Urinary Exposure to Chemical Additives in Healthy Older Adults in China: Characterization, Determinants, and Health Risks from the China BAPE Study

Abstract Polymer- and rubber-associated chemical additives are widely used in consumer products and are increasingly recognized as emerging contaminants of concern; however, urinary biomonitoring data for older adults remain scarce. Accordingly, the objectives were to characterize urinary exposure profiles, identify potential exposure determinants, and assess screening-level health risks among healthy older Chinese adults. A repeated-measures panel design was used, in which 76 adults aged 60–69 years in Jinan provided urine samples over five monthly visits. Among 84 additives from five classes, detection frequencies ranged from 0.3% to 94.2%, with five detected in > 40% of samples: 4-hydroxyacetophenone (4-HAP), 4,4′-di-tert-octyldiphenylamine (DTODPA), 9,10-phenanthrenequinone (9,10-PQ), 2,4-di-tert-butylphenol (DBP), and 2-hydroxyquinoline (2-HQ). Concentrations of these predominant additives were generally higher in females and varied across visits. In covariate-adjusted seasonal models, winter concentrations were lower for DBP but higher for 2-HQ and 9,10-PQ; DTODPA showed only a nominal winter increase. Repeated questionnaire data identified several exposure determinants, including inverse associations of bean intake with DBP and DTODPA, a positive association of milk intake with 4-HAP, and associations of road distance and fresh-air-system use with 2-HQ. Under the primary assumptions, DTODPA accounted for most estimated hazard quotient (HQ) exceedances, with 13.4% of samples showing an HQ > 1 and 15.2% of samples showing a summed hazard quotient (ΣHQ) > 1, whereas no HQ exceedance was observed for DBP or 4-HAP. These findings provide biomonitoring evidence for emerging chemical additives in healthy older adults, identify DTODPA as a priority compound for further investigation, and indicate chemical-specific seasonal variability.