Neuro-Audiology (NA)
Sarah Ferguson, Bachelors of Science
Audiology Graduate Student
The Ohio State Univeristy, United States
Christina M. Roup, PhD
Associate Professor
Ohio State University
Columbus, Ohio, United States
This study evaluated the effects of noise and ototoxic inhalants on the auditory processing abilities of career firefighters. Firefighters are at high risk of exposure to ototoxic inhalants (e.g., cleaning supplies, furniture, etc.) during the teardown phase of a fire when respirators are not required. Two groups participated that differed in age and years on the job. The auditory processing test battery included extended high-frequency thresholds, otoacoustic emissions, dichotic and speech-in-noise recognition, gaps-in-noise, and the masking level difference. Results indicate middle-aged firefighters have poorer extended high-frequency thresholds, and exhibit poorer temporal processing and speech-in-noise performance compared to younger firefighters.
Summary:
Rationale It is well known that firefighters experience threshold elevation due to noise exposure on the job. Firefighters are also exposed to toxic inhalants such as carbon monoxide, benzene, and asbestos that are known to cause damage to the central auditory nervous system. Firefighters are at a high risk of exposure to these toxins during the teardown phase of a fire when respirators are not required. The simultaneous exposure to noise and inhaled toxins can have a synergistic effect resulting in both cochlear and central auditory deficits. It was hypothesized that career firefighters would experience auditory processing deficits due to a history of noise and toxin exposures.
Objectives The objective of this study was to evaluate auditory processing abilities in two groups of firefighters that differed in the number of years on-the-job and therefore different degrees of exposure to noise and toxic inhalants.
Design Two groups of firefighters participated: a young group (19-29 years) with 1-10 years of on-the-job exposures, and a middle-aged group (40-55 years) with 30-40 years of on-the-job exposures. Inclusion criteria included 1) normal pure-tone thresholds from 250-8000 Hz; 2) normal middle ear function; and 3) monaural word recognition scores in quiet ≥ 80%. Auditory function was further assessed via extended high-frequency pure-tone thresholds (10-16 kHz), acoustic reflexes and distortion product otoacoustic emissions. Self-perceived hearing and listening ability was by the Adult Auditory Performance Scale (AAPS). Auditory processing was evaluated with the following measures: 1) dichotic word recognition; 2) Listening in Spatialized Noise test; 3) Gaps-in-Noise test (GIN); and 4) the 500-Hz masking level difference.
Results Preliminary data analysis indicates differences in auditory function between young and middle-aged firefighters. Specifically, the middle-aged firefighters perceived greater hearing and listening difficulties especially in noise, have poorer extended high-frequency thresholds, and exhibit poorer temporal processing and speech-in-noise performance.
Conclusions Over 95% of firefighter’s believe that good hearing is critical for job performance and over 90% believe that hearing loss can contribute to work-related injuries and/or safety concerns. Current NIOSH hearing health recommendations for firefighters only address noise-exposure and the risk for noise-induced hearing loss. Results from the present study suggest that older firefighters experience deficits in auditory processing and perceive substantial difficulty hearing and listening in noise. Further, results support the importance of assessing and monitoring all aspects of firefighter’s auditory function, including auditory processing.