Kermit to Kermette? by Frank J. Dinan

Part II—A Different Approach

When Professor Tyrone Hayes submitted his report detailing the outcome of his study to Syngenta, the company rejected his findings and informed him that they would no longer support his work. After terminating its association with Hayes, Syngenta funded new studies of atrazine’s safety headed by James Carr, a professor at Texas Tech University, and a team of researchers at Michigan State University (MSU) led by John Gisey, an MSU professor. In Carr’s study, frog larvae were exposed to atrazine in nominal (assumed) concentrations of 0, 0.1, 10, and 25 micrograms per liter (ppb) of the herbicide in de-chlorinated laboratory water. The graphs shown below summarize the data reported by Carr’s group on the effects of atrazine-induced hermaphroditism, the presence of both male and female gonads, in frogs (Carr, 2003).

Questions

A Syngenta press release quotes James Carr, head of the Texas Tech team, as saying, “We have been unable to reproduce the low-concentration effects of atrazine on amphibians reported elsewhere in the scientific literature.” This statement refers to Hayes’ results (Hayes, 2002, 2003). Comment on the accuracy of this statement, and explain your reasoning.
The Hayes study (Hayes, 2003) was conducted using water samples collected from ponds and streams in agricultural and non-agricultural regions of the Midwest. The study conducted by Carr’s group added varying amounts of atrazine to de-chlorinated laboratory water. Which set of experimental conditions, if either, would be more likely to lead to valid experimental results? Explain your reasoning.
Comment on the significance of the Carr data, shown above, that reports the percent of male frogs having gonadal abnormalities at a nominal atrazine concentration of zero micrograms per liter and a nominal dose of zero micrograms per liter.

Go to Part III—“More from Hayes”

Originally published at http://www.sciencecases.org/kermit/kermit2.asp