The hypothesis that ‘microplastic will transfer hazardous hydrophobic organic chemicals (HOC) to marine animals’ has been central to the perceived hazard and risk of plastic in the marine environment. The hypothesis is often cited and has gained momentum, turning it into paradigm status. We provide a critical evaluation of the scientific literature regarding this hypothesis. Using new calculations based on published studies, we explain the sometimes contrasting views and unify them in one interpretive framework. One explanation for the contrasting views among studies is that they test different hypotheses. When reframed in the context of the above hypothesis, the available data become consistent. We show that HOC microplastic-water partitioning can be assumed to be at equilibrium for most microplastic residing in the oceans. We calculate the fraction of total HOC sorbed by plastics to be small compared to that sorbed by other media in the ocean. We further demonstrate consistency among (a) measured HOC tr...

Microplastic as a Vector for Chemicals in the Aquatic Environment: Critical Review and Model-Supported Reinterpretation of Empirical Studies

Indirect effects of contaminants in aquatic ecosystems.

The science of sediment toxicology essentially began in the late 1970s. It was largely a product of dredging concerns and recognition of widespread contamination of sediments. During the past few years, sediment toxicity research activity has increased dramatically. Currently, most tests are of an acute nature with fewer available for determining sublethal endpoints of chronic toxicity. Test systems of single and multiple species have included most levels of biological organization in aquatic ecosystems and have been conducted in the laboratory on whole sediments, interstitial waters, elutriates, or other extractable fractions under a wide variety of conditions. Evaluations of methodological effects and comparisons with in situ toxicity using surrogate test species and indigenous communities have, on occasion, shown significant differences in test responses. These differences may be attributed to laboratory-controlled parameters (e.g., light, species, life stage, exposure conditions, test phase, spiking method); sampling and laboratory-induced disruption of sediment integrity; alteration of toxicant partitioning due to manipulations and temporal effects; and failure to recognize other influencing ecosystem variables (e.g., organism niche and life cycle, sediment partitioning and gradient dynamics, physicochemical and biological process integration, biotic and abiotic disturbances, micro- and macrobiota patches, food-web interactions). Optimizing and standardizing test methods will require further studies of these variables to improve inter-laboratory comparisons and ecosystem validity. Despite the many unknowns that exist, a variety of sediment toxicity tests have been effectively used in assessing toxicant contamination by measuring the bioavailable fraction of the in-place pollutants. The optimal assays vary with the study and its objectives. Intergrative studies using several chemical, community, and toxicity measures are currently the most effective at defining ecosystem perturbations.

https://setac.onlinelibrary.wiley.com/doi/pdf/10.1002/etc.5620101204

Assessing the toxicity of freshwater sediments

Fungicides are indispensable to global food security and their use is forecasted to intensify. Fungicides can reach aquatic ecosystems and occur in surface water bodies in agricultural catchments throughout the entire growing season due to their frequent, prophylactic application. However, in comparison to herbicides and insecticides, the exposure to and effects of fungicides have received less attention. We provide an overview of the risk of fungicides to aquatic ecosystems covering fungicide exposure (i.e., environmental fate, exposure modeling, and mitigation measures) as well as direct and indirect effects of fungicides on microorganisms, macrophytes, invertebrates, and vertebrates. We show that fungicides occur widely in aquatic systems, that the accuracy of predicted environmental concentrations is debatable, and that fungicide exposure can be effectively mitigated. We additionally demonstrate that fungicides can be highly toxic to a broad range of organisms and can pose a risk to aquatic biota. Finally, we outline central research gaps that currently challenge our ability to predict fungicide exposure and effects, promising research avenues, and shortcomings of the current environmental risk assessment for fungicides.

Fungicides: An overlooked pesticide class?

European Union Risk Assessment Report

Enhanced elimination of hexachlorobenzene in rats by light liquid paraffin

Paraffin-stimulated excretion of 2,4,6,2′,4′-pentachlorobi[14C]phenyl by rats

Enhanced elimination of kepone-14C in rats fed liquid paraffin.

Influence of 2,4,6-trichlorophenol and pentachlorophenol on the biota of aquatic systems

Longterm effects of the herbicides Atrazine and Dichlobenil upon the phytoplankton density and physico-chemical conditions in compartments of a freshwater pond

J.P. Lay

Papers

Enhanced elimination of hexachlorobenzene in rats by light liquid paraffin

Paraffin-stimulated excretion of 2,4,6,2′,4′-pentachlorobi[14C]phenyl by rats

Enhanced elimination of kepone-14C in rats fed liquid paraffin.

Influence of 2,4,6-trichlorophenol and pentachlorophenol on the biota of aquatic systems

Longterm effects of the herbicides Atrazine and Dichlobenil upon the phytoplankton density and physico-chemical conditions in compartments of a freshwater pond