# Click evoked otoacoustic emissions in occupational exposure to lead, concentrations of selected essential elements and markers of oxidative stress

## TL;DR

This study shows that high lead exposure at work is linked to hearing damage through oxidative stress, with higher lead levels causing worse hearing test results.

## Contribution

The study links elevated blood lead levels to increased oxidative stress markers and hearing deterioration in workers.

## Key findings

- Higher blood lead levels correlated with increased malondialdehyde and lipofuscin, markers of oxidative stress.
- Click evoked otoacoustic emission amplitudes were significantly reduced in workers with high lead exposure.
- CEOAE parameters negatively correlated with lead and cadmium concentrations, and positively with calcium and zinc.

## Abstract

This study focused on the selected markers of oxidative stress, impact of elevated lead levels on long-term hearing quality. We investigated whether the presence of certain essential minerals might provide protection to the auditory system against the effects of lead (and cadmium) compounds.

The research group included 280 male employees of the zinc and lead smelter, which was divided into: L-Pb—low blood lead concentration (PbB) subgroup, H-Pb—high PbB subgroup. Hearing tests were performed using the click evoked otoacoustic emission (CEOAE).

Zinc protoporphyrin level was significantly higher in the H-Pb subgroup by 68%. Cd concentration was significantly higher in H-Pb by 33%. The Ca concentration was significantly lower in the H-Pb by − 2%. Selected oxidative stress markers concentration were significantly higher in the H-Pb group: malondialdehyde (MDA) by 4%, and lipofuscin (LPS) by 9%. In the CEOAE results showed statistically significant differences between the L-Pb and H-Pb subgroups. Larger negative changes in otoemission amplitude were observed in H-Pb subgroup. All otoemission results showed a statistically significant negative correlation with age, time of work, MDA concentration, and with PbB. Selected CEOAE parameters showed a significant negative correlation with cadmium blood concentration (CdB), and a positive correlation with Ca and Zn.

Elevated blood lead content in occupational exposure is associated with an increase in MDA and LPS concentration, which negatively correlates with CEOAE parameters. This suggests an important role of oxidative stress in the long-term deterioration of hearing.