Background
Methods
Study design
Ethical approval
Study participants and data collection
Workplace environment
Exposure classifications
Jet fuel exposure group | |||
---|---|---|---|
Variable | Low (n = 18) | Moderate (n = 15) | High (n = 24) |
Age, years | 42.3 (range: 25–60) | 37.8 (range: 23–64) | 38.7 (range: 24–55) |
Gender | Female = 6 | Female = 1 | Female = 0 |
Male = 12 | Male = 14 | Male = 24 | |
Tenure in defence, years | 17.8, 10.3 (5–41) | 14.8, 13.0 (3–40) | 19.7, 9.9 (5–38) |
Job categories | Cook, training system officer, environmental health officer, air surveillance operator, information manager, administration, pilot, air traffic control, air refuelling operator, electrical engineer, vehicle administration, aircraft maintainer, firefighter | Warrant officer, avionics instructor, instructor, flighty sergeant, staff officer capability level, logistics, movements, aviation refueller, GSE fitter mechanic, GSE fitter mechanic trainee, technician, avionics technician | Aircraft technician, GT-1 armtech sergeant, air traffic controller, movements, airfield operations support, ops clerk, GSE fitter mechanic, avionics technician, loadmaster, structures technician, weapons/explosives technician, petroleum manager, safety advisor, |
Audiological assessment
Audiometric thresholds
Otoacoustic emissions (OAEs)
Auditory brainstem response (ABR)
Speech perception and central auditory function
Data analysis
Results
Hearing thresholds
Frequency | Low exposure (95% CI) | Moderate exposure (95% CI) | High exposure (95% CI) |
p-value
c
|
---|---|---|---|---|
1 kHz | ||||
Right ear | 5.51 (1.84–9.19) | 7.00 (2.61–11.40) | 4.40 (1.89–6.91) | 0.521 |
Left ear | 4.40 (0.36–8.43) | 4.10 (−0.18–8.37) | 5.60 (2.06–9.14) | 0.830 |
2 kHz | ||||
Right ear | 2.22 (−1.49–5.93) | 6.48 (1.42–11.55) | 7.20 (2.78–11.61) | 0.295 |
Left ear | 4.91 (1.34–8.50) | 8.52 (3.94–13.10) | 6.40 (3.17–9.64) | 0.525 |
3 kHz | ||||
Right ear | 3.80 (−0.20–7.81) | 8.34 (0.72–15.96) | 11.73 (7.15–16.30) | 0.062 |
Left ear | 6.39 (1.60–11.19) | 11.73 (5.37–18.08) | 14.96 (9.24–20.68) | 0.104 |
4 kHz | ||||
Right ear | 5.85 (1.44–10.25) | 15.80 (8.41–23.20) | 16.99 (11.05–22.92) |
0.017
|
Left ear | 7.88 (2.92–12.85) | 24.04 (13.66–34.42) | 19.27 (12.82–25.72) |
0.007
|
6 kHz | ||||
Right ear | 11.07 (5.30–16.84) | 19.92 (11.29–28.55) | 16.54 (10.84–22.25) | 0.228 |
Left ear | 10.60 (4.97–16.23) | 23.29 (12.09–34.50) | 21.45 (13.90–29.01) | 0.061 |
8 kHz | ||||
Right ear | 6.98 (1.86–12.10) | 20.59 (9.81–31.36) | 15.65 (9.35–21.95) |
0.041
|
Left ear | 9.68 (3.13–16.23) | 21.59 (12.16–31.03) | 20.91 (13.46–28.36) | 0.060 |
10 kHz | ||||
Right ear | 14.18 (6.71–21.66) | 28.33 (18.69–37.97) | 21.45 (14.67–28.23) | 0.085 |
Left ear | 13.18 (5.15–21.20) | 27.92 (18.27–37.58) | 25.37 (18.32–23.43) | 0.038 |
12 kHz | ||||
Right ear | 24.94 (17.29–32.60) | 33.58 (25.44–41.72) | 32.39 (24.14–40.63) | 0.328 |
Left ear | 24.84 (15.43–34.25) | 32.91 (24.26–41.57) | 36.01 (27.37–44.64) | 0.268 |
Better ear 1–8 kHz | 4.70 (1.39–8.01) | 12.10 (6.35–17.80) | 11.57 (7.49–15.65) |
0.037
|
