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Khoza-Shangase K, editor. Preventive Audiology: An African perspective [Internet]. Cape Town: AOSIS; 2022. doi: 10.4102/aosis.2022.BK209.011
Noise-induced hearing loss (NIHL) is 100% preventable through HCPs. The goal of an HCP is to eliminate the presence of noise as a risk factor, thereby preventing the development of NIHL in people exposed to hazardous noise levels. The principles underpinning HCPs are aligned with health promotion and disease prevention interventions. Therefore, this chapter seeks to demonstrate how disease prevention interventions complement the HCP pillars and the hierarchy of noise control. Furthermore, this chapter discusses the contextual factors contributing to the current status of the implemented HCPs. This is followed by a summary of recent advances in the prevention of NIHL. Lastly, the chapter offers recommendations on the management of NIHL within the African context.
Noise, an unwanted sound (Basner et al. 2014), is a ubiquitous environmental hazard of the modern world (Khan et al. 2010). It emanates from various recreational activities such as concerts, sporting events, lifestyle activities and places of worship. Environmental sources include traffic and occupational activities such as construction, mining and manufacturing (Lusk et al. 2016; Oguntunde et al. 2019). According to Jamir, Nongkynrih and Gupta (2014), noise occurs in two major settings, namely, environmental noise and occupational noise. Environmental noise emanates from all sources, excluding noise produced in the industrial workplace (Jamir et al. 2014). The most common sources of environmental noise include traffic noise, loudspeakers, recreational activities and fireworks, to name a few. On the contrary, occupational noise emanating from work-related processes during the execution or performance of one’s occupation.
Prolonged exposure to noise is associated with a range of adverse effects including, but not limited to, annoyance, sleep disturbances, impaired cognitive performance and cardiovascular diseases such as hypertension (Dale et al. 2015). Noise-induced hearing loss is also a common disability in noisy occupations (Ding, Yan & Liu 2019). Lusk et al. (2016) argued that the impact extends beyond annoyance. It is a public health hazard with significant negative effects on the health outcomes and economic outcomes of individuals exposed to excessive noise. As such, hazardous noise exposure is ranked a major public health agenda, particularly in LMICs (Yongbing & Martin 2013).
The effects of noise can be grouped into direct/auditory or indirect/non-auditory impacts. The auditory effects (direct impact of exposure) include tinnitus (Delecrode et al. 2012), temporary and permanent threshold shift, and hearing loss (Ryan et al. 2016). Non-auditory effects (resulting from the indirect impact of exposure) include annoyance, masking of warning signals, communication difficulties and increased blood pressure (Basner et al. 2014; Park et al. 2017).
The health effects associated with hazardous noise exposure cannot be overemphasised. As such, Fink (2017) maintained that the safe noise level for the prevention of hearing loss is 70-decibel time-weighted average for a 24-h period, despite the National Institute for Occupational Safety and Health (NIOSH) recommending 85 A-weighted decibels as the minimum exposure level, beyond which the employer is mandated to implement an HCP (Fink 2017).
Hazardous noise exposure can potentially cause NIHL, which is a progressive sensorineural hearing impairment, because of prolonged exposure to excessive noise (Ding et al. 2019). Globally, NIHL is the second most common cause of acquired hearing loss, after presbyacusis (Mostaghaci et al. 2013). In 2017, WHO (2017) reported that globally, 360 million people have severe hearing loss, with close to 1.1 billion young people (aged between 12 and 35 years) having a propensity to develop a hearing loss, a portion of which is because of excessive noise exposure (Chadha & Cieza 2017; Ding et al. 2019).
Noise-induced hearing loss is not life-threatening, even though it is associated with cardiovascular disease. However, the effects of poorly managed hearing loss impact the financial health and well-being of the affected individual, their family, colleagues, employer and the State (Moroe 2018). Fortunately, NIHL is 100% preventable through effectively managed and well-executed HCPs (Le et al. 2017). However, once present, it is irreparable (Arenas & Suter 2014; Kardous 2016). Moroe (2020a) described an HCP as a theory and evidence-based intervention built from seven non-linear but interacting pillars that act both independently and interdependently. These pillars are active in that their effectiveness is influenced by the engagement of different stakeholders during the formulation, implementation and evaluation of HCPs. Furthermore, the pillars are fragile and are embedded in multiple social systems that may include personal, interpersonal and environmental factors that may be outside of intervention efforts. Lastly, HCPs are open systems that feedback on themselves (Moroe 2018).
