Hearing threshold for workers in a printing office

ABSTRACT

Forty five exposed workers, [in a printing office in Menoufia University], and 45 controls were chosen for this study. All were subjected to clinical evaluation [personal history and clinical examination] and laboratory tests [determination of blood lead and pure tone audiometry]. Environmental study included detection of total respirable lead in fumes and particles in the work atmosphere in addition to measuring noise level. The results revealed that the total respirable lead was up to 23.7 ug/m3 and noise level up to 50 dB. The mean blood lead level for exposed workers was significantly higher than that for controls [36.94 +/- 4.36 and 11.5 +/- 1.22 ug/dl, respectively] There was a significant increase in hearing thresholds among exposed than controls at frequencies 1000-8000 Hz. Within the exposed group, there was a significant association between blood lead level and hearing threshold as one increased as the other increased specially at the frequency of 8000 Hz. Also, the hearing threshold of the exposed workers got higher as the duration of work increased reaching a maximum at the frequency of 8000 Hz. In conclusion, exposure to lead could lead to increase of hearing threshold level even if exposure to noise was below threshold limit value of noise exposure