Exposure to oxybenzone from sunscreens: daily transdermal uptake estimation

Area of Science:

• Environmental Chemistry
• Dermal Toxicology
• Cosmetic Science

Background:

• Fugacity is key to transdermal chemical absorption but hard to predict in complex mixtures like personal care products.
• Accurate prediction of chemical uptake from consumer products requires understanding their behavior in non-ideal mixtures.

Purpose of the Study:

• To compare predicted transdermal uptake of benzophenone-3 (BP-3) from sunscreen lotions with human subject experimental data.
• To validate a model using direct fugacity measurements of BP-3 in sunscreen formulations.

Main Methods:

• Measured BP-3 fugacity in commercial sunscreens and lab mixtures using solid-phase microextraction (SPME).
• Integrated measured fugacity data into a transdermal uptake model.
• Simulated BP-3 urinary excretion rates based on published human subject study conditions.

Main Results:

• Fugacities in commercial lotions (3-6% BP-3) were approximately 20% of the supercooled liquid vapor pressure.
• Simulated dermal uptake was within a factor of 3 of mean results from two human studies.
• The model underpredicted uptake in two other studies, possibly due to input limitations like lotion fugacity.

Conclusions:

• Combining measured fugacity with transdermal models offers order-of-magnitude accurate predictions for BP-3 uptake from sunscreens.
• This approach enhances the reliability of assessing chemical exposure from personal care products.