Modelling scenarios on feed-to-fillet transfer of dioxins and dioxin- like PCBs in future feeds to farmed Atlantic salmon (Salmo salar) Marc H.G. Berntssen * , Monica Sanden, Helge Hove, Øyvind Lie National Institute of Nutrition and Seafood Research (NIFES), Bergen, Norway highlights  A salmon dioxin kinetic transfer model was validated with two salmon trials.  The model was used to predict future fillet salmon dioxin and dioxin like PCB levels when using novel feed.  Predicted future fillet levels of 1.7 ng WHO 2005 -TEQs kg 1 lw are near the limit of quantification and levels found in bovine meat. article info Article history: Received 17 June 2016 Received in revised form 12 August 2016 Accepted 13 August 2016 Handling Editor: Prof. J. de Boer Keywords: Atlantic salmon Dioxins Transfer Modelling Novel feeds abstract The salmon feed composition has changed the last decade with a replacement of traditionally use of fish oil and fishmeal diets with vegetable ingredients and the use decontaminated fish oils, causing reduced concentrations of dioxins and dioxin-like PCBs in farmed Norwegian Atlantic salmon. The development of novel salmon feeds has prompted the need for prediction on dioxins and dl-PCB concentrations in future farmed salmon. Prediction on fillet dioxins and dl-PCB concentrations from different feed composition scenarios are made using a simple one-compartmental transfer model based on earlier established dioxin and dl-PCB congener specific uptake and elimination kinetics rates. The model is validated with two independent feeding trials, with a significant linear correlation (r 2 ¼ 0.96, y ¼ 1.0x, p < 0.0001, n ¼ 116) between observed and predicted values. Model fillet predictions are made for the following four scenarios; (1) general feed composition of 1999, (2) feed composition of 2013, (3) future feed composition with high fish oil and meal replacement, (4) future feed composition with high fish oil and meal replacement and decontaminated fish oil. Model predictions of fillet dioxin and dl-PCB con- centrations from 1999 (1.05 ng WHO 2005 -TEQs kg 1 ww) and 2013 (0.57 ng WHO 2005 -TEQs kg 1 ww) are in line with the data observed in national surveillance programs of those years (1.1 and 0.52 ng WHO 2005 - TEQs kg 1 ww, respectively). Future use of high replacement and decontaminated oils feeds gave pre- dicted fillet concentrations of 0.27 ng WHO 2005 -TEQs kg 1 ww, which is near the limit of quantification. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction Farmed Atlantic salmon (Salmo salar) is known to contain rela- tively high concentrations of persistent environmental pollutants (POPs) which are potentially hazardous to the consumers. These POPs include polychlorinated biphenyls (PCBs), dioxins [poly- chlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated di- benzofurans (PCDFs)], polybrominated diphenyl ethers (PBDEs), hexabromocyclodecane (HBCD), and organochlorine pesticides (OCPs) (Hites et al., 2004; Maule et al., 2007; Shaw et al., 2008; van Leeuwen et al., 2009). Farmed oily fish, such as Atlantic salmon, has higher concentrations of these persistent organic pollutants (POPs) than lean farmed fish species such as tilapia (Oreochromis mos- sambicus, Oreochromis niloticus) and pangasius (Pangasius hypo- phthalmus)(Nacher-Mestre et al., 2009; van Leeuwen et al., 2009). Fish oils, obtained from pelagic fish species and used as a feed ingredient in the high energy salmonid feeds, are the main source of POPs in farmed Atlantic salmon fillets (Berntssen et al., 2005, 2010c; Easton et al., 2002; Jacobs et al., 2002). Seafood, and oily fish in particular, is a dominant contributor to POP exposure such as PCDD/Fs and dioxin-like PCBs (dl-PCBs) in the adult diets (Bergkvist et al., 2008; De Mul et al., 2008; Fattore et al., 2008; Kvalem et al., 2009; van Leeuwen et al., 2009; Voorspoels et al., 2008). * Corresponding author. National Institute of Nutrition and Seafood Research, Postbox 2029, Nordnes, 5817 Bergen, Norway. E-mail address: marc.berntssen@nifes.no (M.H.G. Berntssen). Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere http://dx.doi.org/10.1016/j.chemosphere.2016.08.067 0045-6535/© 2016 Elsevier Ltd. All rights reserved. Chemosphere 163 (2016) 413e421