Noise exposure is a common hazard to workforce in general although at varying degrees depending on the occupation, as many workers are exposed for long periods of time to potentially hazardous noise. Every year, twenty-two million workers are exposed to potentially damaging noise at work. In 2015 U.S. businesses paid over $1.5 million in penalties for not protecting workers from noise. (OSHA, 2016). There may be a direct or indirect consequence of the possibilities of overexposure to noise notwithstanding the compulsory hearing protection requests for the occupations with potential hazards, and these exposures usually arise from the various types of heavy repair equipment and tools related to the job functions. In the United States ten million people have noise related hearing loss (CDC, 2016) and damage done to the ear is not noticed until earing diminishes significantly. One of the noisiest occupations there are include the flight ground crews and flight maintenance personnel otherwise categorized as Ground Operation Workers. These categories of workers have varying functions in the noisiest area at the ramp, and this exposes them to noise that could lead to hearing impairment or permanent ear damage. This study was focused on workers on the ramps at the international airport of a large US city. These workers also are known as ground handling staff, and these employees perform different tasks on the airline ramp, which include unloading luggage from the airline, picking up and moving luggage from the belt room, and to loading baggage onto the airline. This study was conducted using personal dosimeters which were calibrated before and after each sampling event out on four different employees over a period of four days and the collected data were downloaded to a personal computer for further analysis. From the results of this study, the highest noise exposures occurred on a ground operation worker 3 (GOW3) with an 8-hr TWA exposure of 85.6 dBA using OSHA PEL measurement specifications and this occurred on the fourth day of sampling which was a Saturday. The second highest exposure occurred on ground operation worker 1 (GOW1) on the fourth day with an 8-hr TWA exposure of 85.0 dBA. For ground operations worker 2 (GOW2) and ground operation worker 4 (GOW4), the highest exposure occurred on the second day with 79.8 dBA and 73.4 dBA as their time weighted averages, respectively. None of the workers exposures exceeded the OSHA permissible exposure limit of 90 dBA. The United States Navy uses the OSHA noise standard to evaluate noise exposure on ships and all Navy installations. According to University of South Florida institutional review Board, this study is categorized as a program evaluation that has no intervention with human subjects. The workers that participated in this study did so voluntarily.

Every year, twenty-two million workers are exposed to potentially damaging noise at work. Last year, U.S. businesses paid more than $1.5 million in penalties for not protecting workers from noise. (OSHA, 2016). In the United States ten million people have some kind of noise related hearing loss (CDC, 2016) and noise damage to the ear may not be detected until it is great enough to cause hearing impairment. Grounds keeper’s functions consist of a variety of activities that require the use of powered tools such as mowers, riding mowers, leaf blowers, pressure washers, trimmers/edgers and chainsaws. OSHA has stated that “noise is a potential hazard for most jobs that involve abrasive or high-power machinery, impact of rapidly moving parts (product or machinery), or power tools”. (OSHA, 2016) in addition to this, their job is mostly outdoors exposing them to the added noise of traffic, construction and people. The purpose of this research study was to obtain occupational noise exposure data for groundskeepers who use powered equipment to do their job. The groundskeepers who participated in this research study were volunteers and worked in a University campus in the State of Florida. Personal noise dosimeters were used to collect the data in this study. Exposure information was collected over 6 days for 8-hour work shifts during the summer months of the year. Dosimetry was done on a maximum of five groundskeepers per monitoring day, ranging from 1 to 5 employees per day depending on availability. Results of this study indicate that the highest noise exposures occurred on groundskeepers in charge of mowing by means of a riding mower. Results of this study indicate that the highest 8-hr TWA noise exposure for the groundskeepers (GK) 1 and 2 occurred the first day of testing which was a Monday. Using the OSHA PEL measurement method GK1 exposure was 98.5 dBA, GK2 was 97.6 dBA. Using the same measurement method the highest exposure to GK3: 89.2 dBA, occurred on day five of the assessment. For GK4 the highest exposure occurred on the third day of testing with an exposure measurement of 86.1 dBA. GK5 was only assessed one day and his exposure measured at 84.5 dBA. GK6 AND GK7 were evaluated two days and their highest exposures measured at GK6: 89.3 dBA and GK7: 85.7 dBA. Using the OSHA Hearing Conversation Act measurement method, GK1 was exposed to excessive noise levels (>85 dBA as an 8-hr TWA) on five days of the six day assessment period. GK2 was exposed to hazardous noise levels on all four days he was assessed. GK3 and GK4 exceeded the OSHA HCA standard one of the two days they were monitored. GK 5 did not have noise exposure levels above 85 dBA on the day he volunteered for monitoring. GK6 had exposures over 85 dBA on both days he volunteered to be monitored. Finally, GK7 exceeded the 85 dBA limit on one of the two days they volunteered for this study.

