Keywords
police - occupational noise - hearing loss
Palavras-chave
polícia - ruído ocupacional - perda auditiva
Introduction
Exposure to noise over a long period of time can cause major differences to human,
the noise-induced hearing loss (NIHL) is characterized by a change in hearing thresholds,
sensorineural, progressive and irreversible. Hearing loss affects mainly the cochlear
hair cells located about 50 to 10 mm of the vestibular window, just in the region
receiving stimuli from 4 to 6 kHz[1]. A PAIR initially affects the frequency range between 3 and 6 kHz, where the threshold
for 8 kHz must be better than the worst threshold (3, 4 or 6 kHz)[2]
[3].
Some studies found that the frequency of 6 kHz is the most affected in the audiometric
tests suggestive of NIHL[4]
[5]
[6], while other studies have indicated that the frequency of 4 kHz is the most compromised[7]
[8]
[9].
Tinnitus and hearing loss are important complaints related to NIHL reported in the
literature[10]
[11]. In a study to assess the prevalence and degree of noise-induced hearing loss in
soldiers, hearing loss were diagnosed in 68% (n = 475) of cases, in 42.5% of these
were continuous tinnitus[12].
The investigation of the auditory effects in workers exposed to occupational noise
in a study of 400 individuals found that the longer the exposure, the greater the
impairment of hearing thresholds obtained. In this population, 24.75% of the audiograms
showed hearing loss induced by noise[8].
The Standard Occupational Hygiene[13] Fundacentro gives a formula for calculating the amount of impact pulses to which
the employee may be exposed on each working day, according to the magnitude of the
impulse. The Regulatory Standard 15 (NR-15) also stipulates that workers should not
be exposed to sound pressure levels exceeding 130 dB (C)[14].
In a recent study on the acoustics and psychoacoustics of noise of the main weapons
used by military police, we analyzed the firing of the .38 revolver and .40 pistol
(both in Taurus), with the use of digital sound level meter and acoustic analysis
through Praat software. Data were compared with the audiograms of 30 police officers with hearing loss (worse
than 25 dB threshold). The maximum peak of 113.1 dB were measured (C) .40 pistol and
116.8 dB (C) for 38 revolver. The values obtained in psychoacoustic analysis were
between 17.9 ± 0.3 Barks, corresponding to the band between 4120 and 4580 Hz audiometric
measurements showed greater hearing loss in the range 4 kHz to 86.7% of cases, followed
by frequency 6 kHz (66, 7%).Conclusions from the acoustic analysis of the shots, we
could demonstrate cause and effect between the main areas of excitation energy in
the cochlea (cochleogram Praat) and frequencies with a decrease of auditory acuity[9].
During training in the firing range, the number of police participants ranged between
12 and 15, and each individual made 50 shots. Thus, multiplying the number of shots,
the number of individuals were calculated from 600 to 750 pulses per period of training
impact[9].
Studies on the auditory in military conducted in Brazil revealed a high rate of hearing
loss in this population, which is associated with excessive exposure to impact noise
without the use of personal protective equipment, since the measurement of sound pressure
level sound emitted by the light automatic rifle (FAL 7.62 mm) was 147 dB (C)[15].
A survey of the auditory profile of the Brazilian Army, conducted through interviews,
otoscopy and audiometric observed otological picture suggestive of noise-induced loss
Audio in 38.1% of patients evaluated in the military. Also found that hearing loss
was more severe with increasing age and length of service[6].
Another study examined the prevalence of deafness among workers in the maintenance
sector of rotorcraft in a unit of the Brazilian Air Force. Our study has shown a prevalence
of sensorineural hearing loss by continuous exposure to high sound pressure levels
of 32.4 %, which can be identified as main factors behind the loss: working time and
age[16].
Relevant research in the field of hearing health showed statistically significant
correlation between duration of occupational noise exposure and hearing thresholds[6]
[8]
[17]. In the Singapore Armed Forces an experiment was conducted to investigate the effects
of basic military training at the hearing. The authors analyzed the audiograms of
85 soldiers before and after training and found a prevalence of 9.4% of hearing loss,
which remained the same after one year. The study concluded that the existing hearing
conservation program in the Singapore Armed Forces is efficient and protects the hearing
health of their military[18].
