The cochlea is the part of the inner ear that takes vibrations, transferred from sound waves hitting the eardrum (tympanic membrane) and converts them into signals for the auditory nerve. Different parts of the cochlea "encode" different frequencies (pitches) of sound. Therefore, if only part of the cochlea is damaged, a person may lose the ability to hear certain frequencies of sound. If it is damaged enough, the person may lose the ability to hear completely in one ear.
The cochlea is the main hearing-related organ of the inner ear. When it is damaged, permanent hearing loss is the result. Tiny "hair cells" on the cochlea are responsible for sensing specific sounds, and cochlea damage is caused by the bending and/or breaking of these "hair cells."
Blood transfusions, protection from infection in damaged organs, and possibly the use of newer stimulants to blood formation can save many victims i
Engines can be damaged by just humidity, so direct exposure to the elements should be avoided if possible.
The way to stop being damaged by exposure to x-rays is to reduce or eliminate your exposure to x-rays from man-made sources. There is little you can do about naturally occurring x-rays.
The permanent one is damage to the cochlea. Artificial implants are now available though.
skin cancer :D
Nerves can get damaged due to physical injuries that directly impact the nerves, due to infection by pathogens such as meningococcal bacteria or poliovirus, or due to exposure to poisons such as mercury.
Recognizing which compartments are damaged and minimizing that damage.
Loud noises can damage the ear drum. Sometimes the cochlea can also be damaged which could cause permanant deafness. Wax in your ear canal can cause temporary deafness