POPs, PFAS and metals in ringed seals (Pusa hispida botnica) from the Baltic 1978-2015

By Anna Roos, Britt-Marie B├Ącklin Ingrid Ericson Jogsten, Thanh Wang, Raed Awad and Jonathan Benskin
Swed. Museum of Nat. Hist.
September 30, 2019

Twenty two pooled samples from 69 juvenile ringed seals collected between 1974 and 2015 were analyzed for PCB (22 congeners), pesticides, PFAS, metals and selenium. Most seals were bycaught in fishing gear.

All CB congeners were above the detection limits. CB-138 and -153 accounted for ca 50% of ∑PCB. CB-180 and -101 stood for ca 10 % each. ∑PCB decreased over the study period with approximately -4.6% annually and since 2000 the mean concentrations (i.e. in pooled samples) were below 9 mg/kg in these juvenile seals, which is the lowest suggested threshold for onset of physiological effects in experimental marine mammal studies. 

sDDT decreased with a rate of ca -8.9% yearly. The proportion of p,p’DDE increased over time as p,p’DDT decreased. Chlordanes and nonachlor also decreased over time (-4.6%). Trans-nonachlor was the most predominating compound. Finally, mirex decreased over time at a rate of approximately -2.3% annually.

Nine PBDE congeners were analyzed in blubber. The predominating BDE was BDE-47 (ca 70%) followed by BDE-99 and BDE-100. Most BDE congeners peaked during the 1990s.

Eleven perfluorinated substances were analysed. PFHxA and PFHpA were below detection limits in all but three samples not included in the statistical analyses. All but FOSA showed increasing trends over the study period, with increasing rates of +5-9% annually. However, if only looking at the last 15 years the concentrations appear stable (i.e. not increasing or decreasing). FOSA showed decreasing rates over the full period as well as the last 15 years. PFOS was observed in the highest concentrations (range 9.4-400 ng/g ww) and was the predominant PFAS. PFNA was the predominant PFCA followed by PFDA and PFUnDA.

Arsenic (As), cadmium (Cd), cobalt (Co), copper (Cu), (Cr), mercury (Hg), manganese (Mn), nickel (Ni), selenium (Se) and zinc (Zn) were analysed in seal liver. Cr was below detection limit in all samples but one, which was at detection limit. Ni was below detection limit in all samples. Only Co showed slight decreasing concentrations, the concentrations of the other metals were stable over time. However, concentrations of Pb were very low, and after 2000 below detection limit (<0.03 mg/kg ww), indicating decreasing concentrations. The relationship Hg vs Se on a molar basis showed no trend over time. Generally, the ratio was slightly below 1, but in five samples it did exceeded 1 (mean ratio was 0.9).