An important research conducted the survey of audiological profile of five instructors
from the military police shooting of Montes Claros - MG. In the measurement of sound
pressure levels, the average level found at the shooting range was 97.4 dB and analyzed
two of the five policemen had audiometric curve with slot configuration, one unilateral
and one bilateral and one had sensorineural hearing loss mild at high frequencies,
with configuration of audiometric curve in gout[19].
In France a study was conducted to assess the risk of noise-induced hearing loss in
the police. The results demonstrated that the police were 1.4 times more likely to
have hearing loss in relation to civil servants. This probability increased to three
times, considered the police motorcyclists. The authors stressed the need to work
with police because of the scarcity of such studies compared with the soldiers[20].
The prevalence of noise-induced hearing loss among traffic policemen in Dhaka Metropolitan
City (Bangladesh) showed hearing loss in 24% of 100 police officers evaluated, and
the frequencies most affected were those of 4 and 6 kHz. Regarding medical history,
23 subjects had tinnitus and only 5 complained of hearing loss[21].
In the military police in São Paulo state is evident from the high level of unhealthiness
in the firing range, however we have to consider other sectors and / or police services
that can also expose the officer to the risk of hearing loss, they are: the Monetary
Policy Committee ( Operations Center of Military Police) telephony sector provided
by the corporation to meet the emergency police and for coordinating the activities
of patrolling, the police road that runs the monitoring services, policing and traffic
control and Rocam (Rounds with Ostensivas Motorcycle Support) which has had major
role in road safety[22].
The aim of this study was to investigate the audiological profile in the military
police in the state of Sao Paulo, and to correlate the age and duration of occupational
exposure to the audiological findings.
Method
The present study evaluated 200 military police of the 9th Military Police Battalion
of the Interior - 9 ° BPM-I, with 169 (84.5%) were male and 31 (15.5%) females, aged
between 25 and 45 years (mean 38.83 ± 5.05), mean service time of 16.80 ± 6.27 years.
The officers participated in the audiological evaluation on a voluntary basis, the
study included all officers who were older in the age group proposal.
The procedures used were audiologic interview ([Appendix]), otoscopy, pure tone audiometry and tympanometry.
Annex.
Audiological Anamnesis.
|
The audiometric tests were performed in a soundproof booth, using Grason Stadler GSI 61. To measure the acoustic impedance was used immittanciometer GSI 38 Grason Stadler.
This study was approved by the Research Ethics Committee (Protocol No. 2762/2007).
The police are properly equipped with personal protective equipment (PPE), according
to NR 620, Ordinance 3214/78[14], being relevant to our study emphasize the use of hearing protection (shell type),
with Certificate of Approval (CA ) by the Ministry of Labor and Employment.
Regarding the data analysis were performed: comparison between threshold with age
and exposure time, was also carried out the classification of hearing loss according
to Merluzzi et al.[23] For comparative analysis was applied to Spearman correlation analysis with a significance level of 5%.
Results
The main complains during audiologic interview were tinnitus (n = 52/26%), deafness
(n = 36/18%), ear fullness (n = 24/12%) and autofonia (n = 24/12%).
Tympanometry were found in 100% of type A curves[24], and recruitment was present in 20 (10%) cases.
Regarding the results of audiometry, it was observed that the population studied in
22.75% (OD = OE = 21.5% and 24%) of cases noise-induced hearing loss, below is [Table 1] with the classification of hearing loss, according to Merluzzi et al.[23].
Table 1.
