According to the researchers from Yale School of Medicine it is found that chloride ions are critical to hearing in mammals. Joseph Santos-Sacchi, professor in the Departments of Surgery and Neurobiology and first author of the study said that hearing in marine and other mammals could be affected by environmental toxins, such as TBT (tributyl tin).
The study indicates that this environmental pollutant appears to alter the balance of chloride ions in the outer hair cell. Sensitive hearing in mammals relies on cochlear amplification resulting from the motor activity of outer hair cells. Hence marine mammals are the only group of animals that have outer hair cells.
Apart from this other studies show that TBT is known to damage the immune and hormonal systems of marine mammals. The author conducted the study on guinea pigs and tested whether TBT interfered with the guinea pigs' ability to hear. TBT or salicylate is a chemical that occurs naturally in plants and is a component of aspirin. He found that TBT altered the extracellular chloride levels in the cochleas.
This further interfered with the balance of chloride in the outer hair cells and caused profound changes in sound amplification in the inner ear. TBT is thought to have altered sound localization abilities of the mammals. He suggests that this could be one of the many reasons that many marine mammals beaching and hitting ships. The reason behind that could be attributed to the effects of TBT because marine mammals use echolocation or sonar to get around.