Inquinanti ambientali causano riduzione dell'udito dei mammiferi marini

Yale researchers find environmental toxins disruptive to hearing in
mammals

New Haven, Conn.-Yale School of Medicine researchers have new data
showing chloride ions are critical to hearing in mammals, which
builds on previous research showing a chemical used to keep
barnacles off boats might disrupt the balance of these ions in ear
cells.

"Our data are the first to directly show that chloride ions are
crucial for our exquisite sense of hearing," said Joseph Santos-
Sacchi, professor in the Departments of Surgery and Neurobiology and
first author of the study in the Journal of Neuroscience. "These
data also indicate that the hearing in marine and other mammals
could be affected by environmental toxins, such as TBT (tributyl
tin), because they appear 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. They are the
only group of animals that have outer hair cells. Additionally, TBT
is known to damage the immune and hormonal systems of marine mammals.

In this study on guinea pigs, Santos-Sacchi tested whether TBT or
salicylate, which is a chemical that occurs naturally in plants and
is a component of aspirin, interfered with the guinea pigs' ability
to hear. He found that TBT, salicylate, or otherwise altering the
extracellular chloride levels in the cochleas, interfered with the
balance of chloride in the outer hair cells and caused profound
changes in sound amplification in the inner ear.

In his previous study using TBT on isolated cells only, Santos-
Sacchi had proposed that the ear's ability to perceive sound would
be compromised. He also speculated that whales and other marine
mammals exposed to TBT would have altered sound localization
abilities. The present findings confirm that their hearing is
altered in mammals.

"Since many marine mammals use echolocation or sonar to get around,
this could be contributing to whales and dolphins beaching and
hitting ships," Santos-Sacchi said.