Polychlorinated Biphenyls (PCBs) and Sex Hormone Concentrations in Ringed and Grey Seals: A Possible Link to Endocrine Disruption?

Abstract

Polychlorinated biphenyls (PCBs) are recognised reproductive and immune system toxicants in marine mammals mediated by endocrine-disrupting mechanisms. As with other predators, seals are exposed to elevated bioaccumulated concentrations of PCBs and other persistent organic pollutants (POPs). Cryopreserved plasma samples from adult ringed (Phoca hispida; n = 39) and grey (Halichoerus grypus; n = 38) seals, sampled between 1998 and 2002 from Baltic Sea, Svalbard, and Sable Island (Canada) were used to investigate relationships between PCB exposure and sex hormone concentrations (progesterone; P4, 17α-hydroxy progesterone; 17α-OH-P4, testosterone; T4, 17β-estradiol; E2, estrone; E3). Immunoassay methods were used for quantification of analytes due to the limited sample volumes available. PCB concentrations were found to be significantly higher in Baltic seals than other sampling locations and were classed as "Exposed" seals while Svalbard and Sable Is seal were classed "Reference" seals (sexes and species separate). Mean hormone concentrations in Exposed seal were lower than Reference seals, and this was statistically significantly for 17α-OH-P4 (both sexes and both species), E2 (ringed and grey seal females), and E3 (grey seal females). Regression analyses (PCB v hormone concentrations) for each sex and species revealed significant correlations for P4 (Sable Is. female grey seals and female ringed seals), 17α-OH-P4 (Sable Is. male grey seals and Svalbard male ringed seals), T4 (Svalbard male ringed seals), E2 (female ringed seals), and E3 (female ringed seals and Baltic female grey seals). Although significant correlations are not evidence of cause and effect, the potential impact of hormone changes on endocrine homeostasis and reproductive health for seal populations warrants further investigation given that PCB concentrations found here are in the same range as those currently reported in seals from these populations.

Variation of blubber thickness for three marine mammal species in the southern Baltic Sea

“…This may translate into misjudgments regarding the health of the population based on blubber thickness—even if sampling occurs following standardized age categories and sampling seasons, variations related to unknown factors can bias the interpretation of the blubber thickness data. Studies in several seal species demonstrate that a qualitative and quantitative analysis of various parameters in and of the blubber have the potential to reveal further information about health and physiology like fatty acid composition and stratification ( Walton and Pomeroy 2003 ; Guerrero et al, 2017 ), hormone levels and profiles and pollutants ( Kershaw and Hall 2016 ; Troisi et al, 2020 ; Ogloff et al, 2022 ). Thus, further investigations including various analyses of some additional blubber parameters are strongly desired for a better evaluation of the overall health condition of individuals.…”

Structure design and sealing performance analysis of the sealing mechanism of the drilling tractor

“…Contact is a nonlinear behaviour. When the sealing ring is in contact with the rigid body, the change of its contact area is also a nonlinear problem 26 The volume is incompressible, the rubber material is approximately incompressible in volume.…”

Evaluating suitability of saliva to measure steroid concentrations in grey seal pups

“…Differences in steroid concentrations between nutritional categories and sex may thus have consequences for pups' behavior, immunity (Hall et al, 2002), energy balance (Bennett et al, 2013) and sensitivity to endocrine disrupting chemicals (Troisi et al, 2020) and may contribute to reported sex differences in their survival (Hall et al, 2001).…”