Current testing programs for pesticides adequately capture endocrine activity and adversity for protection of vertebrate wildlife.

The toxicity and ecotoxicity of pesticide active ingredients are evaluated by a number of standardized test methods using vertebrate animals. These standard test methods are required under various regulatory programs for the registration of pesticides. Over the past two decades, additional test methods have been developed with endpoints that are responsive to endocrine activity and subsequent adverse effects. This article examines the available test methods and their endpoints that are relevant to an assessment of endocrine-disrupting properties of pesticides. Furthermore, the article highlights how weight-of-evidence approaches should be applied to determine whether an adverse response in (eco)toxicity tests is caused by an endocrine mechanism of action. The large number of endpoints in the current testing paradigms for pesticides make it unlikely that endocrine activity and adversity is being overlooked. Integr Environ Assess Manag 2023;19:1089-1109. © 2023 Bayer CropScience and The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Critical Review of Read-Across Potential in Testing for Endocrine-Related Effects in Vertebrate Ecological Receptors.

Recent regulatory testing programs have been designed to evaluate whether a chemical has the potential to interact with the endocrine system and could cause adverse effects. Some endocrine pathways are highly conserved among vertebrates, providing a potential to extrapolate data generated for one vertebrate taxonomic group to others (i.e., biological read-across). To assess the potential for biological read-across, we reviewed tools and approaches that support species extrapolation for fish, amphibians, birds, and reptiles. For each of the estrogen, androgen, thyroid, and steroidogenesis (EATS) pathways, we considered the pathway conservation across species and the responses of endocrine-sensitive endpoints. The available data show a high degree of confidence in the conservation of the hypothalamus-pituitary-gonadal axis between fish and mammals and the hypothalamus-pituitary-thyroid axis between amphibians and mammals. Comparatively, there is less empirical evidence for the conservation of other EATS pathways between other taxonomic groups, but this may be due to limited data. Although more information on sensitive pathways and endpoints would be useful, current developments in the use of molecular target sequencing similarity tools and thoughtful application of the adverse outcome pathway concept show promise for further advancement of read-across approaches for testing EATS pathways in vertebrate ecological receptors. Environ Toxicol Chem 2020;39:739-753. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

Variability in Nontarget Terrestrial Plant Studies Should Inform Endpoint Selection.

Inherent variability in nontarget terrestrial plant (NTTP) testing of pesticides creates challenges for using and interpreting these data for risk assessment. Standardized NTTP testing protocols were initially designed to calculate the application rate causing a 25% effect (ER25, used in the United States) or a 50% effect (ER50, used in Europe) for various measures based on the observed dose-response. More recently, the requirement to generate a no-observed-effect rate (NOER), or, in the absence of an NOER, the rate causing a 5% effect (ER05), has raised questions about the inherent variability in, and statistical detectability of, these tests. Statistically significant differences observed between test and control groups may be a product of this inherent variability and may not represent biological relevance. Attempting to derive an ER05 and the associated risk-assessment conclusions drawn from these values can overestimate risk. To address these concerns, we evaluated historical data from approximately 100 seedling emergence and vegetative vigor guideline studies on pesticides to assess the variability of control results across studies for each plant species, examined potential causes for the variation in control results, and defined the minimum percent effect that can be reliably detected. The results indicate that with current test design and implementation, the ER05 cannot be reliably estimated. Integr Environ Assess Manag 2018;14:639-648. © 2018 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals, Inc. on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Evaluation of an acute oral gavage method for assessment of pesticide toxicity in terrestrial amphibians.

Development of an acute oral toxicity test with a terrestrial-phase amphibian was considered necessary to remove the uncertainty within the field of agrochemical risk assessments. The bullfrog (Lithobates catesbeianus) was selected for use as it is a representative of the family Ranidae and historically this species has been used as an amphibian test model species. Prior to definitive study, oral gavage methods were developed with fenthion and tetraethyl pyrophosphate. Dimethoate and malathion were subsequently tested with both male and female juvenile bullfrogs in comprehensive acute oral median lethal dose (LD50) studies. Juvenile bullfrogs were administered a single dose of the test article via oral gavage of a single gelatin capsule of dimethoate technical (dimethoate) or neat liquid Fyfanon® Technical (synonym malathion), returned to their respective aquaria, and monitored for survival for 14 d. The primary endpoint was mortality, whereas behavioral responses, food consumption, body weight, and snout-vent length (SVL) were used to evaluate indications of sublethal toxicity (secondary endpoints). Acute oral LD50 values (95% fiducial interval) for dimethoate were 1459 (1176-1810, males) and 1528 (1275-1831, females), and for malathion they were 1829 (1480-2259, males) and 1672 (1280-2183, females) mg active substance/kg body weight, respectively. Based on the results of these studies, the methodology for the acute oral gavage administration of test items to terrestrial-phase amphibians was demonstrated as being a practical method of providing data for risk assessments. Environ Toxicol Chem 2018;37:436-450. © 2017 SETAC.

