YOUNG MALE RATS ARE 'DEMASCULINIZED' AND 'FEMINIZED' BY LOW DOSES OF DIOXIN Three new studies by researchers at University of Wisconsin reveal that very low doses of dioxin alter the sexual development of young male rats, causing demasculinization and feminization. [1,2,3] Dr. Linda S. Birnbaum, a scientist with U.S. EPA [Environmental Protection Agency] calls the new studies "highly significant."[4] Birnbaum is one of the chief scientists conducting the EPA's formal reassessment of the toxicity of dioxin (see RHWN #269, #270, #275). As we reported earlier (RHWN #279), many scientists, including Birnbaum, now consider dioxin an "environmental hormone." The new Wisconsin studies support that view. The Wisconsin researchers, led by Dr. Richard E. Peterson, showed that dioxin interferes with the sexual development of male rats exposed to dioxin before, and shortly after, birth. Pregnant female rats were given a single oral dose of dioxin on the 15th day of pregnancy; their male offspring showed reduced levels of male hormones in their blood and a variety of sexual aberrations that stayed with them as they matured. The young males are demasculinized and feminized by doses of dioxin too low to cause any measurable toxicity in the mother rat. The sexual changes in the young males are both physiological and behavioral, and last into adulthood. Dioxin passes through the placenta and enters the fetus, so the rat fetuses received part of the mother's dose almost immediately. After birth, the baby rats continued to receive a small dose of dioxin through their mother's milk. Peterson says the baby rats received the bulk of their dose through milk. In rats and humans both, females rid their bodies of dioxin chiefly by excreting it in their milk. Dioxin is soluble in fats and oils, and milk is high in fat. Dioxin is the common name for a family of 75 toxins, the most potent of which is TCDD [2,3,7,8-tetrachlorodibenzo-P-dioxin]. The Wisconsin researchers used TCDD in their experiments. More on this shocking story inc.Terror in times beach at http://www.ejnet.org/rachel/rhwn290.htm part of http://www.ejnet.org/dioxin/index.html