Effects of exposure duration on potentiation of noise induced hearing loss by carbon monoxide.
Rao-DB; Chen-GD; Fechter-LD
Toxicologist 1999 Mar; 48(1-S):292
Noise induced hearing loss (NIHL) is still the most common occupational disease in the U.S. Concurrent noise exposures with chemical asphyxiants such as carbon monoxide (CO) is common in work environments of firefighters, automobile mechanics and tunnel-toll booth workers. Potentiation of NIHL following acute exposure to noise (102-103 dB, broad band) and CO (1500 ppm) has been demonstrated previously. It is well known that noise exposure of varying duration is related to exposure intensities. The equal energy principle states that an increase in exposure intensity is compensated for by a corresponding decrease (halving) in exposure duration. This study investigates whether or no the NIHL resulting from combined exposures complies with the equal energy principle. Adult male Long Evans hooded rats were acutely exposed to noise alone (100dBLo 9.6-19.2 kHz), CO alone (1500 ppm), noise & CO, and air (controls). Duration of exposure varied between 2 and 4 hours. Auditory sensitivity was measured four weeks post-exposure. End points measured were electrophysiological, namely, compound action potential (CAP) an cochlear microphonic (CM). CAP is a measure of cochlear output generated at the inner hair cell-type I spiral ganglion synapse, and , CM is generated largely by the outer hair cell. These potentials were recorded in response to pure tomes between 2 and 40 kHz NIHL was found to comply with the principle of equal energy. However, hearing loss resulting from combined exposure did not follow a similar pattern.
Hearing-protection; Noise-induced-hearing-loss; Synergistic-effects; Ototoxicity; Tunnel-workers; Toolbooth-workers; Mechanics; Automotive-emissions; Laboratory-animals; Animal-studies; Statistical-analysis; Analytical-chemistry; Analytical-methods; Chemical-analysis; Dose-response; Exposure-assessment; Hearing-tests; Hearing-disorders; Fire-fighting; Fire-fighters; Noise-exposure
University of Oklahoma Health Sciences Center, Department of Pharmacology and Toxicology, Oklahoma City, Oklahoma 73190
Disease and Injury: Hearing Loss
The Toxicologist. Society of Toxicology 38th Annual Meeting, March 14-18, 1999, New Orleans, Louisiana
University of Oklahoma, Health Sciences Center, Oklahoma Center for Toxicology, Oklahoma City, Oklahoma