Occurrence and Human Exposure Assessment of Emerging Hindered Amine Light Stabilizers in Paired Breast Milk and Urine from Nursing Mothers in South China.

Hindered amine light stabilizers (HALSs) have been detected in various environmental media, yet human biomonitoring evidence remains absent. Herein, we determined 11 HALSs in paired breast milk and urine samples from nursing mothers in South China. At least one HALS was detected in 98.7% of breast milk samples and 98.7% of urine samples, with ∑HALS concentration ranges of < MDL-19.9 ng/mL (median: 2.20 ng/mL) and < MDL-23.0 ng/mL (median: 1.29 ng/mL), respectively. HALS compositions differed between breast milk and urine samples and 4-hydroxy-1-(2-hydroxyethyl)-2,2,6,6-tetramethylpiperidine (HA 201) was the dominant compound. Most intercompound correlations were weak, suggesting compound-specific sources and toxicokinetic behaviors. In paired-sample regression analyses, breast milk concentrations of HA 201 and methyl 1,2,2,6,6-pentamethyl-4-piperidyl sebacate (HS 508) showed weak but statistically significant positive associations with corresponding urinary concentrations. In exploratory analyses, recent home renovation, frequent plastic-packaged convenience food consumption, and greater personal care product use were associated with higher HALS levels. Under high exposure scenario, breastfeeding-mediated intakes of bis(1,2,2,6,6-pentamethyl-4-piperidyl) butyl(3,5-ditert-butyl-4-hydroxybenzyl) malonate (Tinuvin 144) in infants younger than 3 months exceeded the predicted reference dose, indicating a screening-level risk signal. This biomonitoring evidence of HALSs in human biological samples highlights the need for expanded exposure and toxicity studies.