OCCUPATIONAL HEARING LOSS CAUSED BY NOISE

Abstract

When studying noise-induced hearing loss, it is essential to consider that there are other causative agents that can not only cause hearing loss regardless of exposure to noise, but also enhance its effects when combined with it. Among these agents, exposure to certain chemicals, vibrations and the use of some medications stand out, which can amplify hearing damage.

Noise-Induced Hearing Loss (NIHL) is one of the main occupational diseases, resulting from prolonged exposure to high levels of noise in work environments. This condition, of the sensorineural type, is usually bilateral, irreversible and progressive over the time of exposure. NIHL occurs due to permanent damage to the sensory cells of the cochlea and may or may not be associated with the presence of chemical substances in the work environment. Its impacts include communication difficulties, reduced worker quality of life, and increased risk of accidents.

Several terms can be used as synonyms for Noise-Induced Hearing Loss, including: hearing loss due to exposure to noise at work, occupational hearing loss, occupational deafness, occupational hearing loss, hearing loss induced by high sound pressure levels, hearing loss induced by occupational noise and sensorineural hearing loss resulting from continuous or sudden exposure to high levels of sound pressure of occupational origin.

Morata and Lemasters (2001) suggested the adoption of the term "occupational hearing loss" because it is more comprehensive. This term recognizes noise as the most common causal agent, but also considers other factors that can contribute to hearing loss, covering aspects such as diagnosis, preventive measures, safety limits, and legislative issues.

Harger; Barbosa-Branco (2004) highlight that the main factors that influence the risk of NIHL include the physical characteristics of the noise, such as its type, spectrum and level of sound pressure, the duration of exposure and the individual susceptibility of each worker. In addition, the risk of hearing loss increases significantly when the average exposure to noise exceeds 85 dB(A) for eight hours a day (BRASIL, 2006).

Continuous noise exposures are more harmful than intermittent ones. However, short exposures to intense noise levels can also cause hearing loss. Thus, when analyzing the use of hearing protectors in the occupational history of the worker, it is essential to consider relevant aspects, such as the effective attenuation of noise provided by the equipment, verifying whether the hearing protection was adequate for the exposure; the individual characteristics of the worker; and the real conditions of exposure to noise in the work environment (BRASIL, 2006).

Intense occupational noise exposure can result in different types of hearing damage, including acoustic trauma (sudden hearing loss due to a single exposure to loud noise), temporary threshold alteration (temporary elevation of the audibility threshold, which gradually recovers after noise exposure), and Hearing Loss Induced by High Sound Pressure Levels (PAINPSE),  characterized by the degeneration of the hair cells of the organ of Corti.

The presence of other factors, such as vibration, heat and certain chemical agents in the environment and in work processes, can influence the development of hearing loss by interacting with occupational sound pressure levels (BRASIL; PAN AMERICAN HEALTH ORGANIZATION, 2001).

Programs such as the Hearing Conservation Program (PCA) are essential to prevent Occupational Hearing Loss (OAP). They combine surveillance, hearing health promotion and training for the proper use of Personal Protective Equipment (PPE). In addition, measures such as the use of Collective Protective Equipment (CPE), modernization and maintenance of machinery help reduce exposure to noise.

Health education and awareness campaigns are also crucial, offering courses on the risks of noise and chemicals and instructing on the correct use of PPE. These actions preserve hearing health, improve quality of life and promote safety at work.