Chapter 37 - Contaminants

Abstract

This chapter is focused on the major classes of contaminants that are monitored in Bering–Chukchi–Beaufort Seas (BCB) bowhead whales, which are characterized as petroleum-related, metals (nonessential elements), and persistent organics. Exposure to these contaminants occurs primarily through ingestion of contaminated prey or particulate matter although direct contact and inhalation may also be important. Petroleum-related contaminants commonly originate from unintentional releases during marine industrial activities. Polycyclic aromatic hydrocarbons (PAHs) are considered the most toxic of petroleum-related contaminants. We recently assessed PAH levels in muscle and blubber from male bowhead whales harvested from 2006 to 2015 and observed only a few samples with quantifiable PAHs, up to 140ng/g wet weight. With regard to metals, the consensus is concentrations are comparable to those measured in other marine mammal species. We determined elemental content of bowhead liver and kidney tissue samples collected from over 50 individuals of varying age. The tissue concentrations of the toxic metals cadmium and mercury increased in concentration with age. Recently measured cadmium levels were similar to those reported in prior studies, indicating tissue levels are not increasing since monitoring began approximately 35 years ago. More effort has been placed on monitoring persistent organic pollutants (POPs). All data on POPs levels are from BCB stock whales sampled during subsistence hunts by Alaskan Native villages. Frequently measured POPs are polychlorinated biphenyls (PCBs) and chlorinated pesticides such as chlordanes (CHLs), hexachlorocyclohexanes (HCHs), dieldrin, hexachlorobenzene (HCB), and dichlorodiphenyltrichloroethane-related pesticides (DDTs). Recent data indicate concentrations in blubber are ordered ΣHCHs>ΣCHLs~HCB>ΣPCBs>ΣDDTs~dieldrin. Levels appear to have peaked in bowhead blubber and are declining approximately 1%–8% per year. On the other hand, the growing human activity in the Arctic is expected to increase contaminant releases, emphasizing the need for continued surveillance of established contaminants but should also be expanded to include more emerging contaminants.