Agentes Químicos Ototóxicos (para além dos Solventes)
Authors: Santos Mónica , Almeida Armando , Lopes Catarina , Oliveira Tiago 
Published: January 2021

Introduction / framework / objectives Classically in Occupational Health Hypoacusis is associated to noise exposure; however, there are several chemical agents with this capability. Among these, the most frequently associated are solvents, although not always with irrefutable scientific evidence for some cases. Within other classes of chemical agents the data is even scarcer and less robust. The aim of this review was to summarize the most recent and pertinent publications on ototoxic agents (other than solvents). Methodology This is an Integrative Bibliographic Review, initiated at September 2019 on the databases “CINALH plus with full text, Medline with full text, Database of Abstracts of Reviews of Effects, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, Cochrane Methodology Register, Nursing and Allied Health Collection: Comprehensive, MedicLatina, Academic Search Ultimate, Science Direct, Web of Science, SCOPUS and RCAAP”. Content The most commonly mentioned classes are solvents (there is already an article published in this journal related to the risk of hypoacusis), heavy metals, asphyxiants and pesticides. It is also described that some antibiotics, anticancer drugs and diuretics may be ototoxic directly. In turn, hydrogen cyanide and carbon monoxide can have a synergistic effect with noise, as well as some heavy metals, asphyxiants and pesticides. However, in contexts where there is noise and ototoxic chemical agents, it is difficult to understand the contribution of each, and synergism may occur. Moreover, the situation seems to be clearer in animals; In humans some researchers assume that further studies are needed and the levels at which injury arises are not known clearly. At higher concentrations, hypoacusis seems evident, but for smaller amounts, data are not always consensual. There is also no consensus on the lowest dose that will induce damage. In addition, in most occupational situations exposure includes several chemical agents and not one isolated. Animal is not equivalent to human metabolism, so generalizations of results should be made with reservations. At work level, there are fewer standards for chemical versus noise agents in the context of hearing loss. Global ototoxicity is believed to be related to oxidative stress; not only due to the formation of reactive oxygen species, but also through the attenuation of antioxidant defense mechanisms. Discussion, Limitations, and Conclusions Most of the published studies on this subject are not very robust, besides that they have heterogeneous conditions among themselves. Hence, the conclusions of these studies cannot be generalized directly to the population of workers exposed to ototoxic agents. Still, among the latter there are some that seem to associate more clearly with hearing loss. Whenever the association is proven and/ or suspected, the Occupational Health team should provide measures that mitigate exposure to provide the safest and healthiest working environment possible. It would be relevant to know more about the national reality and to have published data of professionals working in companies with these agents, comparing the effect of different concentrations/ products and/ or simultaneous exposure to noise (possibly at different intensities), depending on the existing production process.