Polyvinylpyrolidone-functionalized silver nanoparticles do not affect aerobic performance or fractional rates of protein synthesis in rainbow trout (Oncorhynchus mykiss).

Aerobic performance in fish is linked to individual and population fitness and can be impacted by anthropogenic contaminants. Exposure to some engineered nanomaterials, including silver nanoparticles (nAg), reduces rates of oxygen consumption in some fish species, but the underlying mechanisms remain unclear. In addition, their effects on swim performance have not been studied. Our aim was to quantify the impact of exposure to functionalized nAg on aerobic scope and swim performance in rainbow trout (Oncorhychus mykiss) and to characterize the contribution of changing rates of protein synthesis to these physiological endpoints. Fish were exposed for 48 h to 5 nm polyvinylpyrolidone-functionalized nAg (nAgPVP; 100 µg L-1) or 0.22 µg L-1 Ag+ (as AgNO3), which was the measured quantity of Ag released from the nAgPVP over that time period. Aerobic scope, critical swimming speed (Ucrit), and fractional rates of protein synthesis (Ks), were then assessed, along with indicators of osmoregulation and cardiotoxicity. Neither nAgPVP, nor Ag+ exposure significantly altered aerobic scope, its component parts, or swim performance. Ks was similarly unaffected in 8 tissue types, though it tended to be lower in liver of nAgPVP treated fish. The treatments tended to decrease gill Na+/K+-ATPase activity, but effects were not significant. The latter results suggest that a longer or more concentrated nAgPVP exposure may induce significant effects. Although this same formulation of nAgPVP is bioactive in other fish, it had no effects on rainbow trout under the conditions tested. Such findings on common model animals like trout may thus misrepresent the safety of nAg to more sensitive species.

Functionalized silver nanoparticles depress aerobic metabolism in the absence of overt toxicity in brackish water killifish, Fundulus heteroclitus.

Engineered nanomaterials (ENMs) tend to precipitate in saline waters so the majority of aquatic toxicity studies have focused on freshwaters, where bioavailability is presumed to be higher. Recent studies have illustrated that some ENM formulations are bioavailable and bioactive in salt water and that their effects are more pronounced at the physiological than biochemical level. These findings raise concerns regarding the effects of ENMs on marine organisms. Therefore, our goal was to characterize the effects of polyvinylpyrolidone-functionalized silver ENMs (nAg) on aerobic performance in the killifish (Fundulus heteroclitus), a common euryhaline teleost. Fish were exposed to 80 µg L-1 of 5 nm nAg for 48 h in brackish water (12 ppt) and routine (MO2min) and maximum (MO2max) rates of oxygen consumption were quantified. Silver dissolution was minimal and nAg remained well dispersed in brackish water, with a hydrodynamic diameter of 21.0 nm, compared to 19.3 in freshwater. Both MO2min and MO2max were significantly lower (by 53 and 30%, respectively) in killifish exposed to nAg and a reduction in MO2 variability suggested spontaneous activity was suppressed. Neither gill Na+/K+-ATPase activity, nor various other biochemical markers were affected by nAg exposure. The results illustrate that a common ENM formulation is bioactive in salt water and, as in previous studies on functionalized copper ENMs, that effects are more pronounced at the whole animal than the biochemical level.

Geostatistical modelling of arsenic in drinking water wells and related toenail arsenic concentrations across Nova Scotia, Canada.

Arsenic is a naturally occurring class 1 human carcinogen that is widespread in private drinking water wells throughout the province of Nova Scotia in Canada. In this paper we explore the spatial variation in toenail arsenic concentrations (arsenic body burden) in Nova Scotia. We describe the regional distribution of arsenic concentrations in private well water supplies in the province, and evaluate the geological and environmental features associated with higher levels of arsenic in well water. We develop geostatistical process models to predict high toenail arsenic concentrations and high well water arsenic concentrations, which have utility for studies where no direct measurements of arsenic body burden or arsenic exposure are available. 892 men and women who participated in the Atlantic Partnership for Tomorrow's Health Project provided both drinking water and toenail clipping samples. Information on socio-demographic, lifestyle and health factors was obtained with a set of standardized questionnaires. Anthropometric indices and arsenic concentrations in drinking water and toenails were measured. In addition, data on arsenic concentrations in 10,498 private wells were provided by the Nova Scotia Department of Environment. We utilised stepwise multivariable logistic regression modelling to develop separate statistical models to: a) predict high toenail arsenic concentrations (defined as toenail arsenic levels ≥0.12 µg g(-1)) and b) predict high well water arsenic concentrations (defined as well water arsenic levels ≥5.0 µg L(-1)). We found that the geological and environmental information that predicted well water arsenic concentrations can also be used to accurately predict toenail arsenic concentrations. We conclude that geological and environmental factors contributing to arsenic contamination in well water are the major contributing influences on arsenic body burden among Nova Scotia residents. Further studies are warranted to assess appropriate intervention strategies for reducing arsenic body burden among human populations.

A kinetic study of nickel complexation in model systems by adsorptive cathodic stripping voltammetry.

Adsorptive cathodic stripping voltammetry (AdCSV) in conjunction with the competing ligand-exchange method (CLEM) was investigated as a tool for measuring dissociation rate coefficients of nickel complexes in model systems. Dimethylglyoxime (DMG) was used as the competing ligand. Citric acid (CA) and a well-characterized fulvic acid (FA) were used as model ligands. The rate coefficients were calculated, and the consistency of equilibrium and kinetic data was discussed. The contributions of the disjunctive pathway (proceeding by the dissociation of the initial complex) and the adjunctive pathway (proceeding by the formation of an intermediate complex as a result of direct attack of the competing ligand on the initial complex) on the overall reactions were investigated. The reactions of Ni-CA or Ni-FA complexes with DMG were demonstrated to proceed by both disjunctive and adjunctive pathways. The predominant pathway for the overall reaction depends on the nickel-to-initial ligand and the DMG-to-initial ligand ratios. The reactions follow predominantly the disjunctive pathway for [DMG] > or = 3 mM and Ni-to-dissolved organic carbon (DOC) ratios greater than 10 nM Ni 2+/g of DOC. Since free nickel ion in freshwaters is reported to be toxic, its rate and pathway of formation are of environmental concern.