Neurotoxicity induced by exposure to toluene

Abstract

The object of the present study was to evaluate, with the aid of electrophysiologic techniques, the alterations induced in the auditory nervous system by exposure to toluene in a group of rotogravure workers. From 300 workers who were apparently in good health but were professionally exposed to toluene, we selected a sample of 40 workers of normal hearing ability. They were examined with an adaptation test studied by the brainstem auditory evoked potential technique with 11 and 90 stimulus repetitions a second. The results were compared with those in a group of workers of the same age but not professionally exposed to solvents. Our study demonstrates that exposure to toluene is able to induce a statistically significant alteration in the electric responses with both 11 and 90 stimuli repetitions. This alteration can be explained as a toluene exposure-induced modification, of physiologic stimulus conduction mechanisms, even in the absence of any clinical sign of neuropathy. Furthermore, such a modification could be observed in the electric responses of the entire auditory system, from peripheral receptors to brainstem nuclei.

The Effects of Toluene Plus Noise on Hearing Thresholds: An Evaluation Based on Repeated Measurements in the German Printing Industry

“…Taking into account that our study did not reveal any toluene-induced hearing impairments, this information on long-term exposure in our study gives valuable supplementary information for the search of a no-effect-level which has to comprise not only information on current exposure. Potential problems of, and questions to the present study may comprise the following points, which were to some extent already discussed in a previous publication [6]: (1) No unexposed group was included. (2) Is a healthy worker effect possible?…”

“…In 1993, Abbate et al revealed alterations in acoustically evoked potentials for a selected group of 40 printing workers exposed to 97 ppm toluene for ~13 years on average [1]. In 1993, Morata et al compared three groups of workers (n = 190) exposed to noise, to noise and toluene, and to a mixture of solvents including toluene to an unexposed control group [2].…”

Auditory neuropathy in a patient exposed to xylene: case report

“…These authors found a significant delay in ABR latencies, and a significant delay in interpeak latencies (compared with a control group) for waves I, III and V at click rates of 11.1 and 90 clicks per second, for workers professionally exposed to toluene. 13 Both groups were controlled for noise exposure and neurological diseases, and all workers had thresholds below 20 dB. Interestingly, waves I-III were more significantly altered than wave V. Central auditory tests were not carried out.…”

“…10 For example, significantly delayed auditory brainstem responses (ABRs) were measured in a group of normally hearing workers professionally exposed to toluene. 13 Xylene is a solvent structurally related to toluene. 14 There is no literature on the effect of xylene, acting as a single agent, on the auditory pathway in humans.…”

Richtwerte für Toluol und gesundheitliche Bewertung von C7-C8-Alkylbenzolen in der Innenraumluft

“…Einige Arbeitsplatzstudien weisen darauf, dass Toluol bei Konzentrationen um 372 mg/m³ ototoxisch [77] wirkt bzw. den ototoxischen Effekt von Lärm verstärkt [80].…”