Background The three chemical ultraviolet absorbers benzophenone-3 (BP-3), octyl-methoxycinnamate (OMC) and 3-(4-methylbenzylidene) camphor (4-MBC) are commercially used in sunscreens worldwide. Apart from sun protection, they may possess endocrine-disrupting effects in animals and in vitro. For all three compounds, only sporadic measurements of percutaneous absorption and excretion after topical application in humans have been described.
Methods In this study, 32 healthy volunteers, 15 young males and 17 postmenopausal females, were exposed to daily whole-body topical application of 2 mg/cm2 of sunscreen formulation at 10% (w/w) of each for 4 days. Blood concentrations were measured at 0, 1, 2, 3, 4, 24 and 96 h and urine concentrations at 0, 24, 48, 72 and 96 h.
Results Almost all three sunscreens were undetectable in plasma and urine before the first application. One to 2 h after the first application, all three sunscreens were detectable in plasma. The maximum median plasma concentrations were 187 ng/mL BP-3, 16 ng/mL 4-MBC and 7 ng/mL OMC for females and 238 ng/mL BP-3, 18 ng/mL 4-MBC and 16 ng/mL OMC for men. In the females, urine levels of 44 ng/mL BP-3 and 4 ng/mL of 4-MBC and 6 ng/mL OMC were found, and in the males, urine levels of 81 ng/mL BP-3, 4 ng/mL of 4-MBC and OMC were found. In plasma, the 96-h median concentrations were higher compared with the 24-h concentrations for 4-MBC and OMC in men and for BP-3 and 4-MBC in females.