Research demonstrates that persistent organochlorine pollutants (POPs) show up in the tissues of whales, in some cases after they have been banned. POPs, which are neurotoxins, include chemicals such as DDT, dioxins, and PCBs. Scientists believe that these pollutants evaporate into the air on land, and when that air subsequently condenses, the POPs enter the ocean and are absorbed by marine life such as krill. Since whales consume large amounts of krill, they then take up large amounts of pollutants.
The presence of POPs in whale blubber is worrisome because of the toxicity of these chemicals. As whales travel around the ocean, they often burn blubber for fuel, releasing POPs into the bloodstream and potentially affecting the whales' ability to reproduce.
This research adds to the difficulty of determining safe levels of chemicals for the environment. Even when scientists cannot prove that exposure causes immediate human health problems, policymakers must consider the broader impact of chemicals on whole ecosystems to get a true picture of the potential impact of a particular substance.