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EMERGING TRENDS AND TECHNOLOGIES
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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