Noise, induced hearing loss

According to the U.S. Bureau of the Census, Statistical Abstract of the United States, there are over 7.2 million workers employed in the construction industry (6% of all employment). NIOSH and National Occupational Exposure Survey (NOES) estimate that 421,000 construction workers are exposed to noise above 85 dBA. NIOSH estimates that 15% of workers exposed to noise levels of 85 dBA or higher will develop material hearing impairment. 

There are a variety of control techniques documented in the literature to reduce the overall worker exposure to noise. Such controls reduce the amount of sound energy released by the noise source, divert the flow of sound energy away from the receiver, or protect the receiver from the sound energy reaching him or her. For example, types of noise controls include proper maintenance of equipment, revised operating procedures, equipment replacements, acoustical shields and barriers, equipment redesign, enclosures, administrative controls, and PPE. 

OCCUPATIONAL HEALTH AND SAFETY MANAGEMENT A PRACTICAL APPROACH 

Source Courtesy of Occupational Safety and Health Administration. 

Sometimes the loss of hearing due to industrial noise is called the silent epidemic. Since this type of hearing loss is not correctable by either surgery or the use of hearing aids, it is certainly a monumental loss to the worker. It distorts communication both at work and socially. It may cause the worker to lose his or her job if acute hearing is required to perform effectively. The loss of hearing is definitely a handicap to the worker. 

Research demonstrates that construction workers are regularly overexposed to noise. The extent of the daily exposure to noise in the construction industry depends upon the nature and duration of the work. 

For example rock drilling—up to 115 dBA chain saw—up to 125 dBA abrasive blasting—105 to 112 dBA heavy equipment operation—95 to 110 dBA demolition—up to 117 dBA and needle guns—up to 112 dBA. Exposure to 115 dBA is permitted for a maximum of 15 minutes for an eight-hour workday. No exposure above 115 dBA is permitted. Traditional dosimetric measurement may substantially underestimate noise exposure levels for construction workers since shortterm peak exposures, which may be responsible for acute and chronic effects, can be lost in lower, full-shifttime-weighted average measurements. 

For example, types of noise controls include proper maintenance of equipment, revised operating procedures, equipment replacements, acoustical shields and barriers, equipment redesign, enclosures, administrative controls, and personal protective equipment. 

The hearing conservation program requires anployers to monitor noise exposure levels in a manner that will accurately identify employees who are exposed to noise at or above 85 decibels (dBA) averaged over eight working hours, or an 8-hour TWA. That is, employers must monitor all employees whose noise exposure is equivalent to or greater than a noise 

FIG U RE 23.10 Example of a testing booth for conducting hearing test. (Source Courtesy of the National Mine Health and Safety Academy.) 

What we perceive as sound is a series of compressions and rarefactions transmitted by some vibrating source and propagated in waves through the air. The compressions and rarefactions impinge on the eardrum (tympanic membrane) causing it to vibrate and transfer the movements through three small bones in the middle ear to the fluid of the inner ear. There they are received by rows of hairs (in the organ of corti), which vary in their response to different frequencies of sound, and are then transmitted to the brain and interpreted as sound. 

The ear can interpret frequencies between 20 and 20 000 Hz approximately. Frequencies below (infrasonic) and above (ultrasonic) this range are not heard. The range of frequency for speech is between 400 and 4000 Hz. 

Noise is commonly defined as unwanted sound. The definition is dependent on individual interpretation and may or may not include the recognition that some sounds produce harmful effects. Some sounds cause annoyance. 

Exposure to noise levels of about 85dBA for even a few minutes may induce a temporary threshold shift (change of the threshold at which sound can just be heard), lasting from seconds to hours, and which can be detected by audiometry. Temporary threshold shift (TTS) may be accompanied by noises in the ears (tinnitus) and may be a warning sign of suscephbility to permanent threshold shift (PTS) which is an irreversible deafness. 

The onset of permanent deafness may be sudden, as with very loud explosive noises, or it may be gradual. A gradual onset of deaftiess is more usual in industry and may be imperceptible until familiar sounds are lost, or there is difficulty in comprehending speech. The consonants of speech are the first to be missed f, p, t, s and k. These are of high frequency compared with the vowel sounds, which are of low frequency. Speech can still be heard, but without the consonants it is unintelligible. There is a risk too that a person exposed to excessive noise may believe himself to be adjusting to it when, in fact, partial deafness has already developed. 

