A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in partial fulfillment of the requirements for the degree of Masters in Public Health: Occupational Hygiene Johannesburg, June 2017 / Introduction The quantification and interpretation of personal noise exposure levels in the platinum processing industry of South Africa is an important research topic. Very few studies have been done nationally and internationally on noise exposure in this industry, given the serious health effects of over exposure to noise and the large number of people employed in this industry, this study is important. Objectives The objectives of this study were to describe personal noise exposure measurements of permanent and long term contractor employees during 2012 to 2014 at five Platinum Concentrator operations; to compare the personal noise exposure levels of the different activity areas between the five Platinum Concentrator operations; and to compare the personal noise exposure measurements of the Platinum Concentrator operations to national and international exposure limits. Methods This study was a cross-sectional secondary data analysis of personal noise exposure levels measured as part of routine Occupational Hygiene sampling programme during the period of 2012 to 2014 and was done in five platinum concentrator operations situated in the Bushveld Complex of South Africa. A total of 720 samples were extracted from an electronic database and descriptive statistics were applied to analyse the data. Results This study found that the Processor Grade 2 occupation within platinum concentrator no.3 had the highest personal noise exposure (104.7dBA) with a median personal noise exposure of 87.35dBA and a geometric mean personal noise exposure of 87.4dBA. Sixty seven percent of the personal noise measurements within the five Concentrator Operations exceeded the South African Occupational Exposure Limit of 85dBA and 19.71% of the personal noise measurement results exceeded the OSHA Exposure Limit of 90dBA. Conclusion This study indicated that over exposure to noise in the platinum processing industry can occur; therefore further research on this topic and in this industry is warranted. / MT2017

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Earlier retrospective noise exposure assessments for use in epidemiological research were not adequately characterized because they did not properly account for use of hearing protection devices (HPD) which would result in potential misclassification. Exposure misclassification has been shown to attenuate exposure-outcomes relations. In the case of already subtle relationships such as noise and cardiovascular diseases, this would potentially annihilate any association. We investigated two approaches using Workers’ Compensation Board (WorkSafe BC) audiometric surveillance data to (i) re-assess the noise exposure in a cohort of lumber mill workers in British Columbia using data on the use of HPD and the determinants of their use available through WorkSafe BC, and (ii) test the validity of the new exposure measures by testing their predictions of noise-induced hearing loss, a well-established association. Work history, noise exposure measurements, and audiometric surveillance data were merged together, forming job-exposure-audiometric information for each of 13,147 lumber mill workers. Correction factors specific to each type and class of HPD were determined based on research and standards. HPD-relevant correction factors were created using 1) deterministic methods and self-reported HPD use after filling gaps in the exposure history, or 2) a model of the determinants of use of HPD, then adjusting noise estimates according to the methods’ predictions and attenuation factors. For both methods, the HPD-adjusted and unadjusted noise exposure estimates were cumulated across all jobs each worker held in a cohort-participating lumber mill. Finally, these noise metrics were compared by examining how well each predicted hearing loss. Analyses controlled for gender, age, race as well as medical and non-occupational risk factors. Both methods led to a strengthening of the noise-hearing loss relationships compared to methods using HPD-unadjusted noise estimates. The method based on the modeling of HPD use had the best performance with a four-fold increase in the slope compared to the unadjusted noise-hearing loss slope. Accounting for HPD use in noise exposure assessment is necessary since we have shown that misclassification attenuated the exposure-response relationships. Exposure-response analyses subsequent to exposure reassessment provide predictive validity and gives confidence in the exposure adjustment methods.

