Solvent-Induced Hearing Loss: Mechanisms and Prevention Strategy

Abstract

While noise exposure is the most significant contributor to occupational hearing loss, evidence gained over the last 10 years, has pointed to organic solvents as additional contributors to occupational hearing disorders. Despite the implications of this finding, no significant measure has been undertaken to limit exposure to occupational solvents, or to occupational solvents and noise, within the European community. Guidelines for improving hearing protection of people exposed to solvents, or to solvents and noise, are addressed in the present article. Recently, it has been shown that the lowest-observed-adverseeffect level (LOAEL) of styrene was 300 ppm in active (working wheel) rats, and that the same amount of styrene-induced hearing loss (SIHL) can be obtained with styrene concentration difference of 200 ppm between active and sedentary (inactive) rats. Supported by a reasonable safety factor (SF) of 10, the authors proposed to decrease the French threshold limit value of styrene from 50 to 30 ppm (RfD = LOAEL/SF) to ensure a higher level of protection for human hearing. It is widely acknowledged that outer hair cells in the organ of Corti can be considered as the first target tissue of solvents, while little is known about the action of aromatic solvents on the auditory efferent system. In a recent experiment using both the cochlear microphonic and compound action potentials, the authors have shown that toluene can inhibit the action of the middle ear reflex by modifying the cholinergic receptors. It is likely that toluene affects the cholinergic receptors at the brainstem level. By its anticholinergic-like effect, toluene could allow higher acoustic energy penetration into the cochlea exposed to both noise and solvent. Based on this phenomenon, the authors recommend the use of hearing protection for the lower exposure action value: Lex, 8h = 80 dB(A) in noisy environments polluted by solvents.

The Influence of Selected Risk Factors on the Hearing Threshold Level of Noise Exposed Employees

“…Our results are also in good agreement with the results of the animal studies made by Campo and Maguin (2007). Their result is that daily exposure limit 80 dB is the threshold value below which no combined effect with styrene exist.…”

RPSO, Volume 4 - Julho a dezembro de 2017

“…De acordo com o National Institute for Ocupational Safety and Health (24) , nos países desenvolvidos aproximadamente 30 milhões de trabalhadores são expostos a níveis de pressão sonora elevados, potencialmente lesivos à saúde.…”

“…Os resultados dos estudos parecem indicar que as diferenças encontradas poderão ser melhor explicadas pelos ambientes de prática de cuidados encontrados, tal como sugerem os estudos sobre os hospitais íman 24 , assim denominados pelo reconhecimento da sua capacidade para recrutar e reter os profissionais de saúde.…”

“…Deve ser criado um sistema de informação comum e integrado relativo a acidentes de trabalho e doenças profissionais de forma a garantir fidedignidade e tratamento da informação 24,25 , incluindo os que envolvem trabalhadores da Administração Pública e do sector privado com critérios normalizados seguidos pelo EUROSTAT 26, 27 que pretende uma homogeneidade para o mercado profissional de toda Europa.…”

Chemical Contaminants Associated with Palm Wine from Nigeria Are Potential Food Safety Hazards

“…Adverse properties of styrene exposure have been reported and styrene has been linked to eosinophilic bronchitis [19] and transient bilateral vestibular dysfunction [20]. It has also been reported that styrene has an effect on hearing loss [21,22] and may affect neurological behavior [23,24]. The effect of occupational exposure to styrene on frequencies of chromosomal aberrations and binucleated cells with micronuclei and on single-strand break levels in peripheral blood lymphocytes has also been studied in styrene-exposed lamination workers [25].…”