A Summary of the "Contaminants of Emerging Concern for Fish: Assessing Exposure and Effects Across Biological Scales" Session at the Nashville Meeting
Susanne Brander, University of North Carolina, Wilmington, Scott Hecht, U.S. National Oceanic and Atmospheric Administration and Kathryn Kuivila, U.S. Geological Survey
Thursday’s day-long session at the SETAC North America 34th Annual Meeting in Nashville, Tenn., focused on contaminants of emerging concern (CECs) such as current-use pesticides, industrial contaminants, pharmaceuticals and personal care products. These CECs are consistently detected in aquatic habitats worldwide and may pose a threat to rare and vulnerable fishes. This session showcased state-of-the-art science on exposure and resulting adverse responses of fishes from the molecular to the population level. Studies highlighted links between tissue residues of particular CECs and concomitant adverse effects in various species of fish, including rainbow trout, silversides, zebrafish, medaka, fathead minnow, yellow perch, Chinook salmon, cutthroat trout, Pacific lamprey and white sturgeon. Many of these fish species have been developed as sentinels or laboratory models, but threatened and endangered species were also represented.
CECs ranged from pesticides such as the pyrethroid bifenthrin to industrial chemicals such as flame retardants and plasticizers (BPA), as well as environmental mixtures downstream of concentrated animal feedlots and treated wastewater outfalls. The ultimate goal of the studies featured in this session was to bridge the gap between small to large-scale effects and from mechanistic to field studies. Speakers hailed from a diverse group of academic institutions and government agencies from both the United States and Canada, including the Universities of California at Riverside and Davis, University of North Carolina at Wilmington, North Carolina State University, Duke University Nicholas School of the Environment, Baylor University, St. Cloud State University, Trent University, Environment Canada, U.S. Environmental Protection Agency (USEPA) Mid-Continent Division and the U.S. Geological Survey (USGS).
Most of the morning talks focused on fish exposures to a single CEC, demonstrating effects on gene expression that often correlated with higher-level impacts. Research presented on bifenthrin exposures indicated that bifenthrin might interfere with dopamine signaling and increase levels of plasma estradiol (Crago, UC Riverside), and appears to also alter the expression of estrogen and androgen-dependent genes, which might lead to reduced fecundity (Brander, UNC Wilmington). According to research underway at the University of Waterloo, the effects of bisphenol-a (BPA) exposure might span multiple generations, impacting growth rates of the F2 generation whose parents were exposed (Birceanu), and other industrial chemicals – organophosphate flame retardants – appear to alter neurodevelopmental pathways (Dishaw). Pharmaceuticals were also highlighted, with ibuprofen implicated in altered endocrine-related gene expression (Jeffries, UC Davis). Mixture effects were also explored, with an evaluation of diphenhydramine and an organophosphate insecticide that showed additive toxicity rather than the expected reduction in lethality (Kristofco). For endocrine active chemicals, Villeneuve of the USEPA emphasized the importance of pairing the exposure time-scale with the effect of interest since compensatory responses can take place over a longer time.
The afternoon session included several presentations on environmental mixture effects, with a particular focus on approaches to evaluating the sub-lethal toxicity of treated wastewater effluent and concentrated animal feedlot run-off. Research recently published by North Carolina State University found that fish exposed to different components of swine effluent had responses that differed from the traditionally utilized yeast estrogen screen (YES) assay, and hence in vitro assays specific to medaka estrogen receptors (ERs) were developed to determine which ER isoforms played a critical role in medaka estrogenic response. Another study involved fish exposure to samples of various types of feedlot runoff (poultry, swine, dairy), with observations of reduced survival, growth and altered predator avoidance often concomitant with environmental estrogens present. Four studies on fish exposure to treated wastewater effluent were presented during the afternoon session. These studies showed that CECs such as flame retardants, perfluoralkyl substances, metals, pharmaceuticals, personal care products, estrogens and androgens were elevated proximal to outfalls. More specifically, fish (yellow perch) in the St. Lawrence River had altered gene expression that occurred concomitantly with alterations in cellular respiration and other metabolic processes (Houde, Environment Canada), and caged fathead minnows from another study done in several Canadian rivers had increased cytochrome P450 induction, vitellogenin expression and altered steroidogeneis (Metcalfe, Trent Univ). Rainbow darter collected downstream from the Waterloo and Kitchener plants had altered fertilization success and embryo survival (Fuzzen, Univ Waterloo), but another study in Washington State saw no response in salmon (caged) and trout (collected) in vitellogenin protein or gene expression (cDNA microarray) from sites downstream of wastewater treatment plants in the Stillaguamish River, as well as low recovery of any contaminants (Moran, USGS ). Studies of bioaccumulation in species of biological importance (largescale sucker, Pacific lamprey, white sturgeon) showed that negative impacts to the foodweb resulted from accumulation of CECs, particularly flame retardants (PBDEs) and pesticides (Nilsen, USGS). The session ended with a talk from Schroeder of the USEPA, highlighting use of the Comparative Toxicogenomics Database (CTD) and Search Tool for Interactions of Chemicals (STITCH) to identify known interactions between chemicals detected in a study done in the Great Lakes, which illustrated an approach for generating hypotheses for studies that involve complex environmental mixtures.
Overall, the session was a success and was also a venue for a number of excellent student presentations. In addition to many well-attended talks, the session also included nine posters displayed during Thursday’s poster session. The session’s topic is an active research area that is expanding quickly and is expected to see a growing body of work in the future. Establishing clear links between molecular, organismal and population-level responses will allow for better predictive use of biomarkers and a more accurate evaluation of the potential threat that CECs pose to fishes. An article featuring experts from academia and government agencies further describing the rationale behind this session and the supporting research will also be featured in an upcoming Environmental Toxicology and Chemistry Perspectives column.
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