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Journal Article 
The ototoxic effects of ethyl benzene in rats 
Cappaert, NLM; Klis, SFL; Muijser, H; de Groot, JCMJ; Kulig, BM; Smoorenburg, GF 
Hearing Research
ISSN: 0378-5955 
Exposure to organic solvents has been shown to be ototoxic in animals and there is evidence that these solvents can induce hearing
loss in humans. In this study, the effects of inhalation of the possibly ototoxic solvent ethyl benzene on the cochlear function and
morphology were evaluated using three complementary techniques: (1) reflex modification audiometry (RMA), (2) electrocochleography
and (3) histological examination of the cochleas. Rats were exposed to either ethyl benzene (800 ppm, 8 h/day for
5 days) or to control conditions. The RMA threshold increased significantly by about 25 dB, 1 and 4 weeks after the exposure,
irrespective of the stimulus frequency tested (4-24 kHz). Electrocochleography was performed between 8 and 11 weeks after
exposure to the organic solvent. The threshold for the compound action potential increased significantly by 10^30 dB at all
frequencies tested (1-24 kHz). Histological examination of the cochlea showed outer hair cell (OHC) loss, especially in the upper
basal and lower middle turns (corresponding to the mid-frequency region) to an extent of 65%. We conclude that exposure to 800
ppm ethyl benzene for 8 h/day during 5 days induces hearing loss in rats due to OHC loss. 
rat; ethyl benzene; ototoxicity; reflex modification audiometry; electrocochleography; histology 
Administration, Inhalation