A comprehensive and effective HCP comprises seven pillars, namely, periodic noise exposure monitoring, engineering controls, administrative controls, personal hearing protection, audiometric evaluations, employee or management education and training and record-keeping (Hong et al. 2013). The goal of an HCP is to eliminate the presence of noise as a risk factor, thereby preventing the development of NIHL in people exposed to hazardous noise. Therefore, an HCP is designed and implemented according to the hierarchy of noise control which, in turn, is aligned with health promotion and disease prevention levels and strategies as depicted in Figure 11.1.
Diagram depicting the synergy of the components of noise-induced hearing loss prevention.
Health promotion is concerned with empowering people to exercise control over their health outcomes (Olukemi 2019). Prevention, on the contrary, is concerned with ‘measures to not only prevent the occurrence of disease but to also arrest progression and reduce consequences’ (Duplaga et al. 2016:478). The need for prevention cannot be overemphasised. Prevention is stratified into five levels, given as follows:
Correspondingly, preventive occupational audiology in the form of an HCP encompasses these five levels.
In discussing prevention and HCPs in this chapter, it should be noted that the pillars of an HCP will not be discussed in a specific pattern. For instance, applying administrative controls such as rotating workers from a noisy area to a quieter area at the secondary level is aimed at delaying the development of ONIHL; at the tertiary level, the aim is to minimise the progression and the impact of excessive noise on an employee who has already suffered hearing loss. Additionally, the interventions that will be presented in this chapter are more in line with occupational noise exposure as these industries have legislations in place which govern their practises and response to health and safety in the workplace. Education, however, is applicable as a pillar that cuts across all levels of prevention and hierarchies of controls, and this will be illustrated in the discussion.
Primordial prevention is concerned with interventions aimed at preventing the penetration of risk factors into the population (Pandve 2014a). This involves the implementation of interventions and education to avert health risk factors through individual and mass education on environmental, economic, social and behavioural attributes and cultural patterns of living. Therefore, primordial prevention is concerned with broader health determinants beyond personal exposure to risk, which is the focus of primary prevention (Pandve 2014a).
Concerning environmental and occupational noise, primordial prevention focuses on education, which is one of the pillars of an HCP, to conscientise people about noise, both the exposed and the unexposed. Hearing loss is an invisible disability (Tye-Murray 2009), and its effects are delayed and only realised when the damage has already occurred. Therefore, educating the general population on the effects of noise will potentially contribute towards health promotion that encourages people to take control of their ear-and-hearing health care actively. According to Victor Hugo, as cited by Elahi (2006), ‘No cause can succeed without first making education its ally’. At the individual level, education can focus, for instance, on the impact of environmental noise, particularly on the use of personal listening devices and the impact of traffic noise on hearing. There is a growing concern about the increased exposure to recreational noise in settings such as nightclubs, bars, cinemas, concerts, live sporting events, fitness classes and even churches (WHO 2015). There is an increase in the use of recreational devices such as personal music players and video game consoles that emit sounds commonly operated at unsafe volumes (WHO 2015). Keppler, Dhooge and Vinck (2015) argued that the maximum equivalent continuous output levels of personal music players (PMPs) range between 97 dBA and 103 dBA for earbuds (insert earphones) and supra-aural headphones, respectively, while sound intensity levels at concerts and clubs can amount to 105 dBA and 112 dBA, respectively. These concerns are also echoed by Tung and Chao (2013), who lamented that in modern living environments, in addition to the general use of personal listening devices and going to clubs and concerts, many teenagers have developed a habit of using personal listening devices while reading, taking public transport or while sleeping.
Traffic noise is the biggest contributor to environmental noise. Reportedly, vehicular traffic contributes to approximately 55% of total urban noise (Vijay et al. 2015). Traffic noise adversely affects people exposed, with the biggest impact being on drivers. Interestingly, drivers are exposed to both environmental and occupational noise in that vehicles are a source of traffic/environmental noise and the source of occupational noise for them. Consequently, drivers are exposed to many physical and physiological stresses such as traffic noise, vibration, temperature fluctuations, ergonomic problems and safety risks such as accidents (Ansari et al. 2016), over and above communication difficulties. Kirchner et al. (2012) argued that the inability to hear poses a safety concern, as drivers’ hearing may be compromised and they may miss warning signals such as sirens, thereby increasing the risk of accidents. Therefore, education can go a long way in raising awareness among drivers and those affected by environmental noise about the dangers of excessive noise exposure. Furthermore, education can promote early detection of hearing loss where drivers can routinely undergo hearing assessments to monitor their hearing. Lastly, over and above the effects of environmental noise, people exposed to high levels of occupational noise face two big threats: the loss of employment and exposure to excessive noise for many hours each day over several years.
