Organochlorine pesticide residue and PCBs in harbour porpoise ( Phocoena phocoena) incidentally caught in Scandinavian waters

Abstract

During Norwegian and Danish harbour porpoise projects 1987–1991, subcutaneous blubber samples of 34 male harbour porpoises ( Phocoena phocoena) were collected. Animals from three geographical locations, ranging from 56°N, 12°E to 71°N, 26°E, were chosen in order to study the organochlorine (OC) contamination in this species inhabiting the northeastern part of the North Atlantic Ocean, the northern North Sea and Kattegat, at the locations of Tufjord, Vestlandet and Gilleleje, respectively. Analytical standards used consisted of the industrial chemicals PCBs (22 individual PCB congeners and 6 industrial mixtures which contained 104 PCB congeners or group of congeners) and HCB, and the organochlorine pesticides DDT, HCH, the cyclodienes endrin, dieldrin and the chlordane metabolites oxychlordane and trans-nonachlor, and heptachlor epoxide. A total of 16 PCB congeners or groups of congeners, all the DDT metabolites except o,p'-DDD, and all the pesticides were detected in all animals. The concentrations of ∑PCB (sum of concentrations of 47 detected PCB congeners) and ∑DDT (sum of concentrations of all DDT detected compounds) ranged from 3·7–65·3 and 3·2–45·0 μg g −1 lipid weight, respectively. The range of mean concentrations of dieldrin, endrin and trans-nonachlor was 1–3 μg g −1, while mean concentrations of HCHs, heptachlor epoxide, and HCB were <1 μg g −1. No significant variation in PCB congener pattern was apparent between geographical areas. The major PCB congeners nos 147/123, 153, 138/163/164, 182/187 and 180 at Gilleleje, Vestlandet and Tufjord represented 53%, 45% and 44% of ∑PCB, respectively. A significant difference was found between the number of PCB congeners in blubber of newborn and older porpoises. This might indicate the presence of a blood/placenta barrier and/or selective mammary transport of PCBs with specific structures. A significant OC accumulation with age was apparent, with the exception of HCB and HCHs. Geographical differences in the levels of OCs were apparent for all compounds except for dieldrin and heptachlor epoxide. Significantly higher levels of chlordane metabolites ( trans-nonachlor and oxychlordane) and endrin were found in the group of animals from the northern location Tufjord, while ∑DDT, p,p'-DDTs, HCHs and PCBs were highest in the group of animals from the southern location Gilleleje. Highest levels of the o,p'-substituted DDTs were found in specimens from the middle location Vestlandet. These findings indicate little or no regular migration of harbour porpoise between these three locations. No correlations were found between OC concentrations and blubber thickness. Although mean values of ∑DDT and ∑PCB were in the lower end of previously reported levels in harbour porpoise from adjacent waters in the eastern part of the North Atlantic Ocean and along the coasts of North America, these levels are relatively high. The organochlorine concentrations in harbour porpoises in the present study were 2–3 times higher than corresponding OC levels detected in harbour seals ( Phoca vitulina) from the same areas.