Tag: herbicide

Atrazine, The news, And the reality

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.

My Favorite Drug

I love coffee, but I’m not a big coffee drinker.  On average I probably consume a cup of coffee every week or two.  Why don’t I drink it more often?  For a few reasons: First, I’m too jumpy/jittery/nervous to begin with and I don’t need this stuff making it worse, second, it tends to upset my stomach if I haven’t had a meal beforehand, and third, while I like regular coffee, the stuff that I really love are those insane fru-fru coffee drinks that you can only get at specialty shops for five or six bucks — which seems like a waste of money to me.  As you may have guessed, at this very moment, I have an overwhelming urge for a vanilla latte and so, in lieu of that, I have decided to submit this post.

Anyway, as most of you know, coffee is a horticultural crop, and so are most of the other sources from which most of us obtain our (legal) chemical stimulants like chocolate and tea.  What most people don’t realize is that the stimulants in chocolate and tea are actually somewhat different than caffeine.  Chocolate does contain some caffeine, but its major stimulant is the closely related theobromine (which doesn’t actually have any bromine in it…).  Tea (which also has very low amounts of caffeine), on the other hand contains the stimulant theophylline which is, again, closely related to, but not the same as, caffeine.

What blows me away about caffeine is how toxic it is.  If caffeine were a pesticide it would need to be labeled as category 2 (there are 4 classes with 1 being the most toxic).  Its LD50 (in other words, the amount of this chemical that, if fed to a person, would have a 50% chance of killing him/her) is estimated at about 75 milligrams per pound that a person weighs.  According to Starbucks website, one of their tall vanilla lattes contains about that much caffeine, and so you could assume that a 150 pound person could kill themselves by drinking about 150 lattes (or 150 of the smaller cups of espresso from which the coffee is made).  Additionally, though findings are inconsistent, caffeine has been linked to certain cancers.  The current thinking is that it may affect hormone levels in the body which, in turn, influence hormone related cancers like breast cancer, etc.  This research is far from conclusive, but it is concerning.

OK, so here’s the thing that’s interesting to me.  There is a small but real contingent of people out there who want to ban the herbicide 2,4 D (I picked 2,4 D randomly – I could have picked Round-up,  Sevin, or any other pesticide – but I was thinking of summer, and so 2,4 D, the most commonly used turf herbicide, is what I chose).  I’m no fan of 2,4 D and would love to see it used less frequently than it currently is, but it is a useful herbicide, particularly in the production of grassy crops (like corn).  In lawns its overuse borders on the insane.

Opponents of 2,4 D would like to see it gone, in large part, because of its toxicity and potential to cause cancer.  And, indeed, there are some studies that show that 2,4 D has the potential to cause cancer, though these findings are inconsistent and ultimately inconclusive.  Additionally, in terms of 2,4 D’s LD50, it’s about 170 milligrams per pound that a person weighs – over two times LESS toxic than caffeine.  I’m not going to bother figuring out how much 2,4 D would be in an average glass of 2,4 D because, well, I’ve never been served a cup of 2,4 D before and hopefully I never will.  (If you’re curious as to how much 2,4 D would be in a cup of spray if you scooped it right out of the spray tank — then about 50 mg is a good estimate though it could be higher or lower depending on a lot of factors).

Anyway, this leads me to a ton of further questions, the most important of which is, without doubt, do anti-pesticide activists who fear the health dangers posed by 2,4 D drink coffee?

For those of you interested in these types of questions I encourage you to look over this article: http://www.marshall.org/article.php?id=73  It is posted on the website of a conservative group (which will probably alienate some of you and make others happy) – but it was originally published a number of years ago in a well respected journal and is one of my favorite articles ever in terms of getting the old brain thinking (Please don’t get the idea that I agree with everything in the article – I do not).  Bruce Ames, one of the authors, is what we call in academia a “heavy hitter” and so, even if you don’t agree with what he says, his words are well worth reading.