The Economic Times

In 2007, scientists recovered a blue whale earplug off Santa Barbara; its 24 wax layers archived 12 years of hormones, mercury, and man-made pollutants

The earwax plug of a blue whale serves as a remarkable indicator of its life history. This wax revealed its exposure to harmful pollutants from birth to its twelfth year. It also showed an increase in stress and testosterone levels as the whale matured. Major stressors included ship noise and pollution, underscoring the significant effects of human activities on marine creatures.