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.

Room-temperature ionic liquids (ILs) are a class of novel green chemicals being designed to replace traditional volatile organic solvents in industrial processes. The potential effects of ILs on aquatic ecosystems have been poorly studied, despite the possibility of unintentional discharge into rivers and lakes, and their intentional disposal in wastewater treatment plants. We studied the effects of three imidazolium ionic liquids, 1-butyl-, 1-hexyl-and 1-octyl-3-methylimidazolium bromide, on the growth rates of two freshwater algae, Scenedesmus quadricauda and Chlamydomonas reinhardtii, in 96 h standard toxicity bioassays. Increases in alkyl chain length increased the toxicity of these ionic liquids to both S. quadricauda (EC 50 values of 0.005-13.23 mg L 21 ) and C. reinhardtii (EC 50 values of 4.07-2138 mg L 21 ). Bioassays were performed in both nutrient-amended media and low-nutrient groundwater to evaluate if test conditions altered IL toxicity. EC 50 values for S. quadricauda were similar between nutrient media and groundwater for all ILs tested, while the presence of nutrient media appeared to partially mitigate the toxicity of ILs to C. reinhardtii (groundwater EC 50 , media EC 50 ). Overall, S. quadricauda was much more sensitive than C. reinhardtii to all ILs tested, perhaps reflecting differences in cell wall structure. EC 50 values suggest that ILs are more, or just as, toxic to algae than many of the solvents they are intended to replace. Results of this study show that ionic liquids can elicit a range of algal responses, suggesting that a diversity of target organisms be tested in order to predict the effects of ILs in natural environments.

Merging the disciplines of green chemistry, ecotoxicology and ecology to develop environmentally-friendly industrial chemicals represents a significant collaborative challenge. This challenge can be met by extending already-informative standard toxicity and biodegradability assays to include further information about the potential persistence and biotransformation of pollutants in the environment. Development of ionic liquids (ILs) provides an ideal and proactive test system to determine several levels of environmental impact using academically interesting and industrially relevant green chemical prototypes. In this study, we investigated the biodegradability of three ILs, 1-butyl-3-methylpyridinium bromide, 1-hexyl-3-methylpyridinium bromide and 1-octyl-3-methylpyridinium bromide, by activated sludge microbial communities. We determined that all three ILs could be fully mineralized, but that only the octyl-substituted cation could be classified as "readily biodegradable". We directly examined biodegradation products of the ILs using reverse-phase high performance liquid chromatography/mass spectrometry and MS/MS methods, and identified several unique preliminary degradation products. Finally, we determined that IL-biodegradation products were less toxic than the initial compound to a standard aquatic test organism, Daphnia magna, suggesting that biodegradation in an aquatic environment would decrease toxicity hazards associated with the initial compound. This study provides further information about pyridinium IL-biodegradation and guidelines to structure future IL design and research.

The biologically active properties of many nanomaterials, coupled with their rapidly expanding production and use, has generated concern that certain types of nanoparticles could have unintended impacts when released into natural ecosystems. In the present study, the authors report the results of an experiment in which they grew three common species of stream algae as monocultures and together as polycultures in the biofilms of stream mesocosms that were exposed to 0, 0.1, or 1.0 ppm nanoparticle titanium dioxide (nTiO(2) ). The nTiO(2) did not alter the growth trajectory of any algal biofilm over 10+ generations. However, Ti accrual in biofilms not only differed among the algal species but was also higher in polycultures than in the average monoculture. Variation in accrual among species compositions was readily predicted by differences in the total biomass achieved by the different biofilms. When biofilms were fed to the herbivorous snail Physa acuta at the end of the experiment, initial concentrations of nTiO(2) did not alter short-term rates of herbivory. However, because of differences in palatability among the algae, biofilm composition influenced the amount of nTiO(2) that accumulated in the herbivore tissue. The results have important implications for understanding how efficiently nTiO(2) is removed from surface waters and the potential transfer of nanomaterials to higher trophic levels.