Hearing thresholds of workers in a printing facility.

Forty-five exposed workers from a printing facility at Menoufia University and 45 controls were chosen for this study. All subjects underwent evaluations (personal histories and clinical examinations) and laboratory tests to determine blood lead levels and pure tone hearing thresholds. The work environment was tested for total respirable lead in fumes and particles and for noise levels. Total respirable lead was as high as 23.7 microg/m3; the noise level was as high as 50 dB. The exposed workers' mean blood lead level was significantly higher than that of the controls (36.94 +/- 4.36 and 11.51 +/- 1.22 microg/dl, respectively) and higher than the biological exposure index of 30 microg/dl, which was established by the American Conference of Governmental Industrial Hygienists. There was a significant increase in hearing thresholds among exposed workers compared to controls at frequencies of 1000-8000 Hz. Within the exposed workers, a significant association was found between hearing thresholds and blood lead levels; the hearing threshold rose as the blood lead level increased, especially at 8000 Hz. As duration of work increased (that is, years of exposure), the exposed workers' hearing thresholds increased, reaching a maximum at 8000 Hz. In conclusion, lead exposure can lead to an increase in hearing threshold level, even when exposure to noise is below the threshold limit value.