Abstract
BackgroundCarbon disulfide (CS2) exacerbates the effect of noise on hearing, and disrupts the vestibular system. The goal of this study was to determine whether these effects are also observed with intermittent CS2 exposure.MethodsRats were exposed for 4 weeks (5 days/week, 6 h/day) to a band noise at 106 dB SPL either alone or combined with continuous (63 ppm or 250 ppm) or intermittent (15 min/h or 2 × 15 min/h at 250 ppm) CS2. Hearing function was assessed by measuring distortion product otoacoustic emissions (DPOAEs); balance was monitored based on the vestibulo-ocular reflex (VOR). Functional measurements were performed before, at the end of exposure and 4 weeks later. Histological analyses of the inner ear were also performed following exposure and after the 4-week recovery period.ResultsThe results obtained here confirmed that CS2 exposure exerts two differential temporary effects on hearing: (1) it attenuates the noise-induced DPOAE decrease below 6 kHz probably through action on the middle ear reflex when exposure lasts 15 min per hour, and (2) continuous exposure to 250 ppm for 6 h extends the frequency range affected by noise up to 9.6 kHz (instead of 6 kHz with noise alone). With regard to balance, the VOR was reversibly disrupted at the two highest doses of CS2 (2 × 15 min/h and continuous 250 ppm). No morphological alterations to the inner ear were observed.ConclusionThese results reveal that short periods of CS2 exposure can alter the sensitivity of the cochlea to noise at a dose equivalent to only 10 times the short-term occupational limit value, and intermittent exposure to CS2 (2 × 15 min/h) can alter the function of the vestibular system.
Highlights
Carbon disulfide (CS2) exacerbates the effect of noise on hearing, and disrupts the vestibular system
General health Over the 4 weeks of exposure, the weights of the animals co-exposed to continuous CS2 at 250 ppm and noise remained stable between T0 and T1, whereas controls, noise-exposed animals, animals co-exposed to continuous CS2 at 63 ppm and noise and animals intermittently co-exposed to CS2 and noise gained some significant weight
The 250ppm CS2 concentration delivered continuously can be considered as the threshold for toxicity
Summary
Carbon disulfide (CS2) exacerbates the effect of noise on hearing, and disrupts the vestibular system. The goal of this study was to determine whether these effects are observed with intermittent CS2 exposure. Carbon disulfide (CS2) is a lipophilic, volatile, inflammable solvent, used in large quantities in the production of viscose rayon fibres and cellophane films [1]. To better understand its toxicity, CS2 has been extensively studied in rats, where an abnormal accumulation of neurofilaments in the long axons of the peripheral (PNS) and central nervous system (CNS) has been observed [7, 10,11,12]. At the level of the auditory system, several studies examining auditory brainstem responses reported conduction dysfunction [13,14,15]
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