Classification of audiometric findings according to Merluzzi et al.[23]
|
|
Levels of Hearing Loss
|
|
|
Normal
|
1
|
2
|
3
|
4
|
5
|
6
|
7
|
Total
|
|
RE
|
146
|
24
|
16
|
1
|
2
|
0
|
0
|
11
|
200
|
|
%
|
73
|
12
|
8
|
0,5
|
1
|
0
|
0
|
5,5
|
100
|
|
LE
|
144
|
22
|
23
|
2
|
1
|
0
|
0
|
8
|
200
|
|
%
|
72
|
11
|
11,5
|
1
|
0,5
|
0
|
0
|
4
|
100
|
Legend: The levels of hearing loss is equivalent to: Levels 1-5 = hearing loss induced by
noise, Level 6 = mixed hearing loss (noise + other cause), Level 7 = hearing loss
of varying aetiology noise.
Statistical analysis of the correlation between time of exposure at work and hearing
thresholds, we observed a significant correlation in the right ear at frequencies
of 1, 3, 4, 6 and 8 kHz in the left ear in the frequencies of 4, 6 and 8 kHz.
Regarding the correlation between age and average hearing thresholds, statistical
significance was found in both ears from the frequency of 2 kHz. [Tables 2] and [3] show the correlation between exposure time and age with hearing thresholds.
Table 2.
Correlation between duration of occupational exposure and the average hearing thresholds
of 200 police officers (Spearman correlation analysis).
|
Frequency (Hz)
|
r
|
p
|
|
RE
|
LE
|
RE
|
LE
|
|
500
|
0,083
|
0,058
|
0,418
|
0,241
|
|
1000
|
0,058
|
0,803
|
0,018*
|
0,415
|
|
2000
|
0,064
|
0,056
|
0,432
|
0,369
|
|
3000
|
0,137
|
0,175
|
0,013*
|
0,053
|
|
4000
|
0,286
|
0,218
|
0,002*
|
< 0,001*
|
|
6000
|
0,224
|
0,231
|
0,001*
|
< 0,001*
|
|
8000
|
0,152
|
0,221
|
0,002*
|
0,031*
|
Legend: RE - the right ear / LE - left ear
r = correlation coefficient
* = Significant p <0.05
Table 3.
Correlation between age and average hearing thresholds of 200 police officers (Spearman correlation analysis).
|
Frequency (Hz)
|
r
|
p
|
|
OD
|
OE
|
OD
|
OE
|
|
500
|
0,159
|
0,122
|
0,025*
|
0,084
|
|
1000
|
0,108
|
0,087
|
0,126
|
0,221
|
|
2000
|
0,153
|
0,187
|
0,031*
|
0,008*
|
|
3000
|
0,286
|
0,284
|
< 0,001*
|
< 0,001*
|
|
4000
|
0,351
|
0,388
|
< 0,001*
|
< 0,001*
|
|
6000
|
0,352
|
0,308
|
< 0,001*
|
< 0,001*
|
|
8000
|
0,337
|
0,392
|
< 0,001*
|
< 0,001*
|
Legend: RE - the right ear / LE - left ear
r = correlation coefficient
* = Significant p <0.05
[Table 4] shows the distribution of audiometric change measured in the sample population by
age for military service time were considered the ears with hearing loss, all cases
with a threshold higher than 25 dB in one or more frequencies of the audiogram (54
cases right ear and left ear in 56 cases). The results showed a greater number of
cases of hearing loss at frequencies of 4 kHz (56.22%) and 6 kHz (67.19%).
Table 4.
Distribution of audiometric change measured in the sample population of military personnel
with hearing loss (threshold greater than 25 dB) for full-time service.
