People are polluted and whales are too. Sperm whales throughout the Pacific carry evidence of exposure to polycyclic aromatic hydrocarbons (PAHs), which occur in oil, coal, and tar deposits, and are produced as byproducts of fuel burning. Some of them are carcinogenic, and high levels of PAHs are found in meat cooked at high temperatures (such as grilling or barbecuing), as well as in smoked fish.

Whales also reveal exposure to DDT, which is banned in most Western countries, but still used to kill mosquitoes throughout much of the world. During 1999–2001, researchers biopsied skin and blubber from 234 male and female sperm whales in five locations (NOTE: Subscribers can still listen to this show) across the Pacific Ocean and analyzed them for the expression of an enzyme that metabolizes certain aromatic hydrocarbons–the more CYP1A1 is expressed, the more likely the animal has been exposed to those compounds.

The whale tissues from were also were analyzed for DDT. Exposure to these substances was highest in whales from the Galapagos Islands, second highest in those from the Gulf of California, and lowest in those from waters farthest from the continents. Sperm whales may be important sentinels of ocean health: Since they are so long-lived (up to 70 years), their skin carries evidence of the history of ocean (and Earth) pollution.

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