 There has been speculation that falling sperm counts in males may be due to increased estrogen exposure in utero.Sharpe in a 2005 review indicated that external estrogenic substances are too weak in their cumulative effects to alter male reproductive functioning, but indicates that the situation appears to be more complex as external chemicals may affect the internal testosterone-estrogen balance.The ubiquitous presence of such estrogenic substances is a significant health concern, both individually and for a population.