Exposure to noise above-causes permanent hearing loss –
## Core Concept
Permanent hearing loss due to noise exposure is a significant concern in occupational and environmental health. The risk of permanent hearing loss is directly related to the intensity and duration of noise exposure. **Noise-induced hearing loss (NIHL)** is a type of sensorineural hearing loss caused by damage to the hair cells in the cochlea.
## Why the Correct Answer is Right
The correct answer, , indicates that exposure to noise above 90 dB can cause permanent hearing loss. Prolonged exposure to sounds at or above 90 dB can lead to NIHL. The **National Institute for Occupational Safety and Health (NIOSH)** and other health organizations have established guidelines for noise exposure limits. According to NIOSH, exposure to noise above 90 dB for an extended period increases the risk of permanent hearing loss.
## Why Each Wrong Option is Incorrect
* **Option A:** . This option is incorrect because 60 dB is a relatively low level of noise, typically associated with normal conversation, and is not considered hazardous for causing permanent hearing loss.
* **Option B:** . This option is incorrect because, although 80 dB is a level that can cause hearing problems with prolonged exposure, it is generally not considered the threshold for permanent hearing loss.
* **Option D:** . This option is incorrect because 100 dB, while certainly hazardous and capable of causing hearing loss with prolonged exposure, is not the minimum threshold for permanent damage; levels as low as 90 dB can cause permanent hearing loss with sufficient exposure.
## Clinical Pearl / High-Yield Fact
A key point to remember is that the risk of NIHL is not just about the intensity of the noise but also the duration of exposure. The **NIOSH hearing conservation program** recommends that workers exposed to noise at or above 85 dB should have their hearing tested annually. A simple way to remember the risk is that prolonged exposure to noises louder than a lawnmower (about 90 dB) can lead to permanent hearing loss.
## Correct Answer: C. 90 dB.