Purpose: In thermal paper, Bisphenol S (BPS) is one of the alternatives for bisphenol A (BPA). Due to its structural similarity to BPA, concern has been raised about the safety of BPS. Indeed, handling thermal paper receipts could be a source of occupational exposure to BPS among cashiers, as it was previously described for BPA. In this study, we investigated whether frequent contacts with thermal paper are associated with an increase in urinary BPS levels in cashiers.
Method: Total (unconjugated and conjugated forms) and free (unconjugated) BPS were measured in urine samples from 17 cashiers and 15 controls, using LC-MS/MS. Spot urine samples, including pre-shift and post-sift samples and first morning void were collected from each volunteer. BPS concentration in thermal paper was determined and the number of receipts handled by cashiers was estimated as well.
Results: The median urinary total BPS concentration was 0.67 μg/L (0.52 μg/g creatinine) for controls and 2.53 μg/L (2.07 μg/g creatinine) for cashiers. Total BPS concentration was significantly higher in cashiers than in controls. Free BPS was detected in less than 20% of urine samples collected from controls and in less than 50% of urine samples collected from cashiers.
Conclusion: The detectable levels of BPS in urine of controls suggest an exposure to BPS of the general population. In addition, frequent contact with thermal paper could be responsible for an increase in urinary concentration of total BPS in cashiers.
Keywords: Biomonitoring; Bisphenol S; Cashiers; Exposure; Thermal paper; Urine.
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