[Noise-induced hearing loss: are health service surveillance programs always effective?]

To evaluate noise-induced hearing loss in a group of workers at a steel engineering works over a 20 year period (1979-1999).

A total of 2431 audiometric tests were performed in 708 workers (in 1979, 1984, 1989, 1994 and 1999). Audiometric tests were classified so that hearing loss could be assessed over time. Additionally, personal noise exposure was measured for each worker (average, 85 dB(A) in tests carried out in 1992, 1996 and 1999).

Over 5 years of noise exposure, mean cumulative incidence of noise-induced hearing loss was 8,2%. Over 10 years ofexposure (1979-89 or 1984-94 or 1989-99), the mean incidence was 15,3%. This percentage increased to 22,9% and 25,7% when the exposure lasted 15 or 20 years respectively.

The considerable incidence of noise-induced hearing loss within the wide group of steel workers examined greatly exceeds the expected incidence related to the occupational exposure limits. The Evidence Based Occupational Medicine suggests that our health surveillance was not effective enough.