A large number of studies in animals and cells have shown that the chemicals affect reproduction and development by altering reproductive and thyroid hormones, although the evidence is mixed for some studies (Krause 2012). Derivatives of benzophenone, such as benzophenone-2 (BP2) and oxybenzone (benzophenone-3 or BP3), and octinoxate are common ingredients in sunscreen.
Animal studies report lower sperm counts and sperm abnormalities after exposure to oxybenzone and octinoxate, delayed puberty after exposure to octinoxate, and altered estrous cycling for female mice exposed to oxybenzone. Recently, Danish researchers reported that eight of 13 chemical sunscreen ingredients allowed in the U.S. affected calcium signaling of male sperm cells in laboratory tests, which the researchers suggest could reduce male fertility (Endocrine Society 2016).
In addition to the relationship between oxybenzone and testosterone levels in adolescents, preliminary investigations by a team of researchers at the National Institutes of Health and The State University of New York, Albany, suggest a link between higher concentrations of benzophenones and poorer reproductive success in men seeking assistance at a fertility clinic. Men with greater exposures to benzophenone-2 and/or 4-hydroxyoxybenzone had poorer sperm quality (Louis 2015) and reported that it took longer for their partners to conceive (Buck-Louis 2014). Female exposures to oxybenzone and related chemicals have been linked to increased risk of endometriosis (Kunisue 2012).