Assessing the exposure to the UV filter DHHB in urine samples from the German Environmental Specimen Bank (2000-2021): Evaluating the impact of a potential impurity of di-n-hexyl phthalate in DHHB.

Summary

Across 250 24-h urine samples (2000–2021), specific metabolites of the UV filter DHHB (DHB, EHB) emerged from 2012 onward, indicating increasing exposure, though estimated intake remained far below a no-effect level. Retrospective dosing experiments demonstrated that di-n-hexyl phthalate (DnHexP) impurities in DHHB lead to measurable phthalate metabolite excretion, suggesting contaminated DHHB can contribute to phthalate exposure.

Key Findings

• In 250 24-h urine samples (2000–2021), specific DHHB metabolites DHB (18%) and EHB (13%) were detected, with first appearances in 2012 and rising thereafter.
• Estimated median daily intake was 37 ng/kg bw/d, far below the derived no-effect level of 2900 mg/kg bw/d.
• AHB (87% detection) was not specific to DHHB, limiting its utility for exposure assessment.
• Retrospective oral dosing revealed dose-dependent excretion of DnHexP metabolites from DHHB impurity; a rough 45% excretion fraction was derived for MnHexP.
• Findings warrant re-assessment of DHHB cosmetic safety and surveillance of both DHHB and DnHexP in biomonitoring.

Clinical Implications

Dermatologists and public health clinicians should be aware that DHHB-containing products may introduce DnHexP exposure if contaminated; consider counseling high-risk populations and monitoring emerging guidance. Regulators and manufacturers should audit DHHB purity and surveil DnHexP metabolites in HBM programs.

Limitations

• ESB samples were collected in winter, likely underestimating sunscreen-related exposure.
• AHB lacked specificity for DHHB, complicating exposure attribution.
• Dose allocation uncertainties limited precise excretion fraction estimates in dosing experiments.
• Cross-sectional design cannot define individual longitudinal exposure patterns.

Future Directions

Audit DHHB supply chains for DnHexP contamination, expand HBM to summer seasons and diverse populations, establish product-level impurity thresholds, and validate specific biomarkers for DHHB exposure.