“…Although many reviews have been published that focus on, for example,1 )environmental realism of test conditions, [33] 2) modeling approaches, [34] 3) effects of organic matter on toxicity, [35] and 4) ecotoxicological effects of various ENPs, [36][37][38][39] there still seems to be al ack of reviews assessing nanoparticle effects in terms of test setups and effects observed. Handy et al [40] and Petersen et al [41] reviewed and presented aw ide range of practical considerations to be considered when conducting ecotoxicological tests with ENPs.H owever,t he practical considerations and the confounding factors of ENPs in test setups have to,o ur knowledge,n ot been reviewed in regard to assessing the effects of the nanoparticles.Isolating the nanoparticle effect caused by the novel intrinsic properties of the ENPs because of their size is not possible from the currently published reviews.Throughout this Review the implications of the properties of ENPs and their related behavior in test media before,d uring,a nd after ecotoxicity testing will be evaluated with aspecific focus on the base set of aquatic organisms (fish, crustaceans,a nd algae) used for classification, labeling,a nd concentrationresponse assessment to determine the nanoparticle effect.…”