Objective Noise has been considered as the main risk factor for occupational hearing loss. In addition, ototoxic substances, such as organic solvents and heavy metals, contribute to this disease. However, conjoint exposures of these risk factors need further attention. Therefore, the aim of the study was to determine if there is an association between hearing thresholds and exposure to organic solvents and lead, alone or in combination with noise, in Mexican workers.

Methods A cross-sectional study was conducted including workers at a printing press in Mexico City exposed to noise and organic solvents (n=279); and workers from Tlaxcala in central Mexico exposed to lead who produce glazed clay pottery at small workshops (n=188). Organic solvents exposure was assessed by questionnaire; noise was measured with a sound level meter. Moreover, lead exposure was defined according to blood lead levels. Individuals were categorized as exposed or non-exposed in both samples. Hearing thresholds were compared across exposure categories. Multiple linear regression models were built to explain changes in hearing thresholds.

Results Exposure to organic solvents >10 years and blood lead levels >30 micrograms per deciliter were associated with worse hearing thresholds. Compared to the non-exposed group, mean hearing thresholds in exposed workers increased as years of exposure to organic solvents increased (≤5 years: 2.7 dB [0.46, 5.01]; >5–10 years: 6.3 dB [3.87, 8.77]; >10 years: 8.2 dB [6.00, 10.4]). The same behavior was observed with increasing blood lead levels, compared to workers with >30 micrograms per deciliter: 3.26 dB [0.09, 6.42]). When analyzed altogether, there was no evidence of interaction between noise, organic solvents and lead on hearing thresholds.

Conclusion Occupational exposure to organic solvents and lead was associated with worse hearing thresholds among workers from different job settings.