Mark Da Silva reviews the literature to ascertain the elements a hearing conservation programme must contain in order to prevent noise induced hearing loss.
A hearing conservation programme (HCP) is a set of guidelines established to ensure employees do not suffer hearing loss from hazardous noise levels. For decades, regulations have mandated HCPs in workplaces to protect workers who are exposed to harmful noise from developing noise induced hearing loss, or NIHL.
The cause of NIHL is, by definition, overexposure to loud noise. The first record of the injurious effect of industrial noise on hearing was made by Fosbroke in 1830, when he described the hearing loss sustained by blacksmiths, as cited in Glorig.
Today, the condition is recognised as a pervasive and complex problem, and it has been suggested that current occupational noise is an issue due to the lack of consideration of noise elements at the design stage.
The factors leading to this phenomenon are an incompetency in acoustics and the limitations of time, money and technical resources. The result is the adoption of hearing protection devices (HPDs) as noise control – despite these being the lowest consideration in the hierarchy of controls.
Developed for the National Institue for Occupational Safety and Health (NIOSH) the components of HCP are:
• Noise exposure monitoring
• Engineering and administrative controls
• Audiometric evaluation
• Use of hearing protection devices
• Education and motivation
• Record keeping
• Programme evaluation
• Hearing loss prevention programme audit
The OSHA standard (2002) contains a series of programme requirements, which consist of engineering controls; monitoring carried out through noise level surveys; an audiometric testing programme; hearing protectors; training; and record keeping.
The most desirable engineering control method is the reduction of noise at the source. Melnick (1984) found that another effective method was to reduce the amount of noise transmitted through the air or building structures. Lusk, Kerr and Kauffman (1998) advocate purchasing or retrofitting quieter equipment, especially in the construction industry.
Through a study of HCPs in Tennessee’s metal fabrication industries, Mohammadi (2008) found that when the sound level is in excess of 90dB a programme of engineering controls should be developed to reduce the sound intensity. When this isn’t feasible, administrative controls should be used.
Mohammadi concluded that the engineering control programme may have lulled the company into a false sense of security, resulting in complacency. Prince et al’s (2004) study on how focus groups can contribute to the evaluation of HCP effectiveness mirrors these conclusions, finding that “Partial engineering controls may have led to complacency, decreased HPD use where still needed and thus more hearing loss than predicted.”
Leinster, Baum, Tong and Whitehead (1994) suggest that an effective HCP requires:
• Leadership from senior management
• Ability of middle management to enforce hearing conservation measures
• Specialist technical knowledge of noise and relevant legislation
The study points to the need for more education and motivation of senior managers as the priority in improving standards of hearing conservation and noise control.
Management commitment is often quoted as being critical to the success of any occupational health and safety (OHS) programme, and hearing conservation programmes are no different. Research has shown that managerial support, commitment and leadership are conducive to occupational safety outcomes and workforce compliance.
To ensure the HCP is effective, there is a general consensus that a dedicated person or focus group is needed to evaluate the effectiveness of the HCP, including the level of management commitment. Management commitment in the form of employing appropriately qualified OHS personnel has also been shown to improve compliance with HPD usage.
Although management commitment is generally considered important, Melamed’s study of an Israeli manufacturing plant showed that while 87.5% of participants acknowledged the existence of management pressure to use HPDs, only 42% of workers used them regularly. This may indicate that this organisational variable has a limited affect on influencing health behaviour.
Education and motivation
The use of hearing protectors with an appropriate education and instruction programme, along with regularly updated training has been advocated as part of the occupational noise management process for many years (AS 1269:1989; NIOSH: 1996; WHO: 2001).
Educating and motivating employees is essential, as there can be an acceptance that hearing loss is an inevitable occupational consequence. The belief that accidents and illnesses are natural consequences of work has been referred to as ‘fatalism’, which is a barrier to achieving safety in the workplace.
Mohammadi found that giving special training to management, supervisors and employees improved the effectiveness of an HCP. Education has been shown to have a lesser effect on compliance with HPD usage than enforcement; however, as one of many elements in an HCP it still provides a vital function in risk awareness.
NIOSH recommends that further research should be undertaken “to develop materials and programmes that more fully involve the worker in the process and give the worker ownership of the HLPP.” This is consistent with adult learning theory, which states that to be effective, learning should be problem based and should require learners to actively participate in generating solutions.
Royster and Royster define audiometric testing as the phase of an HCP that “not only identifies the employees with significant temporary or permanent hearing changes, but also provides the greatest opportunity to motivate employees to increase their level of protection on and off the job.”
Melnick states that audiometric test data is affected by calibration of audiometric equipment, background noise in the test environment and the characteristics of the person being tested, such as levels of motivation and intelligence.
Approximately 15% of people tested showed a retest variation of 10dB or more.
Through their study on focus groups, Prince et al found that employees were sensitive to the quality of their company’s testing programme and perceived that insufficiencies in testing procedures and scheduling were indicative of the company’s lack of commitment. As testing improved, employees were found to pay more attention to their test results and attributed a greater sense of commitment to their organisation.
Noise level surveys
Noise level surveys are an essential component of HCPs. Mohammadi recommends that “A complete noise survey should be conducted by a well trained person and either repeated annually, when a new machine is used, or when a manufacturing process is changed.”
Melnick reports that data from the noise level surveys must be analysed in order to provide an assessment of workers’ exposure.
Factors that need to be considered are:
• The overall magnitude of the noise
• The sound spectrum – distribution of sound energy by frequency
• The duration and temporal distribution of noise during a typical working day
• The expected cumulative noise exposure for a given duration of days, weeks or years
Accurate noise assessment is difficult and can vary throughout the working day. Noise exposure from dosimeters ranges from five to 20dB higher than those using stationary sound level monitors.
