Attitudes Toward Use of Hearing Protection Devices and Effects of an Intervention on Fit-Testing Results Pegeen S. Smith, MS, RN, COHN-S; Barbara A. Monaco, MS; Sally L. Lusk, PhD, RN, FAAN, FAAOHN
ABSTRACT This study assessed attitudes toward the use of hearing protection devices (HPDs) and the effect of an educational intervention on fit-testing results by comparing personal attenuation ratings (PAR50) before and after the intervention. Employees (n = 327) from a large metal container manufacturer at four geographic locations were tested with a field attenuation estimation system (FAES) to identify workers (n = 91) requiring intervention. PAR50 values significantly increased from baseline to post-intervention (p < .001, 15.1 to 26.9) and at the 6-month follow-up (p < .001, 95% confidence interval = -11.2, -6.3). Perceived self-efficacy scores for using HPDs significantly declined from baseline to post-intervention (p = .006, 95% confidence interval = 0.3, 1.9), but were not significantly related to PAR50. Therefore, a FAES can assist the occupational health nurse to identify workers at high risk (low PAR50), teach proper fit and use of HPDs, and improve hearing protector selection. [Workplace Health Saf 2014;62(12):491-499.]
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earing loss and tinnitus can be debilitating consequences of working in high noise areas. These deleterious conditions have been documented since the Roman Empire (Thurston, 2013). According to Masterson et al. (2012), the National Institute for Occupational Safety and Health (NIOSH) found that 22 million workers in the United States are exposed to hazardous noise. Hearing loss prevalence data showed that 18% of U.S. workers had a material hearing loss defined by pure-tone average thresholds of 25 dB or more across frequencies 1,000, 2,000, 3,000, and 4,000 Hz in either ear (Masterson et al., 2012). Not surprisingly, workers in the mining, manufacturing, and construction sectors are at ABOUT THE AUTHORS
Ms. Smith is Technical Service Specialist, and Ms. Monaco is Lean Six Sigma Coach and Statistician, 3M Company, St. Paul, Minnesota. Dr. Lusk is Professor Emerita, University of Michigan School of Nursing, Ann Arbor, Michigan. Submitted: May 28, 2014; Accepted: July 25, 2014; Posted online: September 9, 2014 This study was supported by 3M Company–Personal Safety Division and approved by 3M IRB HUM00060704. The authors thank Silgan Containers for partnering with them to conduct this important research. Correspondence: Pegeen S. Smith, MS, RN, COHN-S, Personal Safety Division, 620 Holly Road, Cadillac, MI 49601. E-mail: [email protected] doi:10.3928/21650799-20140902-01
the highest risk for developing hearing loss. The NIOSH study recommended employers reduce noise through engineering controls and called for better hearing conservation strategies. In 2012, the Bureau of Labor Statistics reported recordable hearing loss at 12% of the total nonfatal occupational illness in the private sector (Bureau of Labor Statistics, 2012). Manufacturing and specifically primary metal manufacturing consistently demonstrated high hearing loss rates among employees. An average of 16% of all adult-onset hearing loss identified globally was attributable to occupational noise (Nelson, Nelson, Concha-Barrientos, & Fingerhut, 2005). The goal of any hearing conservation program is to prevent hearing loss caused by noise in the workplace. Rogers et al. (2009) described a successful program, based on Occupational Health and Safety Administration (OSHA) mandates for hearing conservation programs, as having a multi-disciplinary approach and including noise assessment and monitoring, employee training and education, audiometric testing, and mandatory recordkeeping. Engineering controls are the first line of protection against a noise hazard and may include preventing noise creation at its source (e.g., “buying quiet,” erecting barriers or enclosures that isolate or block the noise, or conducting simple maintenance activities so equipment runs
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Applying Research to Practice Fit testing of hearing protectors is a valuable tool in hearing protector selection and employee training on the proper use and fit of hearing protectors. Identifying workers who are at high risk (low binaural personal attenuation ratings [PAR50]) provides occupational health nurses with a unique opportunity to intervene before potential permanent hearing threshold shifts occur. Workers identified at high risk for hearing loss may benefit from frequent monitoring.
more smoothly, more efficiently, and with less noise). In some cases, it may be impossible to engineer the noise out of the work environment, so hearing protectors are used to provide a noise barrier for workers. According to OSHA (1983), employees are required to wear hearing protectors if exposed to noise levels at or exceeding an 8-hour time-weighted average of 85 dB. Employers are required to provide employees, free of charge, with at least one type of earplug and one type of earmuff. Employers must also provide training in the use and care of all hearing protection devices (HPDs), ensure proper initial fitting, and supervise the correct use of all hearing protectors. Because individual workers may have unique ear anatomy and earplug fitting skills, it is not surprising that a suitable variety of hearing protectors is recommended to meet individual needs for all workers. Personal preference, working conditions, comfort, size, compatibility with other personal safety equipment, and ease of use are just a few of the comparative features of earplugs and earmuffs that influence selection and constant use (Berger, 2000). Given the plethora of hearing protection choices in the marketplace, how do occupational health nurses decide which hearing protector will give employees optimal protection? Hearing Protector Attenuation
In North America, hearing protector attenuation is measured in a laboratory environment in conformance with American National Standards Institute (ANSI) guidelines (ANSI, 1974). The laboratory procedures call for determining the highest achievable attenuation Noise Reduction Rating (NRR) for a particular hearing protector regardless of comfort, working conditions, or wear time, and may overestimate the attenuation achieved by individual workers. Berger (1993) stated, “Emphasis on noise reduction data as a purchasing criterion, and reliance on such numbers for predicting protection, are both unwarranted and potentially deleterious to the effectiveness of a hearing conservation program” (p. 1). In an attempt to determine the relative performance of a hearing protector, several different NRR derating schemes have been proposed around the globe (NIOSH, 1998; OSHA, 2013; Wheeler, 2012). Despite adjustments to the NRR, there is no certainty that
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the adjusted value is closer to the protection an individual worker can expect when wearing a specific HPD. The labeled value and various derating schemes offer inadequate guidance to the occupational health nurses assisting employees to select hearing protectors. To compound the problem, many employees working in noisy environments may not wear hearing protectors. Just minutes of accumulated unprotected exposure during an 8-hour work shift can substantially reduce the effectiveness of a hearing protector. “A device with lower attenuation (and perhaps greater comfort), if worn consistently and correctly, can provide greater protection than a less-regularly applied higher-attenuation HPD” (Berger, 2000, p. 424). The National Health and Nutrition Examination Survey conducted by the National Center for Health Statistics gathered self-reported HPD use among workers exposed to workplace noise. An analysis of data from 1999 to 2004 found that nearly one in six U.S. workers is exposed to workplace noise defined as “noise so loud that you have to speak in a raised voice to be heard.” However, one in three U.S. workers exposed to noise reported they did not use HPDs (Tak, Davis, & Calvert, 2009). Healthy People 2020 called for a 10% increase in the use of HPDs among adults and adolescents, and a reduction of hearing loss in high frequencies by 10% (Healthy People 2020, 2013). Furthermore, one of the top 14 research priorities identified by the American Association of Occupational Health Nurses calls for “strategies for increasing compliance with or motivating workers to use personal protective equipment” (American Association of Occupational Health Nurses, 2012, web page). HPDs are often chosen based on the NRR value alone, which, as addressed earlier, is not indicative of the actual attenuation achieved for an individual worker. Also, hearing protectors may be incorrectly fitted or the size of the HPD may be inappropriate for the size and shape of the ear canal. An alternative to group-based averages of HPD attenuation is individual worker measurements of attenuation using a field attenuation estimation system (FAES) (Hager, 2011). The FAES computes a personal attenuation rating (PAR) that can be directly subtracted from an A-weighted noise exposure and does not require derating. Although fit testing has been conducted in laboratory settings for nearly 30 years, commercial availability of portable systems suitable for use in an industrial setting is a more recent development. Individual fit testing of hearing protectors offers several benefits, including facilitating employee hearing protector training, encouraging trainthe-trainer opportunities, assisting with hearing protector selection, enhancing standard threshold shift monitoring, and documenting hearing conservation efforts (Berger, Voix, & Kieper, 2007). The use of a FAES has been recognized as a best practice (OSHA/NHCA/NIOSH Alliance, 2008), implemented by successful hearing conservation programs (NIOSH Safe in Sound, 2007), and is accepted in the marketplace. Training in combination with individual fit testing of hearing protectors was recommended by NIOSH as a hearing conservation strategy to promote the hearing health of fire fighters (Centers for Disease Control and Prevention, 2013). Over time, many
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employers have embraced a variety of FAES technologies commercially available, but a need exists to assess the value of FAES in promoting effective use of HPDs in work settings. Applying a Theoretical Model to HPD Use
