Metal pollution in the ocean is a worldwide concern. We study the impact of metals, such as mercury, chromium and lead, on whales. Metals can accumulate in whale tissues, but its poorly understood how these metal levels change over time. In 2000, we analyzed metal levels in whales from the Sea of Cortez. Now, 16 years later we plan to return to the Sea of Cortez to measure how whale metal levels have changed. These data will help in the conservation and protection of these important animals.