Education can raise awareness on risk factors associated with hazardous noise exposure at a mass or population level. These risk factors are grouped into non-modifiable and modifiable factors. Non-modifiable factors include age (Kerketta, Gartia & Bagh 2012), race (Pyykkö et al. 2007) and sex (Pratt et al. 2009), while modifiable factors include smoking (Fabry et al. 2010), ototoxic agents (Kirchner et al. 2012) and ototoxic drugs used to treat diseases like HIV, AIDS, TB and cancer (Khoza-Shangase 2020a). Furthermore, education at this level can address auditory and non-auditory effects of hearing loss (Delecrode et al. 2012). Auditory effects are caused by the direct impact of noise, and these may include temporary and permanent threshold shifts resulting in hearing loss (Hind et al. 2011; Pienkowski 2017; Ryan et al. 2016), while non-auditory effects result from indirect impact of exposure to excessive noise. These effects may manifest through annoyance, masking of warning signals, communication difficulties and increased blood pressure (Basner et al. 2014; Omer Ahmed 2012; Park et al. 2017).
It is important to raise awareness about the risk factors and effects of excessive exposure as the general population may not be aware of their susceptibility or the relationship between noise exposure and some medical conditions with which they may present. Education can promote collaboration between the general population and audiologists. This may create an environment where people can be made aware of the need to attend hearing evaluations and promote World Hearing Days as well as Deafness Awareness Weeks. A key benefit would be to promote and highlight the role of audiologists in the preservation of hearing across one’s lifespan. Education can also provide the population with communication strategies and address stigma associated with hearing loss. Occupationally, audiologists can be involved in teaching and training workers to adhere to the pillars of an HCP. More specifically, education can focus on the use of hearing protection devices (HPDs) when in noisy areas, compliance to audiometry screening and assessments, medical surveillance, monitoring changes to hearing patterns and reporting of comorbidities that may render a worker susceptible to hearing loss and/or more significant hearing loss. Last, but not least, education at this prevention level can serve to sensitise the general population and individuals exposed to occupational and environmental noise to their rights. This encourages policymakers to develop regulations and permissible noise levels that are environmentally and occupationally friendly. Therefore, if the goal of primordial prevention is to prevent or stop the appearance of risk factors at a population level (Pandve 2014a), education needs to be prioritised at all levels of prevention.
Primary prevention is concerned with precluding the onset of a disease or injury through risk reduction by either modifying exposures that potentially cause the disease or the enhancement of resistance to a disease agent (Duplaga et al. 2016; Pandve 2014a). Therefore, in preventive occupational audiology, primary prevention entails implementing comprehensive evidence and theory-based HCPs to reduce the risk of exposure in industries prone to excessive noise production such as mining, construction and the military (Feder et al. 2017).
According to the hierarchy of noise control, elimination is the primary preventive intervention in precluding the onset of ONIHL. However, noise is ubiquitous in these industries because of the machinery used. Chaudhary (2017) argued that noisy machinery is often a necessary component of certain work processes, and while machines can be made safer, they cannot be eliminated. Where elimination is not feasible, noisy machinery can be substituted or replaced. Substitution is the second most effective intervention for controlling risk factors by swapping one risk for another. Noisy machinery can be replaced with less noisy equipment, a strategy known as ‘buying quiet’. Buying quiet is an initiative aimed at buying quieter equipment as a measure to control noise at the source (Gumede et al. 2014). This is a long-term investment and is potentially arduous and costly (Bruce 2007; Suter 2012), although research shows that the benefits may far outweigh the perceived cost. As far as effective intervention for controlling risk factors is concerned, the next level of intervention is isolation. Isolation entails separating the risk factor in time or space from the people at risk through containment or enclosure, i.e., keeping the hazard ‘in’ and the worker ‘out’ or vice versa (Chaudhary 2017).
The most effective isolation strategy is mechanisation. This is a process that involves the substitution of manual tasks with machinery, with the machines becoming the interface between humans and the task (Gumede 2018). Gumede (2018) asserted that mechanisation promotes and has the potential to improve competitiveness, health and safety, profitability and improvements that have varying impacts on different stakeholders. This is particularly true for workers who may lose their jobs to mechanisation. As such, Gumede (2018) cautioned that while in the medium to long term, mechanisation will yield benefits, it potentially has a negative impact on the labour complement and on the communities in which these companies operate. In instances where the aforementioned primary prevention interventions – elimination, substitution and isolation – are not feasible, the next point of call is engineering controls.
