Noise-induced hearing loss in different carbon monoxide environments.
Chen-GD; McWilliams-ML; Fecter-LD
Toxicologist 1999 Mar; 48(1-S):292
Intense noise, especially its high frequency components, may cause hearing loss (HL). The noise-induced-HL (NIHL) can be enhanced by simultaneous carbon monoxide (CO) exposure. Carbon monoxide exists in many environments. For example, pure cigarette smoking may cause an alveolar CO-level of about 300 ppm. Therefore, it is important to know the lowest CO-level at which the CO interacts with intense noise and makes the noise-induced auditory impairment worse. In the present study, high-frequency octave-band noise (9.6-19.2 kHz, 100dBlo) and CO-levels of 1200 ppm, 700 ppm, 500 ppm, 300 ppm and 0 ppm were applied. The hearing loss was determined by recording of CAP (compound action potential) from the round window, 4 weeks after exposure. The octave-band noise alone (0-ppm-CO) induced an approximate 30-dB permanent hearing loss in rats at frequencies higher than 10 kHz. CO alone did not induce any hearing loss, even at 30 minutes following the exposure. The combined exposure of the noise and 1200-ppm-CO, however, caused a much greater permanent hearing loss, especially in high frequency region. The HL-enhancement phenomenon by CO was obvious. The enhancement of the noise-induced hearing loss lessened gradually with CO-level. The hearing loss to the combined exposure with 300-ppm-CO was similar to the noise alone (0-ppm-CO). The lowest CO-level which shows interaction with intense noise, must be between 300 ppm and 500 ppm. In human subjects the lowest CO-level, showing interaction with intense noise, might be lower than the data obtained in the rats.
Hearing-protection; Noise-induced-hearing-loss; Synergistic-effects; Cigarette-smoking; Ototoxicity; Laboratory-animals; Animal-studies; Statistical-analysis; Analytical-chemistry; Analytical-methods; Chemical-analysis; Dose-response; Exposure-assessment; Hearing-tests; Hearing-disorders; Noise-exposure; Noise-frequencies; Noise-levels
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