Emerging Trends and Technologies

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The domain of hearing loss prevention embraces many technical disciplines: hearing science, audiology, industrial hygiene, occupational health, psychology, sociology, electroacoustics, and mechanical engineering, to name a few. Each of these is a dynamic specialty. Within any of these fields, what constituted "standard practice" only a few years ago is unlikely to be today's standard. It follows that today's standards will also evolve. Because hearing loss prevention represents the integration of many vibrant elements, it too, must change. Indeed, the fact that this guide has been revised only five years after its initial publication verifies this change. This section has been included to give the reader a preview of technologies or concepts that may influence future hearing loss prevention programs. It is not intended to serve as an exhaustive resource of emerging technologies, nor are any of the concepts discussed below even certain to affect hearing loss prevention. By highlighting a few concepts, the authors hope to dispel any notion that hearing loss prevention is a "mature" technology and to encourage the reader to anticipate and even participate in the evolution of this field.

Record Keeping and Audiometric Monitoring

The information explosion and the challenges associated with information management are being met by the introduction of advanced technologies. There is no doubt that the record keeping element of future hearing loss prevention programs will reflect the application of these technologies. The following discussion identifies just one example of a new technology and how its use can expand the reach of hearing loss prevention programs not only in terms of workers served but also with respect to the types of services provided.

Present approaches for storing and retrieving hearing loss prevention records work well in some, but not all situations. Many workers (e.g., construction workers) routinely move from job to job. Other workers may do part time work, work that is migratory in nature, or be self-employed. Traditional record management techniques may be impractical for these workers. Emerging information management hardware and software can provide solutions to the problems associated with managing the records of a mobile or itinerant workforce. In particular, optical card technology may be useful in developing hearing loss prevention programs that serve these workers.

About the size of a credit card, an optical card has a storage capacity of up to 6 megabytes (the equivalent of more than 2,400 pages of typewritten text). Each optical card can therefore accommodate all data fields and records pertinent to a worker's participation in a hearing loss prevention program. By comparison, the typical 3.5" floppy disk can store only 1.4 megabytes of data and a so-called smart card can hold only 256 kilobytes of data. Each optical card will be able to contain all records of occupational and non-occupational noise/solvent exposure histories, relevant medical histories, training records, protective equipment use histories, and related medical records from previous evaluations. Unlike a floppy disk, an optical card is small enough and sturdy enough to be carried in a wallet like a credit card. Also, the data stored on the optical card enjoys a high degree of security. The worker controls access to the card through use of a personal identification number (PIN) in the same manner that access to a bank card is controlled. Because of its large storage capacity, the optical card can be formatted to provide multiple areas, each accessed by a different PIN.

Although optical card technology offers significant advances in storage capacity and data security, its most significant benefit may be its potential to facilitate the provision of audiometric monitoring services for a mobile or itinerant workforce such as construction and agricultural workers. Historically, such workers have, at best, had access to personal hearing protective devices. Perhaps a fortunate minority may have even received training in the use and care of their hearing protectors. They almost certainly would not have been served by an audiometric monitoring component of a hearing loss prevention program. By its very nature, audiometric monitoring is a longitudinal process. It is understandable that there would be little practical incentive to establish an audiometric monitoring program for a transient work force. Recall that current hearing loss prevention programs are site-based; all aspects of the program stay with the site. If a worker leaves, his/her audiometric and noise exposure records remain at the site. By contrast, an optical card will be in the possession of the worker. When the worker changes jobs, the worker will carry his/her "records" to the next job. The continuity of care for a worker would be assured whether s/he received hearing health services from one or many occupational health care providers. Such continuity of care would make it feasible to establish an audiometric baseline and monitor the hearing of a mobile or itinerant worker. Finally, optical card technology can enable the development of creative approaches in which either the worker or management or both adopt responsibility for procuring audiometric test services.

Another use for the optical card may be the storage of noise samples taken during exposure assessment efforts. The card can store an entire digitized noise sample, especially if appropriate data compression strategies are used. The card, built within a sound level meter, could be written to as noises are measured and then used for a variety of projects from exposure assessment for the individual worker to noise control engineering.

A Holistic Approach to Hearing Loss Prevention: Looking at Factors Other Than Noise

Occupational hearing loss prevention has focused almost entirely on the prevention of disorders due to noise exposure. Since noise has been one of the most widespread occupational hazards, this attention has been justifiable. Other factors may affect hearing or interact with noise.

