Levels, patterns, trends and significance of polychlorinated naphthalenes (PCNs) in Great Lakes fish

Highlights: • PCNs were measured in fillets of 18 species of Great Lakes fish in Canadian waters. • Spatial trend was: the Detroit River > Lakes Erie > Ontario > Huron > Superior. • Major congeners PCN-66/67 likely declined by 24–77% between 2006/07 and 2012. • PCNs typically contribute 2–13% to ∑ TEQ (dioxins, furans, dioxin-like PCBs, PCNs). • Wholebody PCNs were 1.4–3.2 × higher than the fillets; likely driven by lipid content. Polychlorinated naphthalenes (PCNs) were introduced to market about a century ago and their production is thought to have ceased by the early 1980s. However, relatively limited knowledge exists on their abundance in the edible portion of a variety of Great Lakes fish to aid in understanding their potential risk to human consumers. We studied levels, patterns, trends and significance of PCNs in a total 470 fillet samples of 18 fish species collected from the Canadian waters of the Great Lakes between 2006 and 2013. A limited comparison of fillet and wholebody concentrations in Carp and Bullhead was also conducted. The ∑ PCN ranged from 0.006–6.7 ng/g wet weight (ww) and 0.15–190 ng/g lipid weight (lw) with the dominant congeners being PCN-52/60 (34%), -42 (21%) and -66/67 (15%). The concentrations spatially varied in the order of the Detroit River > Lakes Erie > Ontario > Huron > Superior. PCN-66/67 was the dominating congener contributing on average 76–80% of toxic equivalent concentration (TEQ_PCN). Contribution of TEQ_PCN to TEQ_Total (TEQ_{Dioxins + Furans + dioxin-likePCBs + PCNs}) was mostly < 15%, especially at higher TEQ_Total, and PCB-126 remains the major congener contributing to TEQ_Total. The congener pattern suggests that impurities in PCB formulations and thereby historical PCB contamination, instead of unintentional releases from industrial thermal processes, could be an important source of PCNs in Great Lakes fish. A limited temporal change analysis indicated declines in the levels of PCN-66/67 between 2006 and 2012, complemented by previously reported decrease in PCNs in Lake Ontario Lake Trout between 1979 and 2004. The whole body concentrations were 1.4–3.2 fold higher than the corresponding fillets of Carp and Bullhead. Overall, the study results suggest that only targeted monitoring of PCNs in Great Lakes fish, especially at the Detroit River, Lake Erie and Lake Ontario, is necessary to assess continued future improvements of this group of contaminants of concern.