adminPneumoconiosis Act that seeks to protect workers who work in dusty environments. There is continued research in highrisk areas, while sentiments have been echoed that some occupational related diseases are going undetected.
An example is the risk factors associated with heavy manual lifting of goods that can lead to musculoskeletal disease. However, the issue of occupational induced hearing loss has also been overlooked, with employers being ignorant of the precious gift of hearing their workers may lose in adverse conditions.
The issue was very topical during last year’s National Social Security Authority Annual General Meeting held in Harare. Although natural failure of hearing may occur with advancing age, degenerative changes in the inner ear caused by some occupations may lead to hearing loss.
In extreme cases where workers may be at risk of losing their hearing, employers are encouraged to use ear protectors and noise meters. The noise meter flash application plays different sounds and sound intensities of everyday objects. It shows
how long it takes before a particular sound level becomes dangerous to the human ear. Potential harmful noise exposures can be described according to industry, some which have more potential of causing permanent hearing loss.
Some of the workers risking exposure to excessive noise include sheet-metal workers, engineers, carpenters, ironworkers, labourers and tile-setters.
Everyday, ordinary people experience sound in our environment such as the sound of television, radio, house-hold appliances and traffic among many others.
However, when people are exposed to harmful noise too loud or that lasts a long time, sensitive structures in our inner ear can be damaged. These structures are called hair cells. They are small sensory cells that convert sound energy into electrical signal that travel to the brain. Once damaged, the hair cells cannot grow back, meaning that the damage is permanent just like pneumoconiosis (caused by working in dusty environments). Sound is measured in decibels. On the decibel scale, an increase of 10 means that a sound is 10 times more intense, or powerful. To our ears, it sounds twice as loud. The humming of a fridge is 45 decibels, conversation is 60 decibels, while traffic is around 85 decibels. Motorcycles or firecrackers, small
firearms can cause noise induced hearing loss (all from 120 to 150 decibels).
Long or repeated exposure to sound above 85 decibels can cause hearing loss. Sounds of less than 75 decibels, after long exposure, are likely to cause hearing loss. Permanent noise induced hearing is therefore associated with a history of long
term exposure to noise being the main cause.
This usually occurs gradually in periods ranging between five and 10 years. The louder the sound, the shorter the time period before noise induced hearing loss can occur. Although being aware of decibel levels is an important factor in protecting one’s hearing, distance from the source of the sound and duration of exposure to the sound are equally important.
A good rule of thump is to avoid noises that are “too loud” and “too close” or that last “too long.”
Noise hearing loss may also occur due to impulse sound. This kind of hearing loss may be accompanied by tinnitus – a ringing, buzzing, or roaring in the ears or head – which may subside over time.
Hearing loss and tinnitus may be experienced in one or both ears, and tinnitus may continue constantly or occasionally throughout a lifetime. Exposure to impulse and continuous noise may cause only a temporary hearing loss. If a person regains hearing, the temporary hearing loss is called a temporary threshold shift. The temporary threshold shift largely disappears 16 to 48 hours after exposure to loud noise. One can prevent noise induced hearing loss from both impulse and continuous noise by regularly using earplugs or earmuffs. Scientists believe that, depending on the type of noise, the pure force of vibration from the noise can cause hearing loss. Recent studies also show that exposure to harmful noise levels triggers the formation of molecules inside the ear that damage hair cells and result in hearing loss.
These destructive molecules play an important role in hearing loss in children and adults who listen to loud music or noise for too long. Although the prevalence in Zimbabwe is not well known, noise induced hearing loss is a major cause of learning disabilities, while it also affects a victim’s social life. According to the World Health Organisation 2005 report, 278 million people worldwide suffer from hearing impairment and deafness. In developed countries, noise induced hearing loss is the greatest cause of hearing impairment.
About 80 percent of hearing impaired or deaf people live in developing countries, while current annual production of hearing aids meets less than 10 percent of global needs. It should be noted that noise induced hearing loss can be completely avoided through appropriate intervention.
According to the industrial hearing conservation, there are certain legal aspects that should be observed by employers. It is the employers’ responsibility to assess risk, monitor noise, carry our medical surveillance, conduct noise training, provide hearing protection devices and keep records.
According to industrial conservation legal aspects, an employee also has responsibilities. This includes attending training, using protection devises correctly, report noise sources, medical problems and perceived lack of protection. Failure to comply with the safety aspects have been attributed to lack of knowledge, no service provider who meets the legal standards and lack of capacity to implement hearing conservation programmes. Lack of capacity to enforce compliance, operational
challenges and organisation culture challenges have also been cited.
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