Hidden threats in blood: uncovering the differential retention and limited renal clearance of carcinogenic primary aromatic amines in humans.

Primary aromatic amines (PAAs) are carcinogenic contaminants with limited toxicokinetic data. We measured 22 PAAs in paired blood and urine samples from 180 adults recruited in Shenzhen, South China. PAAs were frequently detected in both matrices, and total concentrations were higher in blood than in urine (p < 0.001), suggesting matrix-specific distribution. 3,4-Diaminoanisole and aniline were the predominant compounds. Estimated renal clearance differed among PAAs and was the lowest for ortho-anisidine (median: 0.05 mL per day per kg). Lower clearance estimates in females and older adults suggest potential demographic variability, but these patterns should be interpreted cautiously because urine dilution, body weight, urine volume, and hematocrit were not individually measured. Molecular docking indicated possible interactions with hemoglobin and transport-related proteins, but these results are hypothesis-generating. This paired-matrix study highlights the value of blood-urine biomonitoring for screening PAA distribution and elimination.