Many environmental hazards are usually observed in work environments. Combined with other organizational and psychosocial stressors, they are potentially hazardous to health. It has been observed that a worker may be exposed to as many as nine concurrent hazards, and the average worker is exposed to 2 to 3 hazardous agents simultaneously. Even considering only chemicals, the number of agents used and possible combinations is substantial.

It may be inappropriate to restrict the term occupational hearing loss to a synonym for noise-induced hearing loss, even though the two terms previously have been used as such. Ototoxic properties have been identified among at least three classes of industrial chemicals: metals, solvents and asphyxiants. The indication that occupational chemicals could alter auditory function by either ototoxicity, neurotoxicity, or a combination of both processes, has serious implications. It is plausible to expect that if these chemicals were present in the workplace in sufficiently high concentrations, these could affect hearing despite the lack of occupational exposure to noise. It is important that those involved in hearing loss prevention take into account exposure to chemicals during the various phases of the process (monitoring for hazards, assessing hearing, controlling exposures).

Currently, ototoxic properties of industrial chemicals and interactions between them and noise have only been investigated for a very small number of substances. This poses an obstacle for the appraisal of risk. When specific ototoxicity information is not available on the chemical in question, the program implementor should then gather information on the agent's general toxicity, neurotoxicity and complaints from exposed populations. As the ototoxic properties of chemicals are more thoroughly explored, it may be advisable to derive new hearing damage risk criteria that address the risk associated with exposure to noise and/or chemicals.

Task-Based Exposure Assessment

For many workers, (e.g., those in the construction trades) an 8 hour time-weighted average (TWA) represents a complex mixture of events. While the TWA is an extremely useful metric, it may be of limited use in predicting the exposure of workers with frequently changing environments and/or who perform multiple tasks of variable duration. The Task-Based Exposure Assessment Model (T-BEAM) may prove useful in developing a rational approach for health and safety professionals who must deal with these types of noise exposures. The T-BEAM concept uses work tasks as the central organizing principle for collecting descriptive information on variables used to assess the hearing hazard for a worker. T-BEAM methods are also being developed not only to characterize hazardous noise, but also the hazards associated with occupational exposures to asbestos, lead, silica, and solvents.

To apply the T-BEAM process, the hazardous agent to be studied is first identified - in this case, noise. Next, "experts" (e.g., journeymen), who are familiar with the processes associated with a given occupation, develop a list of tasks associated with each process. This becomes the basis for a hazardous task inventory which may then be used in developing approaches for surveying the tasks. The results of the ensuing task surveys are then applied towards developing intervention strategies. As might be the case with traditional surveys, the results could be used to prioritize candidates for engineering controls as well as for assessing tasks where engineering controls have already been applied. Because a T-BEAM survey is focused on tasks instead of shifts or areas, the survey results can be used to protect workers from hazards associated with specific tasks. Consider the case of a worker who frequently changes job sites and whose main noise exposure comes from the intermittent use of power tools or machinery. Assume the worker's equipment produces a 100-dB(A) noise level. Under present OSHA guidelines, a two-hour cumulative exposure would equate to a 100% dose. Continuing with this example, assume that some days the worker uses this equipment for two hours or more. A hazard survey conducted on such days would identify this worker for inclusion in a hearing loss prevention program. A hazard survey conducted on other days might not. In situations such as these, the task rather than the shift should be the focus of intervention strategies.

This approach is conceptually analogous to how other intermittent noise exposures are addressed. A police officer may only be exposed to hazardous noise in the course of periodic weapons training. Nevertheless, during weapons training the officer is provided hearing protectors, instructed in their proper use and may well be enrolled in an audiometric monitoring program. Many manufacturing operations require persons walking through hazardous noise areas to wear hearing protectors. The point is, a singular focus on the time-weighted average should not be the sole basis for decisions regarding hearing loss prevention measures. Workers engaged in tasks in which they are routinely exposed to hazardous noise or ototoxic agents should be included in hearing loss prevention activities.

The above examples point to the need for an alternate method for use in situations where current dosimetry or area monitoring may not identify workers exposed to hazardous noise. Current studies are assessing approaches for developing hazardous task inventories for individual occupations and crafts within the construction industry. To be effective, a hazardous task inventory must classify distinctive tasks, should quantify time-to-task parameters, and be able to account for the effects of adjacent noise. If research demonstrates T-BEAM methods are effective, hazardous task inventory's can be used to establish databases representing the occupational hazards associated with many trades. Such databases would enable one to characterize a worker's exposure profile without requiring an individual hazard assessment survey. Although, at least for noise, the exposure profile may not be able to predict the specific exposure for an individual worker, it still may be possible to categorize a worker as having no risk, having some risk, or having substantial risk of hazardous noise exposure. Such categorization could be used to select an efficient intervention strategy based on and tailored to the degree of risk predicted for the worker.

