Combined Effects of Ototoxic Solvents and Noise on Hearing in Automobile Plant Workers in Iran

Abstract

Exposure of workers to mixtures of organic solvents and to occupational noise is frequent in a number of industries. Recent studies suggest that exposure to both can cause a more severe hearing loss than exposure to noise alone. Our cross-sectional study included 411 workers of a large automobile plant divided in three groups. The fi rst group included assembly workers exposed to noise alone; the second included workers in a new paint shop, who were exposed to a mixture of organic solvents at a permissible level; and the third group included paint shop workers exposed to both noise and higher than permissible levels of organic solvents in an old paint shop. These groups were compared in terms of low-frequency hearing loss (model 1; average hearing threshold >25 dB at 0.5 kHz, 1 kHz, and 2 kHz) and high-frequency hearing loss (model 2; average hearing threshold >25 dB at 3 kHz, 4 kHz, 6 kHz, and 8 kHz). High-frequency hearing loss was more common in workers exposed to a combination of noise and mixed organic solvents even at permissible levels than in workers exposed to noise alone even after correction for confounding variables. This study shows that combined exposure to mixed organic solvents and occupational noise can exacerbate hearing loss in workers. Therefore, an appropriate hearing protection programme is recommended, that would include short-interval audiometric examinations and effi cient hearing protectors.

Ototoxic Substances at the Workplace: a Brief Update

“…Publications issued since 2009 do not focus on particular substances, but rather on complex mixtures such as organic solvents (7,8), on exposure to chemicals in a steel company (9), or even on the complex environment of military forces (10).…”

Sensorineural Hearing Impairment and Subclinical Atherosclerosis in Rheumatoid Arthritis Patients Without Traditional Cardiovascular Risk Factors

“…Since most of the patients are not aware of their HI and have no clinical complaints, it is important that physicians consider hearing damage in these patients. 2,3,14 Despite of the increasing number of research on this topic, there is no clear evidence for the direct cause of HI, since the physiopathology remains unclear. 2,6,11 There is no consensus about audiometric evaluation methods and clinical screening in RA patients tested for HI.…”

“…2,3,14 Despite of the increasing number of research on this topic, there is no clear evidence for the direct cause of HI, since the physiopathology remains unclear. 2,6,11 There is no consensus about audiometric evaluation methods and clinical screening in RA patients tested for HI. In this context, we are unable to differentiate the importance of RA itself and other comorbidities causing HI.…”

“…1,2 Diabetes mellitus, hypertension, and smoking are traditional cardiovascular risk factors considered as a contributing factor of HI among adults. [2][3][4][5][6] HI may be classified as conductive hearing impairment (CHI), sensorineural hearing impairment (SNHI), and mixed. Rheumatoid arthritis (RA) patients have higher frequency of HI than healthy controls (42% vs. 15.9%).…”

Perda auditiva associada à exposição ocupacional a solventes orgânicos: uma revisão sistemática

“…Levels of exposure to organic solvent mixture exceeded recommended local and/or international tolerance limits in some studies 10,13,18,40 . Among them, only one showed levels of exposure to noise below the allowed tolerance limit Morata et al 10 described an increased likelihood of HL with OR=1.76 for each gram of hippuric acid per gram of creatinine found in urine, with the risk of developing HL being four times higher (OR=4.4) when the considered threshold was 2.5 g/g of creatinine (100 ppm in the air).…”