Table 1
Socio-demographic characteristics of the study population (n = 106).
| Characteristics | Plant A | Plant B | Plant C |
|---|---|---|---|
| Age (AM (SD)) years | 36.5(10.0) | 42.7(11.7) | 43.4(12.2) |
| Age group (n (%)) | |||
| 20–29 | 9(28.1) | 6(18.2) | 8(19.5) |
| 30–39 | 13(40.6) | 8(24.2) | 7(17.1) |
| 40–49 | 5(15.6) | 4(12.1) | 6(14.6) |
| 50–59 | 5(15.6) | 15(45.5) | 20(48.8) |
| Sex (n (%)) | |||
| Male | 30(93.8) | 31(93.9) | 40(97.6) |
| Female | 2(6.2) | 2(6.1) | 1(2.4) |
| Marital status (n (%)) | |||
| Single | 10(31.2) | 7(21.2) | 8(19.5) |
| Married | 22(68.8) | 25(75.8) | 32(78.0) |
| Widowed | 0(0.0) | 1(3.0) | 1(2.4) |
| Educational Level (n (%)) | |||
| Primary | 0(0.0) | 2(6.1) | 7(17.1) |
| Secondary | 1(3.1) | 5(15.2) | 4(9.8) |
| Tertiary | 31(96.9) | 26(78.8) | 30(73.2) |
Figure 1
Noise exposure score and Personal noise exposure levels in dB(A).
Table 2
Noise exposure level and noise exposure score in work section among gas-fired electric plant workers.
| n | Mean | Std. Deviation | 95% CI for Mean | |||
|---|---|---|---|---|---|---|
| Lower Bound | Upper Bound | |||||
| Noise exposure level(dBA) | Maintenance | 14 | 89.643 | 13.95 | 81.590 | 97.696 |
| Operation | 18 | 91.189 | 9.89 | 86.268 | 96.109 | |
| Operation and Maintenance | 5 | 96.660 | 4.03 | 91.658 | 101.662 | |
| LAeq noise Level(dBA) | Maintenance | 14 | 98.529 | 12.40 | 91.368 | 105.690 |
| Operation | 18 | 97.717 | 8.7939 | 93.344 | 102.090 | |
| Operation and Maintenance | 5 | 101.980 | 3.5647 | 97.554 | 106.406 | |
| Peak level(dBA) | Maintenance | 14 | 137.050 | 14.4332 | 128.717 | 145.383 |
| Operation | 18 | 141.172 | 3.6200 | 139.372 | 142.972 | |
| Operation and Maintenance | 5 | 140.660 | 4.4168 | 135.176 | 146.144 | |
| Maintenance | 61 | 6.85 | 3.478 | 5.96 | 7.74 | |
| Noise exposure score | Operation | 37 | 7.16 | 3.149 | 6.11 | 8.21 |
| Operation and Maintenance | 8 | 6.13 | 2.588 | 3.96 | 8.29 | |
Table 3
Specific task, reported noise exposure score, noise exposure level (TWA) and peak noise level among gas-fired electric plant.
| n | Mean | Std. Deviation | 95% CI for Mean | |||
|---|---|---|---|---|---|---|
| Lower Bound | Upper Bound | |||||
| Noise score | Shift Supervisor | 13 | 7.31 | 3.637 | 5.11 | 9.51 |
| Technician | 45 | 6.36 | 3.439 | 5.32 | 7.39 | |
| Attendant | 11 | 8.55 | 2.296 | 7.00 | 10.09 | |
| Artisan | 10 | 8.00 | 2.749 | 6.03 | 9.97 | |
| Fitter | 7 | 7.86 | 3.579 | 4.55 | 11.17 | |
| Operator | 9 | 7.33 | 3.041 | 5.00 | 9.67 | |
| Engineer | 11 | 5.09 | 2.914 | 3.13 | 7.05 | |
| Noise level LAeq | Shift Supervisor | 7 | 89.171 | 11.7237 | 78.329 | 100.014 |
| Technician | 10 | 92.150 | 11.4088 | 83.989 | 100.311 | |
| Attendant | 3 | 95.200 | 3.0414 | 87.645 | 102.755 | |
| Artisan | 6 | 98.183 | 2.3310 | 95.737 | 100.630 | |
| Fitter | 1 | 96.900 | ||||
| Operator | 6 | 91.417 | 11.5574 | 79.288 | 103.545 | |
| Engineer | 4 | 78.475 | 14.9734 | 54.649 | 102.301 | |
| Shift Supervisor | 7 | 141.857 | 3.2134 | 138.885 | 144.829 | |
| Peak level | Technician | 10 | 137.470 | 12.3516 | 128.634 | 146.306 |
| Attendant | 3 | 138.100 | 3.4641 | 129.495 | 146.705 | |
| Artisan | 6 | 143.617 | 3.7280 | 139.704 | 147.529 | |
| Fitter | 1 | 145.500 | ||||
| Operator | 6 | 141.833 | 3.6401 | 138.013 | 145.653 | |
| Engineer | 4 | 130.725 | 18.1744 | 101.805 | 159.645 | |
Table 4
Previous illnesses affecting hearing loss reported by participants.
