Function of the Auditory and Visual Systems, and of Peripheral Nerve, in Rats after Long‐Term Combined Exposure to n‐Hexane and Methylated Benzene Derivatives. I. Toluene

Abstract

Rats were exposed to n-hexane, toluene, or toluene together with n-hexane, each solvent 1000 p.p.m. (1000 + 1000 p.p.m. in combined exposure), 21 hr/day, 7 days/week during 28 days. Neurophysiological recordings were made 2 days, 3 months, and one year after end of exposure. A reduction in auditory sensitivity, recorded by click evoked auditory brainstem response, was observed 2 days after exposure to toluene alone, or to toluene together with n-hexane, but not after exposure to n-hexane alone. The reduction lasted one year after the exposure. Three months after combined exposure, a synergistic enhancement of loss of auditory sensitivity was observed in the mixed exposure group. One amplitude in the flash evoked potentials was lowered in the n-hexane exposed group 2 days after exposure. No such reduction was seen after simultaneous exposure to toluene. Exposure to n-hexane alone caused a marked decrease in peripheral nerve conduction velocity 2 days and 3 months after exposure, while exposure to n-hexane together with toluene had only a small effect on this velocity.

The risk of hearing loss associated with occupational exposure to organic solvents mixture with and without concurrent noise exposure: A systematic review and meta-analysis

“…Our analysis provided evidence that when the number of solvents exceeded 5, the risk estimate was 4.22 times higher. Several animal studies have confirmed that exposure to combinations of some solvents (mixtures of solvents) will contribute to greater hearing loss than it was found in single-solvent exposures [49][50][51][52][53]. The human studies have also confirmed such results [35].…”

Toluene-induced hearing loss among rotogravure printing workers

“…For the solvents investigated in our study, there is evidence available on the ototoxicity of high concentrations of toluene, both alone or as a component of solvent mixtures (1,2,7,15,31). Animal experiments which evaluated the effects of combined exposures to toluene and ethanol (2 of the solvents used in the studied company), revealed that exclusive exposure to ethanol did not affect the auditory system (32,33).…”

Toluene [MAK Value Documentation, 1996]

“…Loss of hair cells in the cochlea was found to result from the toluene exposure a, Nylen et al 1994, Pryor et al 1983. The symptoms of the serotonin syndrome are changed (CastillaSerna et al 1993) and changes in the circadian susceptibility are suggested (Harabuchi et al 1993).…”