, 2013). Although the Cd levels in salmon feed increased from 2000 until 2010, with mean values ranging from 0.2 to 0.4 mg kg− 1 dry feed (Sissener et al., 2013), their levels were usually below the LOQ in salmon

fillets. This in line with earlier observations that, Cd together with Pb and inorganic As, have limited ability to accumulate in the muscle of Atlantic salmon (Berntssen et al., 2010). Our data show a clear decline in the content of total As and total Hg in Norwegian farmed Atlantic salmon Ulixertinib supplier over the last 5 to 6 years. The decreasing level of As is likely due to the concurrent decline in the use of fish meal and fish oil in commercial fish feed. Furthermore, the As mass fraction in farmed salmon fillet is related to the fisheries of wild fish such as blue whiting (Micromesistius poutassou) and their subsequent inclusion in the feed ( Sissener et al., 2013). Seafood is

considered to be the largest contributor GSK2118436 of total As to human exposure, but the levels are not considered toxic because it is mainly present in fish as arsenobetaine ( Borak and Hosgood, 2007 and Kaise and Fukui, 1992). The organic form of Hg, methylmercury (MeHg+), is the most toxic, and it is estimated that 70 to 100% of the Hg in fish is present as MeHg+ ( Amlund et al., 2007). EFSA has established a TWI for MeHg+, and the food safety issues related to the levels shown here in Norwegian farmed Atlantic salmon are discussed below. Dioxins and dl-PCBs are persistent organic pollutants which bioaccumulate in the marine food chain. Dioxins and dl-PCBs are also well known for their toxic effects in humans, which

are described Rucaparib chemical structure elsewhere (Larsen, 2006). The levels of both total dioxins and dl-PCBs declined from 1999 to 2011, which was mainly related to the substitution of fish oils by vegetable oils in the feed (Berntssen et al., 2005 and Turchini et al., 2009). In particular, the decline in the sum of dioxins from 2003 to 2004 was considerable. This may be due to the geographical origin and species used for producing the fish oil, thereby altering the ratio of dioxins versus dl-PCBs in the sum dioxins and dl-PCBs. This ratio has previously been shown to vary considerably both between, and within, food items (EFSA, 2010), and the dioxins and dl-PCBs in feed based on different fish oil and fish meal have also been shown to affect the congener profile in Atlantic Salmon (Isosaari et al., 2004). The levels of dioxins and dl-PCBs presented in this study are generally lower than those found in other reports (Hites et al., 2004, Jacobs et al., 2002 and Shaw et al., 2006). However, as dioxins and dl-PCBs are lipophilic, their accumulation in Atlantic salmon muscle may be directly related to the fat content in the fillets. Excluding the skin from the analyses may impact the fat content of each sample.