Endocrine Disruptor Impacts on Fish From Chile: The Influence of Wastewaters

Indexación ScopusIndustrial wastewaters and urban discharges contain complex mixtures of chemicals capable of impacting reproductive performance in freshwater fish, called endocrine-disrupting compounds (EDCs). In Chile, the issue was highlighted by our group beginning over 15 years ago, by analyzing the impacts of pulp and paper mill effluents (PPME) in the Biobio, Itata, and Cruces River basins. All of the rivers studied are important freshwater ecosystems located in the Mediterranean region of Central Chile, each with a unique fish biodiversity. Sequentially, we developed a strategy based on laboratory assays, semicontrolled-field experiments (e.g., caging) and wild fish population assessments to explore the issue of reproductive impacts on both introduced and native fish in Chile. The integration of watershed, field, and laboratory studies was effective at understanding the endocrine responses in Chilean freshwater systems. The studies demonstrated that regardless of the type of treatment, pulp mill effluents can contain compounds capable of impacting endocrine systems. Urban wastewater treatment plant effluents (WWTP) were also investigated using the same integrated strategy. Although not directly compared, PPME and WWTP effluent seem to cause similar estrogenic effects in fish after waterborne exposure, with differing intensities. This body of work underscores the urgent need for further studies on the basic biology of Chilean native fish species, and an improved understanding on reproductive development and variability across Chilean ecosystems. The lack of knowledge of the ontogeny of Chilean fish, especially maturation and sexual development, with an emphasis on associated habitats and landscapes, are impediment factors for their conservation and protection against the threat of EDCs. The assessment of effects on native species in the receiving environment is critical for supporting and designing protective regulations and remediation strategies, and for conserving the unique Chilean fish biodiversity. © Copyright © 2021 Barra, Chiang, Saavedra, Orrego, Servos, Hewitt, McMaster, Bahamonde, Tucca and Munkittrick.https://www.frontiersin.org/articles/10.3389/fendo.2021.611281/ful

Developing Biological Endpoints for Defining Virtual Elimination: a Case Study for PCDDs and PCDFs

Abstract Defining virtual elimination has created considerable debate. A traditional approach has been to use chemically defined detection limits or levels of quantification that are determined using the best currently available methodologies. Ever increasing improvements in analytical techniques could lead to corresponding pressure to reduce the targets for virtual elimination. The current Toxic Substances Management Policy in Canada recognizes this and clearly states that it is not the intent of virtual elimination to have a moving target or to chase down the last molecule of the chemical of concern. Although it may be possible to reduce a chemical to less than some extremely sensitive detection limit, the chemical may or may not exert biological effects at that level. The chemically defined detection limits may be much lower than background levels in the environment, making it an unrealistic target. Conversely biological responses may result from trace levels of a compound that are not detectable in effluents or selected compartments of the environment (i.e., water) using current chemical techniques. Alternatively, an effect-based approach can establish biologically meaningful endpoints to defining virtual elimination. Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) are used in this study as an example to evaluate the advantages and limitations of several possible approaches of using biological endpoints to determine the presence of these compounds in the environment and ultimately define virtual elimination. A review of the biological responses to PCDD/PCDFs is included to demonstrate the importance of selecting appropriate biological endpoints. Mixed function oxygenase (MFO) induction, although not recommended at this point, is used as an example of a possible sensitive endpoint that could potentially be used to detect exposure of biota to these chemicals. Three different approaches are explored: (1) measuring MFO induction in a sentinel species in the environment; (2) testing environmental extracts for MFO induction in cell lines; and (3) using biological endpoints (MFO induction) to define chemical targets for virtual elimination. While the use of biological end-points is the most desirable approach to defining virtual elimination, there are significant knowledge gaps which limit our selection and application of this approach.</jats:p

Inability of Resin Acid Exposure to Elevate EROD Activity in Rainbow Trout (Oncorhynchus mykiss)

Abstract The induction of mixed function oxygenase enzymes, including ethoxyresorufin-o-deethylase (EROD), has been reported in fish downstream of bleached kraft mills in both Scandinavia and Canada. The compound(s) responsible have not been identified. Several experiments were conducted to determine if resin acids can induce EROD activity in rainbow trout (Oncorhynchus mykiss). Interperitoneal injections (i.p.) of dehydroabietic and abietic acid (50 mg/kg) did not elevate EROD activity after 2, 4 or 10 days. Dehydroabietic acid i.p. at 500 mg/kg did not increase EROD activity after 4 days. A mixture of ten resin acids i.p. at 370 mg/kg or water borne exposure at 100 µg/L did not induce EROD after 4, 8, or 16 days. Rosin gum i.p. at 370 mg/kg also did not induce EROD. These results suggest that resin acids are not the compounds primarily responsible for EROD induction below bleached kraft pulp mills.</jats:p

Differential recovery of δ¹³C in multiple tissues of white sucker across age classes after the closure of a pulp mill

Techniques to document recovery after the closure of pulp mills that discharge enriching effluents are not well established, but δ13C may be a useful tool. In the 1990s, the muscle tissue of white sucker (Catostomus commersonii) collected downstream of two pulp and paper mills discharging into separate streams (Mattagami and Kapuskasing rivers) was enriched in 13C compared with upstream fish, suggesting uptake of pulp-derived C. The Mattagami River mill was closed in 2006, and analysis of muscle and gonad for δ13C was performed in 2011. As expected, fish captured in 2011 downstream of the operational Kapuskasing mill still showed the influence of the pulp-derived C in muscle and gonad tissue. After the closure of the Mattagami River mill, muscle tissue of white sucker was still enriched in 13C compared with upstream fish, while gonad tissue was not. The patterns observed in the Mattagami River were, however, related to age; the oldest fish showed enrichment of δ13C in both muscle and gonad tissue, suggesting the residual occurrence of pulp-derived C. This study suggests that measurements of stable isotopes in fish across a broad age range may indicate ecosystem improvements. These techniques may also be useful where no data prior to the upgrade or closure are available for comparison. </jats:p