Troy Ross

Project title: Hazards to Hearing and Threshold Shifts: The Results of Deployment to a Combat Environment

Degree: MPH | Program: Occupational and Environmental Medicine (OEM) | Project type: Thesis/Dissertation
Completed in: 2006 | Faculty advisor: William E. Daniell


Hearing loss is a disabling chronic health problem. In addition to the direct costs of disability and worker productivity, there are many other aspects of a person’s life that are affected. It has been demonstrated that people with hearing loss are less satisfied with their lives, lose independence, and have relational problems because of their decreased ability to communicate. The National Institute of Health’s National Institute on Deafness estimates that 10 million Americans are affected by noise induced hearing loss (NIHL) and 12 million suffer from tinnitus. Approximately one million those are classified as severely disabled. It is estimated that 30 million civilian workers are exposed to hazardous noise in the workplace and of those 7.5 million will suffer permanent damage to their hearing. The military’s experience has been similar. In 200 there were over 88,000 new cases of hearing loss handled by the Veteran’s Administration with a total compensation of over $786 million. Since 1977 the VA has paid over $7.4 billion in compensation claims for hearing loss. In 2005 the Army was responsible for 52% of cases and 61% of the cost arising from Veterans of all services.

Standards for hearing protection in the workplace were established b the Occupational Safety and Health Administration (OSHA) in 1983. The Department of Defense issued similar regulations soon thereafter. These standards and regulations defined exposure limits and actions levels that would require industry to perform monitoring of work environments that could be hazardous to a worker’s hearing, and require hearing exams for those exposed individuals. Soldiers that are in a workplace with noise levels of 85 dBA or higher for an eight our period or impulse noise 140 dBA or higher at any time must be enrolled in a hearing conservation program. While this regulation covers noise hazards well it does not address the unanticipated exposures that many soldiers may encounter, especially in a combat environment. There are many potential exposures, from flights on helicopters to convoy ambushes, where hearing conversation programs and engineering controls cannot protect the soldier. The one measure that can reduce the risk of hearing loss is effective hearing protection that soldiers will wear consistently.

Several previous studies of NIHL in the military have been conducted. The majority of these studies report prevalence and examine specific occupations or exposure scenarios. The data on the incidence of NIHL is scant, and no reports in the last twenty years have addressed the soldier in combat. The lack of information surrounding this topic is a critical gap in the knowledge base of hearing conservation.

Objective of the Present Study: This study was developed to determine the incidence of NIHL in a cohort of soldiers who spent a one year combat deployment in Iraq. Baseline screening audiograms were obtained prior to deployment and follow up exams were completed as part of a post-deployment health screening. In addition to the post deployment screening a voluntary survey was administered to the group. The purpose of the survey was to characterize symptoms of hearing loss, use of hearing protection, noise exposures, and smoking behavior. The goal of this study was to determine the incidence of hearing loss in the cohort and compare the effects of combat exposure by job category.

Taken from the beginning of thesis.