Urinary quaternary ammonium compounds among healthy elderly in the China BAPE study: exposure characteristics, determinants, and health risk assessment

Quaternary ammonium compounds (QACs) are a broad class of cationic surfactants with antimicrobial properties that are widely used in industrial and household applications, raising growing public health concerns. However, biomonitoring data on internal exposure and associated health risks in the elderly population remain scarce. This study aimed to characterize urinary concentrations of 29 traditional and emerging QACs in a healthy Chinese elderly panel and to explore potential factors associated with exposure. In a longitudinal panel study conducted from September 2018 to January 2019, five monthly follow-ups were performed, yielding 350 urine samples from 76 participants aged 60–69 years. Samples were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). All 29 QACs were detected, with a median total concentration of 2.07 μg/L (3.19 μg/g creatinine), and traditional QACs were the dominant contributors (64.02%). Several creatinine-adjusted QAC concentrations were significantly higher in females, and modest temporal variation was observed over the study period. Exploratory analyses suggested that some questionnaire-derived dietary factors and residential behaviors may be associated with urinary QAC levels. These hypothesis-generating findings warrant validation in larger independent cohorts. Risk assessment based on three representative QACs (C10-BAC, C12-BAC and C8-DDAC) yielded hazard index (HI) values well below 1 (median HI = 1.80 × 10 −3 ). These findings suggest low non-cancer risk under the assumptions applied. This study provides pre-pandemic baseline data on urinary parent QACs in an elderly population in China. However, because urinary excretion is not the dominant elimination pathway for many QACs and only parent compounds were measured, the results should be interpreted as complementary biomonitoring evidence rather than a complete characterization of internal dose or total body burden. Nevertheless, the potential chronic health implications of long-term, low-dose exposure to QACs require further in-depth investigation.