Toxicokinetic Differences between Dermal and Oral Exposure to Ultraviolet Absorbers: Exploring Pathway-Specific...

Area of Science:

• Environmental Chemistry
• Toxicology
• Pharmacokinetics

Background:

• Ultraviolet absorbers (UVAs) are widely used in products like sunscreens and food packaging.
• Human exposure occurs via dermal and oral routes, but pathway-specific toxicokinetics remain poorly understood.

Purpose of the Study:

• To investigate the toxicokinetics and major metabolites of five typical UVAs across different exposure pathways.
• To compare oral versus dermal absorption, distribution, metabolism, and excretion (ADME) of UVAs.
• To assess human exposure pathways for UVAs using urine analysis.

Main Methods:

• In vitro experiments
• Animal administration studies
• Analysis of 24-hour human urine samples from environmentally exposed individuals.

Main Results:

• 2-ethylhexyl p-methoxycinnamate (EHMC) showed longer elimination half-life and larger volume of distribution after oral vs. dermal exposure.
• UV-328 exhibited high bioaccumulation but limited systemic absorption, suggesting enterohepatic circulation.
• An oxidative metabolite of UV-328 indicated oral exposure, while human urine data suggested non-oral routes are dominant for UV-328 in the general population.

Conclusions:

• Understanding pathway-specific toxicokinetics is crucial for accurate exposure assessment of UVAs.
• Oral exposure to certain UVAs may lead to higher systemic exposure and potential risks.
• Non-oral pathways are significant contributors to UV-328 exposure in the general population.