Table 7:
Cross-sectional studies (without controls)
| Reference | Population | Exposure source | Exposure level | Methodology | Findings |
|---|---|---|---|---|---|
| (40) | 2004 | Five noisy industries | 85 dB(A) | Audiometric | The prevalence of hearing loss: 22.5%, mild hearing loss: 53.6%, moderate hearing loss: 27.3%, severe hearing loss: 14.9%, absolute deafness: 1.3% |
| (41) | 45 | Rolling workshop of a Steel Industry | 75–105 dB(A) | Noise measurement; Audiometric | Permanent loss in both ears =14 dB(A), correlation between the permanent loss of the right/left ears, with work experience, respectively: 0.7099, 0.7127 |
| (42) | 70 | Coppersmith | 100 dB(A) | Noise measurement; Audiometric | Correlation between Hearing thresholds and work experience: experience <10 years: hearing thresholds at low frequencies16.4 dB(A) at conversation frequencies 7.9 dB(A) 10–20 years of work experience: hearing thresholds, respectively 30.7 and 14.8 dB(A), 30–20 years of experience: hearing thresholds, respectively 40.9 and 16.7 dB(A), Experience> 40 years: hearing thresholds, respectively 42, 20.5 dB (A). |
| (43) | 209 | Cleaning plants | 76–103 dB(A) | Noise measurement-Audiometric | Hearing loss had significant relationship with noise levels and work experience in both ears at different frequencies ( P value <0.001) |
| (44) | 150 | Mining activities | 91–140 | Audiometric | Relationship between hearing loss and duration of exposure ( P value <0.001) |
| (45) | 2016 | 4 steel industry | >85 dB(A) | Noise measurement-Audiometric | The relationship between Workplace Sound level and hearing threshold shift (
P
value
<0.001) 85–90 dB: hearing threshold shift in 30.1% >90 dB: hearing threshold shift in 56.9% |
| (46) | 441 | Paint shop and the assembly of an automobile industry | 85 dB(A) | Noise measurement-Audiometric | Hearing loss more than 25 dB(A) at frequencies 3, 4, 6, 8 kHz in workers exposed to noise and mixed organic solvents at levels above the exposure limit were significantly higher than that in workers who were exposed only to noise. In frequencies 0.5, 1 and 2 kHz were not significant. |
| (47) | 809 | Glass industry, milk and food industry | 82–96 dB(A) | Noise measurement-Audiometric | Average hearing loss in workers who used protective equipment was 43.36 dB (A) and that in unprotected workers 44.3 dB (A) (
P
value
>0.05). The Prevalence of hearing loss in unprotected group was 93.83% and in protected group was 92.89% |
| (6) | 40 | Barry Stone Workshop | 61–100 dB(A) | Noise measurement-Audiometric | Correlation between Leq8h and hearing loss for the right, left and both ears were .056, .0135, 0.73, respectively. |
| (48) | 50 | Smooth car workshops | 90–104 dB(A) | Noise measurement-Audiometric | Hearing loss in both ears was 22.1 dB (A) and the correlation between left and right ear hearing loss was significant (R=0.87,
P
value
<0. 05). 64% healthy adults, 34% had minor damage, and 2% were moderately damaged. |
| (7) | 100 | Textile Industry | 81.9–99.5 dB(A) | Noise measurement-Audiometric | Minimum, maximum and average overall hearing loss was 10.21 dB, 46.46 dB (A) and 21.11 dB, respectively. The Relationship between sound intensity and hearing loss was significant ( P value <0. 05). |
| (1) | 310 | Steel industry | >85 dB(A) | Noise measurement-Audiometric | 22.3% of workers in 2008 and 41.3% in 2009 had hearing loss in both ears. The Relationship between sound intensity and hearing threshold shift was significant ( P value <0. 001). The Relationship between sound intensity and hearing loss in high-frequencies was significant ( P value <0.001). |
| (23) | 60 | Manufacturing appliances | 87–100 dB(A) | Noise measurement-Audiometric | 51.7% normal, 35% with mild hearing loss, 10.4% with moderate hearing loss and 1.7% with severe hearing loss. The relationship of age and work experience with hearing loss was significant ( P value <0. 01). |
| (49) | 905 | Zanjan city industries | 80–104 dB(A) | Noise measurement-Audiometric | <80 dB: hearing loss 6.4 dB 80–85 dB: hearing loss 13.5 dB 85–90 dB: hearing loss 17.9 dB 90–95 dB: hearing loss 26.3 dB 95–100 dB: hearing loss 31.6 dB >100 dB: hearing loss 54.9 dB |
| (50) | 245 | Car driven manufacturing workshop | 98–115 dB(A) | Noise measurement-Audiometric | Minimal hearing loss: 17.45dB, maximum hearing loss: 56.67dB, the average hearing loss: 27.84 dB (A). there was 0.21dB(A) decrease in the Hearing loss with a 1 dB(A) increase in Leq, the relationship Between noise exposure and hearing loss was significant ( P value <0. 05). |
| (51) | 743 | Steel Industry | 70–101 dB(A) | Noise measurement-Audiometric | Hearing loss in people who were exposed to noise>85 dB (A) was higher than that in people exposed to noise <85 dB(A). Noise levels and hearing loss was significantly associated ( P value <0. 05). |