Killer Whales (Orcinus orca) Face Protracted Health Risks Associated with Lifetime Exposure to PCBs

Abstract

Polychlorinated biphenyl (PCB) concentrations declined rapidly in environmental compartments and most biota following implementation of regulations in the 1970s. However, the metabolic recalcitrance of PCBs may delay responses to such declines in large, long-lived species, such as the endangered and highly PCB-contaminated resident killer whales (Orcinus orca) of the Northeastern Pacific Ocean. To investigate the influence of life history on PCB-related health risks, we developed models to estimate PCB concentrations in killer whales during the period from 1930 forward to 2030, both within a lifetime (∼50 years) and across generations, and then evaluated these in the context of health effects thresholds established for marine mammals. Modeled PCB concentrations in killer whales responded slowly to changes in loadings to the environment as evidenced by slower accumulation and lower magnitude increases in PCB concentrations relative to prey, and a delayed decline that was particularly evident in adult males. Since PCBs attained peak levels well above the effects threshold (17 mg/kg lipid) in ∼1969, estimated concentrations in both the northern and the more contaminated southern resident populations have declined gradually. Projections suggest that the northern resident population could largely fall below the threshold concentration by 2030 while the endangered southern residents may not do so until at least 2063. Long-lived aquatic mammals are therefore not protected from PCBs by current dietary residue guidelines.

Assessing the effect of persistent organic pollutants on reproductive activity in common dolphins and harbour porpoises

“…This was attributed to either hormonal disturbance, direct dominant-lethal action or to an embryo lethal effect caused by toxicants (Reijnders, 1986). It should be noted that the Kannan et al, (2000) PCB threshold of 17 μg g -1 lipid is less protective than that proposed of 10 μg g -1 lipid, which was associated with increased calf mortality in wild bottlenose dolphins (Hall et al, 2006b;Hickie et al, 2007). Further, the analysis in the current study only assessed the effects of 16 CB congeners on reproductive activity, and did not include the most immunotoxic IUPAC congeners, such as CB77 and CB126.…”

“…Not only does an individual's POP burden reflect its dietary preferences, it is influenced by its body size, body condition, nutritive condition, disease, metabolism, excretion, age and sex (Aguilar et al, 1999). Furthermore, it is an indication of the conditions it experienced in early life: contaminant levels in its mother, the duration of nursing, birth order and the length of the calving interval preceding its birth (Hickie et al, 1999;Hickie et al, 2000;Ross et al, 2000;Ylitalo et al, 2001;Hickie et al, 2007). Females, through mobilization of lipid-associated toxins from the blubber during periods of high energy requirements, transfer toxic compounds to their offspring during gestation (via the placenta) and lactation (via their lipid rich-milk), resulting in a high exposure of newborns to those chemicals (O'Hara and O'Shea, 2005).…”

Overview of the Current State-of-the-Art for Bioaccumulation Models in Marine Mammals

“…For marine mammal models, a range of software has been used to date (see overview Table 1). Models for the bioaccumulation of POPs (persistent organic pollutants) in bottlenose dolphins [9], killer whales (Orcinus orca) [8], beluga whales [12,13] and ringed seals [14] were initially made using BASIC (free programming software), but were later upgraded to Visual Basic for Applications within the Excel spreadsheet in Microsoft Office. Models for the bioaccumulation of PCBs in bottlenose dolphins [7] and for the bioaccumulation of PCBs and of PBDEs (polybrominated diphenyl ethers) in killer whales [15] were developed in R (R Development Core Team 2006).…”

“…Nevertheless, kinetic models have applications on their own in the field of risk assessment as they are a useful framework to interpret existing biomonitoring and effect studies [5,6]. For marine mammals, predicted tissue concentrations of polychlorinated biphenyls (PCBs) from models for several species have been used to assess risk of adverse health effects by comparing them to established effects thresholds [7][8][9].…”

Revision of sediment quality triad indicators in Puget Sound (Washington, USA): I. a Sediment Chemistry Index and targets for mixtures of toxicants

“…However, high levels of some toxic chemicals (e.g., PCBs, PAHs, metals) are still being measured in species throughout different trophic levels in Puget Sound, including southern resident killer whales (Ross et al 2000;Ross 2006), harbor seals (Ross et al 2004;Hickie et al 2007), Chinook salmon (O'Neill and West 2009), Pacific herring , and blue mussels (Kimbrough et al 2008). Contaminants of emerging concern (CECs), including phthalates, pharmaceuticals, and others, may also be harming biota.…”