The health promotion model has served as a theoretical framework for studying the factors that influence the adoption of a variety of health-related behaviors. The health promotion model has provided the foundation for developing and measuring the effectiveness of intervention programs aimed at hearing protector use (Lusk, 2002; Lusk, Kerr, Ronis, & Eakin, 1999; Lusk et al., 2003; McCullagh, 2011). When applied specifically to the use of hearing protectors, the following factors were identified as predictors of HPD use: perceived benefits, perceived barriers, perceived self-efficacy, and interpersonal relationships (Kim, Jeong, & Hong, 2010; Lusk & Kelemen, 1993; Lusk, Ronis, & Hogan, 1997; Lusk, Ronis, & Kerr, 1995; McCullagh, Ronis, & Lusk, 2010). “Perceived competence or self-efficacy to execute a given behavior increases the likelihood of commitment to action and actual performance of the behavior,” according to one of the theoretical propositions of the health promotion model (Pender, 2011, p. 6). Arezes and Miguel (2006) concluded that perceived self-efficacy was the primary predictor of HPD use, and efforts focused on increasing employees’ perceived selfefficacy were more effective than enforcement of HPD use. Although studies have investigated predictors of hearing protector use, few have examined whether the workers are using hearing protection correctly or achieving adequate protection. One study of perceived barriers and benefits and PAR was conducted in a largely Hispanic population of workers (Rabinowitz & Duran, 2001). Although the selfreport of perceived barriers to hearing protector use was a significant predictor of hearing protector fit, perceived self-efficacy and perceived benefits were not significantly related to PARs. Occupational health nurses are frequently charged with managing hearing conservation programs. However, despite best efforts to prevent noise-induced hearing loss, employers struggle to minimize noise-induced hearing loss cases. This study investigated the effect of using a FAES by comparing the PAR50 before and after an educational intervention and measuring perceived self-efficacy, benefits, and barriers to predict PAR50. Finally, data were collected at a later encounter (approximately 6 months later) to determine if the training conducted at the initial visit influenced PAR50 measured at that time, and if workers’ perceptions of the benefits, barriers, and self-efficacy of hearing protector use changed over time. METHODS The study was conducted at a large metal can manufacturing company with several sites in the United States. The North American Industry Classification code for this company is 33241, defined as the manufacturing of metal cans, lids, and ends. The 327 study participants were employees who voluntarily agreed to participate in the study and were currently enrolled in the company’s OSHA
hearing conservation program (i.e., due to noise exposure averaging more than 85 dB), claimed to be using hearing protectors (earplugs and/or earplugs plus earmuffs), and were naïve to the process of fit testing hearing protectors. Workers experiencing an earache in either or both ears at the time of the fit test or found to have excessive cerumen via an otoscopic inspection were disqualified from participating in the study. Employees exclusively using earmuffs were also not included because the FAES used in this study could only measure earplug fit. As can be seen in Table 1, the majority of the population were male, older, and long-time employees. Four separate locations participated in the study, but manufacturing processes were identical in all four facilities. Therefore, employees working in similar positions in different locations had similar noise exposures with similar exposure groups defined as ranging from 90 to 105 dBA time-weighted average, depending on where they worked in each plant. Instruments
Two instruments were used in this research, a FAES and a questionnaire. The FAES for this study was the 3MTM E-A-RfitTM Validation system based on field microphone-in-real-ear (F-MIRE) technology, commercially available since 2007 (Berger, Voix, Kieper, & Le Cocq, 2011). The FAES consisted of a hardware/software system along with surrogate ear test plugs. When a worker fits the test plug in an ear, a dual-element microphone is attached. The individual sits in front of a speaker equipped with a digital signal processor. The speaker presents a broad-band test signal and sound pressure levels are measured at seven octave-band frequencies outside the test plug (reference measurement) and compared to sound pressure levels measured in the ear canal by the internal microphone (internal measurement). This difference, adjusted for various associated acoustical factors, is the hearing protector’s attenuation and is displayed as a PAR. Measurements are performed on each ear separately and a binaural measurement (PAR50) is calculated. PAR50 represents the mean binaural value calculated by the FAES software similar to the noise reduction statistic (NRS50) in ANSI S12.68-2007 (R2012) (American National Standards Institute, 2012). Baseline PAR50 values were measured on all participants. Post-intervention PAR50 values were measured on the workers who qualified for the intervention group. Additional PAR50 values were measured for individuals in the invention group approximately 6 months from the initial measurement. The second instrument was a questionnaire that collected demographic information, hearing protector preference, and hand dominance, and measured perceived benefits, barriers, and self-efficacy regarding use of HPDs using scales validated in studies conducted by Lusk et al. (2003). The questionnaire was completed in the test area via an online electronic tablet in either English or Spanish. Workers were asked to report the type of HPD they preferred (foam roll-down earplugs, push-to-fit earplugs, premolded reusable earplugs, banded earplugs, or earmuffs). Time worked at the plant was elicited with categorical responses of less
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TABLE 1
Cross Tabulation of Study Population by Gender, Age, and Years of Experience at the Facility (Timework) Age (years) Time Worked (years) 20 Total
Gender
< 21
22 to 29
30 to 39
40 to 49
50 to 59
> 60
Total
Male
3
7
6
2
3
0
21
Female
1
0
2
1
0
0
4
Male
1
11
8
5
9
0
34
Female
0
0
1
3
1
0
5
Male
0
9
5
8
4
3
29
Female
0
0
4
1
2
1
8
Male
0
5
18
12
9
2
46
Female
0
1
1
2
0
0
4
Male
0
0
10
14
8
3
35
Female
0
0
1
4
3
1
9
Male
0
0
4
11
7
5
27
Female
0
0
0
2
4
0
6
Male
0
0
0
10
41
36
87
Female
0
0
1
1
9
1
12
Male
4
32
51
62
81
49
279
Female
1
1
10
14
19
3
48
Total
5
33
61
76
100
52
327
than 1 year, 1 to 3 years, 4 to 6 years, 7 to 10 years, 11 to 15 years, 16 to 20 years, or more than 20 years. Age categories included 21 years or younger, 22 to 29 years, 30 to 39 years, 40 to 49 years, 50 to 59 years, or 60 years or older. Six statements about self-efficacy ascertained how confident the employees felt about correctly and effectively fitting their hearing protectors. Five statements measured the perceived benefits of wearing hearing protectors, such as hearing loss and tinnitus prevention. Five statements measured the perceived barriers to wearing hearing protectors, such as feelings of isolation and discomfort. The workers were asked to indicate their level of agreement to each self-efficacy, perceived benefits, and perceived barriers statement using a 6-point Likert Scale (strongly disagree, moderately disagree, slightly disagree, slightly agree, moderately agree, and strongly agree). The questionnaire was completed three times: prior to baseline PAR50 (baseline) for all workers, immediately after the post-intervention PAR50 (post-intervention) for the intervention group, and after the PAR50 for the intervention group approximately 6 months later. Study Procedure
At the initial visit, workers entered the test area and, after consent, completed the baseline questionnaire. The investigators were present to assist and clarify any ques-
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tions during completion of the questionnaire and worked one-on-one with workers. After the baseline questionnaire was completed, workers were instructed on the fittest procedure and asked to choose the hearing protector they typically wore while working in noise. Employees were then asked to insert the surrogate equivalent test plugs into their ears the way they normally wore them during their work shift. The investigator watched and observed the fitting technique without coaching or intervening in any way for the initial baseline PAR measurements. The PAR “pass” criteria were defined as the PAR50 value being greater than the target minimum attenuation (i.e., employee exposure minus the company exposure limit), with two exceptions. Even in the event of adequate protection, if the software identified a large discrepancy between left and right PAR50 values (15 dB or more) or if low-frequency attenuation was low (less than 10 dB attenuation at 125 Hz), intervention was warranted. Workers who passed because they achieved adequate baseline protection were in the non-intervention group and were given their results. Those who did not meet the pass criteria, or who had unacceptable asymmetry or low-frequency attenuation were placed in the intervention group. The intervention group was trained by the investigator immediately following the baseline PAR50 measurement on the proper fitting of earplugs according to published training
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practices and procedures (Berger, 2000), and then PAR measurements were repeated. PAR50 measurements were repeated until the pass criterion was met and the best result recorded as the post-intervention PAR50. The intervention consisted of training on their preferred earplug and selection of a different size or style of hearing protector and otoscopy when necessary. The intervention group completed the post-intervention questionnaire. Approximately 6 months later, the intervention group at all four locations received additional PAR50 measurements and completed the follow-up questionnaire. Using the previously discussed criteria, individuals who did not pass post-intervention were retrained and retested until adequate protection was achieved. RESULTS Intervention Group
The intervention group was composed of a subset of the sample that required additional training at baseline and fell into one of the following two groups: required retraining with the same earplug and required retraining with a different size or different style of earplug. The criteria for the assigned groups described in the study procedure section yielded a pass rate of 70% (229 of 327), resulting in an intervention group of 28% of the study population, or 91 workers. Individuals who had excessive cerumen or were assigned earmuffs to wear rather than earplugs were disqualified from the study (2%). Statistical Analysis
To determine the relationship between two categorical variables, the Monte Carlo test with 2,000 replicates was used as reported by Hope (1968). The Monte Carlo test was used because assumptions were not met for asymptotic chi-square, the more commonly used statistical test for categorical variables. Patterns in counts were assessed for the different levels: gender, age, and time worked for each outcome using clustered bar charts to determine if any other patterns in the data were present. Outcome was defined as: 0 = pass, 1 = retrained on preferred earplug, 2 = new style or size earplug was assigned, 3 = earmuffs assigned, 4 = excessive cerumen. For each outcome, no relationship was found between outcome and gender, a finding that was supported statistically by the Monte Carlo test (p = .7546). Age and time worked also had consistent patterns for each outcome, thus no relationship between age and outcome or timework and outcome was found. The p values from the Monte Carlo simulations were p = .3673 and .3308, respectively, supporting the conclusion that no relationship between age and outcome or timework and outcome existed. Using a two-tailed paired t test, the average difference between baseline PAR50 and post-intervention PAR50 was analyzed. At the initial visit, for all members of the intervention group, the average difference between baseline PAR50 and post-intervention PAR50 was statistically significant (p < .001, 95% confidence interval [CI] = -13.4, -10.3 dB). Thus, training had statistically significant benefits on participants’ ability to use hearing pro-
