DOI: 10.1093/annhyg/meg058 Occupational Toluene Exposure and Auditory Function: Results from a Follow-up Study

Abstract

The ototoxicity of occupational exposure to toluene below 50 p.p.m. was investigated in a longi-tudinal study over 5 yr with four repeated examinations starting with 333 male workers from rotogravure printing plants. Past lifetime weighted average exposures (LWAE) to toluene and noise were determined from individual work histories; recent individual exposures were meas-ured 10 times during the study (toluene, active sampling; noise, stationary measurements). The auditory thresholds were measured with pure tone audiometry. The mean LWAE exposures to toluene and noise were 45 ± 17 p.p.m. plus 82 ± 7 dB(A) for printers (high toluene intensity) and 10 ± 7 p.p.m. plus 82 ± 4 dB(A) for end-processors (low toluene intensity). The mean current exposures to toluene and noise during the study were 26 ± 20 p.p.m. plus 81 ± 4 dB(A) for printers and 3 ± 3 p.p.m. plus 82 ± 4 dB(A) for end-processors. Repeated measurement analyses (grouping factors: toluene intensity, exposure duration and noise intensity) and logistic regres-sions did not reveal significant effects of toluene intensity, of exposure duration and of inter-actions between toluene intensity and noise intensity. The stratification dependent on noise intensity itself [79 ± 3 versus 84 ± 1 dB(A)] was significantly associated with the auditory thresholds. Regarding the missing toluene effects, it was concluded that the threshold level for developing a hearing loss as a result of occupational toluene exposure might be above the actual limit of 50 p.p.m