Degradation and transformation of 17α-trenbolone in aerobic water-sediment systems.

Synovex® ONE is an extended-release implant containing the active ingredients estradiol benzoate and trenbolone acetate for use in beef steers and heifers. Trenbolone acetate is rapidly hydrolyzed in cattle to form 17ß-trenbolone and its isomer, 17α-trenbolone, which are further transformed to a secondary metabolite, trendione. As part of the environmental assessment for the use of Synovex ONE, data were generated to characterize the fate of 17α-trenbolone, which is the principal metabolite found in cattle excreta, in the environment. A study was conducted to determine the degradation and transformation of [14 C]-17α-trenbolone in 2 representative water-sediment systems under aerobic conditions. The same transformation products, 17ß-trenbolone and trendione, were formed, principally in the sediment phase, in both systems. From the production of these transformation products, the 50% disappearance time (DT50) values of 17ß-trenbolone and trendione were determined, along with the DT50 values of the parent compound and the total drug (17α-trenbolone + 17ß-trenbolone + trendione). The DT50 values for the total system (aqueous and sediment phase) and for the total residues (17α-trenbolone + 17ß-trenbolone + trendione) in the 2 systems were 34.7 d and 53.3 d, respectively. Environ Toxicol Chem 2017;36:630-635. © 2016 SETAC.

Degradation and transformation of 17α-estradiol in water-sediment systems under controlled aerobic and anaerobic conditions.

One of the principal metabolites in cattle excreta following the administration of Synovex® ONE, which contains estradiol benzoate and trenbolone acetate, is 17α-estradiol. As part of the environmental assessment of the use of Synovex ONE, data were generated to characterize the fate of 17α-estradiol in the environment. Studies were conducted to determine the degradation and transformation of 17α-[14 C]-estradiol in 2 representative water-sediment systems each under aerobic and anaerobic conditions. The same transformation products-estriol, 17ß-estradiol, and estrone-were formed, principally in the sediment phase, under both conditions in both systems. From the production of these transformation products, the 50% disappearance time (DT50) values of estrone and 17ß-estradiol were determined, along with the DT50 values of 17α-estradiol and the total drug (17α-estradiol + 17ß-estradiol + estrone). The results indicate that 17 α-[14 C]-estradiol was more persistent under anaerobic conditions than under aerobic conditions and that 17 α-[14 C]-estradiol was less persistent than its transformation products. The DT50 values for the total system (aqueous and sediment phases) and for the total residues (17α-estradiol, 17ß-estradiol, and estrone) were selected for use in modeling the environmental fate of estradiol benzoate. For aerobic degradation in the water-sediment system, the DT50 was 31.1 d, and it was 107.8 d for the anaerobic system. Environ Toxicol Chem 2017;36:621-629. © 2016 SETAC.

Reproductive effects on freshwater fish exposed to 17α-trenbolone and 17α-estradiol.

17α-Trenbolone and 17α-estradiol are principal metabolites in cattle excreta following the administration of Synovex® ONE, which contains trenbolone acetate and estradiol benzoate. As part of the environmental assessment of the use of Synovex® ONE, data were generated to characterize the effects of 17α-trenbolone and 17α-estradiol on the reproduction of freshwater fish. These substances are known endocrine disruptors, so the purpose of testing was not to clarify these properties but to identify concentrations representing population-relevant effects for use in risk characterization. The short-term reproduction assay was conducted with 17α-trenbolone using the fathead minnow (Pimephales promelas) and the medaka (Oryzias latipes) and with 17α-estradiol using the fathead minnow. Adverse effects on the population-relevant endpoints of survival and fecundity were used to establish the no-observed-effect concentration (NOEC) and the lowest-observed-effect concentration (LOEC) for each study. For 17α-trenbolone, adverse effects on fecundity of the fathead minnow occurred at 120 ng/L; this was the LOEC, and the NOEC was 35 ng/L. 17ß-Trenbolone did not adversely affect survival and fecundity of medaka at the concentrations tested, resulting in a NOEC of 110 ng/L and a LOEC of >110 ng/L. 17α-Estradiol did not adversely impact survival and fecundity of the fathead minnow at the concentrations tested, resulting in a NOEC and LOEC of 250 ng/L and >250 ng/L, respectively. Environ Toxicol Chem 2017;36:636-644. © 2016 SETAC.