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While a clear causitive role has been established for PMCA2 in hearing loss, further studies on hypomorphic alleles could address their effect on age-related or noise-induced hearing loss. Generating a mouse model of the human V586M mutation should provide an even less affected hypomorph for further studies. 

Skinner, 1980] Skinner, M. (1980). Speech intelligibility in noise-induced hearing loss Effects of high-frequency compensation. J. Acoust. Soc. Am., 67 306-317. 

Damage to hearing caused by one very loud event, as in the case of an SRV, may however be different in onset and character to the observed noise-induced hearing loss from lower but more continuous levels. In this situation, damage to the inner ear is caused to the whole organ rather than to certain cells. 

Noise-induced hearing loss is a problem of epidemic proportion in modern society, and is currently the second most common form of hearing impairment in the United States (after age-related hearing loss). Although it is difficult to accurately assess the extent of the problem, the US Centers for Disease Control and Prevention has estimated that 12.5% of US children aged 6-19 years have some form of noise-induced hearing loss in one or both ears, and a 1990 Consensus Statement issued by the US National Institutes of Health estimated that over one-third of the 28 million people in the United States suffering from... 

Hakuba N, Koga K, Gyo K, Usami S, Tanaka K (2000) Exacerbation of noise-induced hearing loss in mice lacking the glutamate transporter GLAST. J Neurosci (in press). 

There have also been significant reductions in the number of cases of work-related allergy and noise-induced hearing loss. 

Noise-induced hearing loss Yes Low Potehtial drug ihteractiohs... 

G. Occupational ototoxicity is common but is usually noise induced rather than chemical related. Preexisting noise-induced hearing loss may magnify the impact of common ototoxic drugs. 

Rabinowitz, RM., Noise-induced hearing loss, American Family Physician, 61(9), 2000,2759-2760. 

The modern industrial worksite can be a noisy place. This poses two safety and health related problems. First, there is the problem of distraction. Any operation that requires oral communication will suffer from a noisy environment. Interference with communications can create misunderstandings about information transmitted from one person to another. When such communications relate to hazardous activities, any misunderstandings can lead to accidents. Second, there is the problem of hearing loss. Exposure to noise that exceeds prescribed levels can result in permanent hearing loss. Occupational exposure to loud sounds is the most common cause of what is often called noise-induced hearing loss. 

T/F) Occupational noise-induced hearing loss occurs over a period of several years. 

Use of hearing protection in both occupational and non-occupational environments is intended to help reduce noise exposure levels and noise-induced hearing loss (NIHL). In the absence of feasible engineering and administrative noise reduction control methods, use of earplugs or earmuffs is common practice. Unfortunately there are still many myths surrounding the use and effectiveness of hearing protection devices (HPDs). In this article, some of the more common myths and the realities are addressed. 

ILLUSTRATION OF THE DEVELOPMENT OF NOISE INDUCED HEARING LOSS ... 

Hz. The authors conclude that BLL under 10 pg/dL may enhance noise-induced hearing loss. 

Hwang, Y.H., H.Y. Chiang, M.C. Yen-Jean, and J.D. Wang. 2009. The association between low levels of lead in blood and occupational noise-induced hearing loss in steelworkers. Sci. Total Environ. 408(l) 43-49. 

There is no cure for noise-induced hearing loss, so preventing exposure to excessive noise is... 

Occupational illness may involve skin diseases or disorders caused by work exposure to chemicals, plants or other substances. They may be respiratory conditions associated with breathing hazardous biological agents, chemicals, dust, gases, vqjors, or fumes at work. They may also be poisonings, noise-induced hearing loss, or other occupational illnesses. 

There are many effects of noise on people. Most effects are detrimental. The best-known effect of noise is noise-induced hearing loss. There are many other effects that contribute to accidents and health problems. 

Many famous musicians have noise-induced hearing loss from a long history of noise exposure. Two with hearing loss are Ozzy Osborne (Black Sabbath) and Pete Townshend (The Who). 

The greatest safety concern is noise-induced hearing loss. Exposure to noise can produce hearing loss. Both duration of exposure and sound intensity can lead to hearing loss. High frequency noise is more damaging than low frequency noise. Continual noise is more damaging than intermittent noise. 

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