tection more effectively (Table 2). These findings were consistent across individual plant locations. At the 6-month follow-up, 70 individuals in the intervention group were tested. Attrition of 21 was due to illness, vacations, conflict of work and testing schedules, and retirements. The average difference between baseline PAR50 and 6-month PAR50 measures was also statistically significant (p < .001, 95% CI = -11.2, -6.3 dB). Thus training was effective in improving participants’ ability to fit their hearing protection effectively, even 6 months after initial training. The average difference between post-intervention PAR50 and 6-month PAR50 significantly decreased (p = .001, 95% CI = 1.3, 4.9 dB), indicating that the initial gain in PAR50 was not sustained at the same level. However, the training was effective because a sustained increase from the baseline measure to the 6-month measure was found, as previously reported (Table 2). Perceived self-efficacy scores were collected and computed three times: prior to the baseline PAR50 measurement (baseline questionnaire for all participants), after the post-intervention PAR50 measurement (postintervention for the intervention group), and after the 6-month PAR50 measurement (intervention group). Using regression, the perceived self-efficacy scores (baseline) were not a significant predictor of baseline PAR50 (R2 = 0.04%) (Figure 1). This finding indicates that participants reported high perceived self-efficacy scores (average scores were 33.1 on a 36-point scale) regardless of baseline PAR50. From baseline to post-intervention, perceived self-efficacy scores for the intervention group showed a statistically significant decrease (p = .006, 95% CI = 0.3, 1.9). No significant changes from baseline to 6-month measurement or from post-intervention to 6-month measurement were found (Table 2). Also, no difference was found in the baseline measures of perceived self-efficacy between the intervention group and the non-intervention group (p = .544) and using multiple regression, perceived self-efficacy scores did not significantly differ by gender, time worked, or age. Using a two-tailed two-sample t test, participants in one location had a statistically significant increase in self-efficacy scores from baseline to follow-up as compared to participants in other locations (p = .03, 95% CI = 0.3, 4.8). No other effects of location could be detected. Baseline perceived barriers scores were low for the intervention group (on average 10.5 on a 30-point scale). Average perceived barriers scores did not significantly change from baseline to post-intervention (p = .557), from baseline to 6-month follow-up (p = 1.00), or from post-intervention to 6-month follow-up (p = .682). In contrast, average baseline perceived benefit scores for the intervention group were high for this population (average score 25.9 on a 30-point scale). In comparing baseline to 6-month follow-up perceived benefits, scores were borderline significantly different (p = .051, 95% CI = -1.2, 0.0), but based on the 95% CI, the average increase in score is 1.1 at most. No significant changes in perceived benefits and barriers from baseline to 6-month followup or from post-intervention to 6-month follow-up were found (Table 2). Also, no significant differences in base-
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TABLE 2
Comparisons of Intervention Group Scores at Baseline, Post-Intervention, and 6-Month Follow-Up Category
p
95% CIa
n
(-13.4 dB, -10.3 dB)
91
(-11.2 dB, -6.3 dB)
70
(1.3 dB, 4.9 dB)
70
PAR50 < .001b
Baseline–post-intervention Baseline–6-month follow-up
< .001
Post-intervention–6-month follow-up
.001
b
b
Self-efficacy Baseline–post-intervention
.006c
(0.3, 1.9)
91
Baseline–6-month follow-up
.521
(-0.7, 1.4)
70
Post-intervention–6-month follow-up
.120
(-1.9, 0.2)
70
Baseline–post-intervention
.557
(-1.2, 0.6)
91
Baseline–6-month follow-up
1.00
(-1.1, 1.1)
70
Post-intervention–6-month follow-up
.682
(-0.8, 1.2)
70
.051d
(-1.2, 0.0)
91
Baseline–6-month follow-up
d
.095
(-1.6, 0.1)
70
Post-intervention–6-month follow-up
.489
(-1.3, 0.6)
70
Barriers
Benefits Baseline–post-intervention
CI = confidence interval; PAR50 = binaural personal attenuation rating a Negatives indicate an increase in scores over time. b p < .001, two-tailed. c p < .05, two-tailed. d p < .10, two-tailed. Figure 1. Regression model of baseline self-efficacy scores versus baseline personal attenuation ratings (PAR50).
line measures of perceived benefits or barriers between the intervention group and the non-intervention group were found (p = .2 and .9, respectively) and using multiple regression, no significant effects on perceived benefits or barriers scores by gender, time worked, or age were
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found. Using a two-tailed two-sample t test, participants in one location had a statistically significant increase in perceived benefits scores from baseline to 6-month follow-up (p = .016, 95% CI = 0.4, 3.9) and post-intervention to 6-month monitoring (p = .020, 95% CI = 0.4,
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4.3), as well as a statistically significant decrease in perceived barriers scores from baseline to post-intervention (p = .039, 95% CI = -3.7, -0.1) compared to participants in other locations. No other effects of location could be detected. When analyses were conducted for only the 70 (Table 2) participants who fully participated in the study by completing the 6-month follow-up measures, the results were essentially the same with one exception: the borderline significant result on the perceived benefits score was no longer significant. DISCUSSION The FAES identified those workers whose HPDs were not providing sufficient attenuation, and the intervention significantly increased the effectiveness of their HPDs at post-intervention and at 6-month monitoring. Although some reduction in the effect at 6-months was found, workers’ PAR50 scores remained significantly improved over baseline. Despite having been trained annually on the proper way to fit hearing protectors, some employees discovered for the first time that they were not receiving adequate protection or that the hearing protector they were wearing was not the right size or style to provide adequate attenuation. After retraining and fitting a new HPD, significant increases in PAR50 values from baseline to postintervention were found. This finding is consistent with other studies that assessed individualized interventions. Murphy (2004) found that simple instruction significantly improved hearing protector performance. Murphy, Stephenson, Witt, and Duran (2011) found that individualized one-on-one training of employees in proper hearing protector fitting was superior to video or manufacturer’s written instruction. A meta-analysis of seven intervention studies found that “individual tailored education was more effective in improving HPD use compared with target education programs which address shared work characteristics” (El Dib, Mathew, & Martins, 2012). As previously described, to be selected for the intervention group, individuals’ baseline PAR had to meet one or more of the following criteria: low PAR50, less than 10 dB attenuation at 125 Hz, or a large discrepancy between PARs, left versus right ear. Although other studies have used baseline PAR50 values less than 15 dB as the selection criterion for the intervention group (Johnson, 2011; Kunz, Johnson, & Logan, 2013), a conservative approach was selected for this study to ensure that participants potentially at risk for noise-induced hearing loss received the intervention. Had the less conservative approach been employed in this study, the criteria would have yielded a higher pass rate of 88% (287 of 327) and a smaller intervention group (n = 35). Overall, the study population had high perceived selfefficacy using hearing protectors, high perceived benefits for wearing hearing protectors, and low perceived barriers to use that were not related to effective use of HPDs, unlike other studies using the health promotion model where beliefs regarding perceived self-efficacy, benefits, and barriers were predictive of HPD use. However, these other studies did not assess effective use of HPDs by
measuring attenuation, but instead only the self-reported use of HPDs. Surprisingly, perceived self-efficacy regarding the use of hearing protectors was not significantly related to baseline PAR50 values in this population. Overall, the high self-efficacy scores for this population may be attributed to this company’s focus on hearing conservation initiatives that go beyond mandated annual OSHA training. In addition, most employees had annually received routine training for many years, contributing to their belief that they were knowledgeable about how to successfully use HPDs, without the validation of fit testing. Another explanation for these high self-efficacy scores may be that employees who are confident in their hearing protection fitting skills are more likely to volunteer for such a study. Regardless of the reason for high self-efficacy scores, HPD use and confidence in wearing hearing protectors does not necessarily translate into employees choosing the correct style or size or using HPD properly. Further, a decrease in perceived self-efficacy scores after participants learned about their FAES results and received the intervention suggests that study participants may have determined that their self-confidence was misplaced. Fit testing provides a teachable moment tailored for individual workers based on FAES findings. In this study, with the exception of the baseline to post-intervention perceived benefits scores in one location, the perceived barriers and benefits scores did not significantly change from baseline to post-intervention or 6-month follow-up. Implications for Hearing Conservation Programs
The inclusion of a FAES enhanced the effectiveness of this hearing conservation program because it provided an additional three-pronged teaching opportunity. The worker could see the PAR values and the pass/fail indicators on the software screen. They were instructed that the higher the number, the higher the attenuation and could compare the measurements before and after training. When a hearing protector was fitted properly, they could feel the difference in their ear canal as opposed to the feel of a poorly fitted earplug. They could also hear the difference during the fit test because the loud speaker test signal was quieter when the earplug fit properly. Adjustments to their fitting technique or change in the type of earplug could be quickly measured, providing immediate feedback and illustrating to the worker the effectiveness of a specific HPD. However, the 6-month follow-up was more complicated. After 6-months, it was discovered that some of the previously assigned hearing protectors were not kept in stock by the employer. No access to the assigned hearing protector posed a critical problem because use of the new HPD was limited to the time of the fit test. This situation highlights the difficulties of coordinating a hearing conservation program, even in a controlled study. Therefore, ensuring access to appropriate HPD soon after the fit-testing session is recommended. Some workers stated that they “wear whatever is available” as they enter noisy areas, even if it is not their hearing protector of choice.