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La surdité professionnelle constitue un problème de santé publique important, avec une prévalence estimée de 10 à 16%. Les études animales ont mis en évidence une perte des synapses entre les cellules ciliées internes et le nerf auditif et des fibres auditives présentant une activité spontanée faible. Cette synaptopathie cochléaire se manifesterait avant la dégradation des seuils auditifs et la perte des cellules ciliées externes, étant ainsi un précurseur à la surdité professionnelle. L’audiogramme utilisé en milieu clinique ne permet pas de mesurer la synaptopathie cochléaire, se contentant seulement de quantifier la perte d’audibilité causée par l’exposition au bruit. Des études post-mortem humaines ont permis d’identifier une synaptopathie cochléaire, similaire à celle observée dans le modèle animal. Étant donné que la quantification des synapses chez l'humain vivant n'est pas possible, les chercheurs se sont concentrés sur le développement d’outils pouvant servir de marqueur indirect de la synaptopathie cochléaire. À cet égard, les résultats sont divergents d’une étude à l’autre. Il est possible que ces outils ne soient pas sensibles ou que l’exposition au bruit investiguée dans la littérature ne soit pas suffisante pour entraîner une synaptopathie cochléaire chez l’humain. L’objectif de cette thèse est donc d’évaluer les effets d’une exposition au bruit industriel continu et au bruit impulsionnel, qui pourraient s’avérer plus nocives et entraîner un processus précoce de synaptopathie cochléaire. Des individus présentant des seuils auditifs et des émissions otoacoustiques dans la normale ont été investigués à l’aide de mesures électrophysiologiques et psychoacoustiques. Dans la première étude, 40 participants exposés au bruit industriel continu et 40 participants sans exposition au bruit industriel continu ont été recrutés et évalués à l’aide d’un test de perception de la parole dans le bruit (SPiN) et de différentes composantes du potentiels évoqués auditifs du tronc cérébral (PEATC). L’exposition au bruit des participants a été mesurée par dosimétrie. Les résultats ne montrent pas d’association entre l’exposition au bruit et les variables du PEATC et du SPiN. Dans la deuxième étude, 27 participants militaires exposés au bruit impulsionnel et 13 participants sans exposition au bruit impulsionnel ont été recrutés. Les PEATC, l’électrocochléographie, le SPiN et la largeur des filtres auditifs rectangulaires équivalents (ERB) ont été mesurés. L’exposition au bruit des participants a été quantifiée à l’aide du Noise Exposure Structured Interview. Les résultats montrent une réduction de l’amplitude de l’onde I, un allongement de la latence de l’onde V, des performances réduites de SPiN et un ERB plus large à 4 kHz chez les militaires exposés au bruit impulsionnel, en comparaison aux participants sans exposition au bruit impulsionnel. Cette thèse est importante d’un point de vue de santé publique puisqu’elle suggère que certains outils cliniques simples, comme la mesure des filtres auditifs, pourraient permettre de détecter les premiers signes d’un dommage auditif avant l’apparition d’une surdité professionnelle mesurée par l’audiogramme. Les résultats renforcent l’importance de la sensibilisation aux risques induits par l’exposition au bruit afin de prévenir l’apparition des troubles de communication et des situations de handicap découlant de la présence d’une surdité professionnelle. / Occupational hearing loss constitutes an important public health problem, with an estimated prevalence of 10 to 16%. Animal studies have shown a phenomenon of synapses dysfunction between the inner hair cells and the auditory nerve and a preferential loss of low spontaneous rate auditory fibers. This cochlear synaptopathy manifests itself before the degradation of hearing thresholds and the loss of outer hair cells, thus being a precursor damage to occupational hearing loss. The audiogram used in a clinical setting does not measure cochlear synaptopathy, only quantifying the loss of audibility caused by noise exposure. In humans, post-mortem studies have identified a process of cochlear synaptopathy, similar to that observed in the animal model. Since quantification of synapses in living humans is not possible, researchers focused on developing a noninvasive measurement that could serve as an indirect marker for cochlear synaptopathy. Several tools have been proposed, but the results vary from one study to another. It is possible that these tools are not sensitive or that noise exposures investigated in the literature is not sufficient to cause cochlear synaptopathy in humans. The objective of this thesis is therefore to evaluate the effects of exposure to continuous industrial noise and impulse noise, which could prove to be more harmful and lead to an accelerated process of cochlear synaptopathy. To this end, individuals with normal hearing thresholds and otoacoustic emissions were investigated using electrophysiological and psychoacoustical measurements. In the first study, 40 participants with occupational noise exposure and 40 participants without occupational noise exposure were recruited and evaluated using a speech perception in noise (SPiN) test and different components of the auditory brainstem response (ABR). Participants’ noise exposure was measured by dosimetry. The results do not show an association between noise exposure and the ABR and SPiN variables. In the second study, 27 military participants exposed to impulse noise and 13 participants without exposure to impulse noise were recruited. ABR, electrocochleography, SPiN and the equivalent rectangular bandwidth (ERB) of auditory filters were measured. Participants' noise exposure was quantified using the Noise Exposure Structured Interview. Results show a reduced wave I amplitude, a lengthened wave V latency, a reduced SPiN performance, and a broader ERB at 4 kHz in military recruits exposed to impulse noise, compared to participants without exposure to impulse noise. This thesis is important from a public health point of view since it suggests that certain simple clinical tools, such as the measurement of auditory filters, might make it possible to detect the first signs of auditory damage before the onset of hearing loss measured by the audiogram. Results reinforce the importance of raising awareness to the risks induced by noise exposure in order to prevent the appearance of communication disorders and handicaps resulting from the presence of occupational hearing loss.