to 14 human therapeutic agents were selected as representative compounds to assess both their fate and effects within model aquatic systems. Considering sediments often serve as a repository for aquatic contaminants, the interaction of the selected pharmaceuticals with sediment was assessed. The sorption of the selected pharmaceuticals was found to be highly variable. Furthermore, the solution pH and ionic strength, due to Ca2+, were found to exert a large degree of influence on the extent of sorption observed. These solution parameters, among others, may therefore make it difficult to predict the fate of pharmaceuticals, in terms of their association with sediments, using standardised assessment methods alone. There is an extensive pool of knowledge on pharmaceuticals, in terms of their pharmacological profile, so their distribution within the human body (using the volume of distribution or VD) was compared with their distribution within a sediment / water system (using the partition coefficient or Kd). The correlation between the VD and Kd indicated this relationship provided a reasonable basis for estimating the distribution of drugs within the test sediment / water systems. This finding suggests that further exploration of the use of pharmacological data in understanding the potential fate of pharmaceuticals in aquatic systems is warranted. The extent of the pharmaceuticals respective desorption values was also found to be highly variable within a standard test system. Further analysis on the desorption of carbamazepine, an anti-epileptic drug, was undertaken using an isotopic dilution technique. Observations from the isotopic dilution study indicated that both contact time with sediment and the quality of organic carbon could play an important role in the potential for sediments to irreversibly sorb carbamazepine present in aquatic systems. The desorption hysteresis observed for the other pharmaceuticals also indicates considerable effort is still required to address the issue of whether sediments can be a means of reducing exposure of pharmaceuticals to aquatic organisms (a “sink”) or a means of increasing exposure to sediment-dependent organisms (a “source”). The necessity for further work on investigating the role that sorption with sediments may play in the fate and effects of human pharmaceuticals was highlighted by a series of ecotoxicological assays in both sediment and solution-only systems. Sediment-dwelling freshwater midges, Chironomus tepperi, were exposed to carbamazepine in both short- and long-term assays. Wet weight was found to be significantly reduced during short-term assays, while the development of C. tepperi larvae was found to be significantly inhibited when exposed to spiked sediment, over a longer exposure period. For these assays, the aqueous phase may have been a more important route of exposure of carbamazepine for the midges. This study has indicated that sediments are likely to play an important role in the fate of pharmaceuticals and, subsequently, their effects. However, considerably more effort is required to assess the role sediments have and how this knowledge can be linked with current regulatory ecological risk assessments. / http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1298389 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2007

There is relatively little known about the fate of human pharmaceuticals once they are released into the aquatic environment and what adverse impacts these compounds have on exposed aquatic organisms. Both of these factors are essential in defining the potential risk pharmaceuticals pose in the aquatic environment. For this project up to 14 human therapeutic agents were selected as representative compounds to assess both their fate and effects within model aquatic systems. Considering sediments often serve as a repository for aquatic contaminants, the interaction of the selected pharmaceuticals with sediment was assessed. The sorption of the selected pharmaceuticals was found to be highly variable. Furthermore, the solution pH and ionic strength, due to Ca2+, were found to exert a large degree of influence on the extent of sorption observed. These solution parameters, among others, may therefore make it difficult to predict the fate of pharmaceuticals, in terms of their association with sediments, using standardised assessment methods alone. There is an extensive pool of knowledge on pharmaceuticals, in terms of their pharmacological profile, so their distribution within the human body (using the volume of distribution or VD) was compared with their distribution within a sediment / water system (using the partition coefficient or Kd). The correlation between the VD and Kd indicated this relationship provided a reasonable basis for estimating the distribution of drugs within the test sediment / water systems. This finding suggests that further exploration of the use of pharmacological data in understanding the potential fate of pharmaceuticals in aquatic systems is warranted. The extent of the pharmaceuticals respective desorption values was also found to be highly variable within a standard test system. Further analysis on the desorption of carbamazepine, an anti-epileptic drug, was undertaken using an isotopic dilution technique. Observations from the isotopic dilution study indicated that both contact time with sediment and the quality of organic carbon could play an important role in the potential for sediments to irreversibly sorb carbamazepine present in aquatic systems. The desorption hysteresis observed for the other pharmaceuticals also indicates considerable effort is still required to address the issue of whether sediments can be a means of reducing exposure of pharmaceuticals to aquatic organisms (a “sink”) or a means of increasing exposure to sediment-dependent organisms (a “source”). The necessity for further work on investigating the role that sorption with sediments may play in the fate and effects of human pharmaceuticals was highlighted by a series of ecotoxicological assays in both sediment and solution-only systems. Sediment-dwelling freshwater midges, Chironomus tepperi, were exposed to carbamazepine in both short- and long-term assays. Wet weight was found to be significantly reduced during short-term assays, while the development of C. tepperi larvae was found to be significantly inhibited when exposed to spiked sediment, over a longer exposure period. For these assays, the aqueous phase may have been a more important route of exposure of carbamazepine for the midges. This study has indicated that sediments are likely to play an important role in the fate of pharmaceuticals and, subsequently, their effects. However, considerably more effort is required to assess the role sediments have and how this knowledge can be linked with current regulatory ecological risk assessments. / http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1298389 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2007