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In implementing a fit-testing program, workers should be provided with several different hearing protectors so they have a proven alternative in case their preferred HPD is not available. An effective hearing protector choice is one that not only provides adequate protection, but is worn 100% of the time the worker is exposed to noise. An inverse relationship between HPD comfort and attenuation has been documented (Byrne, Davis, Shaw, Specht, & Holland, 2011). Although not the focus of this study, discomfort was frequently cited by employees at the 6-month follow-up visit as being the reason they reverted back to their original hearing protection despite learning it was not adequately protective. The newly assigned hearing protector was first worn during the short fit-test session and may not have been representative of how comfortable an earplug is when worn for an extended period of time. Therefore, it is imperative to check on the comfort and acceptance of the HPD before workers revert to inadequate attenuation. Given the issues with access and comfort, frequent monitoring is a logical approach to ensuring adequate attenuation over time, but it is less clear how monitoring should be accomplished. The effect of a booster intervention to increase hearing protector use has been studied. Hong, Chin, Fiola, and Kazanis (2013) conducted a randomized controlled trial measuring the effectiveness of booster interventions and found the booster given between 67 and 94 days after the initial intervention significantly increased hearing protector use compared to other time frames. Available resources may prohibit booster interventions. However, more research may identify the type of booster intervention most effective at maintaining PAR50 over time. Occupational health nurses frequently use their observational skills to evaluate the proper use of hearing protectors. Berger (2013) found the depth of insertion with foam roll-down earplugs predicted attenuation. In practice, if the hearing protector appears well inserted behind the tragus, one may assume the employee is receiving adequate protection. Conversely, a hearing protector that appears to be shallow may fit poorly with low attenuation. Although these assumptions may be an effective means of predicting attenuation of a hearing protector for most employees, an occasional employee may have low PAR values despite the HPD being deeply inserted or high PAR values despite a shallow fit. Therefore, the best approach to measuring an individual worker’s hearing protector attenuation is by quantitative fit testing. Future research to investigate whether visual judgment of HPD fit correlates to PAR could yield interesting results. Implications for Practice
Occupational health nurses may be responsible for many or all components of a company’s hearing conservation program and the addition of a FAES could be beneficial. Hearing protector fit testing could be of value in many circumstances, including new hire safety orientation to confirm the employee is choosing the correct hearing protector and wearing the HPD properly. Baseline
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tests gathered on all employees document how individual employees prefer to wear HPDs. Subsequent measurements enable nurses to compare before and after an intervention, quantifying the value of the training. Fit testing should be included when monitoring a standard threshold shift to document the use and fit of hearing protectors and training intervention if necessary. Given the limitations of time and resources in a typical occupational environment, it is advantageous to quickly identify an at-risk group. CONCLUSION In this study population, FAES testing documented most workers (70%) were achieving adequate attenuation when fitting earplugs of their choice. Fit testing can improve PAR50 values for those employees who have not achieved adequate attenuation. A FAES can assist occupational health nurses to identify workers at high risk for noise-induced hearing loss (low PAR50), teach proper fit and use of HPDs, and assist in hearing protector selection. It can be difficult to maintain behavior change. Therefore, workers identified as high risk (low baseline PAR50) may benefit from frequent monitoring to reinforce the importance of fitting HPDs as they were taught. Understanding why PAR50 values deteriorate and the possible impact of frequent ongoing interventions warrant further investigation. REFERENCES
American Association of Occupational Health Nurses. (2012). AAOHN research priorities. Retrieved October 28, 2013, from http://www. aaohn.org/home/aaohn-research-priorities.html American National Standards Institute. (1974). Method for the measurement of real-ear protection of hearing protectors and physical attenuation of earmuffs (ANSI S3.19-1974). New York: Author. American National Standards Institute. (2012). ANSI S12.68.2007. Arezes, P. M., & Miguel, A. S. (2006). Does risk recognition affect workers’ hearing protection utilisation rate? International Journal of Industrial Ergonomics, 36, 1037-1043. Berger, E. H. (1993). The naked truth about NRRs (EARlog20). Retrieved October 30, 2013, from http://multimedia.3m.com/mws/ mediawebserver?mwsId=SSSSSuH8gc7nZxtU5Y_x4Y_BevUqe17zHvTSevTSeSSSSSS--&fn=EARLog%2020.pdf Berger, E. H. (2000). Hearing protection devices. In E. H. Berger, L. H. Royster, J. D. Royster, D. P. Driscoll, & M. Layne (Eds.), The noise manual (5th Ed., pp. 379-454). Fairfax, VA: American Industrial Hygiene Association. Berger, E. H. (2013). ‘Calibrating’ the insertion depth of roll-down foam earplugs. Proceedings of Meetings on Acoustics, 19, 040002. doi:10.1121.1.480046 Berger, E. H., Voix, J., & Kieper, R. W. (2007). Methods of developing and validating a field MIRE approach for measuring hearing protector attenuation. Spectrum, 24(Suppl. 1), 22. Berger, E. H., Voix, J., Kieper, R. W., & Le Cocq, C. (2011). Development and validation of a field microphone-in-real-ear approach for measuring hearing protector attenuation. Noise & Health, 13, 163-175. Bureau of Labor Statistics. (2012). Survey of occupational injuries & illnesses: Summary of estimates charts package. Retrieved December 9, 2013, from http://www.bls.gov/iif/oshwc/osh/os/osch0049. pdf Byrne, D. C., Davis, R. R., Shaw, P. B., Specht, B. M., & Holland, A. N. (2011). Relationship between comfort and attenuation measurements for two types of earplugs. Noise & Health, 13, 86-92. Centers for Disease Control and Prevention. (2013). Promoting hearing health among fire fighters. Retrieved October 28, 2013, from http://
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www.cdc.gov/niosh/docs/wp-solutions/2013-142/pdfs/2013-142. pdf El Dib, R. P., Mathew, J. L., & Martins, R. H. G. (2012). Interventions to promote the wearing of hearing protection. The Cochrane Database of Systematic Reviews, CD005234. Hager, L. D. (2011). Fit-testing hearing protectors: An idea whose time has come. Noise & Health, 13, 147-151. Healthy People 2020. (2013). Hearing and other sensory or communication disorders. Retrieved October 28, 2013, from http:// www.healthypeople.gov/2020/topicsobjectives2020/objectiveslist. aspx?topicId=20 Hong, O., Chin, D. L., Fiola, L A., & Kazanis, A. S. (2013). The effect of a booster intervention to promote hearing protection behavior in operating engineers. American Journal of Industrial Medicine, 56, 258-266. Hope, A. (1968). A simplified Monte Carlo significance test procedure. Journal of the Royal Statistical Society Series B (Methodological), 30, 582-598. Johnson, C. E. (2011). Fit testing of hearing protection in a large occupational survey (Unpublished Master’s thesis). University of Minnesota, Minneapolis, MN. Kim, Y., Jeong, I., & Hong, O. (2010). Predictors of hearing protection behavior among power plant workers. Asian Nursing Research, 4, 10-18. Kunz, J., Johnson, C. E., & Logan, P. W. (2013). Hearing protection attenuation values over time in a population of manufacturing workers using the E-A-Rfit Validation System (Unpublished Master’s thesis). University of Minnesota, Minneapolis, MN. Lusk, S. L. (2002). Interventions to prevent workers’ hearing loss (NIH Grant 2R01NR0250-04). Ann Arbor, MI: University of Michigan. Lusk, S. L., & Kelemen, M. J. (1993). Predicting use of hearing protection: A preliminary study. Public Health Nursing, 10, 189-196. Lusk, S. L., Kerr, M. J., Ronis, D. L., & Eakin, B. L. (1999). Applying the health promotion model to development of a worksite intervention. American Journal of Health Promotion, 13, 219-227. Lusk, S. L., Ronis, D. L., & Hogan, M. M. (1997). Test of the health promotion model as a causal model of construction workers’ use of hearing protection. Research in Nursing and Health, 20, 183-194. Lusk, S. L., Ronis, D. L., Kazanis, A. S., Eakin, B. L., Hong, O. S., & Raymond, D. M. (2003). Effectiveness of a tailored intervention to increase factory workers’ use of hearing protection. Nursing Research, 52, 289-295. Lusk, S. L., Ronis, D. L., & Kerr, M. J. (1995). Predictors of hearing protection use among workers: Implications for training programs. Human Factors, 37, 635-640. Masterson, E. A., Tak, S., Themann, C. L., Wall, D. K., Groenewold, M. R., Deddens, J. A., & Calvert, G. M. (2012). Prevalence of hearing loss in the United States by industry. American Journal of Industrial Medicine, 56, 670-681. McCullagh, M. C. (2011). Effects of a low intensity intervention to increase hearing protector use among noise-exposed workers. Ameri-
