Hearing Acuity Loss Of Operators Of Food Grinding Machines In Calabar, Nigeria

Abstract

Noise has been generally found to cause hearing impairment. This was therefore a comparative study to determine whether chronic exposure to noise generated from food grinding machine can impair hearing acuity. Forty food grinding machine operators in Watt and Marian markets, Calabar, who were exposed to noise for at least 6 months formed the test subjects. Control subjects, however, were age- and sex-matched staff and students of the University of Calabar and University of Calabar Teaching Hospital, Calabar, who were exposed to low noise level. Results obtained showed that noise level in test sites (105.8 ± 9.24dB) was significantly higher than that in the control sites (55.5 ± 1.78dB; P<0.001). At every frequency tested, the machine operators had poorer hearing acuity than control subjects. The hearing threshold of the machine operators positively correlated with their duration of exposure at 2000Hz and 4000Hz, (r = 0.357, P<0.001; r = 0.444, P<0.001 respectively) and age at 2000Hz, 4000Hz and 8000Hz (r = 0.266, P<0.05; r = 0.308, P<0.01, r = 0.292, P<0.01 respectively). The prevalence of hearing loss among the machine operators was significantly higher (62.5%), compared to control (15.79%; P<0.01). The incidence of symptoms such as tinnitus, insomnia and headache was also significantly higher in the test group (26.32%, 21.05% and 34.2%) than in the control (5.26%, 2.63% and 5.26% respectively; P <0.01). Therefore, chronic exposure to food grinding machine noise at 105.8 ± 9.24dB can impair hearing acuity and associated risk factor appears to be prolonged exposure.

Key words: Hearing Acuity, Noise, Grinding machine.

Nigerian Journal of Physiological Sciences Vol.19(1&2) 2004: 20-26