Ototoxicity of trichloroethylene in concentrations relevant for the working environment

Organic solvents can cause hearing loss themselves or promote noise-induced hearing loss. The objective of this study was to review the literature on the effects of low-level exposure to trichloroethylene on the auditory system and consider its relevance for the occupational settings. Both human and animal investigations were evaluated only for realistic exposure concentrations based on the Quebec permissible exposure limits: 50 ppm 8-h time-weighed average exposure value (TWAEV) and 200 ppm short-term exposure value (STEV). In humans, the upper limit for considering ototoxicity data relevant to the occupational exposure situation was set at the STEV. Animal data were evaluated only for exposure concentrations up to 100 times the TWAEV. There is no convincing evidence of trichloroethylene-induced hearing losses in workers. In rats, trichloroethylene affects the auditory function mainly in the cochlear mid- to high-frequency range with a lowest observed adverse effect level (LOAEL) of 2000 ppm. No studies on ototoxic interaction after combined exposure to noise and trichloroethylene were identified in humans. In rats, supra-additive interaction was reported. Further studies with sufficient data on the trichloroethylene exposure of workers are necessary to make a definitive conclusion. In the interim, we recommend considering trichloroethylene as an ototoxic agent.