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Spring Means Weedkiller In Our Water

Mae Wu

Posted May 3, 2010

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So you eat organic, avoid using bug sprays around the house, and keep the yard looking good with elbow grease rather than chemicals.  That’s great!  Does that mean you are safe from pesticides?  Unfortunately, maybe not.  You could very well be swimming in it or drinking it.

Atrazine is a popular weed-killer that is used on mainly corn, sugar cane, lawns, and golf courses.  Last fall, our report Poisoning the Well found that atrazine was detected in most watersheds and drinking water systems that were monitored across the Midwest and the South

We have now updated our report with Still Poisoning the Well with more recent monitoring data and more recent scientific findings about the harms associated with atrazine exposure.  My colleague, Jen Sass, has done a great job of keeping track of all the dangers with atrazine, and our update adds to that growing list

Whenever there are heavy rains after atrazine is applied to a field or lawn, much of it is washed into nearby rivers and streams.  So it doesn’t come as much surprise that all the watersheds that were monitored found atrazine contamination.  What was surprising was that atrazine was showing up in drinking water coming out of the tap – sometimes at alarmingly high levels.

EPA regulates how much atrazine can be in our drinking water (no more than 3 parts per billion), but compliance with the standard is based on the average of 4 samples taken over the course of a year.  The data in our report were from samples taken much more frequently (up to once a week during the growing seasons in the spring and summer) – sometimes up to 30 times a years. 

And what did we find?  High spikes of atrazine in drinking water!  Turns out that when you sample the water more frequently, you can catch spikes of atrazine that last a few weeks, while sampling only once every 3 months (as required by the EPA rules) means it’s easy to miss these spikes. In fact, of the 153 water systems that were sampled between 2005 and 2008, 100 drinking water systems had spikes of atrazine in their untreated water that exceeded 3 ppb.  Two-thirds of these 100 systems had spikes of atrazine greater than 3 ppb in the treated water.  Most troubling, six water systems had high enough atrazine levels to exceed the EPA drinking water standard of 3 ppb. 

And here’s a little secret that Syngenta (the manufacturer of atrazine) doesn’t want people to know: we don’t actually need atrazine.  Studies have shown that not using atrazine might only cause a loss of corn yields as little at 1.19%.  And on the flip side, water systems are spending tens of thousands of dollars treating water to remove contaminants like atrazine. 

So check out our report and see if your system is keeping atrazine out of your water.  If it doesn’t, contact them and ask them why not. 

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JohnJamesMay 3 2010 11:44 AM

Atrazine is safe and has been used for over 50 years. There have been over 6,000 studies performed aloned on Atrazine. During the last 20 years, Atrazine has improved corn yields between 5-11%. World-renowned institutions including the World Health Organization, the National Cancer Institute and EPA all have studied atrazine and found no cancer concerns when used as directed.
Fifty years of scientific study and on-farm use give farmers’ peace of mind that atrazine can be used safely and effectively. That's great news in these days of increasing demand for food and renewable fuels.

Josh MogermanMay 3 2010 12:16 PM


Thanks for taking time to comment. While it is true that atrazine has been studied intensively, the bulk of the studies have been funded by the pesticide maker. It is notable that there is a tidal wave of new, independent, third-party science that points to very significant human health impacts (and wildlife too). This information, along with the massive levels of atrazine contamination of our water, simply cannot be ignored.

JohnJamesMay 3 2010 01:00 PM

Actually, a majority of the studies have been done by our own EPA.
Also, the new questionaable science was done by an admitted anti-atrazine activist who's studies have never been duplicated.

John LiffeeMay 3 2010 01:17 PM

JohnJames - As I recall, a cloud of industry influence and backroom deals hangs over the EPA's studies to date on atrazine. That's why the current EPA leadership is taking another look at the latest science.

Jen SassMay 3 2010 01:45 PM

Thoughtful and knowledgeable comments. Thanks for posting. Yes, Mr. James is correct that much of the studies are conducted by EPA scientist. However, these studies overwhelming demonstrate health harms associated with atrazine exposure. See for example studies by EPA scientists Tammy Stoker, Ralph Cooper, and Susan Laws. Moreover, the new science is much more vast than one individual. Please see the updated science review in our 2010 report.We review a number of well-conducted studies reporting on observed adverse impacts in diverse species and under diverse experimental conditions. No one can reasonably claim that atrazine is safe. Syngenta is saying it is well-studied, as if that were the same as safe. Atrazine is indeed well-studied, and the studies show harm.

JohnJamesMay 3 2010 02:54 PM

I was wondering where Ms. Wu got her statistics saying Atrazine only increases yields 1.9%? I wonder if she has ever talked to a farmer? or even been to a farm? You might want to ask a conventional farmer if they think it works. Besides that, the EPA says that Atrazine saves farmers $28/per acre. Also, Atrazine allows farmers to use no-till farming practices which prevent run-off and soil erosion.

Mae WuMay 3 2010 03:14 PM

Thanks for the comments. You should check out both our original and updated report that I mentioned to get the references. The statistic comes from two reports by the US Department of Agriculture. As to tilling and soil erosion, those are good points, but I don't think there needs to be a trade-off between productive farming and poisoning our water. And don't forget, farmers and their families are exposed to the highest levels of agricultural chemicals; and they deserve to earn a livelihood without having to risk their families' health.

JohnJamesMay 3 2010 03:43 PM

Thank you for responding Mae. I started to read through your reports and was stunned to see the inclusion of Dr. Tyrone Hayes, who has been discredited by the EPA multiple times, which in turn gives your report questionable credibility. Its just tough to believe studies done by an admitted anti-atrazine activist who has spent a decade working with other activists. His work has never been duplicated and has serious flaws.

Mae WuMay 3 2010 05:34 PM

I'm glad that you started reading our report, and it's unfortunate that our one citation to a study by Dr. Hayes would sway your opinion in light of all the other studies that we also cited. Do you think all of those studies showing that atrazine can have adverse effects are also not credible?

Also, Dr. Hayes is a respected expert among his colleagues, his work is published in top-ranked peer-reviewed scientific journals, and he is a professor at Berkeley - a top ranked university. I suspect that his "activism" might come from the science that shows him atrazine is a problem.

Misha KovacMay 3 2010 08:51 PM

JohnJames, I note your particularly careful choice of words. You say "all have studied atrazine and found no cancer concerns when used as directed". Nice red herring there! Cancer isn't the issue. The reason atrazine is e.g. banned in the EU (!) is that it is an endocrine disruptor. I.e. it seriously messes up your hormonal balances, including leading to decreased sperm counts, low birth weights, and menstrual problems. You don't happen to work for Syngenta, do you? ;-)

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