Epidemiology of occupational noise-induced hearing loss in Poland throughout 1971--1979.

In Poland a uniform system for registering occupational diseases is mandatory. Special individual statistical cards of diagnosed cases are delivered from all over the country to the Institute of Occupational Medicine in Lodź, where the incidence of diseases is analysed using electronic data processing system; such procedure is aimed, among others, at specification of prophylactic needs. Due to this, epidemiological studies could be carried out of the prevalence of occupational noise -- induced hearing loss in the total national economy throughout 1971--1979. Of the 35 mln Polish population, approx. 5 mln. 240 thous. persons are employed in industry, in this about 600 000 workers exposed to noise levels posing a risk of the hearing impairment of (Leq greater than or equal to 90 dB-A). It was found that occupational noise -- induced hearing loss was most frequent among all occupational diseases and its incidence rate exceeded 16 new cases annually per 100 000 employees. The highest incidence rate concerned transport means industry, coal mining and textile industry. The data analysis, by age and exposure duration, showed that the disease mostly affects those aged 40 -- 49 and 50 -- 59, as well as those exposed to excessive noise levels for over 20 years. In addition, the distribution of occupational noise -- induced hearing loss in specific areas throughout the country, considering the degree of industrialization, was analysed. The highest incidence rate was found in the Southern and Western areas of Poland. The above information seems to be essential for setting up more efficient hearing conservation program in industry.