Die effek van ototoksiese koolwaterstowwe op die gehoordrempels van werkers by 'n petrochemiese fabriek
Joubert, Wilhelm Hendrik
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The aim of this study was to determine in an empirical manner whether the phenomenon of hearing loss due to the exposure to volatile organic solvents was present in the gasification plants of a petrochemical factory. The experimental groups included unexposed (N=20) workers, workers (N=20) exposed to noise and workers (N=19) exposed to noise and volatile organic solvents. The following assessments were made: diagnostic audiometry for the assessment of hearing thresholds; biological monitoring of ortho-cresol and hippuric acid for the biological markers of toluene; passive air sampling and noise measurements. Questionnaires were completed by the three groups to collect information about age, ethnicity, smoking habits, alcohol consumption and work history regarding the exposure to ototoxic substances as well as the period of employment. There were no statistically significant differences between the average ages of the three groups, but more of the workers in the noise group were from a higher age group. This age composition and the work history of the noise group were considered as possible influences on the results of this hearing study. The results of the passive air sampling show that the levels of volatile organic solvents were lower than the occupational exposure limits on the day of sampling. The biological monitoring shows that the markers, namely hippuric acid and o-cresol, were lower than the biological exposure indices. The noise group was exposed to sound pressure levels of 79-90 dB(A) and the noise + hydrocarbon group to levels of 85-88 dB(A). The average hearing thresholds of the noise group were at most of the frequencies (0.5-8 kHz) significantly higher (p≤0,05) than that of the noise + hydrocarbon group. The average hearing thresholds of the control group were overall lower than the noise group's hearing thresholds, but on average a little higher than the noise + hydrocarbon group's hearing thresholds. No relationship was found in this study between the exposure to volatile organic solvents (for example toluene that was used as marker in this study) and the elevation of hearing thresholds of workers at the gasification plants of the petrochemical factory.