There is relatively little known about the fate of human pharmaceuticals once they are released into the aquatic environment and what adverse impacts these compounds have on exposed aquatic organisms. Both of these factors are essential in defining the potential risk pharmaceuticals pose in the aquatic environment. For this project up to 14 human therapeutic agents were selected as representative compounds to assess both their fate and effects within model aquatic systems. Considering sediments often serve as a repository for aquatic contaminants, the interaction of the selected pharmaceuticals with sediment was assessed. The sorption of the selected pharmaceuticals was found to be highly variable. Furthermore, the solution pH and ionic strength, due to Ca2+, were found to exert a large degree of influence on the extent of sorption observed. These solution parameters, among others, may therefore make it difficult to predict the fate of pharmaceuticals, in terms of their association with sediments, using standardised assessment methods alone. There is an extensive pool of knowledge on pharmaceuticals, in terms of their pharmacological profile, so their distribution within the human body (using the volume of distribution or VD) was compared with their distribution within a sediment / water system (using the partition coefficient or Kd). The correlation between the VD and Kd indicated this relationship provided a reasonable basis for estimating the distribution of drugs within the test sediment / water systems. This finding suggests that further exploration of the use of pharmacological data in understanding the potential fate of pharmaceuticals in aquatic systems is warranted. The extent of the pharmaceuticals respective desorption values was also found to be highly variable within a standard test system. Further analysis on the desorption of carbamazepine, an anti-epileptic drug, was undertaken using an isotopic dilution technique. Observations from the isotopic dilution study indicated that both contact time with sediment and the quality of organic carbon could play an important role in the potential for sediments to irreversibly sorb carbamazepine present in aquatic systems. The desorption hysteresis observed for the other pharmaceuticals also indicates considerable effort is still required to address the issue of whether sediments can be a means of reducing exposure of pharmaceuticals to aquatic organisms (a “sink”) or a means of increasing exposure to sediment-dependent organisms (a “source”). The necessity for further work on investigating the role that sorption with sediments may play in the fate and effects of human pharmaceuticals was highlighted by a series of ecotoxicological assays in both sediment and solution-only systems. Sediment-dwelling freshwater midges, Chironomus tepperi, were exposed to carbamazepine in both short- and long-term assays. Wet weight was found to be significantly reduced during short-term assays, while the development of C. tepperi larvae was found to be significantly inhibited when exposed to spiked sediment, over a longer exposure period. For these assays, the aqueous phase may have been a more important route of exposure of carbamazepine for the midges. This study has indicated that sediments are likely to play an important role in the fate of pharmaceuticals and, subsequently, their effects. However, considerably more effort is required to assess the role sediments have and how this knowledge can be linked with current regulatory ecological risk assessments. / http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1298389 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2007