can Journal of Industrial Medicine, 54, 210-215. McCullagh, M. C., Ronis, D. L., & Lusk, S. L. (2010). Predictors of use of hearing protection among a representative sample of farmers. Research in Nursing and Health, 33, 528-538. Murphy, W. (2004). Instruction and the improvement of hearing protector performance. Noise & Health, 7, 41-47. Murphy, W. J., Stephenson, D. C., Witt, B., & Duran, J. (2011). Effects of training on hearing protector attenuation. Noise & Health, 13, 132-141. National Institute for Occupational Safety and Health. (1998). Criteria for a recommended standard: Occupational noise exposure. Retrieved December 13, 2013, from http://www.cdc.gov/niosh/ docs/98-126/pdfs/98-126.pdf National Institute for Occupational Safety and Health. (2007). Safe in sound: Excellence in hearing loss prevention award. Retrieved October 1, 2013, from http://www.safeinsound.us/ Nelson, D. I., Nelson, R. Y., Concha-Barrientos, M., & Fingerhut, M. (2005). The global burden of occupational noise-induced hearing loss. American Journal of Industrial Medicine, 48, 446-458. Occupational Safety and Health Administration. (1983). Occupational noise exposure: Hearing Conservation Amendment. Retrieved October 30, 2013, from https://www.osha.gov/pls/oshaweb/owadisp. show_document?p_table=STANDARDS&p_id=9737 Occupational Safety and Health Administration. (2013). OSHA technical manual (OTM) - Section III: Chapter 5 - Noise (Appendix E). Retrieved December 13, 2013, from https://www.osha.gov/dts/osta/ otm/new_noise/index.html#appendixe OSHA/NHCA/NIOSH Alliance. (2008). Best practice bulletin: Hearing protection-emerging trends: Individual fit testing. Retrieved October 1, 2013, from http://c.ymcdn.com/sites/www.hearingconservation.org/resource/resmgr/imported/AllianceRecommendationForFitTesting_Final.pdf Pender, N. (2011). The health promotion model - Manual. Retrieved October 11, 2013, from http://deepblue.lib.umich.edu/bitstream/ha ndle/2027.42/85350/?sequence=1 Rabinowitz, P. M., & Duran, R. (2001). Is acculturation related to use of hearing protection? American Industrial Hygiene Association, 62, 611-614. Rogers, B., Meyer, D., Scheessele, D., Atwell, T., Ostendorf, J., Randolph, S., & Buckheit, K. (2009). What makes a successful hearing conservation program? AAOHN Journal, 57, 321-335. Tak, S., Davis, R. R., & Calvert, G. M. (2009). Exposure to hazardous workplace noise and use of hearing protection devices among US workers-NHANES, 1999-2004. American Journal of Industrial Medicine, 52, 358-371. Thurston, F. E. (2013). The worker’s ear: A history of noise-induced hearing loss. American Journal of Industrial Medicine, 56, 367-377. Wheeler, P. D. (2012). De-rating for the attenuation performance of hearing protectors – Is there an alternative? (Unpublished 3M white paper submitted to the CEN/TC159 committee).
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ABSTRACT This study assessed attitudes toward the use of hearing protection devices (HPDs) and the effect of an educational intervention on fit-testing results by comparing personal attenuation ratings (PAR50) before and after the intervention. Employees (n = 327) from a large metal container manufacturer at four geographic locations were tested with a field attenuation estimation system (FAES) to identify workers (n = 91) requiring intervention. PAR50 values significantly increased from baseline to post-intervention (p < .001, 15.1 to 26.9) and at the 6-month follow-up (p < .001, 95% confidence interval = -11.2, -6.3). Perceived self-efficacy scores for using HPDs significantly declined from baseline to post-intervention (p = .006, 95% confidence interval = 0.3, 1.9), but were not significantly related to PAR50. Therefore, a FAES can assist the occupational health nurse to identify workers at high risk (low PAR50), teach proper fit and use of HPDs, and improve hearing protector selection. [Workplace Health Saf 2014;62(12):491-499.]
H
earing loss and tinnitus can be debilitating consequences of working in high noise areas. These deleterious conditions have been documented since the Roman Empire (Thurston, 2013). According to Masterson et al. (2012), the National Institute for Occupational Safety and Health (NIOSH) found that 22 million workers in the United States are exposed to hazardous noise. Hearing loss prevalence data showed that 18% of U.S. workers had a material hearing loss defined by pure-tone average thresholds of 25 dB or more across frequencies 1,000, 2,000, 3,000, and 4,000 Hz in either ear (Masterson et al., 2012). Not surprisingly, workers in the mining, manufacturing, and construction sectors are at ABOUT THE AUTHORS
Ms. Smith is Technical Service Specialist, and Ms. Monaco is Lean Six Sigma Coach and Statistician, 3M Company, St. Paul, Minnesota. Dr. Lusk is Professor Emerita, University of Michigan School of Nursing, Ann Arbor, Michigan. Submitted: May 28, 2014; Accepted: July 25, 2014; Posted online: September 9, 2014 This study was supported by 3M Company–Personal Safety Division and approved by 3M IRB HUM00060704. The authors thank Silgan Containers for partnering with them to conduct this important research. Correspondence: Pegeen S. Smith, MS, RN, COHN-S, Personal Safety Division, 620 Holly Road, Cadillac, MI 49601. E-mail: [email protected] doi:10.3928/21650799-20140902-01
the highest risk for developing hearing loss. The NIOSH study recommended employers reduce noise through engineering controls and called for better hearing conservation strategies. In 2012, the Bureau of Labor Statistics reported recordable hearing loss at 12% of the total nonfatal occupational illness in the private sector (Bureau of Labor Statistics, 2012). Manufacturing and specifically primary metal manufacturing consistently demonstrated high hearing loss rates among employees. An average of 16% of all adult-onset hearing loss identified globally was attributable to occupational noise (Nelson, Nelson, Concha-Barrientos, & Fingerhut, 2005). The goal of any hearing conservation program is to prevent hearing loss caused by noise in the workplace. Rogers et al. (2009) described a successful program, based on Occupational Health and Safety Administration (OSHA) mandates for hearing conservation programs, as having a multi-disciplinary approach and including noise assessment and monitoring, employee training and education, audiometric testing, and mandatory recordkeeping. Engineering controls are the first line of protection against a noise hazard and may include preventing noise creation at its source (e.g., “buying quiet,” erecting barriers or enclosures that isolate or block the noise, or conducting simple maintenance activities so equipment runs
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Applying Research to Practice Fit testing of hearing protectors is a valuable tool in hearing protector selection and employee training on the proper use and fit of hearing protectors. Identifying workers who are at high risk (low binaural personal attenuation ratings [PAR50]) provides occupational health nurses with a unique opportunity to intervene before potential permanent hearing threshold shifts occur. Workers identified at high risk for hearing loss may benefit from frequent monitoring.
