This article provides practical guidance on the use of passive sampling methods (PSMs) that target the freely dissolved concentration (Cfree) for improved exposure assessment of hydrophobic organic chemicals in sediments. Primary considerations for selecting a PSM for a specific application include clear delineation of measurement goals for Cfree, whether laboratory-based “ex situ” and/or field-based “in situ” application is desired, and ultimately which PSM is best-suited to fulfill the measurement objectives. Guidelines for proper calibration and validation of PSMs, including use of provisional values for polymer–water partition coefficients, determination of equilibrium status, and confirmation of nondepletive measurement conditions are defined. A hypothetical example is described to illustrate how the measurement of Cfree afforded by PSMs reduces uncertainty in assessing narcotic toxicity for sediments contaminated with polycyclic aromatic hydrocarbons. The article concludes with a discussion of future research that will improve the quality and robustness of Cfree measurements using PSMs, providing a sound scientific basis to support risk assessment and contaminated sediment management decisions. Integr Environ Assess Manag 2014;10:210–223. © 2014 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals, Inc. on behalf of SETAC.

A state-of-the-science review was conducted to examine the potential for microplastics to sorb hydrophobic organic chemicals (HOCs) from the marine environment, for aquatic organisms to take up these HOCs from the microplastics, and for this exposure to result in adverse effects to ecological and human health. Despite concentrations of HOCs associated with microplastics that can be orders of magnitude greater than surrounding seawater, the relative importance of microplastics as a route of exposure is difficult to quantify because aquatic organisms are typically exposed to HOCs from various compartments, including water, sediment, and food. Results of laboratory experiments and modeling studies indicate that HOCs can partition from microplastics to organisms or from organisms to microplastics, depending on experimental conditions. Very little information is available to evaluate ecological or human health effects from this exposure. Most of the available studies measured biomarkers that are more indicative of exposure than effects, and no studies showed effects to ecologically relevant endpoints. Therefore, evidence is weak to support the occurrence of ecologically significant adverse effects on aquatic life as a result of exposure to HOCs sorbed to microplastics or to wildlife populations and humans from secondary exposure via the food chain. More data are needed to fully understand the relative importance of exposure to HOCs from microplastics compared with other exposure pathways. Environ Toxicol Chem 2016;35:1667-1676. © 2016 SETAC.

Two freshwater amphipods, Hyalella azteca and Diporeia sp., were exposed to sediment spiked with radiolabeled fluoranthene at nominal concentrations of 0.1 (trace) to 1,270 nmol fluoranthene/g dry weight. In two experiments, uptake kinetics and mortality were determined over 30-d exposures. Concentrations of fluoranthene in sediment and pore water were also measured. Mean survival of H. azteca was generally high, greater than 90% after 10 or 16 d, and greater than 74% after 30 d. Mean survival was lower for Diporeia, 14% after a 30-d exposure to the highest sediment concentration in experiment 1, and 53% in experiment 2. Tissue concentrations in Diporeia were as high as 2 to 4 mol/g wet weight, a body burden that could be expected to result in death by narcosis. Hyalella azteca did not typically accumulate more than 1 mol/g wet weight, which is consistent with the lower observed mortality. Apparent steady-state biota-sediment accumulation factors (BSAFs, lipid-and organic-carbon-normalized) for sediment concentrations other than trace level tended to be higher for Diporeia (0.345-0.818) than for H. azteca (0.161-0.612). The BSAFs for trace levels tended to be lower for both species (0.045-0.436) in comparison to higher sediment concentrations. For both organisms, the internal concentration based on body residue was a more reliable indicator of toxicity than were equilibrium partitioning predictions.

Abstract-Polychaete worms which inhabit and ingest contaminated sediments may be exposed to a suite of sediment-sorbed xenobiotics, including polycyclic aromatic hydrocarbons (PAHs) such as benzo[a]pyrene (BaP). This study compared the accumulation and metabolism of sediment-sorbed BaP among various populations of polychaetes, including Leitoscoloplos fragilis, Nereis diversicolor, and Scolecolepides (ϭ Marenzellaria) viridis. After exposure to trace amounts of BaP in sediment, N. diversicolor and S. viridis were found to metabolize BaP extensively, but metabolism of BaP appeared to be much slower in L. fragilis. Within each species, no consistent, significant differences in extent of BaP metabolism were observed between worms collected from contaminated versus reference sites. This result suggests that metabolism of BaP was not induced in worms from contaminated sites. To examine the extent to which metabolism of BaP is inducible in these species, worms were exposed in the lab to 3-methylcholanthrene (3MC), a potent inducer of PAH metabolism in other species. Only one species, S. viridis, showed a small increase in the percent of total tissue BaP that was biotransformed after treatment with 3MC. Whether or not worms were treated with 3MC, biota-sediment accumulation factors (lipid-and organic carbon-normalized tissue to sediment ratios) were highest for L. fragilis.

Abstract-Two 10-d water-only toxicity tests with radiolabeled fluoranthene were conducted with two species of freshwater amphipods, Hyalella azteca and Diporeia sp. For H. azteca, 10-d median lethal concentrations were 564 nmol/L and 481 nmol/L. Tentative median lethal doses, determined from the regressions of body burden of remaining live H. azteca versus survival, were 5.6 and 3.6 mmol fluoranthene/kg wet weight tissue. Diporeia appeared to be less sensitive, because survival in Diporeia was greater than 84% after 10-d exposures. Elimination rates determined for Diporeia, ranging from 0.0011 to 0.0042/h (half-lives of 7-26 d), were much slower than rates determined for H. azteca of 0.128 to 0.188/h (half-lives of 4-6 h). Faster elimination in H. azteca may be related to its greater ability to metabolize fluoranthene. For H. azteca, an average of 17% of its body burden was present as metabolites after 24 h of exposure to radiolabeled fluoranthene, as compared to 5% for Diporeia. For Diporeia, exposure to various water concentrations of fluoranthene for various lengths of time resulted in declines in the conditional uptake clearance rates (ml water cleared/g wet weight tissue/h). A similar, although less dramatic trend was observed for conditional uptake clearance rates in H. azteca.