Based on the CDC’s data, 25% of women in the United States today have phthalate levels in them that are within the range that based on Dr. Swan’s work, we would expect some degree of feminization in the male reproductive tract.

Well there are previous few data, hard scientific data we can use to approach the question that’s posed by the animal experiments, what affect are these compounds having on our sexuality?  Precious few data that we can use.  There are some.  Probably the most pertinent involves some very new results that look at exposure in the womb to a sweet of chemicals called phthalate that from animal experiments we know definitively act to demasculinize and defeminize males exposed in the womb.  There’s just no question about that.  We know the overt affects on structure.  We’ve got multiple cases documenting affects on behavior.  Very clear.  We know some of the genetic signaling mechanisms that have been altered by exposure to these compounds that are called anti-andergynes, the phthalates.  The animal literature is really clear. 

What can we say about people?  Well first of all we know people are exposed widely to phthalates.  The CDC, Centers for Disease Control issue studies has issued a series of studies over the last five years that makes it clear that many people are exposed to levels of phthalate sthat are high enough to be at a level of concern.  So we’re exposed.  We know what they cause in animals.  What can we conclude about people?  Unfortunately it takes a long time for Epidemiologists to answer these questions. The truth is they just started to ask them.  The best study to date has been done by an Epidemiologist, Reproductive Epidemiologist named Dr. Shawna Swan who did this work while she was at the University of Missouri Columbia.  She’s now at the University of Rochester.  She spent some time thinking about the challenges, how hard it is for Epidemiologists to work on these issues and she decided that her approach would be different from what people had done in the past.  She went and talked to the animal people, the animal folks, and she said what measurements would you recommend that I use?  You prove results but you measure things differently than we do.  What measurements might I make in people that can tell me whether what you see in animals is happening in people? 

So what Dr. Swan did was working with the Toxicologist she developed an index of feminization of the reproductive tract and took this from the Toxicologist work and went to babies living in Missouri and Iowa and measure in them, this index, feminization of the reproductive tract, and also measured in the moms how much phthalates was in their urine during pregnancy.  She then looked at the association between feminization and phthalate levels.  She found an extraordinary strong relationship.  Boys born to moms who in their blood and in their urine had high levels of phthalates, therefore indicating that the babies were exposed to high levels in the womb, they were much more likely to have a feminized reproductive tract.  She then did a rather striking calculation where she said okay, I can see this affect in the sample of babies I’ve worked with.  I can see this affect when the level rises to X.  What can we say then based on data from the CDC about how many women in the United States have phthalates levels that rise to X?  Well 25%, based on the CDC’s data, 25% of women in the United States today have phthalate levels in them that are within the range that based on Dr. Swan’s work, we would expect some degree of feminization in the male reproductive tract.