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Population modeling evaluations of pesticide exposure time series were compared with aspects of a currently used risk assessment process. The US Environmental Protection Agency's Office of Pesticide Programs models daily aquatic 30-yr pesticide exposure distributions in its risk assessments, but does not routinely make full use of the information in such time series. We used mysid shrimp Americamysis bahia toxicity and demographic data to demonstrate the value of a toxicokinetic-toxicodynamic model coupled with a series of matrix population models in risk assessment refinements. This species is a small epibenthic marine crustacean routinely used in regulatory toxicity tests. We demonstrate how the model coupling can refine current risk assessments using only existing standard regulatory toxicity test results. Several exposure scenarios (each with the same initial risk characterization as determined by a more traditional organism-based approach) were created within which population modeling documented risks different from those of assessments based on the traditional approach. We also present different acute and chronic toxicity data scenarios by which toxicokinetic-toxicodynamic coupled with population modeling can distinguish responses that traditional risk evaluations are not designed to detect. Our results reinforce the benefits of this type of modeling in risk evaluations, especially related to time-varying exposure concentrations. Environ Toxicol Chem 2018;37:2633-2644. Published 2018 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America. more...

We investigated the toxicity of selenium (Se) to the soil invertebrates Folsomia candida (Collembola) and Enchytraeus crypticus (potworm). Studies were designed to generate ecotoxicological benchmarks for developing ecological soil screening levels (Eco-SSLs) for risk assessments of contaminated soils. For the present studies, we selected Sassafras sandy loam, an aerobic upland soil with soil characteristics (low levels of clay and organic matter, soil pH adjusted from 5.2 to 7.1) that support high relative bioavailability of the anionic Se species that is typically found in aerobic soil. The Se was amended into soil as sodium selenate, subjected to weathering and aging using 21 d of alternating cycles of air-drying/rehydration to 60% of the water-holding capacity of the Sassafras sandy loam soil, under ambient greenhouse conditions. Effective concentrations at 20 and 50% (EC20 and EC50) levels for production of juveniles (reproduction) were 4.7 and 10.9 mg of Se/kg of soil (dry mass basis), respectively, for Collembola, and 4.4 and 6.2 mg/kg, respectively, for the potworms. The data enabled the derivation of toxicity benchmarks, contributing to the development of a soil invertebrate-based Eco-SSL of 4.1 mg/kg for Se. Environ Toxicol Chem 2018;37:846-853. Published 2017 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America. more...

Protocols for terrestrial bioaccumulation assessments are far less-developed than for aquatic systems. This article reviews modeling approaches that can be used to assess the terrestrial bioaccumulation potential of commercial organic chemicals. Models exist for plant, invertebrate, mammal, and avian species and for entire terrestrial food webs, including some that consider spatial factors. Limitations and gaps in terrestrial bioaccumulation modeling include the lack of QSARs for biotransformation and dietary assimilation efficiencies for terrestrial species; the lack of models and QSARs for important terrestrial species such as insects, amphibians and reptiles; the lack of standardized testing protocols for plants with limited development of plant models; and the limited chemical domain of existing bioaccumulation models and QSARs (e.g., primarily applicable to nonionic organic chemicals). There is an urgent need for high-quality field data sets for validating models and assessing their performance. There is a need to improve coordination among laboratory, field, and modeling efforts on bioaccumulative substances in order to improve the state of the science for challenging substances. more...

Standardized laboratory protocols for measuring the accumulation of chemicals from sediments are used in assessing new and existing chemicals, evaluating navigational dredging materials, and establishing site-specific biota–sediment accumulation factors (BSAFs) for contaminated sediment sites. The BSAFs resulting from the testing protocols provide insight into the behavior and risks associated with individual chemicals. In addition to laboratory measurement, BSAFs can also be calculated from field data, including samples from studies using in situ exposure chambers and caging studies. The objective of this report is to compare and evaluate paired laboratory and field measurement of BSAFs and to evaluate the extent of their agreement. The peer-reviewed literature was searched for studies that conducted laboratory and field measurements of chemical bioaccumulation using the same or taxonomically related organisms. In addition, numerous Superfund and contaminated sediment site study reports were examined for relevant data. A limited number of studies were identified with paired laboratory and field measurements of BSAFs. BSAF comparisons were made between field-collected oligochaetes and the laboratory test organism Lumbriculus variegatus and field-collected bivalves and the laboratory test organisms Macoma nasuta and Corbicula fluminea. Our analysis suggests that laboratory BSAFs for the oligochaete L. variegatus are typically within a factor of 2 of the BSAFs for field-collected oligochaetes. Bivalve study results also suggest that laboratory BSAFs can provide reasonable estimates of field BSAF values if certain precautions are taken, such as ensuring that steady-state values are compared and that extrapolation among bivalve species is conducted with caution. Integr Environ Assess Manag 2012;8:32–41. © 2011 SETAC more...

Over the past few years, the "critical body residue" approach for assessing toxicity based on bioaccumulated chemicals has evolved into a more expansive consideration of tissue residues as the dose metric when defining dose-response relationships,evaluating mixtures, developing protective guidelines, and conducting risk assessments. Hence, scientists refer to "tissue residue approach for toxicity assessment" or "tissue residue-effects approach" (TRA) when addressing ecotoxicology issues pertaining to tissue (or internal) concentrations. This introduction provides an overview of a SETAC Pellston Workshop held in 2007 to review the state of the science for using tissue residues as the dose metric in environmental toxicology. The key findings of the workshop are presented, along with recommendations for research to enhance understanding of toxic responses within and between species, and to advance the use of the TRA in assessment and management of chemicals in the environment. more...