What training and skills will the ecotoxicologists of the future require?

Students and academic researchers conduct a diverse range of studies that add to the growing body of ecotoxicology research. Once an academic researcher entertains an applied research topic, there is potential for that research to be used in local, state, or federal regulatory decision or action. The ability of regulatory decision makers to use academic studies to inform decisions is dependent on: 1) the relevance of the experiment to regulatory decisions, 2) the reliability of the laboratory and the study itself, and 3) quality reporting of data such that study relevance and reliability are evident. The purpose of this brief communication is to highlight actions that can be taken by Society of Environmental Toxicology and Chemistry members to enhance the usability of academic research studies in regulatory decision making by promoting training, partnerships, and communication. Integr Environ Assess Manag 2017;13:580-584. © 2016 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals, Inc. on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Sorption and desorption of 17α-trenbolone and trendione on five soils.

The metabolites 17α-trenbolone and 17α-estradiol are principal metabolites in cattle excreta following the administration of Synovex® ONE, which contains trenbolone acetate and estradiol benzoate. As part of the environmental assessment of the use of Synovex ONE, data were generated to characterize the fate of 17α-trenbolone, and its metabolite trendione in the environment. Predictions of the fate and environmental concentrations of these hormones after land application require accurate estimates of the sorption of these compounds in soils. The sorption and desorption of 17α-trenbolone and trendione were measured at 5 nominal concentrations in 5 soils from different geologic settings using a batch equilibrium technique following guideline 106 of the Organisation for Economic Co-operation and Development. Both the sorption and desorption of 17α-trenbolone and trendione to soils were adequately described by the Freundlich sorption model and by linear partition coefficients. The mean sorption coefficients were 9.04 mL/g and 32.2 mL/g for 17α-trenbolone and trendione, respectively. The corresponding mean Freundlich sorption exponents were 0.88 and 0.98, respectively. Sorption of 17α-trenbolone and trendione was correlated principally with soil organic carbon. Average sorption coefficients normalized to soil organic carbon content (KOC ) were 460 mL/g and 1804 mL/g for 17α-trenbolone and trendione, respectively. The mean desorption coefficients were 22.1 mL/g and 43.8 mL/g for 17α-trenbolone and trendione, respectively. Calculated hysteresis coefficients based on the difference in the area between sorption and desorption isotherms indicated that sorption equilibrium was not fully reversible and hysteresis of desorption isotherms occurred for both 17α-trenbolone and trendione. Environ Toxicol Chem 2017;36:613-620. © 2016 SETAC.

Comments on the opinions published by Bergman et al. (2015) on Critical Comments on the WHO-UNEP State of the Science of Endocrine Disrupting Chemicals (Lamb et al., 2014).

Recently Bergman et al. (2015) took issue with our comments (Lamb et al., 2014) on the WHO-UNEP(1) report entitled the "State of the Science of Endocrine Disrupting Chemicals - 2012" (WHO 2013a). We find several key differences between their view and ours regarding the selection of studies and presentation of data related to endocrine disrupting chemicals (EDCs) under the WHO-IPCS(2) definition (2002). In this response we address the factors that we think are most important: 1. the difference between hazard and risk; 2. the different approaches for hazard identification (weight of the evidence [WOE] vs. emphasizing positive findings over null results); and 3. the lack of a justification for conceptual or practical differences between EDCs and other groups of agents.

Critical comments on the WHO-UNEP State of the Science of Endocrine Disrupting Chemicals - 2012.

Early in 2013, the World Health Organization (WHO) released a 2012 update to the 2002 State of the Science of Endocrine Disrupting Chemicals. Several significant concerns have been identified that raise questions about conclusions reached in this report regarding endocrine disruption. First, the report is not a state-of-the-science review and does not follow the 2002 WHO recommended weight-of-evidence approach. Second, endocrine disruption is often presumed to occur based on exposure or a potential mechanism despite a lack of evidence to show that chemicals are causally established as endocrine disruptors. Additionally, causation is often inferred by the presentation of a series of unrelated facts, which collectively do not demonstrate causation. Third, trends in disease incidence or prevalence are discussed without regard to known causes or risk factors; endocrine disruption is implicated as the reason for such trends in the absence of evidence. Fourth, dose and potency are ignored for most chemicals discussed. Finally, controversial topics (i.e., low dose effects, non-monotonic dose response) are presented in a one-sided manner and these topics are important to understanding endocrine disruption. Overall, the 2012 report does not provide a balanced perspective, nor does it accurately reflect the state of the science on endocrine disruption.

Relevance weighting of tier 1 endocrine screening endpoints by rank order.