|
f (kHz)
|
Audiometric change
|
Service time (years)
|
Total
|
Total
|
Average RE/LE
|
|
|
0–10
|
11–15
|
16–20
|
21–25
|
26–34
|
N
|
%
|
%
|
|
< 3,0
|
RE
|
0
|
2
|
3
|
2
|
0
|
7
|
12,96
|
17,19
|
|
LE
|
1
|
3
|
3
|
5
|
0
|
12
|
21,42
|
|
|
3,0
|
RE
|
3
|
3
|
5
|
7
|
2
|
20
|
37,03
|
42,62
|
|
LE
|
5
|
5
|
6
|
8
|
3
|
27
|
48,21
|
|
|
4,0
|
RE
|
2
|
5
|
6
|
10
|
3
|
26
|
48,15
|
56,22
|
|
LE
|
5
|
5
|
10
|
13
|
3
|
36
|
64,29
|
|
|
6,0
|
RE
|
2
|
7
|
13
|
8
|
4
|
34
|
62,96
|
67,19
|
|
LE
|
5
|
8
|
9
|
15
|
3
|
40
|
71,42
|
|
|
8,0
|
RE
|
4
|
6
|
6
|
10
|
6
|
32
|
59,25
|
55,52
|
|
LE
|
4
|
6
|
5
|
9
|
5
|
29
|
51,79
|
|
Legend: RE right ear, LE: left ear, N: number of ears with audiometric change.
Discussion
In the analysis of case histories of the major complaints by the population, tinnitus
(26%) and hearing loss (18%) are the same as those made more frequent by the literature[9]
[10]. However, a study of traffic police, showed a disparity between the complaints of
tinnitus (24%) and hearing loss (5%), possibly by the degree of hearing loss was mild
in 20% of cases and moderate in 4%, a fact this, which minimized the complaints of
hearing loss, tinnitus-front[21].
The cases evaluated in this study did not show any changes and / or obstruction of
the external ear canal that might bias the results of the audiological evaluation.
Thus, in all cases, curves were tympanometry type A[24], consistent with normal operation of the middle ear or sensorineural hearing loss.
The results of audiometry were classified according to Merluzzi et al.[23], and considering the cases diagnosed as NIHL, the data obtained from the right ear
showed that 43 (21.5%) ears had hearing loss. In the left ear were diagnosed 48 (24%)
ears with hearing loss. These data were similar to those obtained by study of industrial
noise environment[8] and with traffic police[21], however comparing the findings with those obtained in military career, there were
more cases in recent loss[6]
[12].
The largest number of cases with hearing loss in military can be explained due to
the type of heavy weaponry used by the army, with noise levels exceeding 147 dB (C)[15]. While measurements in firing range of military police, found values between 113.1 dB
(C) for the pistol and .40 dB 116.8 (C) to the gun 38[9].
Considering the formula recommended by the Standard Occupational Hygiene[13] Fundacentro, the maximum intensity for an exhibition of impact noise measured (compensation
circuit C) to 600 pulses of impact is 109 dB. This data allows us to identify which
military police have the impact noise of a firearm as a principal element harmful
to hearing, since higher values were measured at 113.1 dB (C), at the firing range
military police[9].
Other unhealthy elements for hearing impairment were identified in the police of France
and Bangladesh, which are related to the use of motorcycles and the traffic noise[20]
[21]. The use of motorcycles and exposure to traffic noise, are also present in the performance
elements of the military police of São Paulo[22].
In this study the frequency band with the highest percentage of hearing loss was between
4 and 6 kHz, since this coincides with the literature[1], and studies of traffic policemen in the city of Dhaka[21]. Moreover, a recent study demonstrated the cause and effect relationship between
the noise of firing of firearms, and these areas with the largest lesion in the cochlea[9].
Among these two frequencies (4 and 6 kHz), presented the highest number of cases with
abnormal audiogram, in our results was 6 kHz. This finding is consistent with other
studies of workers exposed to noise[4]
[5]
[6]. However, there is no consensus in the literature regarding the frequency most affected,
since, other studies have described the frequency of 4 kHz with greater percentage
of deterioration in audiometry[7]
[8]
[9].
The study also revealed that there was a significant correlation between increasing
age and years of service with the worsening of hearing thresholds at high frequencies
in both ears. This is corroborated by other studies related to exposure time and PAIR[6]
[8]
[12]
[16]
[17].
Conclusion
From the analysis of the audiological data was verified that the military police are
population presents a risk for developing hearing loss. And the comparison between
age and exposure time with the auditory threshold, there was a significant correlation,
demonstrating the danger of exposure noise. Thus, we see the need for implementation
of hearing conservation program for the military police.