Engineering controls are defined as ‘a physical modification made to the source of noise or the permanent physical environment around the source of the noise’ (The Georgia Tech 2019–2020). According to Bruce (2007, p. 33), engineering controls guarantee ‘permanence, effectiveness with or without worker/supervisor compliance, less absenteeism, easier communication, lower worker compensation costs, and reduced legal costs’. Implementing engineering controls involves four principles (The Georgia Tech 2019–2020):
The above-mentioned interventions are all aimed at eliminating the onset of ONIHL.
Secondary prevention is concerned with controlling or managing the disease before it manifests clinically (Duplaga et al. 2016). This involves implementing interventions that identify and treat pre-clinical pathological changes to manage disease progression (Pandve 2014a). In practice, secondary prevention promotes early detection and intervention through timely screening to detect asymptomatic disease with the aim of improving health outcomes. At this stage, the aim is to prevent a rapid progression of the disease in spite of exposure to the risk factors. In preventive occupational audiology, secondary prevention entails monitoring for early detection and treatment of ONIHL. This requires the implementation of administrative controls, audiometric surveillance, education, the use of PPE and good record-keeping.
According to the hierarchy of noise controls, administrative controls are the next option when elimination, substitution and engineering controls are not feasible. Administrative controls are interventions implemented to reduce risk by minimising the time of exposure to noise (Bauer & Babich 2006). This involves rotating workers from noisy to quieter areas. While this description of administrative controls is too simplistic, Bauer and Babich (2006) argued that administrative controls are not readily implemented because of a lack of trained workers for efficient job rotation, union contract issues and safety concerns. If applied appropriately, administrative controls are an effective tool to change work practices, management policies or worker behaviour (Verbeek et al. 2014), to promote early detection and intervention by ensuring timeous screening for the early development of hearing loss in workers exposed to hazardous noise. Early detection of ONIHL is carried out through audiometry surveillance, which is essentially workplace hearing tests, using pure-tone audiometry as the gold standard (HearSafe Solutions 2018).
Audiometric surveillance is a legal requirement and is legislated as part of compliance in the South African Occupational Health and Safety Act 85 of 1993). The Occupational Safety and Health Act requires that all workers exposed to noise that is more than 85 dBA in intensity be screened for ONIHL (Mostaghaci et al. 2013). Audiometric testing can reveal hearing loss at an early stage (Leshchinsky 2018). Additionally, audiometry creates an opportunity to educate employees on the latent effects of noise exposure and promotes awareness of hazardous noise present in everyday activities (Leshchinsky 2018). This practice promotes the routine use of HPDs in everyday situations (Schulz 2014). Audiometry, including extended high-frequency audiometry and otoacoustic emissions as tools for early detection and diagnosis, helps to identify changes in hearing before clinically significant hearing loss develops (Mostaghaci et al. 2013).
The effectiveness of audiometric surveillance as a preventive strategy lies in monitoring the standard threshold shift (STS) – a 10 dB or more change in the average hearing threshold at 2 000 Hz, 3 000 Hz and 4 000 Hz (Mostaghaci et al. 2013). In the presence of an audiogram depicting hearing within normal limits, a positive STS is critical in identifying workers who may be susceptible to the hazardous effects of noise (Ross et al. 2010). Therefore, it is imperative that a baseline audiogram, which is the first audiogram performed before an individual commences employment or within 30 days of commencement of employment, is conducted to serve as a reference baseline for all subsequent periodic audiometry evaluations to monitor improvement or STS (McDaniel et al. 2013).