This dissertation research explored the capabilities of neuronal networks grown on substrate integrated microelectrode arrays in vitro to be applied to toxicological research and lipid signaling. Chapter 1 details the effects of chlorine on neuronal network spontaneous electrical activity and pharmacological sensitivity. This study demonstrates that neuronal networks can maintain baseline spontaneous activity, and respond normally to pharmacological manipulations in the present of three times the chlorine present in drinking water. The findings suggest that neuronal networks may be used as biological sensors to monitor the quality of water and the presence of novel toxicants that cannot be detected by conventional sensors. Chapter 2 details the neuromodulatory effects of N-acylethanolamides (NAEs) on the spontaneous electrical activity of neuronal networks. NAEs are a group of lipids that can mimic the effects of marijuana and can be derived from a variety of plant sources including soy lecithin. The most prominent NAEs in soy lecithin, palmitoylethanolamide (PEA) and linoleoylethanolamide (LEA), were tested individually and were found to significantly inhibit neuronal spiking and bursting activity. These effects were potentiated by a mixture of NAEs as found in a HPLC enriched fraction from soy lecithin. Cannabinoid receptor-1 (CB1-R) antagonists and other cannabinoid pathway modulators indicated that the CB1-R was not directly involved in the effects of NAEs, but that enzymatic degradation and cellular uptake were more likely targets. The results demonstrate that neuronal networks may also be a viable platform for the elucidation of biochemical pathways and drug mechanisms of action.

Sediments in the Trinity River were chemically, physically and biologically characterized and assessed for toxicity. Laboratory bioassays were conducted to identify sediments which induced toxic responses in test organisms and to document these responses through time. Metal and organic contaminant concentrations in bottom sediments were measured. Relationships between these concentrations and biological responses observed in laboratory bioassays were determined. Toxicity identification / reduction methods were used to characterize sediment toxicants. Sediment oxygen demand was also measured in resuspended and undisturbed bottom sediments through time. The Background Sediment Chemistry Approach and the Sediment Bioassay Approach were used to assess sediment quality. Sediment toxicity was observed in whole sediment bioassays using Chironomus tentans as the test species. A relationship between sediment contaminant concentration and toxicity was observed in approximately sixty percent of the sediments. Oxygen demand of resuspended sediments was elevated in sediments at two locations on the river. Oxygen demand of undisturbed sediments was elevated at one location on the river. Characterization of sediment toxicants was conducted using EDTA, pH, and carbon treatments and manipulations of the sediments. Aeration tests were also used to evaluate the contribution of volatile organic contaminants to observed toxicity.

Research efforts in aquatic toxicology have historically centered on the chemical analyses and toxic effects of waters to aquatic organisms. More recently, sediment-source toxicity has been explored, with efforts concentrated on establishing sensitive and accurate methodologies. This study focused on the toxicity of trivalent chromium, hexavalent chromium, and fluoranthene to Pimephales promelas, Ictalurus punctatus, and Lepomis macrochirus. Test fish were exposed to both water-borne and sediment-source toxicants for 96 hours (h) and 30 days (d). A 96-h and 30-d LC50 (mg/L Cr, ug/L Fluoranthene) was determined for each fish species exposed to aqueous toxicants. In addition, 96-h and 30-d LC50s were determined for each fish species from sediment chromium concentrations (mg/kg) and sediment fluoranthene concentrations (ug/kg). Although lethality endpoints were used throughout this research, acute effects other than mortality were determined for Lepomis macrochirus exposed to hexavalent chromium. Lethal toxicity values (96-h and 30-d LC50 and their 95% confidence limits) for trivalent chromium could not be determined since trivalent chromium concentations above 6.0 mg/L could not be obtained at water pHs compatible with these fish species. Trivalent chromium addition to test waters at pHs compatible with fish survival resulted in a chromium precipitate that was not lethal to test fish. In contrast, fathead minnows, channel catfish, and bluegill sunfish exposed to hexavalent chromium in water and sediments experienced mortality. Fathead minnows exposed to fluoranthene in water for 96h demonstrated a maximum mortality of 69%, while 100% mortality was achieved with channel catfish in similar tests. Sediment tests with fluoranthene resulted in 100% mortality with both fathead minnows and channel catfish.