Potential neurotoxic pesticides and hearing loss


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Many chemical substances are thought to be ototoxic, including toluene, styrene, ethylbenzene, carbon disulfide, lead, mercury and carbon monoxide. Several pesticides are suspected of being neurotoxic in humans and may therefore affect the auditory system. Researchers from the Department of Occupational Hygiene, Monte Porzio Catone, Rome, Italy, have analyzed human and experimental animal studies that tested the hypothesis that exposure to pesticides may be associated with hearing loss.

Analysis focused on epidemiological studies aimed at evaluating associations between hearing loss and exposure to pesticides, and on studies on the effects of pesticides on the auditory system in laboratory animals. The research group’s literature search yielded about 70 references and the pesticides under study included organophosphates (OPs), pyrethroids, dipyridyl compounds and hexachlorobenzene (HCB).

The results of this analysis were published in the journal NeuroToxicology last month. Findings from human studies suggest that exposure to neurotoxic pesticides can induce damage to the central auditory system. However, the authors found that no meaningful conclusions could be drawn due to a number of deficiencies in some of the assessed studies, for instance lack of detailed information on the level and modality of exposure, and confounding factors, particularly noise co-exposure. In addition, they found no evidence on the potentiation of noise-induced auditory impairments.

Given the limited data, the authors suggest further investigations on pesticide ototoxicity. However, as a precautionary measure, they recommend considering pesticides as possible ototoxic agents, particularly in vulnerable populations such as pregnant women and children during early development.

Source: Gatto MP, Fioretti M, et al. Effects of potential neurotoxic pesticides on hearing loss: A review. Neurotoxicology 2014 Apr 2;42C:24-32.