Assessing the effective use of Hearing Protection Devices in industrial settings

Ergonomics Laboratory / Dep. of Productions and Systems / University of Minho / Guimaraes, Portugal+351 253 510 354 / parezes@dps.uminho.ptMiguel, A. SérgioErgonomics Laboratory / Dep. of Productions and Systems / University of Minho / Guimaraes, Portugal+351 253 510 354 / asmiguel@dps.uminho.pt

ABSTRACT

ABSTRACT

Workers’ protection regarding noise exposure is, at least in industrial environments, mostly carried out through the use of Hearing Protection Devices (HPDs). However, workers tend to remove their HPDs a few times during their workshift and this behaviour might affect their attenuation. Thus, it is of important to accurately know the “real” time of use of HPDs. The present work aims to analyze the reliability of 3 different methods for assessing the HPDs use, namely (1) a registry of the self- reported use, (2) the use of a statistical sampling observation method and (3) the use of a video monitoring (recording) of all the workers activity. The obtained results show that self-reported use is a good and practical method, in particular when time-consume, implementation cost and reliability parameters are considered.

Keywords

Keywords

Hearing protection devices, Noise, Exposure, Use, Assessment

INTRODUCTION

INTRODUCTION

Is the same manner as other personal protective equipment, Hearing Protection Devices (HPDs) should only be used temporarily, when waiting for the implementation of more effective measures and, thus, it should be regarded as the last resort concerning workers’ protection. However, due to its relative low cost and easy implementation, HPDs are quite often used as a permanent protection measure [7].

A revision of literature shows that there are several studies showing that HPDs attenuation depends largely on its continuous use [1][2][5]. Therefore, the nominal attenuation, which means the attenuation data reported by manufacturers, can be highly optimistic, in particular if HPDs are not continuously used [4].

The assessment of the time workers use HPDs could be a very complex and demanding task. However, the knowledge of this duration is extremely important for assessing HPDs’ efficiency. In fact, even if HPDs are not used only for short periods, HPDs’ performance will be significantly affected.

By simple observation it is possible to verify that workers tend to remove their HPDs a few times during their entire workshift. Some of them only use HPDs for a very short period each day, or if they feel that someone, for example from the

Health & Safety staff, could identify them. This behaviour affects significantly the attenuation efficiency of the devices. Therefore, it is of main importance to assess the “real” time of use, or non-use, of HPDs and, obviously, that should be carried out using reliable techniques [6].

This study aims at analyzing and comparing different methods for estimating the “real” time of use of the HPDs in industrial workplaces.

METHODOLOGY

Sample Description

The sample considered in this study was selected amongst those who are regular users of HPDs. This selection results in a sample of 74 workers from the weaving and weaving preparation sectors of a large textile company. Workers’ sample selection was carried out based on the assumption that all of them should be regular HPDs users and work in workplaces in which the personal daily exposure level exceed the Portuguese limit value of 87 dB(A), thus, workplaces with compulsory use of HPDs.

Workers were also selected based on the type of used HPDs. Due to the complexity of identifying visually the correct use of earplugs, this study have only comprised the analysis of 4 different models of earmuffs that are frequently used by workers involved in this study.

The population studied was, on average, 39.2±11.3 years old, and a mean seniority of 13.7±4.4 years at the current company and all the workers have participated voluntarily in the study and have expressed their consent to the company direction board.

Assessment of HPDs Use

With the purpose of assess the HPDs use duration, 3 different methodologies were selected and applied. The main idea underlying this application was to obtain the “real” period of time in which HPDs were effectively used.

The 3 selected methods consist in (1) a registry of the self-reported use, (2) the use of a statistical sampling observation method and (3) the use of a video monitoring (recording) of all the workers activity, applied for 8 different workers. Table 1 shows the total number of workers considered by each of the applied techniques.

Table 1. Number of total workers considered by each assessment method.

