Audiological and experimental work was done to evaluate the influence
of lead exposure on the auditory system. The audiological study
was carried out on 40 lead-exposed workers (as a study group) and 20
normal hearing subjects, age and sex matched with the study group. All
subjects were audiologically investigated by basic audiological evaluation.,
Transiently Evoked Otoacoustic Emissions (TEOAEs) and Auditory
Brainstem Response (ABR) testing and their blood lead levels were measured.
This study revealed that lead-exposed workers have poorer pure'
torte thresholds in the high frequency region (4000-8000 Hz), whereas
there were no statistically significant differences between emissions from
both the study and control groups. On the other hand, ABR revealed a
statistically sigMftcant prolongation of brainstem transmission time in
lead-exposed workers.
The experimental study was carried out on 30 healthy pigmented guinea
pigs, randomly assigned to 3 dose groups/ week. Each consisted of 10
animals and was given the following dose of lead acetate : group (1) : 0
mg (control group), group (2) : 10 mg and group (3): 20 mg by intraperitoneal
injection once a week for 5 consecutive weeks. At the end of the 5th
week, the animals were sacrified and the cochleae were shelled out, decalcyfied
and histologically examined by light and electron microscope.
The sensory cells of the inner ear were unaffected while the eighth nerve
fibres showed moderate to severe degeneration depending on lead concentration.
Accordingly, we concluded that lead exposure is hazardous to |
