Noise-induced hearing loss: Are health service surveillance programs alwayseffective?

Objectives: To evaluate noise-induced hearing loss in a group of workers ata steel engineering works over a 20 year period (1979-1999). Methods: A totalof 2431 audiometric tests were performed in 708 workers (in 1979, 1984, 1989,1994 and 1999). Audiometric tests were classified so that hearing loss could beassessed over time. Additionally, personal noise exposure was measured for eachworker (average, 85 dB(A) in tests carried out in 1992, 1996 and 1999). Results:Over 5 years of noise exposure, mean cumulative incidence of noise-inducedhearing loss was 8,2%. Over 10 years of exposure (1979-89 or 1984-94 or1989-99), the mean incidence was 15,3%. This percentage increased to 22,9% and25,7% when the exposure lasted 15 or 20years respectively. Conclusions: Theconsiderable incidence of noise-induced hearing loss within the wide group ofsteel workers examined greatly exceeds the expected incidence related to theoccupational exposure limits. The Evidence Based Occupational Medicine suggeststhat our health surveillance was not effective enough