Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 7522
Title: Sentinel California sea lions provide insight into legacy organochlorine exposure trends and their association with cancer and infectious disease
Author: Nistara Randhawa, Frances M.D. Gulland, Gina Marie Ylitalo, R. DeLong, Jonna Mazet
Publication Year: 2015
Journal: One Health
Volume: 1
Pages: 37-43
DOI: doi:10.1016/j.onehlt.2015.08.003
Keywords: California sea lion,organochlorines,cancer,diseases,PCB,DDT,California sea lions,cancer,infectious disease

Background: Organochlorine contaminants (OCs), like polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethanes (DDTs), are widespread marine pollutants resulting from massive historical use and environmental persistence. Exposure to and health effects of these OCs in the marine environment may be examined by studying California sea lions (Zalophus californianus), which are long lived, apex predators capable of accumulating OCs. Methods: We evaluated PCB and DDT levels in 310 sea lions sampled between 1992 and 2007: 204 individuals stranded along the coast of central California, 60 healthy males from Washington State, and 46 healthy females from southern California. Lipid-normalized contaminant concentrations were analyzed using general linear models and logistic regression to ascertain temporal trends; differences between stranded and healthy sea lions; and association of organochlorines with sex, age, and presence of cancer or fatal infectious disease. Results: Concentrations of the contaminants in stranded adults decreased over time in the study period (adjusted for sex, as adult males had higher mean blubber concentrations than adult females and juveniles). Cancer was almost eight and six times more likely in animals with higher summed PCBs and DDTs, compared to those with lower levels (95% CI 5.55–10.51 and 4.54–7.99, respectively). Fatal infectious diseases were similarly seven and five times more likely in animals with higher contaminant burdens (95% CI 4.20–10.89 and 3.27–7.86, respectively). Mean contaminant loads were significantly higher in stranded sea lions than in healthy live captured animals (p < 0.001). Conclusion: Organochlorine contamination has significant associations with health outcomes in California sea lions, raising concerns for humans and other animals eating tainted seafood. While environmental exposure to these organochlorines appears to be decreasing over time based on levels in sea lion tissues, their persistence in the environment and food web for all predators, including humans, and the associated serious health risks, warrant monitoring, possibly through sentinel species like marine mammals.

Theme: Habitats to Support Sustainable Fisheries and Recovered Populations
Foci: Assess the impacts of toxic chemicals and other pollutants across biological scales, and identify pollution reduction strategies that improve habitat quality.