Audiometric surveillance as a pillar cuts across two prevention levels – secondary and tertiary prevention levels. As a secondary prevention tool, surveillance is concerned with monitoring the STS through periodic hearing evaluation. Internationally, the Occupational Safety and Health Administration (OSHA) and the NIOSH legislations mandate that employees exposed to occupational noise should undergo periodic hearing assessments to monitor and establish that no shift has occurred in the pure-tone threshold. OSHA defines an STS as an average increase of 10 dB or more at 2 KHz, 3 KHz and 4 KHz in one or both ears, while NIOSH defines it as an average increase of 15 dB or more at 500 Hz, 1 KHz, 2 KHz, 3 KHz, 4 KHz or 6 KHz in one or both ears (Brungart et al. 2019). In South Africa, STS is calculated at 2, 3 and 4 KHz (Musiba 2020). Conducting audiometric surveillance is undertaken to identify a permanent threshold shift in the STS. A permanent shift is suggestive of a potential hearing loss, depending on the degree of the shift from the baseline audiogram. As a secondary preventive measure, monitoring the STS is a way of early identification where the individual’s STS is tracked for any sign of a shift. When a permanent shift is noted, EI strategies should be implemented. These can be in the form of administrative controls, as discussed earlier, or the provision and use of HPDs, education and awareness training. Within the South African context, the legislation mandates that an STS of > 2 dB but < 5 dB is prioritised to halt the progression of STS from reaching a 10 dB shift across all the relevant frequencies. Therefore, monitoring the STS becomes crucial as preventive strategies can be subsequently implemented.
In the event that a permanent STS reaches a 10 dB shift, the second arm of audiometric surveillance is activated: tertiary prevention. Tertiary prevention will be discussed in detail later in this chapter. In relation to tertiary prevention, audiometric surveillance is conducted to quantify hearing loss for compensation purposes by calculating the percentage of loss of hearing (PLH) (Bronkhorst & Shutte 2013). To calculate the PLH, the individual’s hearing thresholds and a baseline audiogram are used as a reference value against which the hearing loss is measured (Bronkhorst & Shutte 2013). The PLH is calculated at 500 Hz, 1 KHz, 2 KHz, 3 KHz and 4 KHz per ear according to the quality of hearing in each ear. After calculating the PLH, the test with poorer hearing is said to be the baseline audiogram and will be used as the reference point for future audiograms and to monitor the hearing threshold for monitoring and compensation purposes (Bronkhorst & Shutte 2013). To determine a PLH shift, the baseline PLH is subtracted from the PLH of routine screening audiometry. If a difference of a PLH shift of > 10% is suspected, an audiologist must carry out diagnostic baseline audiometric testing. Where a PLH shift of > 10% is confirmed, the case is referred to the occupational medical practitioner or otorhinolaryngologist to establish the definitive cause of the hearing loss (Bronkhorst & Shutte 2013). If the hearing loss is confirmed to be work-related, the case should be reported to the Compensation Commissioner or the applicable insurance fund for compensation purposes (Bronkhorst & Shutte 2013). This stage is considered the tertiary preventive stage as hearing loss already exists. At this level, the aim is to minimise the impact of the hearing loss on the affected individual. This is accomplished through aural rehabilitation (AR), which will be discussed in detail later in this chapter. From this discussion, the role of audiometry surveillance as a preventive tool cannot be overemphasised. If implemented carefully and routinely, this pillar can effectively be used as an early identification tool and an EI tool if a hearing loss is suspected, and where a hearing loss is confirmed, it can be successfully used to facilitate compensation and AR.
Hearing protection devices are the least effective component of the hierarchy of controls. However, evidence suggests that HPDs are routinely used to reduce excessive noise exposure and lower the incidence of ONIHL (Brown et al. 2015). Globally, evidence indicates a heavy leaning on HPDs in the workplace (Bruce 2007; Bruce & Wood 2003; Hong et al. 2013; Ntlhakana, Kanji & Khoza-Shangase 2015; Suter 2012). Arguments have been put forward highlighting the challenges with using HPDs. These concerns include reduced audibility and distorted acoustic information, as well as discomfort when worn for longer periods (Brown et al. 2015; Ntlhakana et al. 2015). Beamer, McCleery and Hayden (2016) submitted that HPDs can be effective when used in conjunction with all the other pillars of an HCP. The author of this chapter argues that education can lay a firm foundation for the use of HPDs. If employees are informed about the benefits of using PPE, and if administrative and engineering controls are well implemented, the risks can be significantly reduced. A comprehensive record-keeping system with buy-in from all stakeholders will ensure that employees’ hearing health can be monitored to facilitate timely and early identification and intervention.
Tertiary prevention aims to decrease the adverse effects of the disease and optimise the QoL of the affected individual (Duplaga et al. 2016; Pandve 2014b). At this level of prevention, the focus is on rehabilitative interventions that may include vocational rehabilitation to retain workers after injury. Related to preventive audiology, intervention will focus on AR. Aural rehabilitation is defined as a range of services aimed at reducing the adverse effects that a hearing loss has on the individual’s participation and enjoyment of their daily activities, thus improving their QoL. It is a process where individuals who have sustained a hearing loss are provided with intervention and training to minimise the impact of the hearing loss (Brodie, Smith & Ray 2018).