The hearing conservation programme team or project leader needs to be able to ascertain the effectiveness of interventions. To do this a baseline evaluation audit is needed and after this regular audits must be carried out, so that strengths can be identified and weaknesses addressed. As an indicator of the programme’s future level of success, NIOSH (1998) also recommends that programme evaluations should extend beyond audiometric testing, to be able to assess worker uptake and intent to follow the programme. The Australian Standard AS/NZS 1269 also recommends monitoring the condition of HPDs.
Regulatory bodies and experts in the field list HPDs, such as earmuffs and earplugs, as an integral part of HCPs. As mentioned earlier, engineering and administrative noise controls are the most desirable solutions – but unfortunately they are often unrealistic.
Lusk, Ronis and Hogan (1997) found this phenomenon to be especially prevalent in the construction industry, where noise exposure on worksites from tools and the environment changes rapidly, and workers have little control over their environment. This differs from the more static factory environment and makes noise exposure on construction sites less amenable to engineering controls than in a factory setting.
Lusk, Ronis and Hogan report through the work of Sataloff and Sataloff (1986) and Savel and Toothman (1987), that the use of HPDs such as earmuffs and earplugs is known to reduce noise exposure and prevent NIHL. The use of HPDs by workers is continually found to be low and inconsistent, however.
It is generally accepted in the literature that HPDs are not effective in reducing NIHL unless they are worn 100% of the time. Research has found that failure to use HPDs for only 30 minutes a day reduces their effectiveness by 50%, therefore, merely making HPDs available as part of an HCP does not necessarily translate into better workplace protection. HPDs are under the control of the individual and as such require continuous long term action.
With HPD compliance consistently being reported as low, researches have attempted to identify the behavioural predictors of HPD use in order to develop training interventions to increase their use.
Through questionnaires, Arezes and Miguel, Melamed et al and Lusk et al, all found the cognitive-perceptual factors of the health promotion model (HPM) were major predictors in determining HPD use, specifically low self-efficacy, which is an individual’s belief in their capability to successfully perform a particular task.
Lusk Ronis and Kerr, state that “NIHL has not been solved by mandatory HCPs, in part because workers’ perceptions have not been addressed.” Arezes and Miguel recommend that individual risk perception should be considered in the design and implementation of training programmes. In concurrence, Neitzel and Seixas agree that workers’ awareness of the risks of noise and other exposures is low and that health and safety training is often lacking.
The use of educational interventions using the HPM as a framework has delivered some positive and some mixed results in improving HPD use. Lusk et al (1999) tested the effectiveness of a theory based intervention to increase HPD use among 652 Midwestern construction workers and 185 plumber and pipefitter trainers. The workers were asked how often they used HPDs and then were given a training programme consisting of a 20 minute video, plus written handouts and samples of HPDs with guided assistance in fitting.
Although the post-intervention questionnaire taken ten to 12 months later showed that workers’ self-reported use of HPD only ranged from 34 to 64% of the time, it was still significantly higher than the pre-intervention rates.
Neitzel et al also developed a training intervention programme to increase the use of HPDs among construction workers, using the cognitive perceptual predictors of the HPM as a basis. One hour training sessions were delivered by live instructors using visual materials in the form of 35 flip chart pages, with each covering a different concept.
The effects were analysed for 23 workers and it was found that when using an activity card measure there was a statistically significant increase in the use of HPD – with usage doubling post-intervention. Workers’ current and intended future use of HPDs did not significantly change when a post-intervention perception survey was conducted.
Through their study of Israeli manufacturing workers, Melamed et al (1996) uncovered the major barriers to HPD use to be physical discomfort resulting from pressure on the outer ear, irritation of the ear canal lining and perspiration, and communication disturbances.
Lusk, Ronis and Kerr identified the workers’ perception of HPDs as unsafe because they block out danger signals and Melnick stated that “Optimum performance depends on the proper application and fit of the protector.” All these factors need to be taken into consideration when designing the HPD component of an HCP.
Interestingly, there is only one longitudinal study in the literature that uses audiometric data to determine the effectiveness of an HCP. This study was undertaken by Dr Sydney Pell across a five year period, starting in 1966 among 2,770 male employees in seven plants of one company.
A formal HCP was established in 1954 consisting of three elements: noise abatement, periodic audiometric testing and HPDs. Audiometric data was compared from persons who worked in noise levels exceeding 90dBA and those who worked in areas where the noise level was below 90dBA. An analysis of the data across the five year period showed no difference in hearing threshold changes for the two groups. This study indicated that HCPs comprising the elements of ear protection and periodic audiometric testing are effective in preventing NIHL.
HCPs in industry are rarely comprehensive in their elements or assessed for their effectiveness. There is far too much reliance on HPDs – despite their well known deficiencies in acceptance and time of use. Given this is common knowledge it seems irresponsible for management to rely on an HPD programme, or for regulators to accept such programmes as being effective for hearing conservation.
The situation remains that hearing loss is one of the most common OHS issues in the world today. A large proportion of workers are still exposed to noise levels and the complementary substances and vibrations that lead to NIHL. With management commitment and a comprehensive HCP, however, it is possible to reduce both the numbers of workers exposed and the level of the exposure.
Simply put – an effective HCP will benefit each employee’s quality of life. From this, the company benefits directly from the reduced financial burden of hearing loss, and indirectly benefits from staff being more comfortable, able to communicate more easily and with improved safety awareness.
Published: 19th Dec 2012 in Health and Safety Middle East