Effects of occupational exposure to organic solvents and noise on hearing.
Morata-TC; Dunn-DE; Kretschmer-LW; Lemasters-GK; Keith-RW
Scand J Work, Environ & Health 1993 Aug; 19(4):245-254
A study of the effects of exposure to organic solvents and noise on hearing was conducted. The cohort consisted of 50 workers, mean age 36.1 years, exposed to 88 to 97 A-weighted decibel (dBA) noise in the binding and finishing division of a Brazilian printing factory; 50 workers, mean age 32.5 years, exposed to 75 to 600 parts per million toluene (108883) and 88 to 98dBA noise in the rotogravure division of the printing factory; and 39 workers, mean age 31.7 years, exposed to mixed solvents in a Brazilian paint manufacturing facility. The solvent mixture consisted of toluene, xylene (1330207), benzene (71432), methylethyl-ketone (78933), methylisobutyl-ketone (108101), and ethanol (64175). The summed concentrations of the solvents relative to their individual threshold limit values ranged from 0.59 to 1.59. The comparisons consisted of 50 workers, mean age 34.7 years, not exposed to organic solvents or excessive noise. The subjects completed a questionnaire to obtain information on occupational and medical histories and nonoccupational noise exposures. Pure tone and immittance audiometric testing was performed. The extent of hearing loss was determined from the audiograms. The prevalence of bilateral high frequency hearing loss in the workers exposed to both noise and toluene was 53% which was significantly higher than in the comparison group (8%), the noise only group (26%), and the mixed solvents only group (18%). The prevalences of inductive or unilateral hearing loss was similar in all groups. Exposure to noise, noise plus toluene, and the solvent mixture was significantly associated with an elevated risk for high frequency hearing loss. Length of exposure was weakly associated with high frequency hearing loss. Nonoccupational noise exposures were not a risk factor for high frequency hearing loss. The authors conclude that exposure to toluene and mixed solvents increases the risk of noise induced hearing loss. The risk is greater for workers exposed to toluene plus noise. The apparent interaction between toluene and noise suggests that this type of hearing loss involves the central auditory pathway.
NIOSH-Author; Organic-solvents; Occupational-exposure; Noise-exposure; Aromatic-hydrocarbons; Printing-industry; Hearing-loss; Synergism;
Author Keywords: auditory system; interaction; paint manufacturing; rotogravure printers; toluene; xylene
Dr TC Morata, Visiting Scientist, National Institute for Occupational Safety and Health, Bioacoustics and Occupational Vibration Section, Division of Biomedical and Behavioral Science, 4676 Columbia Parkway/ MS C27, Cincinnati, OH 45226-1998, USA
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Scandinavian Journal of Work, Environment and Health