Tuesday, November 06, 2007

Atrazine Brings the Bachelor to Life

When the stork arrives, there is a 50/50 chance that it will bring a girl, Right? Not so, says a team of researchers. Since 1970 there is a "distinct and unexplained trend" of more female births than male. Devra Lee Davis, et al., Declines in Sex Ratio at Birth and Fetal Deaths in Japan and in U.S. Whites, but not African Americans, 115 Enviro. Health Persp. 61 (June 2007). This is especially strange because boys historically outnumber girls 51/49.

Most shocking are the statistics from the Aawjiwnaang First Nation community in Canada. They reported that "sex ratios have dropped from an expected 0.55-0.54 range to 0.45 for the late 1990s, to 0.35 for the 1999-2003 period." Id. This constitutes the greatest rate of change in sex ratio ever reported.

This brings to mind recent research from Tyrone Hayes, the frogman from Berkeley. I don't know if that's how others think of Tyrone Hayes, but he will always be the frogman to me. Hayes has published numerous articles finding that little boy tadpoles who grow up next corn fields often become little girl tadpoles. See e.g., Tyrone Hayes, et al., eminization of Male Frogs in the Wild, 419 Nature 895, 895 (Oct. 31, 2002); Tyrone Hayes et al., Atrazine-Induced Hermaphroditism at 0.1 Ppb in American Leopard Frogs (Rana Pipiens): Laboratory and Field Evidence, 111 Enviro. Health Persp. 568, 574-75 (2003).

In fact, the study's authors posed exposure to endocrine-disrupting hormones as one of the potential causes of the observed sex ratio. They cite altered sex ratio in children of gardeners and farmers as support for this theory. One problem with this theory - if pesticide exposure causes altered sex ratio, then why the variability between blacks and whites. I have my own little theory - more white people live around corn fields. While I just pulled that one out of thin air, I think it is superior to the researchers suggestion that African Americans have "greater exposures to hair care and other personal care products." Out of respect to the researchers, I must note that they pulled that idea out of another paper and mentioned one or two other forgettable explanations. Still, shame on them for citing it!

Because I am interested in pesticide regulation, I might be a little too happy to jump on the pesticide causation theory. Despite my own biases, I think this data should give us a moment of pause about our current use of endocrine-disrupting chemicals. If we don't take that moment of pause, The Bachelor, a really bad t.v. show, could become all too real. Watch it next week - it will strike fear into your heart and motivate you to buy organic and filter your water.


Anonymous Drew Kershen said...

I cannot comment on the sex ratio study but I can comment on Tyrone Hayes, the frogman from Berkeley.

His research on frogs has some interesting results.

First, he finds that the lower the level of atrazine the higher the level of deformities. In other words, there are fewer deformities as the atrazine level increases. In toxicology, dosage matters.

Second, he finds in the field that an Iowa waterbody with no atrazine has the same level of deformities as a Wyoming waterbody with atrazine. Moreover, a Utah waterbody with the same level of atrazine as the Wyoming waterbody had 900% fewer frog deformities. He thus found no correlation.

Third, researchers at four other universities have been unable to replicate the Hayes laboratory results. In science, replication of laboratory results matters.

Fourth, researchers more recently, including one report from U-Wisconsin,Madison, found that parasitic worms were the likely cause of the deformities than others posited.

As the authors of the sex ratio report were apparently pulling "causes" from thin air, along with the poster of the original blog, the use of the Hayes studies is consistent with that approach. Pulling from very thin air indeed!

11/15/2007 12:37 PM  

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