Weight of evidence (WoE) approaches are recommended for interpreting various toxicological data, but few systematic and transparent procedures exist. A hypothesis-based WoE framework was recently published focusing on the U.S. EPA's Tier 1 Endocrine Screening Battery (ESB) as an example. The framework recommends weighting each experimental endpoint according to its relevance for deciding eight hypotheses addressed by the ESB. Here we present detailed rationale for weighting the ESB endpoints according to three rank ordered categories and an interpretive process for using the rankings to reach WoE determinations. Rank 1 was assigned to in vivo endpoints that characterize the fundamental physiological actions for androgen, estrogen, and thyroid activities. Rank 1 endpoints are specific and sensitive for the hypothesis, interpretable without ancillary data, and rarely confounded by artifacts or nonspecific activity. Rank 2 endpoints are specific and interpretable for the hypothesis but less informative than Rank 1, often due to oversensitivity, inclusion of narrowly context-dependent components of the hormonal system (e.g., in vitro endpoints), or confounding by nonspecific activity. Rank 3 endpoints are relevant for the hypothesis but only corroborative of Ranks 1 and 2 endpoints. Rank 3 includes many apical in vivo endpoints that can be affected by systemic toxicity and nonhormonal activity. Although these relevance weight rankings (WREL ) necessarily involve professional judgment, their a priori derivation enhances transparency and renders WoE determinations amenable to methodological scrutiny according to basic scientific premises, characteristics that cannot be assured by processes in which the rationale for decisions is provided post hoc.

A Causal Analysis of Observed Declines in Managed Honey Bees (Apis mellifera).

The European honey bee (Apis mellifera) is a highly valuable, semi-free-ranging managed agricultural species. While the number of managed hives has been increasing, declines in overwinter survival, and the onset of colony collapse disorder in 2006, precipitated a large amount of research on bees' health in an effort to isolate the causative factors. A workshop was convened during which bee experts were introduced to a formal causal analysis approach to compare 39 candidate causes against specified criteria to evaluate their relationship to the reduced overwinter survivability observed since 2006 of commercial bees used in the California almond industry. Candidate causes were categorized as probable, possible, or unlikely; several candidate causes were categorized as indeterminate due to lack of information. Due to time limitations, a full causal analysis was not completed at the workshop. In this article, examples are provided to illustrate the process and provide preliminary findings, using three candidate causes. Varroa mites plus viruses were judged to be a "probable cause" of the reduced survival, while nutrient deficiency was judged to be a "possible cause." Neonicotinoid pesticides were judged to be "unlikely" as the sole cause of this reduced survival, although they could possibly be a contributing factor.

The drive to ban the NOEC/LOEC in favor of ECx is misguided and misinformed.

Challenges to the use of the no observed effect concentration (NOEC) in ecotoxicology have appeared over the years, with a recent call for banning its use in favor of the x% effects concentration (ECx). This article presents an opposing view, providing reasons for the continued use of the NOEC, and for hypothesis testing in general. Although the use of ECx values is appropriate in many situations, there are numerous real-world examples where it is not suitable and offers no advantage over the use of hypothesis testing. These examples are presented with recommended data analysis techniques, illustrating the variety of statistical approaches that are meaningful in analyzing ecotoxicity data. Thoughtful consideration of study design and proper analysis and interpretation of the results will go further to advance the science of ecotoxicology than attempting to implement a blanket prohibition or endorsement of any single statistical approach.

Pharmaceuticals and personal care products in the environment: what are the big questions?

BACKGROUND: Over the past 10-15 years, a substantial amount of work has been done by the scientific, regulatory, and business communities to elucidate the effects and risks of pharmaceuticals and personal care products (PPCPs) in the environment. OBJECTIVE: This review was undertaken to identify key outstanding issues regarding the effects of PPCPs on human and ecological health in order to ensure that future resources will be focused on the most important areas. DATA SOURCES: To better understand and manage the risks of PPCPs in the environment, we used the "key question" approach to identify the principle issues that need to be addressed. Initially, questions were solicited from academic, government, and business communities around the world. A list of 101 questions was then discussed at an international expert workshop, and a top-20 list was developed. Following the workshop, workshop attendees ranked the 20 questions by importance. DATA SYNTHESIS: The top 20 priority questions fell into seven categories: a) prioritization of substances for assessment, b) pathways of exposure, c) bioavailability and uptake, d) effects characterization, e) risk and relative risk, f ) antibiotic resistance, and g) risk management. CONCLUSIONS: A large body of information is now available on PPCPs in the environment. This exercise prioritized the most critical questions to aid in development of future research programs on the topic.