title: A weight of evidence approach for the assessment of the ototoxic potential of industrial chemicals.
abstract: There is accumulating epidemiological evidence that exposure to some solvents, metals, asphyxiants and other substances in humans is associated with an increased risk of acquiring hearing loss. Furthermore, simultaneous and successive exposure to certain chemicals along with noise can increase the susceptibility to noise-induced hearing loss. There are no regulations that require hearing monitoring of workers who are employed at locations in which occupational exposure to potentially ototoxic chemicals occurs in the absence of noise exposure. This project was undertaken to develop a toxicological database allowing the identification of possible ototoxic substances present in the work environment alone or in combination with noise exposure. Critical toxicological data were compiled for chemical substances included in the Quebec occupational health regulation. The data were evaluated only for noise exposure levels that can be encountered in the workplace and for realistic exposure concentrations up to the short-term exposure limit or ceiling value (CV) or 5 times the 8-h time-weighted average occupational exposure limit (TWA OEL) for human data and up to 100 times the 8-h TWA OEL or CV for animal studies. In total, 224 studies (in 150 articles of which 44 evaluated the combined exposure to noise and a chemical) covering 29 substances were evaluated using a weight of evidence approach. For the majority of cases where potential ototoxicity was previously proposed, there is a paucity of toxicological data in the primary literature. Human and animal studies indicate that lead, styrene, toluene and trichloroethylene are ototoxic and ethyl benzene, n-hexane and p-xylene are possibly ototoxic at concentrations that are relevant to the occupational setting. Carbon monoxide appears to exacerbate noise-induced hearing dysfunction. Toluene interacts with noise to induce more severe hearing losses than the noise alone.
authors: Institut de recherche en santé publique de l'Université de Montréal, Département de santé environnementale et santé au travail, Université de Montréal, Canada. adolf.vyskocil@umontreal.ca
authors: A
authors: A
authors: Vyskocil
authors: G
authors: G
authors: Truchon
authors: T
authors: T
authors: Leroux
authors: F
authors: F
authors: Lemay
authors: M
authors: M
authors: Gendron
authors: F
authors: F
authors: Gagnon
authors: N El
authors: NE
authors: Majidi
authors: A
authors: A
authors: Boudjerida
authors: S
authors: S
authors: Lim
authors: C
authors: C
authors: Emond
authors: C
authors: C
authors: Viau
mesh_terms: D000818:Animals; D001555:Benzene Derivatives / Q000633:toxicity; D004249:DNA Damage / Q000187:drug effects; D006309:Hearing / Q000187:drug effects*; D006317:Hearing Loss, Noise-Induced / Q000139:chemically induced*; D006586:Hexanes / Q000633:toxicity; D006801:Humans; D009622:Noise / Q000009:adverse effects; D016273:Occupational Exposure / Q000009:adverse effects*; D011792:Quebec; D018570:Risk Assessment; D012997:Solvents / Q000633:toxicity*; D020058:Styrene / Q000633:toxicity; D014050:Toluene / Q000633:toxicity; D014241:Trichloroethylene / Q000633:toxicity; D017132:Workplace; D014992:Xylenes / Q000633:toxicity
chemical_list: D001555:Benzene Derivatives; D006586:Hexanes; D012997:Solvents; D014992:Xylenes; D014241:Trichloroethylene; C026385:n-hexane; D014050:Toluene; D020058:Styrene; C031286:4-xylene; C004912:ethylbenzene