Earlier retrospective noise exposure assessments for use in epidemiological research were not adequately characterized because they did not properly account for use of hearing protection devices (HPD) which would result in potential misclassification. Exposure misclassification has been shown to attenuate exposure-outcomes relations. In the case of already subtle relationships such as noise and cardiovascular diseases, this would potentially annihilate any association. We investigated two approaches using Workers’ Compensation Board (WorkSafe BC) audiometric surveillance data to (i) re-assess the noise exposure in a cohort of lumber mill workers in British Columbia using data on the use of HPD and the determinants of their use available through WorkSafe BC, and (ii) test the validity of the new exposure measures by testing their predictions of noise-induced hearing loss, a well-established association. Work history, noise exposure measurements, and audiometric surveillance data were merged together, forming job-exposure-audiometric information for each of 13,147 lumber mill workers. Correction factors specific to each type and class of HPD were determined based on research and standards. HPD-relevant correction factors were created using 1) deterministic methods and self-reported HPD use after filling gaps in the exposure history, or 2) a model of the determinants of use of HPD, then adjusting noise estimates according to the methods’ predictions and attenuation factors. For both methods, the HPD-adjusted and unadjusted noise exposure estimates were cumulated across all jobs each worker held in a cohort-participating lumber mill. Finally, these noise metrics were compared by examining how well each predicted hearing loss. Analyses controlled for gender, age, race as well as medical and non-occupational risk factors. Both methods led to a strengthening of the noise-hearing loss relationships compared to methods using HPD-unadjusted noise estimates. The method based on the modeling of HPD use had the best performance with a four-fold increase in the slope compared to the unadjusted noise-hearing loss slope. Accounting for HPD use in noise exposure assessment is necessary since we have shown that misclassification attenuated the exposure-response relationships. Exposure-response analyses subsequent to exposure reassessment provide predictive validity and gives confidence in the exposure adjustment methods.

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.

The Occupational Safety and Health Administration estimates that each year, approximately 30 million people are occupationally exposed to hazardous noise. While many are aware of the noise exposure associated with industrial occupations, there has been little research conducted on bartenders who often work in environments that have high levels of noise. The majority of current published research on occupational noise exposure of bartenders has only evaluated noise levels on one night of business. Bartenders often work multiple days per week, which vary in the amount of patrons and entertainment provided, this variation in business leads to variation in the amount of noise to which they are exposed. The purpose of this research study was to gather occupational noise exposure data for bartenders during a workweek at a Tampa Bay bar establishment that hosts live music on weekends. Personal noise dosimeters were used to collect personal noise exposure data. Area noise level data were collected using a sound level meter. While several bar establishments were approached, one bar establishment part pated as the study site and noise data were collected for seven consecutive days (Thursday-Wednesday). Personal noise exposure data were collected for an entire 8-hour work shift for the Thursday-Sunday portion of the study, and for 6 hours for the Monday-Wednesday portion of the study. Area noise data were collected for the Thursday-Saturday portion of the study. Results of this study indicate that the highest noise exposure for either bartender occurred on Saturday (Bartender 1: 93.1 dBA; Bartender 2: 83.6 dBA) when a live band was performing in the establishment. Using the OSHA Hearing Conversation and OSHA PEL measurement methods, Bartender 1 was exposed to excessive noise levels (>85 dBA) on four (4) nights of the study, while Bartender 2 had no exposures over 85 dBA. However, using the ACGIH measurement method, Bartender 1 was exposed to excessive noise levels six (6) nights of the study, while Bartender 2 was exposed to excessive noise levels two (2) nights of the study.