Aural rehabilitation seeks to help workers get used to their hearing loss, explore appropriate hearing amplification devices and improve conversation and communication in general (Brodie et al. 2018). Therefore, AR incorporates counselling, sensory management, as well as auditory training and instruction, with the goal of minimising the negative psychosocial effects of hearing loss, improving self-management and increasing the efficacy of assistive technology (Coco, Ingram & Marrone 2019). Through the education pillar, counselling can focus on three aspects – informational counselling, personal adjustment counselling and support groups. Informational counselling focuses on providing education to the person with a hearing loss on available treatment interventions. Personal adjustment counselling addresses the person’s psychological, social and emotional acceptance of hearing loss and occupational prospects. Where possible, community groups can be established to offer ongoing support (Sweetow 2018).
Aural rehabilitation can also focus on the use of assistive listening devices, hearing aids or cochlear implants, as well as on environmental modification and vocational counselling to identify and implement specific accommodations or modifications for workplace settings (Sweetow 2018). In an occupational setting, specifically, AR entails implementing administrative controls, particularly rotating workers from a noisy area to a quieter area. Additionally, the use of HPDs will have to be monitored. Workers fitted with hearing aids will need to be educated on the possibility of their hearing becoming progressively worse if continued exposure to excessive noise occurs. Most importantly, these workers need to be monitored with good record-keeping being critical in the tracking of workers’ progress. Tertiary prevention is concerned with minimising the impact of hearing loss and improving the quality of the worker’s life. It, therefore, follows that audiologists have a critical role to play in providing AR services that are responsive to the needs of workers who have sustained hearing loss on duty.
Quaternary prevention entails taking action to identify workers at risk of over-medicalisation and protecting them from new, untested medical remedies while recommending interventions that are ethically sound (Pandve 2014b). Khoza-Shangase (2020b) asserted that NIHL is influenced by health conditions and illnesses such as HIV, AIDS and TB. Other authors have investigated the link between NIHL and blood pressure and hypertension (Kuang, Yu & Tu 2019; Liu et al. 2016; Wang et al. 2018), cardiovascular disease (Ding et al. 2019; Li et al. 2019; Xua & Francis 2019) and diabetes (Ashkezari et al. 2018; Soares et al. 2018; Yadav & Yadav 2018). Furthermore, individuals without a history of hearing loss may acquire hearing loss because of the ototoxic nature of the drug regimen used to treat HIV, AIDS and TB (Khoza-Shangase 2020a). Therefore, it is important for audiologists to keep a detailed record of the risk factors, medical history, and hearing status of individuals exposed to excessive noise.
A paucity of evidence exists in record-keeping in the mining industry. Record-keeping is critical in the workplace as it promotes and maintains accountability, commitment and consistency (Byrne 2005; Khoza-Shangase et al. 2020). Considering that ONIHL develops gradually and over time, the importance of keeping accurate records of each employee is critical and cannot be overemphasised. Records can be used to determine an employee’s exposure to noise, thereby allowing for effective and accurate programme evaluation, which is important for programme sustainability. Accurate record-keeping allows for easy identification of challenges and therefore lays the ground for relevant changes (Byrne 2005). Proper record-keeping facilitates the implementation of effective and appropriate individual conservation programmes, where employees’ multiplicative factors such as concomitant exposure to other toxins – and co-occurrence of TB and HIV with ototoxicity – are considered in employees’ HCP plans (Khoza-Shangase 2020b). Additionally, proper record-keeping facilitates accurate comparative analysis of employee thresholds for compensation purposes when employees are eligible for compensation. Lastly, responsible sound record-keeping identifies responsive research agendas to inform relevant evidence-based information to be accessed by management in order to enhance the mines’ HCPs (Byrne 2005; Ntlhakana et al. 2022).
In South Africa, HCPs were formally implemented over two decades ago, after the declaration of the 1996 Mine Health and Safety Act (President’s Office 1996). Thereafter in 2003, the South African Mine Health and Safety Council (MHSC) comprising representatives from the State, labour and employers, implemented the 2003 MHSC milestones, which were aimed at targeting the elimination of ONIHL in this sector. These milestones were two-pronged and targeted two imperatives. The first milestone aimed to ensure that by December 2008, there would be no deterioration in hearing greater than 10% in occupationally exposed individuals. The second milestone stated that, by December 2013, the total noise emanating from the installed equipment would not exceed a sound pressure level of 110 dB (A) (Edwards & Kritzinger 2012). In 2013, the milestones were evaluated and refined to make them more specific and measurable. Subsequently, in 2014, revised milestones were promulgated. The first milestone stated that by December 2016, no employee’s standard thresholds will exceed 25 dB from the baseline when averaged over 2000 Hz, 3000 Hz and 4000 Hz in one or both ears. The second milestone focused on machinery, the source of noise, and stated that by December 2024, the amount of noise produced by the equipment must not exceed a sound pressure level of 107 dB (A) (MHSC 2014).
