Occupational Safety in Agricultural Workers: Hearing Conservation Programs, Low-Cost Noise Evaluation and The Effect of Noise Combined with Hand Arm Vibration on Hearing Sensitivity

Abstract

Study 1a. Abstract (Literature Review-Performance of Smartphone Noise Applications): Occupational hearing loss is a severe problem that affects millions of workers every year in the United States. However, many individual workers and small businesses have limited access to professional-grade sound measurement instruments due to their relatively high costs. Recently, many sound measurement applications (apps) for smart devices have been developed as a potential alternative to costly sound measurement instruments. This paper briefly reviews the current literature on cost-effective sound measurement apps with two objectives: (1) to summarize the accuracy of various smartphone sound measurement apps, and (2) to identify the apps that have features suitable for occupational exposure assessment. Overall, the Noise Hunter, NoiSee, SoundMeter, Androidboy1, Sound Level Analyzer (SLA) Lite, and NIOSH SLM apps demonstrated mean differences within ± 2 dB(A) of the respective reference sound measurements. Four apps, including NoiSee, SoundMeter, SPLnFFT, and the NIOSH SLM have the features required for occupational noise assessment. These findings have been published in as “Performance of Smart Device Noise Measurement Applications: A Literature Review” in the Professional Safety Journal [1].

Study 1b. Abstract (The Combined Impact of Hand-Arm Vibration and Noise Exposure on Hearing Sensitivity of Agricultural/Forestry Workers – A Literature Review): Hand-arm vibration (HAV), which in addition to potentially causing vibration white finger (VWF) can exacerbate hearing loss when combined with occupational noise. This is a particular concern in the agriculture and forestry industries. Many agricultural workers operate in single-family/small businesses and, thus, are exempt from Occupational Safety and Health Administration (OSHA) laws for noise regulations that are applicable to other industries. Additionally, agricultural/forestry workers have higher noise exposures contributing to hearing loss, as well as working hours that extend beyond a typical 8-hour work shift. The study was conducted to assess the possible association between hearing sensitivity on combined exposure to noise and HAV. A systematic literature review was conducted on exposure to noise and HAV in the agricultural and forestry sectors and the resulting impacts on hearing. Peer-reviewed articles in English were searched with 14 keywords in three databases (PubMed, Ergo Abstracts, and Web of Science) for fully-available articles without any filter for publication year. The database literature search resulted in 72 articles. Forty-seven (47) articles met the search criteria based on title. Abstracts were then reviewed for any relationship between hearing loss and HAV, Raynaud’s phenomenon, or VWF. This left 18 articles. It was found that most agriculture and chainsaw workers are exposed to noise and HAV. Hearing is impacted by both noise and aging. The workers exposed to HAV and noise had greater hearing loss than non-HAV exposed workers, possibly due to the additive effect on temporary threshold shift (TTS). HAV has been linked with multiple physical responses which may contribute to hearing loss. These include vasospasm in the cochlea via autonomous reflexes, vasoconstriction in the inner ear, ischemic damage to the hair cells, and increased oxygen demand. These findings have been published as “The Combined Impact of Hand-Arm Vibration and Noise Exposure on Hearing Sensitivity of Agricultural/Forestry Workers – A Systematic Literature Review” in the International Journal of Environmental Research and Public Health [2].

Study 2 Abstract (Evaluating the Existence and Implementation of Hearing Conversation Programs in the Agricultural Sector): Hearing loss is a common problem in the agricultural sector due to loud noise exposure from various equipment. The objective of study 2 was to survey the existence and implementation of hearing conversation programs (HCPs) in the agricultural sector. The survey was distributed nationwide to people working or involved in the agricultural sector, and a total of 119 individuals completed it. The survey covered four main areas: a) noise evaluation, b) noise control, c) training, and d) documentation and audiometric record keeping. The study found that noise evaluation and noise control in the agricultural sector were self-reported as “effectively implemented.” However, levels of hearing loss among agricultural workers suggest otherwise. Results may be biased in this population by a lack of understanding and appreciation for the impacts of noise.

Study 3 Abstract (Evaluating Smartphone-based Sound Measuring Applications (Apps) for Use as Portable Inexpensive Sound Level Meters, Particularly for Measuring Typical Agricultural Sounds): Loud noise exposure is a serious health hazard in occupational settings and is prevalent worldwide. Accurate and precise noise measurement is necessary for effective management of loud noise in occupational settings. The purpose of study 1a was to evaluate the accuracy of smartphone noise applications for measuring noise and determine if they can be used for occupational noise exposure assessments. In this study, a representative sample of 26 iOS phones, including models 8, XR, 11, 12, 13 and 14, were tested. Four freely available noise measurement applications (apps) were compared side-by-side with a professional-grade laboratory standard Type 2 sound level meter. These apps were: a) NIOSH SLM, b) SLA Lite, c) Decibel X and d) SoundMeter X. The primary factor of interest was the efficacy of sound measurement app, and it was found to be significant (p < 0.05). The specific noise app used, interaction of noise app with phone age (phone generation), and interaction of noise app with sound type (white noise vs. variable agricultural noise) were all significant (p < 0.05). However, the sound level (low, medium, or high) was not found to be significant, indicating that differences between apps and the sound level meter were not impacted by the noise levels studied. The overall average absolute error between SoundMeter X noise application and sound level meter was the least (1.5 dB), followed by the SLA Lite (1.7 dB), NIOSH SLM (2 dB) and finally Decibel X (2.6 dB). The study also researched the effect of phones with and without a protective phone case. No statistically significant differences were found between the two, suggesting that performance was not significantly impacted by using the apps while a protective case covered the phone. Tests were repeated after applying a hypothetical calibration (by adjusting levels using the average error). Results suggested that the NIOSH SLM app had the least post-calibration average absolute difference (0.45 dB) from the reference sound level meter. The SoundMeter X and NIOSH SLM applications have all of the essential functions considered appropriate for noise evaluation, including exchange rate, threshold level and response rate, and frequency weighting.

Study 4 Abstract (Exploring the Interaction Effects of Hand Arm Vibration (HAV) and Noise Exposure on Inner Ear Sensitivity): This study investigated the effect of noise alone versus Noise + Hand Arm Vibration (HAV) exposure on inner ear auditory functioning. A custom-made test device was fabricated for housing a hand-held drill that was used to generate repeatable vibrations (the source of HAV exposure) and noise. The HAV was monitored using sensors placed on three different locations (wrist, above elbow, and head). Otoacoustic Emissions (OAEs) characterize auditory functioning of the inner ear. OAE is measured by inserting a probe microphone in the ear canal of each participant. A total of twenty subjects participated in the study, including thirteen (13) males and seven (7) females. Our investigation revealed a significant increase in OAEs in females when they were exposed to Noise + HAV (synergistic effect) in comparison to noise exposure alone. Males did not experience an increase in OAE with vibration exposure. This suggests that vibration with noise may impact females to a greater degree than males. Increase in OAE of this type may overstimulate the auditory system, potentially increasing noise-related risk with long-term exposure.