[Risk of noise-induced hearing loss in farm tractor operators].

Studies of noise at work site of tractor operators showed that this parameter exceeds allowable values. In order to evaluate the risk of hearing loss in this occupational group, noise-induced permanent threshold shift (NIPTS) values were determined. This parameter is a function of the audiometric frequency, duration of occupational exposure and noise exposure level (LEX,8 h). The procedure recommended by ISO-1999/1990 was used for calculations. The study covered two groups of operators: operators of ZM "Ursus" medium-power tractors (noise exposure level: LEX,8 h = 96.6 dB) and operators of high-power tractors of the same manufacture (LEX,8 h = 89.6 dB) The risk of hearing impairment was determined for the group of men aged 50 years, occupationally exposed to noise for a period of 30 years. The calculation was based on the mean value of expected hearing loss for three selected audiometric frequencies: 1000; 2000; and 4000 Hz. The study showed that the average (median; N0.50) expected hearing loss, excluding that associated with age, after 30 years of employment was 15 dB for operators of medium-power farm tractors, and 6 dB for operators of high-power tractors. The risk of hearing impairment due to occupational exposure to noise (exceeding the maximum allowable hearing loss of 27 dB; according to ISO-1999/1990) that may cause an acoustic trauma was 37.9% for medium-power tractors and 13.0% for high-power tractors. The results of the study show that noise at workplaces of farm tractor operators creates a high risk of hearing impairment.