Con formato: Fuente: (Predeterminado) Verdana, Color de fuente: Negro

Con formato: Fuente: (Predeterminado) Verdana, Color de fuente: Negro

Con formato: Fuente: (Predeterminado) Verdana, Color de fuente: Negro

Con formato: Fuente: (Predeterminado) Verdana, Color de fuente: Negro

Con formato: Fuente: (Predeterminado) Verdana, Color de fuente: Negro

HPD # 1 2 3 4 Self-Assessment (SAM) 8 16 31 19 Statistical Sampling (SSM) 4 7 13 8 Video monitoring (VMM) 2 2 2 2

In the Self-Assessment (SAM) of the HPDs use was obtained by the self- reported period of use by each worker. Workers were asked to quantify their typical HPD use profile through the application of a questionnaire. As reported in other published studies, the tool applied for self-report HPDs use quantification should allow workers to express their perception of the percentage of time they use HPDs. Workers were instructed to define this percentage considering the difference between their entire workshift period and the cumulative time they do not have the HPDs properly positioned in the head.

In order to facilitate this process, a Visual Analogue Scale (VAS) was used. Operationally, the used VAS was composed by a horizontal line, with a 100 mm

length, anchored by two numerical descriptors at each end and one at the middle of the scale, corresponding to 0, 50 and 100% (from left to right) of use during the entire workshift (scale in black/full line in figure 1). Workers should mark on the line (with an ‘X’) the point that they feel represents their percentage of use. The VAS score is determined by measuring, in millimetres, from the left hand end of the line to the point that the worker marks. These scores were divided into 5 different frequency classes (according to red/dash line grid in figure 1).

Figure 1. VAS scale used in the SAM (black/full line) and the corresponding grid for scoring (red/dash line).

0% 50% 100%

0-20 % 20-40 % 40-60 % 60-80 % 80-100 %

VAS were selected due to the fact that it represent a type of scale that typically showed least variability, exhibited the highest construct validity, the most responsive scales, and are the most reliable [3].

The second technique applied for assessing the HPD use was a statistical sampling observation method (SSM). This technique consists in observe a pre- defined group of workers during a pre-defined period of time. The SSM was applied to 32 workers (all from the same work area). The distribution of these workers by each HPD is in accordance to the distribution presented in table 1.

During an entire week, everyday from Monday to Friday, an observer went to the mentioned area and registered if each of the considered workers are using, or not, their HPDs.

This procedure was repeated for 5 consecutive days, one observation period in the morning and other in the afternoon. The specific time of the day in which the observer should go to the work area to register HPD use was generated randomly. The total number of observations, regarding the use/non-use of HPD, was only 285 because some workers were not present in 35 of the 320 observations.

Finally, the last used technique for assessing HPDs’ use was a video monitoring (and recording) method (VMM) and the analysis of all the periods of time that the workers were not using their HPDs.

Using the existing Close-Circuit Television (CCTV) system of the company, 8 workers were intensively observed/monitored during a 4h period each, corresponding to a morning or an afternoon. The main goal was to register the period of time during which the worker remove HPDs from its normal position on the head. The video monitoring was applied during 480 minutes for each of the analyzed HPDs.

RESULTS AND DISCUSSION

Assessment of the HPDs Use

Results obtained by the application of a VAS for the HPD use are presented in table 2. After measure the position of each answer, the score was obtained and classified into one of the considered classes.

Results obtained by the application of the SSM are presented in table 3. Values are expressed as the percentage of the total observations in which workers are using, or not, HPDs.

Overall mean

70.075.069.4

60.5

Table 3. HPD use results by the SSM (expressed in % of the observations).

HPD #

Workers using HPD?

No Yes1 30,0 73,3

2 21,7 78,33 38,5 61,54 41,6 58,4

The application of VMM to asses HPDs’ use implied a division of the total time of the observed workshift (480 minutes) in two fractions, the period in which workers were using HPDs and the period in which HPDs are removed from the normal position.

