Determination and health risk assessment of preservatives in shampoo and hair conditioner products: a case study in Xi’an city, China

This study was conducted to systematically evaluate the usage and associated health risks of preservatives in commercially available shampoos and hair conditioners, with the aim of informing safety supervision. Using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), 42 preservatives were quantified in 80 product batches collected from Xi’an, China, and label claim consistency was assessed. Preservatives were detected in 97.5% of the samples, and regulatory compliance was observed in 97.5% of the products; however, 53.75% exhibited significant discrepancies between the measured content and label declarations. Health risk assessment, based on the Margin of Safety (MoS) calculated via Monte Carlo simulation for dermal exposure, indicated potential concerns for propylparaben and mixed parabens, with MoS values falling below the safety threshold of 100 at the 92.52nd and 73.24th percentiles, respectively. Notably, children and adolescents exhibited substantially lower MoS, particularly in children, where mean MoS values fell below 50, indicating heightened susceptibility in these subpopulations. Although phenoxyethanol and benzoic acid were the most frequently detected preservatives (57.5% and 51.3%, respectively), their MoS values suggested acceptable risk levels. These findings highlighted preservatives as essential yet safety-critical components, underscoring the need for stricter regulatory oversight of labelling accuracy and particular attention to the risks associated with propylparaben and mixed parabens.