Last week, the opening convocation for Black History Month was given by Tyrone Hayes of UC Berkeley. I was impressed: he’s exceptionally personable, and despite the poor organization of his visit (UMM’s fault, entirely) and having to drive for hours through a small blizzard to get here from the airport, he was gracious and fun to talk with. He gave a phenomenally well-organized, lucid talk which managed to describe all the basics of his research in terms a lay audience, most of whom were not science majors of any kind, could comprehend. And as I learned, most of his work is done by undergraduates—he has an enviable research program fueled by entry level students working towards a bachelor’s degree. I am humbled.

I have to say that if you get an opportunity to hear Hayes speak, jump at it. It’s a model of good educational rhetoric. And hey, if you’re on a seminar committee somewhere, look into inviting him out…it will be worth your while.

The subject of his talk was atrazine. Atrazine is a heavily used pesticide in the United States—we hose our cornfields with the stuff around here, using it to control weeds and boost the productivity of our acreage by 1.2%. That may not sound like much, but over the entire midwest, that adds up to really big money, money that flows into the coffers of its manufacturer, Syngenta. Syngenta is a Swiss company, and interestingly, atrazine is banned in Europe. In the US, we’re allowed to have up to 3 parts per billion in our drinking water, and Syngenta initially commissioned Hayes to research possible deleterious effects of atrazine.

Atrazine was thought to be harmless: it’s a compound that interferes with the photosynthetic machinery of many plants (corn has a protective enzyme that neutralizes it), and since we don’t do photosynthesis, it was thought to lack the potential to harm us. Unfortunately, what Hayes found is that it has a secondary effect, activating an enzyme called aromatase, which converts testosterone to estrogen.

And it has effects on frogs at concentrations as low as 0.1 parts per billion.

As you might guess from the fact that atrazine stimulates the conversion of testosterone to estrogen, it feminizes male frogs. He showed lots of examples and a great deal of quantitative data illustrating frogs with shriveled testes, frogs with both testes and ovaries, and in a picture that elicited a few sympathetic moans of pain from the audience, testes that were rupturing with maturing egg cells popping out of them.

Gonads from a treated male R. pipiens (0.1 ppb atrazine) with vitellogenic testicular oocytes. (A) Bouin’s-fixed section; bar = 250 µm.
The posterior portion of the gonad is filled with oocytes that are pro-
truding through the testicular lobules and can be seen on the surface
tions were taken. (B) Transverse cross-sections showing that the ante-
rior testis has poorly developed testicular lobules; the black arrowhead
shows a tangentially sectioned oocyte. (C) and (D) Large vitellogenic
oocytes in the posterior portion of the gonads. Bar = 250 µm for panels
(B-D).

The endocrinology of frogs is not that different from us in this regard. We also have aromatase and testosterone and estrogen. He showed data that correlated infertility rates in humans with levels of atrazine in their urine, and measurements of atrazine in farm workers that vastly exceeded the recommended limits by tens of thousands of times. And ladies, you aren’t off the hook: elevated estrogen levels can promote the growth rate of breast cancers. He also mentioned a statistic that I suspect the Minnesota Tourism Board would like to bury: rates of birth defects in Minnesota spike to twice the level of other seasons for children conceived in the spring, when farmers spray their fields with this stuff.

Speaking of burying the data, remember that this work was commissioned by Syngenta. Syngenta is now doing their best to destroy Hayes’ reputation. They’ve engaged in character assassination, have pressured interest groups to deny him speaking engagements, and have commissioned new studies to cast doubt on Hayes’ work. He didn’t speak too much about that, but did show an example of the results from another Syngenta study that showed no effect of atrazine on frogs: the work was so sloppily done that approximately 97% of the frogs died. That’s one way to flatten the data and make an uncomfortable phenomenon disappear.

He was supposed to be the keynote speaker at a meeting of the Minnesota Pollution Control Agency last year, but was disinvited at the last minute by the MPCA Commissioner, Sheryl Corrigan, a Republican appointee (surprised?). Steven Milloy, the master of Junk Science, has vilified Hayes. This is yet another example of the politicization of science: we have solid data, an easy to understand mechanism, and a legitimate health concern, and wealthy agribusiness lobbyists are blocking any serious consideration of the issue. Hayes has been flying back and forth between Berkeley and St Paul, working to wake people up to common sense, but so far the bills to stop atrazine use have been killed. It’s depressing when atrazine advocates say stupid things like this:

“Do you really believe that the U.S. EPA, under two administrations, one Democrat and one Republican, would disregard a real threat to human health and the environment?” said White. “Do you believe that?”

Yes. Yes, I do.

Hayes T, Haston K, Tsui M Hoang A, Haeffele C, Vonk A (2003) Atrazine-Induced Hermaphroditism at 0.1 ppb in American Leopard Frogs. Environmental Health Perspectives 111(4):568-575.