New Directions in Theories About Self-Protective Behavior

With a wealth of research and published information available to guide the development of effective hearing loss prevention programs, why do some workers in apparently quality programs simply fail to protect themselves? In the past, popular models of health behavior such as the Health Belief Model and the Theory of Reasoned Action have tried to explain this phenomenon by tending to emphasize characteristics and beliefs of the individual worker. For example, a particular worker might hold attitudes or beliefs that conflict with the tenets of the safety program, e.g., "I'm not susceptible to noise-induced hearing loss, so why bother with protectors" or "Protectors interfere with warning signals...better to be deaf than dead!" While still useful as integral parts of newer models, these person-centered models have not adequately addressed many other factors now known to contribute to safe work behavior.

Newer models of health behavior currently under development stress interdisciplinary viewpoints and may contain parameters that focus on the interaction of environmental, psychological, and social determinants of behavior. Social aspects such as shared values and beliefs, the social relationship in which a specific behavior occurs, and the physical context of the behavior have taken on new importance. In particular, the issue of "safety climate" in the workplace is receiving renewed interest. Safety climate can be broadly defined as the general level of safety awareness and commitment among management and workers in the organization. The safety climate guides relevant behavior in the workplace by serving as a central point of reference for decision-making by workers and management about safety concerns. While the construct of safety climate is still somewhat ambiguous, it is anticipated that current research will successfully define the relevant factors that determine safety climate and influence workplace behavior.

One recent report has attempted to incorporate safety climate into a model of employee adherence to safety precautions. In this model, organizational safety climate depends upon such factors as explicit company safety policies and organizational attitudes and responses toward safety concerns. Worker characteristics (such as knowledge about health risks), availability of personal protective equipment in the work area, provision of employee feedback with respect to adherence to the safety program, and the social and physical environment of the workplace also contribute to worker adherence to safety practices.

In a study of medical personnel and adherence to universal precautions (to protect against HIV transmission), it was noted that providing extensive knowledge-based training and adequate supplies of personal protective equipment was not enough to lead to greater adherence to universal precautions (DeJoy, et al., 1995). Maximal adherence depended upon establishing an organizational safety climate, embraced by the workers as well as management, that supported and fostered strict adherence to safety precautions. Such a climate develops when management and workers take ownership for their safety program, and thereby facilitate and reinforce its provisions. Many prior studies designed around the health belief/promotion models have noted that perceived barriers or job hindrances have a strong influence on worker adherence to safety rules. In this new model, it was reported that "Job hindrances was the strongest predictor of adherence to universal precautions, and safety climate was the best predictor of job hindrances."

Most hearing loss prevention professionals agree that passive protection of workers from hearing loss by applying engineering controls to diminish hazards in the workplace is a preferred approach. However, in many occupational settings, protecting the workforce from hearing loss and other occupational hazards ultimately depends upon personal protective equipment (e.g., personal hearing protectors) and the voluntary actions of the hazard-exposed workers. Training programs for these workers will continue to be very important, but the expanding research findings suggest that such programs may need to include more than factual presentations about mechanisms involved in hearing loss and how to properly wear personal protective equipment. Training programs in the future may increasingly concentrate on 1) modifying the organizational climate, and 2) providing workers with the skills and strategies they need to take responsibility for managing their own health by collectively uncovering and reducing barriers to safe work behavior.

Use of Survey Tools to Evaluate Hearing Loss Prevention Program Effectiveness

The Health Promotion Model states that one's behavior concerning health risk is the direct result of one's beliefs about the risk. One's actions to avoid a health risk are strongly related to (1) how firmly one believes he or she will benefit from the steps taken to protect oneself (i.e., how effective the protective measures are believed to be), (2) the amount of control one has over one's health, and (3) one's beliefs regarding the barriers to adopting protective behaviors. The Health Belief Model subscribes to these principles and also considers one's perceptions of susceptibility, (i.e., belief about one's vulnerability or risk of personal harm), "seriousness"of the health threat, and the consequences of inaction when predicting behavior to avoid a health risk.

The Theory of Reasoned Action attempts to predict behavior by understanding an individual's beliefs and attitudes towards the behavior in question. It is believed that these elements in concert with motivational and normative factors contribute to a person's intention to perform a certain behavior. The intention to perform a certain behavior in turn, corresponds directly with the behavior. The figure above diagrams the relationships between each of these elements.

