In addition to neurobehavioral effects, more recent studies have also implicated PCBs in problems associated with sexual development in wildlife and humans. Either natural or induced modifications to the PCB molecule may result in the production of compounds that become more available or perhaps more toxic than the original contaminant. When a PCB molecule is degraded by microorganisms, or through photolysis resulting from ultraviolet light or photocatalytic reactions, there is a reduction in the number of chlorines surrounding the biphenyl ring. As the number of chlorines is reduced, the compound becomes increasingly more soluble thereby more available to organisms. In addition, as the chlorines are removed from the biphenyl ring, it is possible that the chlorine may be replaced by other molecules (such as hydroxyls) which also increases the compounds solubility and thereby alters its physical and chemical properties.
Altered PCBs may become more available to organisms through the loss of chlorines or substitution of a chlorine atom by another compound such as a hydroxyl (OH) which increases the solubility and changes the character of the compound.
Additionally, hydroxylated PCBs can mimic other important hormones including sex hormones. It appears that select hydroxylated PCBs mimic the female sex hormone, estrogen, which can affect male sexual development in fetuses. PCB exposure has resulted in reduced penis size, and failure of testes to fully develop or descend. Florida alligators exposed to high concentrations of DDE, an organic contaminant formed as a breakdown product of the banned chlorinated pesticide DDT, not only experienced demasculinization, but also developed female reproductive characteristics. Estrogenic compounds have also been linked to increased incidences of breast cancer, and research is currently being conducted to determine whether these substances may be tied to increased cancers in exposed women. PCBs are also suspected of affecting thyroid function which can lead to abnormal physical and mental development in growing fetuses including cretinism.
All of these suspected chronic effects occur at very low exposures and although the impacts may not be readily apparent or obvious, they can be as devastating as those resulting from acute exposures. The effects of contaminant exposure are difficult to measure and prove, yet there is growing evidence based on animal and human studies, that PCBs and a host of other environmental contaminants, are having an impact on wildlife and humans that extends far beyond what has been recognized to date.