A plug of ear wax that built up during a blue whale’s 12-year life has offered clues to the levels of pollutants that the whale accumulated from the ocean.

The 9.8-inch-long plug also provides a history of the whale’s maturation into adulthood.

The 68.8-foot male whale died after being struck by a ship off the coast of Santa Barbara, Calif. in 2007. During his life he built up concentric rings of wax in his ear canal.

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Cetologists, or whale scientists, had previously discovered that whales’ ear wax build up in distinct layers as the animals migrate. Like the rings of a tree, the number of wax layers corresponded to the animals’ ages. The wax also collects a record of the chemicals flowing through the animals’ bodies over time.

A team of zoologists and environmental scientists discovered that the dead whale had started accumulating toxins even before he was born. Even the earliest layers of the whale’s wax plug held pesticides, the coolant fluids known as polychlorinated biphenyls (PCBs) and flame retardant polybrominated diphenyl ethers.

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The whale wax also contained a steady dose of mercury along with two distinct spikes in concentration. The study’s authors suggested that the whale may have picked up these mercury spikes from the food it ate in particular regions as it migrated.

The levels of testosterone trapped in the wax rings suggested that the whale had reached sexual maturity only two years before being his fatal encounter with a ship.

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The journal Proceedings of the National Academy of Sciences published the study of the whale’s wax.

Photo: A blue whale. Credit: Getty