These theories of health behavior are being applied towards methods for assessing the effectiveness of hearing loss prevention programs. The conventional methods for assessing the effectiveness of a hearing loss prevention program rely primarily on audiometric data to determine whether year-to-year variability or incidence of significant threshold shift has exceeded a criterion value. While this approach will yield crucial information, it is not without its limitations. In particular, it requires substantial passage of time in order to accumulate sufficient audiometric data to make the necessary appraisals. Alternative approaches are examining the use of self-administered surveys to assess workers' pre- and post-intervention beliefs, attitudes and behavioral intentions toward protecting themselves from occupational noise-induced hearing loss. Such approaches assume that once given adequate knowledge and resources a correlation exists between attitudes regarding hearing loss prevention, intentions to act in ways that will prevent hearing loss, and actual behavior to prevent hearing loss. This assumption draws upon the Theory of Reasoned Action: i.e., behavior can be predicted by surveying attitudes and intentions. It also draws upon the Health Promotion Model and Health Beliefs Model: use of hearing protectors can be predicted by surveying workers' beliefs about (1) their ability to prevent hearing loss, (2) their evaluation of hearing loss as a threat, (3) their susceptibility to hearing loss, and (4) their ability to overcome barriers to hearing protector use.

Current research is studying the value of behavioral survey tools as resources for assessing the effectiveness of hearing loss prevention programs. If survey tools can successfully predict the behaviors of interest, they would offer the distinct advantage of enabling a comparison of worker convictions before and after intervention without requiring the substantial passage of time that accompanies an audiometric monitoring process. In addition, they could be directly applied in developing training and education programs that address worker's beliefs, attitudes and intentions regarding hearing loss prevention. This should enhance the efficiency and effectiveness of training/education.

Further Reading

Ajzen I, Fishbein M [1980]. Understanding Attitudes and Predicting Behavior. Englewood Cliffs, NJ: Prentice Hall.

Barregård L, Axelsson A [1984] Is there an ototraumatic interaction between noise and solvents? Scand Audiol 13:151B155.

Becker MH. [1974] The Health Belief Model and Personal Health Behavior. Health Education Monographs 2(4): 324B473.

Bergström B, Nyström B [1986]. Development of hearing loss during long term exposure to occupational noise. Scand Audiol 15:227B234.

Crofton KM, Lassiter TL, Rebert CS .[1994] Solvent-induced ototoxicity in rats: an atypical selective mid-frequency hearing deficit. Hear Res 80:25B30.

DeJoy DM [1995]. A Critical Review of the Applicability of Models of Health Behavior to Workplace Self-Protective Behavior. Cincinnati, OH. Final Report to National Institute for Occupational Safety and Health.

DeJoy DM, Murphy LR, Gershon RM [1995]. The Influence of Employee, Job/Task, and Organizational Factors on Adherence to Universal Precautions among Nurses. International J of Industrial Ergonomics - Special Issue on Macroergonomic Approaches to Safety.

Hétu R, Phaneuf R, Marien C [1987]. Non-acoustic environmental factor influences on occupational hearing impairment: a preliminary discussion paper. Canadian Acoustics 15(1):17B31.

Jacobsen P, Hein HO, Suadicani P, et al [1993] Mixed solvent exposure and hearing impairment: an epidemiological study of 3284 men. The Copenhagen male study. J Occup Med 43(4): 180B184.

Johnson AC [1994]. The ototoxic effect of toluene and the influence of noise, acetylsalicylic acid or genotype. A study in rats and mice. Scand Audiol Suppl. 39:1B40.

Lusk SL, Ronis DL, Kerr MJ, Atwood JR [1994]. Test of the Health Promotion Model as a Causal Model of Workers' Use of Hearing Protection. Nursing Research, 43(3): 151B157.

Morata TC, Dunn DE, Kretschmer LW, Lemasters GK, Keith RW (1993). Effects of occupational exposure to organic solvents and noise on hearing. Scand J Work Environm Health 19(4):245B254.

Morata T, Franks J, Dunn D [1994] Unmet needs in occupational hearing conservation. The Lancet 344(8920):479.

Nylén P [1994] Organic solvent toxicity in the rat; with emphasis on combined exposure interactions in the nervous system. Arbete och Hälsa 3:1B50.

Ödkvist LM, Arlinger SD, Edling C, et al [1987] Audiological and vestibulo-oculo-motor to findings in workers exposed to solvents and jet-fuel. Scand Audiol 16(2):75B84.

Phaneuf R, Hétu R [1990] An epidemiological perspective of the causes of hearing loss among industrial workers. J Otolaryngol 19(1):31B40.

Rybak LP [1992]. Hearing: The effects of chemicals. Otolaryngol Head Neck Surg 106:677B686.

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