Workers in factories, construction sites, and noisy production facilities are susceptible to hearing loss. It has long been recognized as an occupational disease (a disease caused by one's occupation and eligible for compensation and benefits). In Vietnam, according to inter-ministerial circular 08/TTLB, occupational hearing loss is recognized as one of the eight most common occupational diseases. In industrialized countries, occupational hearing loss ranks first among all occupational diseases.
1. Conditions:
Exposure to high-intensity noise (85 dBA or higher) during work, prolonged exposure (3 months or more), and at least 6 hours per day.
2. Symptoms:
The disease is chronic and insidious, often lasting for years. Patients are usually unaware of it because the only symptom is hearing loss. The condition typically progresses through three stages, with durations varying from person to person:
2.1 Adaptation Stage:
In the first few days of working in noisy environments, patients experience fatigue, discomfort, tinnitus, a feeling of pressure in the ears, and hearing loss after or at the end of work hours. If monitored, hearing loss may initially only be observed at 4096 Hz, possibly up to 40-50 dB, in both ears. After a few weeks, these symptoms lessen and disappear completely, leading the patient to believe they have adapted to the noise, but in reality, hearing loss remains.
2.1 Latent Stage:
The only symptom is hearing loss.
– Hearing loss gradually increases in both ears, spreading to higher frequencies. Hearing loss at everyday frequencies is minimal or not significantly reduced, so patients are often unaware of it. They may notice hearing loss with high-pitched sounds (such as whistles) or a significant reduction in whispered speech compared to normal speech.
– Hearing loss progresses gradually, lasting for months or years depending on the individual.
2.3 The most noticeable stage:
Hearing at everyday frequencies decreases, and the patient becomes aware of their hearing loss due to its impact on language communication. Conductive hearing loss, always symmetrical in both ears, progressively worsens, leading to a decrease in all frequencies, resulting in pronounced deafness and potentially complete deafness in both ears.
The time and degree of progression vary from person to person.
Auditory tests reveal the following patterns:
Conductive hearing loss of the basal conjunctiva, symmetrical in both ears, often with auditory rebound (R+)
Conductive hearing loss of the entire conjunctiva.
With speech hearing loss exhibiting eavesdropping (hearing but not understanding some words, therefore unable to repeat), the audiogram is more horizontal than normal and consistently fails to hear 100% of the tested words.
3. Diagnosis:
3.1 First, determine if the subject works in an environment with noise intensity > 90 dBA for 3 months, 6 hours a day. Only those working in such conditions are likely to suffer from occupational hearing loss.
3.2 Perform preliminary audiometry to detect significant hearing loss at far frequencies (4096 Hz), symmetrical in both ears.
3.3 Perform complete audiometry to determine if there is conductive hearing loss, symmetrical in both ears, basal or total cochlear hearing loss.
3.4 Thoroughly inquire about the patient's history: examine the ears and balance function to rule out cases of inflammation, labyrinthine toxicity, or acoustic trauma.
4. Management Guidelines
4.1 Individuals with occupational hearing loss must have their cases documented and assessed for compensation and benefits according to regulations.
4.2 Individuals working in high-noise environments should undergo regular hearing tests (every 6 months to 1 year) to detect occupational hearing loss early.
4.3 Young individuals with significant or rapidly progressing hearing loss should be re-employed and avoid exposure to noise, as occupational hearing loss is irreversible and there is no cure.
4.4 To prevent occupational hearing loss, all workers exposed to noise should use ear protection devices such as earplugs or earmuffs.
