Linear regression, median, check details interquartile range and range of the sum of dioxins and dl-PCBs are shown in Fig. 2A. Total dioxins and dl-PCBs decreased from 1999 to 2011. Fig. 2B illustrates the contribution of the dioxins fraction and the dl-PCBs fraction to the total TEQ. The median for all years of sum of dioxins and dl-PCBs were 0,9 pg TEQ-WHO 05 g− 1, whilst the median for 2011 specifically was 0.6 pg TEQ-WHO 05 g− 1. From 2002 to 2011, 475 samples were analysed for PCB6. Although some statistical differences were observed, no clear trend in the sum of PCB6 was found
as shown in Fig. 3. The median mass fraction of sum of PCB6 through the years was 5.94 μg/kg w.w. In the period from 2006 to 2011, 324 samples were analysed for various Doxorubicin in vitro pesticides. The sum of DDT is presented as box and whisker plots per year, as well as linear regression in Fig. 4A. The sum of DDT declined from 2002 to 2011, and the median over the years was 9.40 μg/kg w.w. The
levels of the other pesticides were too close to the LOQ for trend analyses. Thus, pesticide data was pooled (except DTT) and statistics were performed on all years combined (Fig. 4B). Hg and dioxins and dl-PCBs were evaluated according to current TWIs. To calculate safe consumption limits, all dioxins and dl-PCBs data were converted to 98 WHO TEQ. The maximum tolerable consumption of Norwegian farmed salmon without reaching the TWI increased over the years and reached 1.3 kg in 2011 (Fig. 5). From 1999 to 2011, dioxins and dl-PCBs represent the limiting factors in terms of safe consumption of Norwegian farmed salmon.
In this study, contaminants were examined in more than 2300 samples, and since most samples were pooled, the total number of fish analysed exceeds 10,000 individual Norwegian farmed salmon. The fish were sampled over a period of 13 years from all regions with aquaculture activity, thereby providing Clostridium perfringens alpha toxin a representative overview of the contaminant levels in Norwegian farmed salmon over the last decade. The amount and types of contaminants investigated were based on EU Council Directive 96/23/EC (EU, 1996). The contaminants chosen were also the same as previously reported in salmonids, both farmed and wild (Hites et al., 2004, Jacobs et al., 2002 and Kelly et al., 2011), as well as in salmon feed (Sissener et al., 2013). In this study, the heavy metals Pb, Cd, Hg and the metalloid As have been measured in fillets from Norwegian farmed Atlantic salmon. The levels of heavy metals described in this paper are comparable to other studies of farmed Atlantic salmon (Foran et al., 2004), as well as for farmed Atlantic-, Coho- and Chinook salmon from British Columbia (Kelly et al., 2008).