more smoothly, more efficiently, and with less noise). In some cases, it may be impossible to engineer the noise out of the work environment, so hearing protectors are used to provide a noise barrier for workers. According to OSHA (1983), employees are required to wear hearing protectors if exposed to noise levels at or exceeding an 8-hour time-weighted average of 85 dB. Employers are required to provide employees, free of charge, with at least one type of earplug and one type of earmuff. Employers must also provide training in the use and care of all hearing protection devices (HPDs), ensure proper initial fitting, and supervise the correct use of all hearing protectors. Because individual workers may have unique ear anatomy and earplug fitting skills, it is not surprising that a suitable variety of hearing protectors is recommended to meet individual needs for all workers. Personal preference, working conditions, comfort, size, compatibility with other personal safety equipment, and ease of use are just a few of the comparative features of earplugs and earmuffs that influence selection and constant use (Berger, 2000). Given the plethora of hearing protection choices in the marketplace, how do occupational health nurses decide which hearing protector will give employees optimal protection? Hearing Protector Attenuation
In North America, hearing protector attenuation is measured in a laboratory environment in conformance with American National Standards Institute (ANSI) guidelines (ANSI, 1974). The laboratory procedures call for determining the highest achievable attenuation Noise Reduction Rating (NRR) for a particular hearing protector regardless of comfort, working conditions, or wear time, and may overestimate the attenuation achieved by individual workers. Berger (1993) stated, “Emphasis on noise reduction data as a purchasing criterion, and reliance on such numbers for predicting protection, are both unwarranted and potentially deleterious to the effectiveness of a hearing conservation program” (p. 1). In an attempt to determine the relative performance of a hearing protector, several different NRR derating schemes have been proposed around the globe (NIOSH, 1998; OSHA, 2013; Wheeler, 2012). Despite adjustments to the NRR, there is no certainty that
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the adjusted value is closer to the protection an individual worker can expect when wearing a specific HPD. The labeled value and various derating schemes offer inadequate guidance to the occupational health nurses assisting employees to select hearing protectors. To compound the problem, many employees working in noisy environments may not wear hearing protectors. Just minutes of accumulated unprotected exposure during an 8-hour work shift can substantially reduce the effectiveness of a hearing protector. “A device with lower attenuation (and perhaps greater comfort), if worn consistently and correctly, can provide greater protection than a less-regularly applied higher-attenuation HPD” (Berger, 2000, p. 424). The National Health and Nutrition Examination Survey conducted by the National Center for Health Statistics gathered self-reported HPD use among workers exposed to workplace noise. An analysis of data from 1999 to 2004 found that nearly one in six U.S. workers is exposed to workplace noise defined as “noise so loud that you have to speak in a raised voice to be heard.” However, one in three U.S. workers exposed to noise reported they did not use HPDs (Tak, Davis, & Calvert, 2009). Healthy People 2020 called for a 10% increase in the use of HPDs among adults and adolescents, and a reduction of hearing loss in high frequencies by 10% (Healthy People 2020, 2013). Furthermore, one of the top 14 research priorities identified by the American Association of Occupational Health Nurses calls for “strategies for increasing compliance with or motivating workers to use personal protective equipment” (American Association of Occupational Health Nurses, 2012, web page). HPDs are often chosen based on the NRR value alone, which, as addressed earlier, is not indicative of the actual attenuation achieved for an individual worker. Also, hearing protectors may be incorrectly fitted or the size of the HPD may be inappropriate for the size and shape of the ear canal. An alternative to group-based averages of HPD attenuation is individual worker measurements of attenuation using a field attenuation estimation system (FAES) (Hager, 2011). The FAES computes a personal attenuation rating (PAR) that can be directly subtracted from an A-weighted noise exposure and does not require derating. Although fit testing has been conducted in laboratory settings for nearly 30 years, commercial availability of portable systems suitable for use in an industrial setting is a more recent development. Individual fit testing of hearing protectors offers several benefits, including facilitating employee hearing protector training, encouraging trainthe-trainer opportunities, assisting with hearing protector selection, enhancing standard threshold shift monitoring, and documenting hearing conservation efforts (Berger, Voix, & Kieper, 2007). The use of a FAES has been recognized as a best practice (OSHA/NHCA/NIOSH Alliance, 2008), implemented by successful hearing conservation programs (NIOSH Safe in Sound, 2007), and is accepted in the marketplace. Training in combination with individual fit testing of hearing protectors was recommended by NIOSH as a hearing conservation strategy to promote the hearing health of fire fighters (Centers for Disease Control and Prevention, 2013). Over time, many
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employers have embraced a variety of FAES technologies commercially available, but a need exists to assess the value of FAES in promoting effective use of HPDs in work settings. Applying a Theoretical Model to HPD Use
The health promotion model has served as a theoretical framework for studying the factors that influence the adoption of a variety of health-related behaviors. The health promotion model has provided the foundation for developing and measuring the effectiveness of intervention programs aimed at hearing protector use (Lusk, 2002; Lusk, Kerr, Ronis, & Eakin, 1999; Lusk et al., 2003; McCullagh, 2011). When applied specifically to the use of hearing protectors, the following factors were identified as predictors of HPD use: perceived benefits, perceived barriers, perceived self-efficacy, and interpersonal relationships (Kim, Jeong, & Hong, 2010; Lusk & Kelemen, 1993; Lusk, Ronis, & Hogan, 1997; Lusk, Ronis, & Kerr, 1995; McCullagh, Ronis, & Lusk, 2010). “Perceived competence or self-efficacy to execute a given behavior increases the likelihood of commitment to action and actual performance of the behavior,” according to one of the theoretical propositions of the health promotion model (Pender, 2011, p. 6). Arezes and Miguel (2006) concluded that perceived self-efficacy was the primary predictor of HPD use, and efforts focused on increasing employees’ perceived selfefficacy were more effective than enforcement of HPD use. Although studies have investigated predictors of hearing protector use, few have examined whether the workers are using hearing protection correctly or achieving adequate protection. One study of perceived barriers and benefits and PAR was conducted in a largely Hispanic population of workers (Rabinowitz & Duran, 2001). Although the selfreport of perceived barriers to hearing protector use was a significant predictor of hearing protector fit, perceived self-efficacy and perceived benefits were not significantly related to PARs. Occupational health nurses are frequently charged with managing hearing conservation programs. However, despite best efforts to prevent noise-induced hearing loss, employers struggle to minimize noise-induced hearing loss cases. This study investigated the effect of using a FAES by comparing the PAR50 before and after an educational intervention and measuring perceived self-efficacy, benefits, and barriers to predict PAR50. Finally, data were collected at a later encounter (approximately 6 months later) to determine if the training conducted at the initial visit influenced PAR50 measured at that time, and if workers’ perceptions of the benefits, barriers, and self-efficacy of hearing protector use changed over time. METHODS The study was conducted at a large metal can manufacturing company with several sites in the United States. The North American Industry Classification code for this company is 33241, defined as the manufacturing of metal cans, lids, and ends. The 327 study participants were employees who voluntarily agreed to participate in the study and were currently enrolled in the company’s OSHA
hearing conservation program (i.e., due to noise exposure averaging more than 85 dB), claimed to be using hearing protectors (earplugs and/or earplugs plus earmuffs), and were naïve to the process of fit testing hearing protectors. Workers experiencing an earache in either or both ears at the time of the fit test or found to have excessive cerumen via an otoscopic inspection were disqualified from participating in the study. Employees exclusively using earmuffs were also not included because the FAES used in this study could only measure earplug fit. As can be seen in Table 1, the majority of the population were male, older, and long-time employees. Four separate locations participated in the study, but manufacturing processes were identical in all four facilities. Therefore, employees working in similar positions in different locations had similar noise exposures with similar exposure groups defined as ranging from 90 to 105 dBA time-weighted average, depending on where they worked in each plant. Instruments
Two instruments were used in this research, a FAES and a questionnaire. The FAES for this study was the 3MTM E-A-RfitTM Validation system based on field microphone-in-real-ear (F-MIRE) technology, commercially available since 2007 (Berger, Voix, Kieper, & Le Cocq, 2011). The FAES consisted of a hardware/software system along with surrogate ear test plugs. When a worker fits the test plug in an ear, a dual-element microphone is attached. The individual sits in front of a speaker equipped with a digital signal processor. The speaker presents a broad-band test signal and sound pressure levels are measured at seven octave-band frequencies outside the test plug (reference measurement) and compared to sound pressure levels measured in the ear canal by the internal microphone (internal measurement). This difference, adjusted for various associated acoustical factors, is the hearing protector’s attenuation and is displayed as a PAR. Measurements are performed on each ear separately and a binaural measurement (PAR50) is calculated. PAR50 represents the mean binaural value calculated by the FAES software similar to the noise reduction statistic (NRS50) in ANSI S12.68-2007 (R2012) (American National Standards Institute, 2012). Baseline PAR50 values were measured on all participants. Post-intervention PAR50 values were measured on the workers who qualified for the intervention group. Additional PAR50 values were measured for individuals in the invention group approximately 6 months from the initial measurement. The second instrument was a questionnaire that collected demographic information, hearing protector preference, and hand dominance, and measured perceived benefits, barriers, and self-efficacy regarding use of HPDs using scales validated in studies conducted by Lusk et al. (2003). The questionnaire was completed in the test area via an online electronic tablet in either English or Spanish. Workers were asked to report the type of HPD they preferred (foam roll-down earplugs, push-to-fit earplugs, premolded reusable earplugs, banded earplugs, or earmuffs). Time worked at the plant was elicited with categorical responses of less
