Safety concerns over parabens arose because they mimic estrogen by binding to estrogen receptors. Parabens have been considered as a possible cause of early puberty in females, lower fertility in males, and breast cancer. Breast cancer tumors have been found to contain 20ng/ml of paraben, however butylparaben is about 10,000 times weaker than estradiol Estrogenic paraben effects were seen in animals at doses 25,000 times higher than preservative levels. Nevertheless, many countries are concerned. In April 2015, the EU limited the concentration of propylparaben and butylparaben from 0.4% to 0.14% and banned the use of these ingredients diaper products. At the present time, the US FDA has determined that paraben preservatives are safe at currently used levels.