Objective: To examine the validity of beachgoers' self-reported sun protection and UV exposure using objective measures.
Design: Eighty-eight participants completed a brief survey when they arrived at the beach; their skin was swabbed for the presence of sunscreen, while an observer recorded their clothing worn to the beach and the presence of sunburn. On leaving the beach, an exit survey detailing activities and sun habits while on the beach was completed by the participants, follow-up sunscreen swabs were obtained, and sunburns were recorded. Clothing observations were made for a subgroup (n = 25) of participants during their beach stay.
Results: Most participants (38 [44%]) reported spending 2 to 3 hours at the beach, which was consistent with researcher observations (Spearman rank correlation, r = 0.75). Moderate to substantial agreement was achieved between reported use of sunscreen for the day and sunscreen swabs (kappa, 0.54, 0.70, and 0.72 for the face, legs, and arms, respectively). Participants' self-report of clothing worn to the beach had substantial agreement with researcher observation: kappa coefficients ranged from 0.63 for footwear to 0.77 for head wear. Agreement was variable for clothing worn while on the beach, with slight to fair agreement for sunglasses (kappa, 0.11) and footwear (kappa, 0.23) and substantial agreement for upper body clothing (kappa, 0.79). Agreement between self-reported and observed sunburn was consistently lower (kappa, 0.21, 0.33, and 0.39 for the face, legs, and arms, respectively), with participants reporting more sunburn on arrival than was observed.
Conclusions: Overall, self-report measures of time outside, sunscreen use, and clothing worn demonstrated good criterion validity when compared with observation and sunscreen swabbing. Sunscreen swabbing proved an effective procedure for detecting sunscreen at a beach setting.