Bioaccessibility of metals in alloys: evaluation of three surrogate biofluids.

Bioaccessibility in vitro tests measure the solubility of materials in surrogate biofluids. However, the lack of uniform methods and the effects of variable test parameters on material solubility limit interpretation. One aim of this study was to measure and compare bioaccessibility of selected economically important alloys and metals in surrogate physiologically based biofluids representing oral, inhalation and dermal exposures. A second aim was to experimentally test different biofluid formulations and residence times in vitro. A third aim was evaluation of dissolution behavior of alloys with in vitro lung and dermal biofluid surrogates. This study evaluated the bioaccessibility of sixteen elements in six alloys and 3 elemental/metal powders. We found that the alloys/metals, the chemical properties of the surrogate fluid, and residence time all had major impacts on metal solubility. The large variability of bioaccessibility indicates the relevancy of assessing alloys as toxicologically distinct relative to individual metals.

Exploiting lipid-free tubing passive samplers and embryonic zebrafish to link site specific contaminant mixtures to biological responses.

The Biological Response Indicator Devices Gauging Environmental Stressors (BRIDGES) bio-analytical tool was developed in response to the need for a quantitative technology for assessing the toxicity of environmentally relevant contaminant mixtures. This tool combines passive samplers with the embryonic zebrafish model. When applied in an urban river it effectively linked site specific, bioavailable contaminant mixtures to multiple biological responses. Embryonic zebrafish exposed to extracts from lipid-free passive samplers that were deployed at five locations, within and outside of the Portland Harbor Superfund Megasite, displayed different responses. Six of the eighteen biological responses observed in 941 exposed zebrafish were significantly different between sites. This demonstrates the sensitivity of the bio-analytical tool for detecting spatially distinct toxicity in aquatic systems; bridging environmental exposure to biological response.

Selenium accumulation patterns in lotic and lentic aquatic systems.

Selenium (Se) concentrations in water column, sediment and insect compartments were measured over 3 years, in conjunction with selected physicochemical parameters, from lotic (flowing water) and lentic (standing water) sites within a single watershed in Utah, USA. There was evidence for steady-state concentrations of total [Se] in the insects, sediment and detritus, while there was no correlation between these concentrations and the concentration in surface water. Insect Se burden may therefore provide a more accurate measurement of food web accumulation risk than surface water Se concentration. The importance of organism-specific factors on Se transfer to higher trophic levels was revealed by the steady-state Se body burden within the same insect taxa occupying similar environmental compartments in both aquatic systems. Additionally, however, insect Se body burdens, even within similar taxa, were up to 7 times greater within the lentic compared with the lotic system, and site-specific biogeochemical processes are also likely to play a role in the pattern and level of Se accumulation between hydrogeochemically different aquatic systems occurring within the same watershed. Though a site-specific relationship was apparent between organic content and sediment and detritus Se concentrations, this factor did not account for insect Se accumulation differences between the lotic and lentic aquatic habitats. If carbon content is to be used as a site-specific predictor of Se accumulation potential, further investigations of it's influence on the food web accumulation rate of Se are required.