Development of a novel rinse-off method for improved sunscreen exposure assessment

Area of Science:

• Environmental Science
• Toxicology
• Cosmetic Science

Background:

• Legislative restrictions on sunscreens are based on perceived aquatic risks, but lack robust data.
• Previous risk assessments used arbitrary assumptions for sunscreen rinse-off rates.
• Coral reefs face multiple stressors, including climate change and pollution.

Purpose of the Study:

• To accurately measure the amount of specific UVFs released from sunscreens into seawater.
• To develop a more reliable method for estimating environmental exposure to UVFs.
• To inform more accurate risk assessments for UVFs in aquatic environments.

Main Methods:

• A novel porcine skin model was used to simulate human sunscreen application and rinsing.
• Four sunscreen products (lotions, spray, stick) with specific UVFs were tested.
• UVFs released into artificial seawater were quantified after multiple rinse cycles.

Main Results:

• Rinse-off proportions varied significantly by UVF, sunscreen formula, and application rate.
• Less than 1.4% of octisalate, homosalate, and octocrylene rinsed off.
• Avobenzone and oxybenzone showed higher rinse-off rates, up to 24% for oxybenzone in lotions.

Conclusions:

• Sunscreen formulation and UVF type critically impact environmental release.
• Existing risk assessments may overestimate UVF exposure due to generic rinse-off assumptions.
• This study provides a method for UVF-specific rinse-off data, supporting more accurate environmental risk assessments.