Researchers in San Francisco, U.S. have found in a latest study that bisphenol A (BPA) and methylparaben, two chemicals commonly used in consumer products, can interfere with the breast cancer drugs, local media reported on Tuesday. In the study, doctors from California Pacific Medical Center in San Francisco found that healthy breast cells from high-risk patients started to find ways to bypass breast cancer drugs after they were exposed to BPA and methylparaben in the lab. The cells exposed to the two chemicals kept growing and didn\'t die after they were introduced with Tamoxifen, a current standard drug therapy for female breast cancer and most common used treatment for male breast cancer, Dr. William Goodson, lead author of the study, told San Francisco Chronicle. Goodson said that BPA and methylparaben not only mimic estrogen \'s ability to drive cancer, but appear to be even better than the natural hormone in bypassing the ability of drugs to treat it. The finds have been published online in the British medical journal Carcinogenesis. The research shows more evidence of safety issues of BPA, a chemical primarily used to make plastic baby bottles, food containers, household electronics and etc, as well as the less known methylparaben, a chemical preservative used in cosmetics and other personal care products. The researchers noted that the breast cancer rates have been growing by about the same amount in men as in women over the past three decades. Scientists have been looking at environmental causes for the disease and wondering where the hormones are coming from. Goodson said BPA and methylparaben are used so widely and even found in household dust, noting that it is still unknown whether the effects of exposure to the chemicals are reversible.Since 2008, several governments issued reports questioning the negative health effects of BPA, especially raising concerns regarding exposure of fetuses, infants and children. BPA use has been banned in baby bottles in a lot of countries and regions. As for methylparaben, the U.S. Food and Drug Administration said on its website that \"at the present time there is no reason for consumers to be concerned about the uses of cosmetics containing parabens (including methylparaben).\"