Association of Hearing Loss with Noise Exposure Time in Farm Machinery Operators / 日本農村医学会雑誌

ABSTRACT

The aim of this study is to clarify the relations between the hearing impairment of farmers and exposure to noise generated by agricultural machines. Some studies have revealed that the equivalent continuous sound level (Leq) from agricultural machines exceeds 80dB (A). But the noise -induced hearing loss experienced by farm machine operators has not received much attention, probably because they are self-employed and their working hours are irregular.<BR>We surveyed 1, 368 farmers, aged 17 to 76 (male 828, female 480), about working hours. We also tested their hearing levels at 1kHz and 4kHz. It was found that 22.3% of the farmers (305 of 1, 368) had some hearing impairment. In the hearing-impaired group, the mean length of working hours on tracters or other machines was 24, 689 ± 21, 155.13 hours. In the healthy group, the mean length of working hours was 16, 077. 65 ± 17, 623. 69 hours. A statistically significant difference was evident in the above results. As the operating hours increased, the incidence of the hearing impairment also increased. To avoid the biases of aging, we examined the results according to each age group. In the 40, 50, and 60-year-old age groups, the operating hours of the hearing impaired group were longer than those of the healthy group. We concluded that the amount of noise exposure probably affects farmers' hearing.