Toluene-induced hearing loss among rotogravure printing workers

This study explored the effects of occupational exposure to solvents and noise on the hearing of rotogravure printing workers from São Paulo, Brazil.

The study group comprised 124 workers exposed to various levels of noise and an organic solvent mixture of toluene, ethyl acetate, and ethanol. Data on work history, psychosocial aspects of the job, medical history, present health, stress, occupational and nonoccupational exposures to noise or chemicals, and life-style factors were collected through an interview. The participants underwent pure-tone audiometry and immittance audiometry testing. Their exposures to noise and solvents were assessed.

Forty-nine percent of the workers had hearing loss. From the numerous variables that were analyzed for their contribution to the development of hearing loss (age, tenure, noise dose, solvent concentrations in air, biological marker for toluene, job category, work and medical history items, smoking, alcohol consumption, work perception scores, nonoccupational exposures), age and hippuric acid (the biologic marker for toluene in urine) were the only variables that met the significance level criterion in the final multiple logistic regression model. The odds ratio estimates for hearing loss were 1.07 times greater for each increment of 1 year of age [95% confidence interval (95% CI) 1.03-1.11] and 1.76 times greater for each gram of hippuric acid per gram of creatinine (95% CI 1.00-2.98).

The findings suggest that exposure to toluene has a toxic effect on the auditory system. Further research is needed on the mechanisms underlying the effects of toluene and on the adequacy of current recommended exposure limits.