The aforementioned 2003 MHSC milestones were not achieved, hence the revised 2014 milestones that are still in effect. Looking at the 2003 milestones, arguably, preventive occupational audiology has not been completely successful in the South African mining sector. The author of this chapter submits that preventive occupational audiology has been unsuccessful because of:
Firstly, arguably, the manner in which the milestones are framed significantly reflects some weaknesses. These weaknesses could potentially explain why HCPs have failed in the mining industry. A close look at the milestones reveals that the targets focused on only two aspects of hearing conservation: hearing deterioration (audiometry surveillance/administrative controls) and noise reduction at source (engineering controls). Undoubtedly, these two pillars are critical and integral in controlling hazardous noise in the workplace. However, they address matters at the managerial level and exclude key stakeholders such as mineworkers who are directly affected by hazardous noise. Arguably, education of and buy-in from the mineworkers serves as a preventive measure which is a key to the success of any intervention involving the miners. Therefore, there ought to be careful deliberation around the role of mineworkers during the setting of targets, if HCPs are to succeed.
Secondly, the manner in which the targets are sequenced raises concerns – hearing deterioration before the noise source is misaligned with the goal. Reducing noise at the source and engineering controls should precede reducing the deterioration of hearing loss, which is an administrative control. Noise is the risk factor and therefore falls under primary prevention. Currently, these milestones seem to promote secondary prevention over primary prevention, thereby undermining the hierarchy of controls in the prevention of ONIHL.
Thirdly, looking at the time frames for achieving these milestones, it is anticipated that reducing exposure to the individual will be achieved prior to reducing noise at the source. In reality, reducing noise at the source should be prioritised over exposure to the individuals, because if noise is controlled at the source, exposure to the individual is greatly reduced.
A perusal of documents on the role of occupational audiologists in South Africa revealed a role limited to audiometric surveillance and compensation of hearing loss (De Koker n.d.; De W Oosthuizen 2006). Furthermore, this role can be undertaken by non-audiologists, such as audiometricians. This undermines the importance of preventive occupational audiology as occupational audiologists undergo specialised and specific training on preventive occupational audiology. A study conducted by Moroe and Khoza-Shangase (2018) identified the following factors as contributing to the limited role of occupational audiologists in preventive occupational audiology:
South Africa is an LMIC grappling with a quadruple threat of burden of diseases, fewer job opportunities, political unrest and economic instability (Leboea 2017). Particularly in the mining sector, the high incidence of this challenge continues to present barriers to the management of ONIHL (Strauss et al. 2012). However, this challenge is not prioritised by the SADoH or the mining sector, despite its devastating effects. Arguably, ONIHL is overshadowed by the high prevalence of diseases such as HIV, AIDS and TB prevalent in the mining sector (Basu et al. 2009; Khoza-Shangase 2020a; Stuckler et al. 2011, 2013). Additionally, ONIHL is an invisible disease that develops gradually over a period of years (Patel et al. 2001; Tye-Murray 2009). Compared with HIV and AIDS, ONIHL is not life-threatening; however, its impact on the economy is devastating.
According to the World Bank, in South Africa alone, the prevalence of TB in the mining sector is estimated to be between 2500 and 3000 cases per 100,000 individuals, which is 10 times the WHO threshold for health emergencies and three times the incidence rate of the general population (Cullinan 2018). Furthermore, miners are three to four times more likely to be infected with HIV and AIDS (Stuckler et al. 2011). Bhunu, Mushayabasa and Smith (2012) asserted that in the presence of an HIV infection, the probability of acquiring TB increases. Therefore, the co-infection of HIV, AIDS and TB implies that affected mineworkers may be on treatment for HIV and AIDS and/or TB (Khoza-Shangase 2010, 2020a). Workers, who are on treatment for HIV, AIDS or TB, if exposed to prolonged excessive noise, are at significant risk of greater clinical hearing loss because of the synergistic effects of noise and ototoxic medications. This may increase the prevalence, onset and progression, nature, as well as the degree and configuration of ONIHL in the affected population (Khoza-Shangase 2010). Recently, Khoza-Shangase (2020a) provided evidence confirming that miners previously treated for TB have poorer high-frequency hearing thresholds compared with workers without a history of TB. The synergistic effects of noise and ototoxic medications highlight the importance of strategic HCPs that consider ototoxicity (Khoza-Shangase 2020b). This requires monitoring through proper record-keeping and possibly the use of otoprotective/chemo-protective agents to promote hearing conservation in at-risk workers infected with HIV, AIDS and TB.
