الفهرس 
Anatomy and physiologyOnly 14 pages are availabe for public view
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Abstract
Exposure to high level of noise exceeding the permissible noise level (90-dBA) provided by Occupational safety and health administration (OSHA) (4) is one of the major environmental health problems (251), and is considered as one of the most common work-related injuries worldwide ( 57), resulting in numerous auditory and non-auditory health problems (252).
Occupational noise induced hearing loss (ONIHL) represents 16% of the disabled hearing loss in adults, with disease burden estimate varying from 7% in developed countries to 21% in developing countries (2).
Methodology
Measurment of noise level at work place was carried out using a portable sound level meter standard (Testo 815 sound level meter; Quest technologies) at all the working sections. All subjects in the study were subjected to the following: Full history taking (hearing loss, exposure data as duration of work, the use of hearing protection devices), otoscopic examination, basic audiological evaluation, genotoxicity testing using the comet assay for evaluation of DNA damage.
Results
The highest level of noise was reported in the spinning section. All exposed workers and control group had within normal tympanometric results.
Exposed workers had significantly higher mean values of hearing thresholds of the right and left ears at higher frequencies (from 2000-8000 Hz) than the controls (p value <0.05).
Summary
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There were no significant differences between the hearing thresholds of the right and the left ears at all frequencies in the exposed workers (P value >0.05%).
The prevalence of hearing loss (in the right and left ears) was higher among the exposed group than the control group which ranged from mild to moderately sever high frequency sensory neural hearing loss.Acoustic notch was found at 4 KHZ in 47.22% of right ears, 50% of left ears and 33.33% bilaterally.
There were significant higher mean values for DNA damage parameters (DNA damage spot, DNA damage % and tail moment in the exposed workers than controls with significant increase in these parameters with the increase in the severity of hearing loss in the exposed workers(ANOVA test ,p value < 0.05).
There were significant positive correlation between age(r=0.35, p-value0.034), duration of work(r=0.38,p-value=0.022) , DNA damage %(r=0.89, p-value<0.001) and tail moment (r=0.89, p-value<0.001) and hearing threshold in the exposed workers.