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TABLE 1
Cross Tabulation of Study Population by Gender, Age, and Years of Experience at the Facility (Timework) Age (years) Time Worked (years) 20 Total
Gender
< 21
22 to 29
30 to 39
40 to 49
50 to 59
> 60
Total
Male
3
7
6
2
3
0
21
Female
1
0
2
1
0
0
4
Male
1
11
8
5
9
0
34
Female
0
0
1
3
1
0
5
Male
0
9
5
8
4
3
29
Female
0
0
4
1
2
1
8
Male
0
5
18
12
9
2
46
Female
0
1
1
2
0
0
4
Male
0
0
10
14
8
3
35
Female
0
0
1
4
3
1
9
Male
0
0
4
11
7
5
27
Female
0
0
0
2
4
0
6
Male
0
0
0
10
41
36
87
Female
0
0
1
1
9
1
12
Male
4
32
51
62
81
49
279
Female
1
1
10
14
19
3
48
Total
5
33
61
76
100
52
327
than 1 year, 1 to 3 years, 4 to 6 years, 7 to 10 years, 11 to 15 years, 16 to 20 years, or more than 20 years. Age categories included 21 years or younger, 22 to 29 years, 30 to 39 years, 40 to 49 years, 50 to 59 years, or 60 years or older. Six statements about self-efficacy ascertained how confident the employees felt about correctly and effectively fitting their hearing protectors. Five statements measured the perceived benefits of wearing hearing protectors, such as hearing loss and tinnitus prevention. Five statements measured the perceived barriers to wearing hearing protectors, such as feelings of isolation and discomfort. The workers were asked to indicate their level of agreement to each self-efficacy, perceived benefits, and perceived barriers statement using a 6-point Likert Scale (strongly disagree, moderately disagree, slightly disagree, slightly agree, moderately agree, and strongly agree). The questionnaire was completed three times: prior to baseline PAR50 (baseline) for all workers, immediately after the post-intervention PAR50 (post-intervention) for the intervention group, and after the PAR50 for the intervention group approximately 6 months later. Study Procedure
At the initial visit, workers entered the test area and, after consent, completed the baseline questionnaire. The investigators were present to assist and clarify any ques-
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tions during completion of the questionnaire and worked one-on-one with workers. After the baseline questionnaire was completed, workers were instructed on the fittest procedure and asked to choose the hearing protector they typically wore while working in noise. Employees were then asked to insert the surrogate equivalent test plugs into their ears the way they normally wore them during their work shift. The investigator watched and observed the fitting technique without coaching or intervening in any way for the initial baseline PAR measurements. The PAR “pass” criteria were defined as the PAR50 value being greater than the target minimum attenuation (i.e., employee exposure minus the company exposure limit), with two exceptions. Even in the event of adequate protection, if the software identified a large discrepancy between left and right PAR50 values (15 dB or more) or if low-frequency attenuation was low (less than 10 dB attenuation at 125 Hz), intervention was warranted. Workers who passed because they achieved adequate baseline protection were in the non-intervention group and were given their results. Those who did not meet the pass criteria, or who had unacceptable asymmetry or low-frequency attenuation were placed in the intervention group. The intervention group was trained by the investigator immediately following the baseline PAR50 measurement on the proper fitting of earplugs according to published training
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practices and procedures (Berger, 2000), and then PAR measurements were repeated. PAR50 measurements were repeated until the pass criterion was met and the best result recorded as the post-intervention PAR50. The intervention consisted of training on their preferred earplug and selection of a different size or style of hearing protector and otoscopy when necessary. The intervention group completed the post-intervention questionnaire. Approximately 6 months later, the intervention group at all four locations received additional PAR50 measurements and completed the follow-up questionnaire. Using the previously discussed criteria, individuals who did not pass post-intervention were retrained and retested until adequate protection was achieved. RESULTS Intervention Group
The intervention group was composed of a subset of the sample that required additional training at baseline and fell into one of the following two groups: required retraining with the same earplug and required retraining with a different size or different style of earplug. The criteria for the assigned groups described in the study procedure section yielded a pass rate of 70% (229 of 327), resulting in an intervention group of 28% of the study population, or 91 workers. Individuals who had excessive cerumen or were assigned earmuffs to wear rather than earplugs were disqualified from the study (2%). Statistical Analysis
To determine the relationship between two categorical variables, the Monte Carlo test with 2,000 replicates was used as reported by Hope (1968). The Monte Carlo test was used because assumptions were not met for asymptotic chi-square, the more commonly used statistical test for categorical variables. Patterns in counts were assessed for the different levels: gender, age, and time worked for each outcome using clustered bar charts to determine if any other patterns in the data were present. Outcome was defined as: 0 = pass, 1 = retrained on preferred earplug, 2 = new style or size earplug was assigned, 3 = earmuffs assigned, 4 = excessive cerumen. For each outcome, no relationship was found between outcome and gender, a finding that was supported statistically by the Monte Carlo test (p = .7546). Age and time worked also had consistent patterns for each outcome, thus no relationship between age and outcome or timework and outcome was found. The p values from the Monte Carlo simulations were p = .3673 and .3308, respectively, supporting the conclusion that no relationship between age and outcome or timework and outcome existed. Using a two-tailed paired t test, the average difference between baseline PAR50 and post-intervention PAR50 was analyzed. At the initial visit, for all members of the intervention group, the average difference between baseline PAR50 and post-intervention PAR50 was statistically significant (p < .001, 95% confidence interval [CI] = -13.4, -10.3 dB). Thus, training had statistically significant benefits on participants’ ability to use hearing pro-
tection more effectively (Table 2). These findings were consistent across individual plant locations. At the 6-month follow-up, 70 individuals in the intervention group were tested. Attrition of 21 was due to illness, vacations, conflict of work and testing schedules, and retirements. The average difference between baseline PAR50 and 6-month PAR50 measures was also statistically significant (p < .001, 95% CI = -11.2, -6.3 dB). Thus training was effective in improving participants’ ability to fit their hearing protection effectively, even 6 months after initial training. The average difference between post-intervention PAR50 and 6-month PAR50 significantly decreased (p = .001, 95% CI = 1.3, 4.9 dB), indicating that the initial gain in PAR50 was not sustained at the same level. However, the training was effective because a sustained increase from the baseline measure to the 6-month measure was found, as previously reported (Table 2). Perceived self-efficacy scores were collected and computed three times: prior to the baseline PAR50 measurement (baseline questionnaire for all participants), after the post-intervention PAR50 measurement (postintervention for the intervention group), and after the 6-month PAR50 measurement (intervention group). Using regression, the perceived self-efficacy scores (baseline) were not a significant predictor of baseline PAR50 (R2 = 0.04%) (Figure 1). This finding indicates that participants reported high perceived self-efficacy scores (average scores were 33.1 on a 36-point scale) regardless of baseline PAR50. From baseline to post-intervention, perceived self-efficacy scores for the intervention group showed a statistically significant decrease (p = .006, 95% CI = 0.3, 1.9). No significant changes from baseline to 6-month measurement or from post-intervention to 6-month measurement were found (Table 2). Also, no difference was found in the baseline measures of perceived self-efficacy between the intervention group and the non-intervention group (p = .544) and using multiple regression, perceived self-efficacy scores did not significantly differ by gender, time worked, or age. Using a two-tailed two-sample t test, participants in one location had a statistically significant increase in self-efficacy scores from baseline to follow-up as compared to participants in other locations (p = .03, 95% CI = 0.3, 4.8). No other effects of location could be detected. Baseline perceived barriers scores were low for the intervention group (on average 10.5 on a 30-point scale). Average perceived barriers scores did not significantly change from baseline to post-intervention (p = .557), from baseline to 6-month follow-up (p = 1.00), or from post-intervention to 6-month follow-up (p = .682). In contrast, average baseline perceived benefit scores for the intervention group were high for this population (average score 25.9 on a 30-point scale). In comparing baseline to 6-month follow-up perceived benefits, scores were borderline significantly different (p = .051, 95% CI = -1.2, 0.0), but based on the 95% CI, the average increase in score is 1.1 at most. No significant changes in perceived benefits and barriers from baseline to 6-month followup or from post-intervention to 6-month follow-up were found (Table 2). Also, no significant differences in base-
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TABLE 2
Comparisons of Intervention Group Scores at Baseline, Post-Intervention, and 6-Month Follow-Up Category
p
95% CIa
n
(-13.4 dB, -10.3 dB)
91
(-11.2 dB, -6.3 dB)
70
(1.3 dB, 4.9 dB)
70
PAR50 < .001b
Baseline–post-intervention Baseline–6-month follow-up
< .001
Post-intervention–6-month follow-up
.001
b
b
Self-efficacy Baseline–post-intervention
.006c
(0.3, 1.9)
91
Baseline–6-month follow-up
.521
(-0.7, 1.4)
70
Post-intervention–6-month follow-up
.120
(-1.9, 0.2)
70
Baseline–post-intervention
.557
(-1.2, 0.6)
91
Baseline–6-month follow-up
1.00
(-1.1, 1.1)
70
Post-intervention–6-month follow-up
.682
(-0.8, 1.2)
70
.051d
(-1.2, 0.0)
91
Baseline–6-month follow-up
d
.095
(-1.6, 0.1)
70
Post-intervention–6-month follow-up
.489
(-1.3, 0.6)
70
Barriers
Benefits Baseline–post-intervention
CI = confidence interval; PAR50 = binaural personal attenuation rating a Negatives indicate an increase in scores over time. b p < .001, two-tailed. c p < .05, two-tailed. d p < .10, two-tailed. Figure 1. Regression model of baseline self-efficacy scores versus baseline personal attenuation ratings (PAR50).
