[A permanent noise-induced shift in the auditory threshold in textile industry workers]

Hearing thresholds have been measured in 236 cotton weaving mill workers (124 women: average age 42.5 +/- 11.2 years, average length of employment 19.5 +/- 10.6 years and 112 men: average age 41.2 +/- 10.3 years, average length of employment 19.0 +/- 11.1 years) exposed to continuous broadband noise of the constant level of approx. 100 dB-A. 90% of subjects exhibited the permanent threshold shift characterized by a great individual variability and maximum loss at the 4 kHz frequency. Those lesions were getting enhanced with increasing length of exposure and were more serious in elder age groups. No significant differences between the hearing loss intensity in men and women were found. The development of the hearing loss is characterized by its rapid increase within 3, 4 and 6 kHz during the initial 8 years of exposure, stabilization between years 9-12 and slow moderate increase within the further 13-31 years of exposure. Those conclusions should be implemented into practice through an increase in the frequency of preventive audiometric tests in the initial period of work in exposure which has such a great impact on the development of the hearing impairment.