Earlier retrospective noise exposure assessments for use in epidemiological research were not adequately characterized because they did not properly account for use of hearing protection devices (HPD) which would result in potential misclassification. Exposure misclassification has been shown to attenuate exposure-outcomes relations. In the case of already subtle relationships such as noise and cardiovascular diseases, this would potentially annihilate any association. We investigated two approaches using Workers’ Compensation Board (WorkSafe BC) audiometric surveillance data to (i) re-assess the noise exposure in a cohort of lumber mill workers in British Columbia using data on the use of HPD and the determinants of their use available through WorkSafe BC, and (ii) test the validity of the new exposure measures by testing their predictions of noise-induced hearing loss, a well-established association. Work history, noise exposure measurements, and audiometric surveillance data were merged together, forming job-exposure-audiometric information for each of 13,147 lumber mill workers. Correction factors specific to each type and class of HPD were determined based on research and standards. HPD-relevant correction factors were created using 1) deterministic methods and self-reported HPD use after filling gaps in the exposure history, or 2) a model of the determinants of use of HPD, then adjusting noise estimates according to the methods’ predictions and attenuation factors. For both methods, the HPD-adjusted and unadjusted noise exposure estimates were cumulated across all jobs each worker held in a cohort-participating lumber mill. Finally, these noise metrics were compared by examining how well each predicted hearing loss. Analyses controlled for gender, age, race as well as medical and non-occupational risk factors. Both methods led to a strengthening of the noise-hearing loss relationships compared to methods using HPD-unadjusted noise estimates. The method based on the modeling of HPD use had the best performance with a four-fold increase in the slope compared to the unadjusted noise-hearing loss slope. Accounting for HPD use in noise exposure assessment is necessary since we have shown that misclassification attenuated the exposure-response relationships. Exposure-response analyses subsequent to exposure reassessment provide predictive validity and gives confidence in the exposure adjustment methods. / Medicine, Faculty of / Population and Public Health (SPPH), School of / Graduate

Hyperacusis is a condition in which sufferers experience everyday sounds in their surroundings as unmanageable and disturbing. The condition is often associated with symptoms such fatigue, headaches, sleep disturbances and difficulties concentrating. Present study aimed to investigate how people are affected when exposed to noise over time. This was operationalized by collecting data from essentially three domains; subjective, physiological and cognitive. Since hyperacusis is largely defined by the individuals’ subjective experience, participants were divided into three groups based on their own subjective reports of discomfort during an exposure to white noise (60db). Cognitive performance was assessed using two well established measurements in the beginning and the end of the exposure session. Contrary to expectations, the groups did not differ significantly in cognitive performance. Heart rate variability was measured during the exposure session and was hypothesized to be lower in participants experiencing higher discomfort. As expected, the groups differed in their expressed variability in the direction of the hypothesis.

Hearing loss is a one of the most common chronic conditions. Although it is most common to be diagnosed with hearing loss later in life due to aging, there are multiple causes of hearing loss across the lifespan. One of the main types of hearing loss is noise-induced hearing loss. Some individuals may complain of decreased hearing or word understanding in background noise but when tested, they appear to have normal hearing sensitivity in the standard audiometric frequencies (250 – 8000 Hz). This may be due to decreased hearing sensitivity in extended high frequencies, above 8000 Hz. There is growing evidence that decreased extended high frequency thresholds may be a precursor to noise-induced hearing loss. This study aimed to analyze how noise exposure affects young adult’s extended high frequency thresholds and word identification in noise as well as traditional audiological testing (pure tones, speech recognition, word discrimination in quiet, etc). Young adults (18-25 years old) were recruited through ETSU affiliated social media, ETSU faculty, and word of mouth. An online noise survey was conducted to calculate each participant’s noise exposure. An otoscopic examination was completed on each study participant. Tympanometry was performed to ensure normal middle ear immittance. If an individual did not have normal middle ear immittance they were dismissed from the study. A 12-frequency diagnostic Distortion Product Otoacoustic Emissions (DPOAEs) was performed to check integrity of the individual’s outer hair cells. Speech Recognition testing was completed to determine the lowest level the individual could repeat back 50% of the words correctly. Word Recognition testing was completed to determine the percentage of words the individual could hear and correctly identify at suprathreshold level. Words-in-Noise testing was completed to determine how an individual could hear and correctly identify speech when in the presence of noise. Puretone air conduction was completed at the standard audiometric frequencies: 250, 500, 1000, 2000, 3000, 4000, 6000, and 8000 Hz. If an individual had abnormal hearing sensitivity in these frequencies, they were dismissed from the study. Finally, extended high frequency testing was completed at 10,000, 12,500, 14,000, and 16,000 Hz. Data collection is still in progress and will close on March 7th, 2022. It is expected that noise exposure will be negatively correlated to extended high frequency thresholds and word understanding in noise (i.e., participants with more noise exposure will have poorer extended high frequency thresholds and poorer word understanding in noise).

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