line measures of perceived benefits or barriers between the intervention group and the non-intervention group were found (p = .2 and .9, respectively) and using multiple regression, no significant effects on perceived benefits or barriers scores by gender, time worked, or age were
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found. Using a two-tailed two-sample t test, participants in one location had a statistically significant increase in perceived benefits scores from baseline to 6-month follow-up (p = .016, 95% CI = 0.4, 3.9) and post-intervention to 6-month monitoring (p = .020, 95% CI = 0.4,
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4.3), as well as a statistically significant decrease in perceived barriers scores from baseline to post-intervention (p = .039, 95% CI = -3.7, -0.1) compared to participants in other locations. No other effects of location could be detected. When analyses were conducted for only the 70 (Table 2) participants who fully participated in the study by completing the 6-month follow-up measures, the results were essentially the same with one exception: the borderline significant result on the perceived benefits score was no longer significant. DISCUSSION The FAES identified those workers whose HPDs were not providing sufficient attenuation, and the intervention significantly increased the effectiveness of their HPDs at post-intervention and at 6-month monitoring. Although some reduction in the effect at 6-months was found, workers’ PAR50 scores remained significantly improved over baseline. Despite having been trained annually on the proper way to fit hearing protectors, some employees discovered for the first time that they were not receiving adequate protection or that the hearing protector they were wearing was not the right size or style to provide adequate attenuation. After retraining and fitting a new HPD, significant increases in PAR50 values from baseline to postintervention were found. This finding is consistent with other studies that assessed individualized interventions. Murphy (2004) found that simple instruction significantly improved hearing protector performance. Murphy, Stephenson, Witt, and Duran (2011) found that individualized one-on-one training of employees in proper hearing protector fitting was superior to video or manufacturer’s written instruction. A meta-analysis of seven intervention studies found that “individual tailored education was more effective in improving HPD use compared with target education programs which address shared work characteristics” (El Dib, Mathew, & Martins, 2012). As previously described, to be selected for the intervention group, individuals’ baseline PAR had to meet one or more of the following criteria: low PAR50, less than 10 dB attenuation at 125 Hz, or a large discrepancy between PARs, left versus right ear. Although other studies have used baseline PAR50 values less than 15 dB as the selection criterion for the intervention group (Johnson, 2011; Kunz, Johnson, & Logan, 2013), a conservative approach was selected for this study to ensure that participants potentially at risk for noise-induced hearing loss received the intervention. Had the less conservative approach been employed in this study, the criteria would have yielded a higher pass rate of 88% (287 of 327) and a smaller intervention group (n = 35). Overall, the study population had high perceived selfefficacy using hearing protectors, high perceived benefits for wearing hearing protectors, and low perceived barriers to use that were not related to effective use of HPDs, unlike other studies using the health promotion model where beliefs regarding perceived self-efficacy, benefits, and barriers were predictive of HPD use. However, these other studies did not assess effective use of HPDs by
measuring attenuation, but instead only the self-reported use of HPDs. Surprisingly, perceived self-efficacy regarding the use of hearing protectors was not significantly related to baseline PAR50 values in this population. Overall, the high self-efficacy scores for this population may be attributed to this company’s focus on hearing conservation initiatives that go beyond mandated annual OSHA training. In addition, most employees had annually received routine training for many years, contributing to their belief that they were knowledgeable about how to successfully use HPDs, without the validation of fit testing. Another explanation for these high self-efficacy scores may be that employees who are confident in their hearing protection fitting skills are more likely to volunteer for such a study. Regardless of the reason for high self-efficacy scores, HPD use and confidence in wearing hearing protectors does not necessarily translate into employees choosing the correct style or size or using HPD properly. Further, a decrease in perceived self-efficacy scores after participants learned about their FAES results and received the intervention suggests that study participants may have determined that their self-confidence was misplaced. Fit testing provides a teachable moment tailored for individual workers based on FAES findings. In this study, with the exception of the baseline to post-intervention perceived benefits scores in one location, the perceived barriers and benefits scores did not significantly change from baseline to post-intervention or 6-month follow-up. Implications for Hearing Conservation Programs
The inclusion of a FAES enhanced the effectiveness of this hearing conservation program because it provided an additional three-pronged teaching opportunity. The worker could see the PAR values and the pass/fail indicators on the software screen. They were instructed that the higher the number, the higher the attenuation and could compare the measurements before and after training. When a hearing protector was fitted properly, they could feel the difference in their ear canal as opposed to the feel of a poorly fitted earplug. They could also hear the difference during the fit test because the loud speaker test signal was quieter when the earplug fit properly. Adjustments to their fitting technique or change in the type of earplug could be quickly measured, providing immediate feedback and illustrating to the worker the effectiveness of a specific HPD. However, the 6-month follow-up was more complicated. After 6-months, it was discovered that some of the previously assigned hearing protectors were not kept in stock by the employer. No access to the assigned hearing protector posed a critical problem because use of the new HPD was limited to the time of the fit test. This situation highlights the difficulties of coordinating a hearing conservation program, even in a controlled study. Therefore, ensuring access to appropriate HPD soon after the fit-testing session is recommended. Some workers stated that they “wear whatever is available” as they enter noisy areas, even if it is not their hearing protector of choice.
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In implementing a fit-testing program, workers should be provided with several different hearing protectors so they have a proven alternative in case their preferred HPD is not available. An effective hearing protector choice is one that not only provides adequate protection, but is worn 100% of the time the worker is exposed to noise. An inverse relationship between HPD comfort and attenuation has been documented (Byrne, Davis, Shaw, Specht, & Holland, 2011). Although not the focus of this study, discomfort was frequently cited by employees at the 6-month follow-up visit as being the reason they reverted back to their original hearing protection despite learning it was not adequately protective. The newly assigned hearing protector was first worn during the short fit-test session and may not have been representative of how comfortable an earplug is when worn for an extended period of time. Therefore, it is imperative to check on the comfort and acceptance of the HPD before workers revert to inadequate attenuation. Given the issues with access and comfort, frequent monitoring is a logical approach to ensuring adequate attenuation over time, but it is less clear how monitoring should be accomplished. The effect of a booster intervention to increase hearing protector use has been studied. Hong, Chin, Fiola, and Kazanis (2013) conducted a randomized controlled trial measuring the effectiveness of booster interventions and found the booster given between 67 and 94 days after the initial intervention significantly increased hearing protector use compared to other time frames. Available resources may prohibit booster interventions. However, more research may identify the type of booster intervention most effective at maintaining PAR50 over time. Occupational health nurses frequently use their observational skills to evaluate the proper use of hearing protectors. Berger (2013) found the depth of insertion with foam roll-down earplugs predicted attenuation. In practice, if the hearing protector appears well inserted behind the tragus, one may assume the employee is receiving adequate protection. Conversely, a hearing protector that appears to be shallow may fit poorly with low attenuation. Although these assumptions may be an effective means of predicting attenuation of a hearing protector for most employees, an occasional employee may have low PAR values despite the HPD being deeply inserted or high PAR values despite a shallow fit. Therefore, the best approach to measuring an individual worker’s hearing protector attenuation is by quantitative fit testing. Future research to investigate whether visual judgment of HPD fit correlates to PAR could yield interesting results. Implications for Practice
Occupational health nurses may be responsible for many or all components of a company’s hearing conservation program and the addition of a FAES could be beneficial. Hearing protector fit testing could be of value in many circumstances, including new hire safety orientation to confirm the employee is choosing the correct hearing protector and wearing the HPD properly. Baseline
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tests gathered on all employees document how individual employees prefer to wear HPDs. Subsequent measurements enable nurses to compare before and after an intervention, quantifying the value of the training. Fit testing should be included when monitoring a standard threshold shift to document the use and fit of hearing protectors and training intervention if necessary. Given the limitations of time and resources in a typical occupational environment, it is advantageous to quickly identify an at-risk group. CONCLUSION In this study population, FAES testing documented most workers (70%) were achieving adequate attenuation when fitting earplugs of their choice. Fit testing can improve PAR50 values for those employees who have not achieved adequate attenuation. A FAES can assist occupational health nurses to identify workers at high risk for noise-induced hearing loss (low PAR50), teach proper fit and use of HPDs, and assist in hearing protector selection. It can be difficult to maintain behavior change. Therefore, workers identified as high risk (low baseline PAR50) may benefit from frequent monitoring to reinforce the importance of fitting HPDs as they were taught. Understanding why PAR50 values deteriorate and the possible impact of frequent ongoing interventions warrant further investigation. REFERENCES
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