Measuring U.S. consumer sunscreen application at home and online: optimizing our methods to determine sunscreen application thickness for improved environmental emissions estimates

•Home study participants applied less than half their estimated amount of sunscreen.•In an online survey, people applied less sunscreen than recommended by the US FDA.•An online survey can be successfully used to improve consumer sunscreen usage.•Sunscreen use data can be used to improve aquatic risk assessments of UV filters. Ultraviolet (UV) filters are chemical ingredients used in sunscreen products to protect the skin from the harmful effects of solar radiation and have come under scrutiny due to concerns of potential aquatic impacts after direct release to the environment. UV filter emissions to the environment are directly influenced by the amount and frequency of sunscreen products applied by consumers. Previous research indicates that consumers have not applied adequate sunscreen thicknesses for several decades. Thus, comprehensive research is needed to investigate a more representative sunscreen application thickness to better estimate UV filter emissions from sunscreen products. A home use study and an online survey was conducted to better estimate sunscreen application thickness potentially exhibited by the general population both during daily skincare routine and when going to the beach. A secondary objective was to further improve the consumer survey method for estimating sunscreen application thickness. During their daily activities, the results of the home usage test suggest that people are applying 0.89 mg/cm2 to their face and 0.85 mg/cm2 to their body on average. Using an online survey to reach a larger sample of the population, the results were higher than the home use study with people applying on average 1.09 and 1.60 mg/cm2 to their face and body, respectively, as part of a regular skincare routine and on average 1.27 and 1.67 mg/cm2 to their face and body, respectively, when planning a day at the beach. The data generated from this study can be used in environmental emissions assessments of UV filters in sunscreen products to provide more realistic and representative estimates. In addition, the online survey instrument developed as part of this research can be used to further investigate sunscreen habits and practices that influence the amount and frequency of sunscreen used by people participating in recreational activities. [Display omitted]