If worker was requested by other worker, or the supervisor, to remove his HPDs, this time was not considered. Time was only registered if the HPD removal was assumed to be carried out voluntarily. For facilitate the registry and observation process, the final values were rounded to the nearest integer multiple of 5.

The results of the application of this video technique are presented in table 4.

Table 4. HPD use results by VMM.

Using HPD? (in minutes)

Using the obtained results, methods were compared in terms of their reliability in reflecting the “real” use of HPDs. Figure 2 present the % of use obtained through the application of the 3 considered techniques for all the earmuffs.

Considering the 4 tested earmuffs, it is possible to verify that only minor differences were found between the techniques. Ideally, and using the video monitoring as the base-line method (top bar in each HPD), the chart should present equal bars for each HPD. However, it is also possible to verify that the great difference was observed in the HPD #3, when comparing sampling and video monitoring. Nevertheless being the highest difference, this is less than 20% in the most notorious case.

If the variable time-consume for the method application is considered in this comparison, it is obvious that the self-report technique seems to be the best technique, considering that only minor differences have been encountered when comparing with the video monitoring values.

It is extremely difficult to quantify exactly the time—consume of each

methodology, but it is easy to understand that SAM is, by far, the least time- consuming technique, followed by SSM and the VMM. This last technique implies that a fulltime observation is carried out and, thus, it is the most time-consume technique of all possible techniques.

Figure 2. HPD use (in % of the workshift) assessed by different observation techniques.

HPD use 50%            60%          70%                   80%              90%

HPD #1 HPD #2 HPD #3

HPD #4

VMM SSM SAM

Therefore, the self-reported values seems to be a good option to be used due to the easiness of this technique, together with its low time consume, low implementation cost and reliability. Therefore, it seems that this technique could be used to as an accurate method for HPDs “real” use assessment.

As reported by Lusk et al. [6], in a similar study carried out to compare other HPDs use assessment, self-report seemed to be a reliable way to measure use of hearing protection.

Those authors also use different techniques, including the self-report and the direct observation, to evaluate the reliability of the obtained values of HPDs use. Based on the correlation between the obtained values, they referred that, considering all the restraints associated to direct observation, self-report is an appropriate measure and may be the best choice when time and monetary resources restrictions are important.

Seixas et al. [8], in a study carried out with constructions workers, also found a reasonable agreement between the observed use of HPDs and the HPDs use reported by workers.

Although it was not the main aim of this particular study, it was possible to verify that HPDs efficiency could be significantly affected by the non-use of HPDs during small periods. If we consider the extreme values obtained in the HPDs use assessment (using VMM), of 58.3 and 86.5%, it is possible to conclude that, in such conditions, and independently of the noise exposure scenarios and the chosen devices, the HPDs will have a maximum attenuation value of 9 and 3.8 dB, respectively. These attenuation values will be, most probably, not high enough to protect workers in noisy areas.

CONCLUSION

This paper has described a comparison between 3 different techniques of assessing HPDs use in industrial settings and the evaluation of the devices’ discomfort, both objectively and subjectively.

The obtained results have shown that self-reported HPDs use is a good and practical method, in particular when time-consume, implementation cost and

reliability parameters are considered. The study also demonstrates that self-report can be done using a Visual Analogue Scale (VAS).

Beyond the evaluation of techniques’ reliability, the study demonstrates that the registered HPDs use was very low, ranging from 58.3 and 86.5%, even if the workers’ sample was constituted exclusively by regular HPDs users, exposed in areas where the use of HPDs is compulsory. In accordance, it is possible to conclude that even if workers use their HPDs, they do not do it continuously and, therefore, there will be a drastic reduction on HPDs’ efficiency. This result demonstrates the need for a carefully selection of the devices in order to protect workers from noise exposure. This reinforces the idea already published by other authors, that the existence of a company protective equipment policy do not seemed to have a clear impact on the HPDs use [4].

REFERENCES

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