A paper was recently published in the Proceedings of the National Academy of Sciences which discussed the dangers of one of the most commonly used weed killers in the United States, atrazine. This paper was written by Tyrone Hayes and colleagues and was immediately embraced by the media because it showed something scary (which the media loves — in case you were wondering). In a nutshell this study showed that frogs were changed from males to females when they were exposed to relatively small amounts of the herbicide atrazine. The next day in class I had a student come up to me and ask me about it and what I thought. I gave him my short answer (class was about to start). Here’s the longer one, but first I want to present you with some notes which will be important as we proceed.
Science does not provide values, instead it is a tool to use with your own personal value system. Some people may put a high value on cheaper production of important food crops such as corn, while others may put a high value the absence of potentially dangerous chemicals. That doesn’t matter to science. Remember that — science doesn’t give a poop what you care about. Furthermore, science doesn’t care what past experiments have found — what one researcher finds another may not find. Who knows why? That’s just the way things happen. On with the story.
Atrazine has been around since 1959. It’s a preemergent herbicide (which means that it kills weed seeds as they germinate) used on a variety of crops, but most frequently on corn. One of the advantages of atrazine is that it works extremely well in no-till growing systems which are used to reduce erosion. Another advantage of atrazine is that it’s cheap. Generally atrazine is considered to have a low toxicity (lower than caffeine for example). Additionally, though there is some data out there showing that it may cause cancer, this is grossly outweighed by data demonstrating that it isn’t carcinogenic. But there is data showing that atrazine is a hormone disruptor potentially affecting such hormones as estrogen and testosterone — and this effect is generally considered real — in other words not many scientists dispute it.
Over the years this hormone effect has been seen as a Bad Thing, but not bad enough to warrant banning this useful herbicide. Then along came Tyrone Hayes — and he started looking at how atrazine affected frogs — despite the recent news surge he has been doing this work for a long time (about 10 years) and has published much of that work. In a nutshell he is showing that atrazine, and to some extent other chemicals, cause hormone problems in frogs, particularly male frogs. Sex change and/or hermaphroditic frogs ensue! Unfortunately (or fortunately depending on how you look at it) other researchers have not been able to show the same things — at least not it the dramatic way that Dr. Hayes has (I’m not implying that they haven’t found problems with atrazine — they have — Dr. Hayes findings just tend to be more dramatic. Speaking of which, if you ever have the opportunity to see Dr. Hayes give a talk GO! He is an amazing public speaker and his slides and words make his findings even more dramatic). There is little to no direct evidence that hormone disruption caused by atrazine is currently affecting humans though many news sources are trying to draw that link. Indirect evidence is pretty weak too — but not nonexistent. The European Union banned atrazine in 2001. Should we follow?
My value judgement follows — yours might be — in fact it probably should be — different.
Here’s what I think. Ban atrazine, or at least regulate it more tightly. Why? Because there are many weeds resistant to it (that’s what happens to old herbicides…). Because there are options which are safer for our ecology (though they are somewhat more expensive). Because this stuff is showing up in groundwater at rates higher than what we’d like to see, and these concentrations will probably continue to rise — a direct result of using the stuff for so many years. Look, we don’t need to cut farmers off from this stuff right now, lets start a phase-out program and get rid of it over the next five years. Why not? If we NEEDED it to produce crops I’d probably be on the other side of the issue, but we don’t, so I reside firmly on the “let’s be cautious about this” side.