A review of ecological risk assessment methods for amphibians: Comparative assessment of testing methodologies and available data.

Historically, ecological risk assessments have rarely included amphibian species, focusing preferentially on other aquatic (fish, invertebrates, algae) and terrestrial wildlife (birds and mammal) species. Often this lack of consideration is due to a paucity of toxicity data, significant variation in study design, uncertainty with regard to exposure, or a combination of all three. Productive risk assessments for amphibians are particularly challenging, given variations in complex life history strategies. Further consideration is needed for the development of useful laboratory animal models and appropriate experimental test procedures that can be effectively applied to the examination of biological response patterns. Using these standardized techniques, risk estimates can be more accurately defined to ensure adequate protection of amphibians from a variety of stress agents. Patterns in toxicity may help to ascertain whether test results from 1 amphibian group (e.g., Urodela) could be sufficiently protective of another (e.g., Anura) and/or whether some nonamphibian aquatic taxonomic groups (e.g., fish or aquatic invertebrates) may be representative of aquatic amphibian life stages. This scope is intended to be a guide in the development of methods that would yield data appropriate for ecological risk decisions applicable to amphibians. Integr Environ Assess Manag 2017;13:601-613. © 2016 SETAC.

An evaluation of cause-effect relationships between polychlorinated biphenyl concentrations and sediment toxicity to benthic invertebrates.

Cause-effect sediment-quality benchmarks for the protection of benthic invertebrates are needed for polychlorinated biphenyls (PCBs) to support predictive risk assessments and retrospective evaluations of the causes of observed sediment toxicity. An in-depth evaluation of PCB aquatic toxicity and organic carbon partitioning was conducted to predict sediment effect concentrations using the equilibrium partitioning (EqP) approach. This evaluation was limited to invertebrate toxicity data, because PCBs may exert toxicity to invertebrates and fish via different toxicological mechanisms. As a result of differences in organic carbon partitioning among PCBs of differing levels of chlorination, the estimated EqP benchmarks increase with increasing degree of chlorination for various commercial and environmental PCB mixtures. Studies of spiked sediment toxicity using PCBs were reviewed, and their results generally were consistent with EqP predictions. Additionally, toxicity and benthic community data were reviewed for eight PCB-contaminated sites; these data also showed agreement with EqP predictions. None of these lines of evidence supports previously proposed, empirical sediment-quality guidelines for PCBs. Reasons for the lack of agreement between cause-effect and association-based benchmarks are discussed, and areas of future research to further refine EqP predictions for PCBs are identified.

Terrestrial ecological risk evaluation for triclosan in land-applied biosolids.

Triclosan is an antimicrobial compound found in many consumer products including soaps and personal care products. Most triclosan is disposed of down household drains, whereupon it is conveyed to wastewater treatment plants. Although a high percentage of triclosan biodegrades during wastewater treatment, most of the remainder is adsorbed to sludge, which may ultimately be applied to land as biosolids. We evaluated terrestrial ecological risks related to triclosan in land-applied biosolids for soil microbes, plants, soil invertebrates, mammals, and birds. Exposures are estimated using a probabilistic fugacity-based model. Triclosan concentrations in biosolids and reported biosolids application rates are compiled to support estimation of triclosan concentrations in soil. Concentrations in biota tissue are estimated using an equilibrium partitioning model for plants and worms and a steady-state model for small mammals; the resulting tissue concentrations are used to model mammalian and avian dietary exposures. Toxicity benchmarks are identified from a review of published and proprietary studies. The results indicate that adverse effects related to soil fertility (i.e., disruption of nitrogen cycling) would be expected only under "worst-case" exposures, under certain soil conditions and would likely be transient. The available data indicate that adverse effects on plants, invertebrates, birds, and mammals due to triclosan in land-applied biosolids are unlikely.

Probabilistic risk evaluation for triclosan in surface water, sediments, and aquatic biota tissues.

Triclosan, an antimicrobial compound used in personal care products, occurs in the aquatic environment due to residual concentrations in municipal wastewater treatment effluent. We evaluate triclosan-related risks to the aquatic environment, for aquatic and sediment-dwelling organisms and for aquatic-feeding wildlife, based on measured and modeled exposure concentrations. Triclosan concentrations in surface water, sediment, and biota tissue are predicted using a fugacity model parameterized to run probabilistically, to supplement the limited available measurements of triclosan in sediment and tissue. Aquatic toxicity is evaluated based on a species sensitivity distribution, which is extrapolated to sediment and tissues assuming equilibrium partitioning. A probabilistic wildlife exposure model is also used, and estimated doses are compared with wildlife toxicity benchmarks identified from a review of published and proprietary studies. The 95th percentiles of measured and modeled triclosan concentrations in surface water, sediment, and biota tissues are consistently below the 5th percentile of the respective species sensitivity distributions, indicating that, under most scenarios, adverse affects due to triclosan are unlikely.