Is fish embryo test (FET) according to OECD 236 sensible enough for delivering quality data for effluent risk assessment?

Abstract

Over the past few years, the fish embryo test (FET) has become widely accepted as an animal-friendly protocol for ecotoxicological research. As Organisation for Economic Co-operation and Development (OECD) 236, the FET has been widely applied for simple mixture exposures under the Registration, Evaluation, Authorisation, and Restriction of Chemicals regulation of the European Union; and now its use is spreading worldwide as a supposedly reliable whole-effluent test (i.e., the testing of complex mixture exposures). However, comparative peer-reviewed data regarding the FET's efficiency for whole-effluent tests are virtually nonexistent. The primary objective of the present study was to make the first comparative test between the FET according to OECD 236 and other standard and slightly modified standard fish protocols used worldwide for whole-effluent tests. For that, we used an untreated hospital effluent considered to be highly toxic but disposed of in municipal sewerage. The base methods were OECD 203 (juvenile), US Environmental Protection Agency method 2000.0 (larvae), and OECD 236 (embryo). We also evaluated the addition of 3 virtually costless sublethal metrics (immobility, nonhatching, and pericardial edema) that could enhance the sensitivity of OECD 236. We observed acute toxicity in all 8 methodologies tested, with a clear escalation in sensitivity (larvae > juvenile ≥ embryo). Larvae were the most sensitive life stage for whole-effluent tests. The addition of sublethal metrics to OECD 236 enhanced its previous sensitivity in over 30%. Thus we conclude that OECD 236 acts below its potential and that the embryonic stage (as used in the FET) may not be the most sensitive life stage for whole-effluent tests. Environ Toxicol Chem 2018;37:2925-2932. © 2018 SETAC.

Species and Life‐Stage Sensitivity of Chinese Rare Minnow (Gobiocypris rarus) to Chemical Exposure: A Critical Review

“…Surprisingly, G. rarus at early life stages (embryos and larvae) showed a lower sensitivity to chemical exposure than the juvenile and adult stages (Figures 3 and 6). This was different from D. rerio , whose embryos generally showed similar sensitivity to fish at other life stages (Belanger et al 2013; Stelzer et al 2018).…”

“…The ban on vertebrate toxicity tests in the European Union triggered the development of alternative test methods, and the D. rerio fish embryo test has become a widely used alternative to the acute fish toxicity (Stelzer et al 2018). Because G. rarus and D. rerio embryos develop similarly from 2‐celled and multicelled phases (Laale 1977; Wang 1992) and the endpoints used in the fish embryo test with D. rerio , such as embryo coagulation, lack of somite formation, nondetachment of the tail, and lack of heartbeat, can also be observed in G. rarus embryos and larvae (Stainier and Fishman 1992; Chen et al 2013; Ma et al 2007), we evaluated the sensitivity of G. rarus at different life stages (embryos, larvae, juveniles, and adults) to investigate the applicability of the G. rarus fish embryo test as an alternative to the acute fish toxicity.…”

“…The lower sensitivity of G. rarus embryos may result from a decreased uptake of chemicals into G. rarus embryos because of the chorion acting as a natural protection for the development of embryos (Chang et al 1995; Pi 2016). The thicker chorion observed in G. rarus (Zhang et al 2019) may explain the lower sensitivity compared to adults, whereas P. promelas and D. rerio embryos have similar sensitivity to their juvenile and adult stages (Belanger et al 2013; Stelzer et al 2018). To optimize the fish embryo test procedures with G. rarus , it is imperative to understand if there are any specificities in G. rarus embryonic structures and functions that could reduce the adverse effects of chemicals.…”

Toxicity Assessment of 4 Azo Dyes in Zebrafish Embryos

“…The next day, fertilized embryos were found at the bottom of spawning tank and then collected into Petri dishes containing E3 medium for washing thoroughly. 18 All the studies on zebrafish were approved by the Institutional Animal Care and Use Committee in Nanjing Medical University.…”

SDHI Fungicide Toxicity and Associated Adverse Outcome Pathways: What Can Zebrafish Tell Us?

“…They have already been described in many reviews [8] and so will not be discussed here. Suffice to say that the zebrafish has been recommended by the OECD as a model organism to study the toxicity of environment-contaminating chemicals and pesticides [9].…”