Better ear 10–12 kHz | 15.93 (8.48–23.39) | 28.97 (20.17–37.78) | 25.25 (18.49–32.02) | 0.085 |
Otoacoustic emissions
DPOAE frequency (f2) | Low exposure (95% CI) | Moderate exposure (95% CI) | High exposure (95% CI) | p-valuec |
---|---|---|---|---|
2 kHz. | ||||
Right ear | 13.20 (8.93–17.47) | 8.11 (3.90–12.32) | 10.67 (6.17–15.17) | 0.270 |
Left ear | 15.56 (12.13–19.00) | 12.97 (9.52–16.42) | 12.55 (9.61–15.48) | 0.414 |
2.8 kHz. | ||||
Right ear | 15.15 (12.01–18.28) | 9.24 (4.65–13.83) | 11.79 (8.07–15.51) | 0.109 |
Left ear | 16.02 (13.43–18.62) | 9.71 (5.68–13.73) | 9.92 (6.17–13.67) |
0.004
|
4 kHz. | ||||
Right ear | 15.52 (12.90–18.14) | 8.57 (5.12–12.02) | 11.26 (7.31–15.22) |
0.010
|
Left ear | 16.68 (14.19–19.16) | 7.67 (3.18–12.16) | 8.79 (4.92–12.67) |
< 0.001
|
6 kHz. | ||||
Right ear | 12.22 (8.10–16.34) | 5.37 (1.25–9.49) | 8.60 (4.76–12.43) | 0.079 |
Left ear | 13.59 (10.64–16.54) | 5.37 (−0.05–10.79) | 6.03 (2.28–9.77) |
0.003
|
8 kHz. | ||||
Right ear | 0.89 (−5.29–7.08) | −7.35 (−12.02– −2.68) | −6.69 (−9.80– −3.58) | 0.081 |
Left ear | −5.31 (−9.80– − 0.82) | −7.68 (−10.99– −4.37) | −7.85 (−10.47– − 5.24) | 0.642 |
Auditory brainstem response
ABR component | Low exposure (95% CI) | Moderate exposure (95%CI) | High exposure (95%CI) | p-valuec |
---|---|---|---|---|
Wave I | ||||
Right ear | 1.47 (1.36–1.59) | 1.57 (1.46–1.68) | 1.59 (1.52–1.67) | 0.288 |
Left ear | 1.46 (1.34–1.57) | 1.59 (1.51–1.67) | 1.59 (1.53–1.65) | 0.142 |
Wave III | ||||
Right ear | 3.65 (3.49–3.80) | 3.76 (3.64–3.88) | 3.82 (3.73–3.90) | 0.257 |
Left ear | 3.59 (3.40–3.78) | 3.96 (3.76–4.16) | 3.84 (3.72–3.96) | 0.073 |
Wave V | ||||
Right ear | 5.08 (4.79–5.37) | 5.63 (5.43–5.82) | 5.65 (5.44–5.86) |
0.028
|
Left ear | 5.27 (4.99–5.54) | 5.65 (5.40–5.91) | 5.55 (5.41–5.69) | 0.180 |
IPL I-V | ||||
Right ear | 3.61 (3.34–3.87) | 4.06 (3.87–4.26) | 4.05 (3.81–4.29) | 0.078 |
Left ear | 3.82 (3.58–4.07) | 4.06 (3.79–4.33) | 3.94 (3.81–4.06) | 0.543 |
IPL I-III | ||||
Right ear | 2.17 (2.02–2.32) | 2.20 (2.06–2.33) | 2.22 (2.11–2.34) | 0.886 |
Left ear | 2.15 (1.97–2.33) | 2.37 (2.13–2.60) | 2.22 (2.11–2.33) | 0.400 |
IPL III-V | ||||
Right ear | 1.44 (1.11–1.76) | 1.86 (1.60–2.13) | 1.83 (1.64–2.02) | 0.206 |
Left ear | 1.67 (1.39–1.96) | 1.69 (1.49–1.89) | 1.71 (1.58–1.85) | 0.960 |
Behavioural procedures exploring the central auditory nervous system
Test | Low exposure (95% CI) | Medium exposure (95% CI) | High exposure (95% CI) |
p-value
c
|
---|---|---|---|---|
Compressed speech, % | 51.80 (47.14–56.46) | 42.07 (36.95–47.20) | 45.60 (41.52–49.69) |
0.039*
|
Words-in-noise, dB SNR | 5.99 (5.24–6.74) | 7.40 (6.55–8.25) | 7.28 (6.43–8.13) |
0.038*
|
Dichotic digits, % | 92.67 (87.80–97.54) | 89.69 (87.08–92.31) | 87.23 (81.93–92.53) | 0.413 |
Pitch pattern sequence, % | 100.0 (98.16–100.0) | 97.28 (94.50–100.0) | 94.13 (89.97–98.30) | 0.082 |
Duration pattern sequence, % | 99.50 (98.08–100.0) | 98.42 (97.00–99.84) | 96.82 (93.53–100.0) | 0.434 |
ATTR, ms | ||||
Within channel | 3.51 (2.31–4.71) | 3.28 (2.46–4.10) | 5.24 (2.91–7.56) | 0.228 |
Across channel | 48.63 (34.90–62.35) | 41.65 (29.40–53.90) | 46.53 (33.98–59.09) | 0.720 |