Hearing conservation programmes implemented in the South African mining industry are currently not achieving the desired results. Over and above the aforementioned reasons, HCPs are complex interventions (Moroe 2018). This complexity can be attributed to the fragile nature of the pillars largely influenced by the active engagement and feedback from various stakeholders involved in their formulation and implementation. Furthermore, the fact that HCPs are ‘built from multiple interacting components, which act both independently and interdependently’ from each other also attests to their complex nature (Shiell et al. 2008). In summary, the complexity of HCPs can be summarised as follows (Moroe 2018):
Hearing conservation programmes are:
South Africa, although an LMIC faced with all the challenges associated with LMICs, has sound and evidence-based HCPs, which are very capable of eradicating NIHL caused by both environmental and occupational sources of noise. Furthermore, as demonstrated in the preceding discussion, the HCPs implemented in South Africa are in line with health promotion and disease prevention and take into account the hierarchy of controls in preventing NIHL. These HCPs would benefit from recent advances in the early detection and management of NIHL.
We live in an era of unprecedented technological advancement that impacts every aspect of our lives, from the way we shop and travel to the way we communicate with friends and family. These trends are resulting in new methods and tools that change the way safety professionals and industrial hygienists prevent hearing loss. (Brauch 2017, p. 1)
With regard to prevention and early detection of ONIHL, advances have led to the use of smartphones and low-cost sensors, and this has subsequently prompted government agencies to promote and implement HCPs to facilitate worker safety and optimal health outcomes (Brauch 2017).
To explore recent advances in the prevention of occupational noise, Moroe and Khoza-Shangase (2020) conducted a systematic review of literature in the last 10 years. The results of the review yielded the following advances: use of metrics, pharmacological interventions and hair cell regeneration, artificial neural networks, audiology assessment measures, noise monitoring advances and conceptual approaches to HCPs. These approaches are presented in Table 11.1 in relation to preventive levels, the hierarchy of noise control and the HCPs. The following chapter, Chapter 12, plunges deeper into these advances, contextualising them to the African context for the achievement of zero ear and hearing harm, specifically within the mining industry.
Summary of recent advances in the prevention of noise-induced hearing loss.
The analysis of the advances in intervention listed in Table 11.1 shows that all the prevention levels, the hierarchy of controls and the pillars of the HCPs are represented. This is encouraging in that it suggests that innovation and new advances are aligned with health promotion and NIHL prevention. There seems to be a preference for primary and secondary prevention in these advances. This is not surprising as the hierarchy of controls and the pillars are concentrated around the primary and secondary prevention levels. This also suggests that there is a focus on prioritising the reduction of the impact and progression of hearing loss. Arguably, if the concerns around the implementation of HCPs in South Africa were to be addressed, the goal of health promotion and prevention for measures to not only prevent the occurrence of disease, such as risk factor reduction, but also to arrest its progression and reduce its consequences once established may be achieved.
There is no disputing that prevention is better than cure, and timely intervention can be less costly and more effective than providing services later in life (Gardner 2019). Environmental and occupational noise exposures have a negative effect on the community at large, as well as on people exposed to occupational noise. It is commendable that HCPs currently implemented incorporate evidence and theory-based interventions in the management of noise as a risk factor. However, as this chapter has illustrated, there are still some factors that impact the success of health promotion and prevention of environmental and occupational NIHL, particularly within LMICs like South Africa. Within the South African context, it is, therefore, important that environmentally, at a national level:
Occupationally, there is a need for industries to ensure the following:
The aforementioned recommendations require central and key involvement of audiologists, with South African audiologists needing to advocate for their role in the prevention of NIHL and the implementation of HCPs.
How to cite: Moroe, NF 2022, ‘Early
detection and management of occupational and environmental
noise’, ed. K Khoza-Shangase, Preventive audiology: An
African perspective, AOSIS Books, Cape Town, pp.
213–233. https://doi
This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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