| Plant A n = 32 | Plant B n = 33 | Plant C n = 41 | All n = 106 | ||
|---|---|---|---|---|---|
| Severe ear infection/injury at childhood | Yes | 1(3.1) | 0(0.0) | 0(0.0) | 1(0.9) |
| No | 31(96.9) | 33(100.0) | 41(100.0) | 105(99.1) | |
| High blood pressure | Yes | 1(3.1) | 2(6.1) | 4(9.8) | 7(6.6) |
| No | 31(96.9) | 31(93.9) | 37(90.2) | 99(93.4) | |
| Diabetes | Yes | 0(0.0) | 1(3.0) | 1(2.4) | 2(1.9) |
| No | 32(100.0) | 32(97.0) | 40(97.6) | 104(98.1) | |
| Ear pain | Yes | 2(6.3) | 2(6.1) | 5(12.5) | 9(8.6) |
| No | 30(93.8) | 31(93.9) | 35(87.5) | 96(91.4) | |
| Use of ototoxic drugs | Yes | 1(3.1) | 0(0.0) | 0(0.0) | 1(0.9) |
| No | 31(96.9) | 33(100.0) | 41(100.0) | 105(99.1) |
Table 5
Self-reported noise-induced hearing loss.
| Self-reported noise-induced hearing loss (NIHL) | Plants n(%) | ||||
|---|---|---|---|---|---|
| Plant A n = 32 | Plant B n = 33 | Plant C n = 41 | All n = 106 | ||
| Feeling hearing loss | Never | 18(56.2) | 20(60.6) | 11(26.4) | 49(46.2) |
| Yes | 14(43.8) | 13(39.4) | 30(73.2) | 57(53.8) | |
| Difficulty hearing people speaking during conversation | Never | 24(75.0) | 24(72.7) | 14(34.1) | 62(58.5) |
| Yes | 8(25.0) | 9(27.3) | 27(65.9) | 44(41.5) | |
| Shouting in order to be understood when you are at three feet away. | Never | 23(71.9) | 25(75.8) | 22(53.7) | 70(66.0) |
| Yes | 9(28.1) | 8(24.2) | 19(46.3) | 36(34.0) | |
| Watching people’s face when they speak | Never | 17(53.1) | 17(51.5) | 17(41.5) | 51(48.1) |
| Yes | 15(46.9) | 16(48.5) | 24(58.5) | 55(51.9) | |
| Respond inappropriately in a conversation | Never | 17(53.1) | 23(69.7) | 18(43.9) | 58(54.7) |
| Yes | 15(46.9) | 10(30.3) | 23(56.1) | 48(45.3) | |
Table 6
Predictors and self-reported noise-induced hearing loss.
| Symptoms | Crude odds ratio (95% C.I) | Adjusted odds ratio (95% C.I) | |
|---|---|---|---|
| Feeling hearing loss | Plant A | ref | – |
| Plant B | 0.84 (0.31–2.24) | 0.49 (0.16–1.51) | |
| Plant C | 3.51 (1.31–9.37) | 2.47 (0.82–7.39) | |
| Difficulty in hearing during conversation | Plant A | Ref | – |
| Plant B | 1.13 (0.37–3.41) | 0.83 (0.26–2.68) | |
| Plant C | 5.79 (2.07–16.18) | 4.22 (1.43–12.42) | |
| People need to shout in order to be understood when three feet away from you | Plant A | Ref | – |
| Plant B | 0.82 (0.27–2.48) | 0.56 (0.18–1.89) | |
| Plant C | 2.21 (0.82–5.91) | 1.46 (0.50–4.23) | |
| Watch people when speaking at three feet away | Plant A | Ref | – |
| Plant B | 1.07 (0.40–2.82) | 1.03 (0.37–2.90) | |
| Plant C | 1.60 (0.63–4.06) | 1.29 (0.4–3.57) |
[i] Odds ratio adjusted for ear pain, age and habit of attending disco.
Table 7
Symptom of NIHL (Tinnitus).
| Plant Address (n (%)) | All | p- value* | X2 Value | ||||
|---|---|---|---|---|---|---|---|
| Plant A | Plant B | Plant C | |||||
| Ringing or buzzing sounds in your ears | Yes | 5(15.6) | 3(9.1) | 13(31.7) | 21(19.8) | ||
| No | 27(84.4) | 30(90.9) | 28(68.3) | 85(80.2) | 0.048 | 6.030 | |
[i] *Fischer’s exact
Table 8
Proportion of HPDs users in gas-fired electric plants.
| Plants n(%) | |||||
|---|---|---|---|---|---|
| USE of HPDs | Plant A n = 32 | Plant B n = 33 | Plant C n = 41 | All n = 106 | |
| Use of HPDs | Yes | 28(87.5) | 32(97.0) | 41(100.0) | 101(95.3) |
| No | 4(12.5) | 1(3.0) | 0(0.0) | 5(4.7) | |
| Type of Hearing protective device | Ear Plug | 0(0.0) | 0(0.0) | 8(19.5) | 8(7.5) |
| Ear Muff | 29(90.6) | 7(21.2) | 5(12.2) | 41(38.7) | |
| Both | 3(9.4) | 26(78.8) | 28(68.3) | 57(53.8) | |
| Training | Yes | 28(87.5) | 29(87.9) | 28(68.3) | 85(80.2) |
| No | 4(12.5) | 4(12.1) | 13(31.7) | 21(19.8) | |
| Enforcement on the use of HPDs | Yes | 18(56.3) | 22(66.7) | 26(63.4) | 66(62.3) |
| No | 14(43.8) | 11(33.3) | 15(36.6) | 40(37.7) | |
| Duration of use of HPDs | Sometimes | 17(53.1) | 3(9.1) | 2(4.9) | 22(20.8) |
| Always | 15(46.9) | 30(90.9) | 39(95.1) | 84(79.2) | |