Additive estrogenic effects of mixtures of frequently used UV filters on pS2-gene transcription in MCF-7 cells

Not all UV filters produced a full concentration-response curve within the concentration range tested (100 nM-1 μM). Therefore, instead of using EC50 values for comparison, the concentration at which each compound caused a 50% increase of basal pS2 gene transcription was defined as the C50 value for that compound and used to calculate relative potencies. For comparison, the EC50 value of a compound is the concentration at which the compound elicits an effect that is 50% of its maximal effect. Individual UV filters increased pS2 gene transcription concentration-dependently with C50 values of 0.12 μM, 0.5 μM, 1.9 μM, and 1.0 μM for BP-1, BP-3, 4-MBC and OMC, respectively. Estradiol (E2) had a C50 value of 4.8 pM. Experiments with equipotent mixtures all supported our null hypothesis that mixtures of UV filters act additively to activate the estrogen receptor (ER). In view of our results and observed plasma levels it cannot be excluded that daily exposure to sunscreen formulations may have estrogenic effects in humans.