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Planetary Watch: Herbicide Links Give Pause

by Bill Chameides | July 8th, 2008
posted by Erica Rowell (Editor)

Permalink | 4 comments


Two new studies linking abnormalities in toads and herbicides should act as a warning. (Photo: Wiki Commons –

With people getting salmonella poisoning around the country, the last thing you want to hear about is a problem with fresh produce. But two new scientific papers suggesting a possibly sinister link between toads and agriculture should put us on notice — for the link may spell trouble for humans too.

‘Endocrine Disruptors’ Play Havoc With Normal Body Functions

Probably many of you have used herbicides to control weeds in your gardens and lawn. I bet you are real careful to avoid getting the stuff on your clothes or body. After all, they’re poisonous, right? Yes, but there are poisons and there are poisons, and what frightens me about herbicides is that many of them act as so-called endocrine disruptors.

Endocrine disruptors mimic natural hormones in an organism and end up playing havoc with normal bodily functions. Laboratory experiments have shown that when an endocrine disruptor comes in contact with a cell, the cell binds the disrupting chemical to a site that is normally reserved for a real hormone. As a result, the function of the hormone never gets done. A short animation of how this occurs can be found here.

Probably the most dangerous of the estrogen disruptors are those that mimic steroid hormones like estrogen. Very bizarre and disturbing reproductive abnormalities in animals have been linked to exposures to this class of chemicals.

A conclusive link between exposure to endocrine disruptors and human disease has yet to be established. But there are hints. Concerns range from breast cancer to low sperm count, testicular cancer, and malformed reproductive organs.

Despite Clear Threat Herbicides in Wide Use

Which brings us back to herbicides. Despite their clear threat, we inundate our land with the stuff. Farmers use huge quantities — 70 percent of all pesticides used in the United States are herbicides. According to a University of Florida report [PDF], U.S. farmers use 280 million pounds of herbicides in a year. And don’t forget, the herbicides are sprayed on the crops that eventually find their way to our dinner table.

Two of the most commonly used herbicides — glyphosate and atrazine — have both been shown in laboratory experiments to interfere with gene activity in human placental cells.

And if that wasn’t bad enough, now we have two more scientific studies to worry about.

In the July 3, 2008 online edition of Environmental Health Perspectives, University of Florida researchers report on a study that establishes a link between agricultural activity and reproductive abnormalities in male toads. In the study toads from five sites were collected. The sites ranged from completely agricultural to completely suburban/non-agricultural. The likelihood of gonadal abnormalities increased in direct correlation with the level of agricultural activity.

So how do we know that herbicides are the culprit in this study? We don’t, but the results of the next study suggest that the answer may very well be herbicides.

Have you ever wondered where all the chemicals go once they are applied to our crops? Some are transported into the atmosphere before returning to earth in rainfall. Many chemicals run off our fields into surface waters. Some are carried down into the soil and move into our groundwater. Under certain conditions the original chemical breaks down into other chemicals (degradation products) that add to the original pollution.

A new USGS study published in the Journal of Environmental Quality found that in agricultural areas across the nation (growing crops as diverse as grapes, apples, and corn and soybeans) herbicides and their degradation products (rather than pesticides and fungicides) were the most frequently detected contaminants in groundwater.

Time to Give Herbicides A Hard Look

The two most persistent classes of herbicides found were triazines and chloroacetanilides. These compounds were found in groundwater dated from 2004 all the way back to 1949 and at all depths tested from 2 to 52 meters below ground surface. These classes of herbicides are endocrine disruptors and include several of the most common agricultural herbicides used in the United States: atrazine, metolachlor, and alachlor. All three compounds are being phased out or are already banned in Europe, but not here.

Clearly we have a problem. We can’t live without food and most farmers will say that they need to use herbicides to get the food we need to the supermarket. And with a world food shortage, steps that might reduce agricultural output are not well advised.

On the other hand, using herbicides is poisoning the very ecosystems that we depend on for sustenance and, very likely, also poisoning ourselves. We need a different way to grow our food — one that gives bounty without such a high price. Some advocate organic farming with more crop rotations and less dependence on monocultures.

I don’t know if that that is the answer, but I am pretty sure we are going to have to find a better way. In the meantime, if you are using one of those handy-dandy herbicides to keep the weeds out of your garden, you might consider doing what I do — get down on you knees and pull the weeds out with your hands. It’s a great way to pass a little time in your yard.

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  1. Stephany Wilson
    Jul 15, 2008

    Dear Bill, I think the broad influence of media creates a safety bubble that lends you to believe that it is safe to use. I used to use round up liberally in my yard, especially for stubborn weeds. I did not take any special precautions. I felt very safe using it, it is depicted as being safe in the media. My friends, a lot of my family all used it as well. It had become a “norm” and I never really worried about it. Years later, after being diagnosed with a thyroid condition, I became more conscious and aware of the chemicals in my home and garden. I do not use any anymore! My yard is a bit weedier but I am not willing to trade on my health. I used to use fungicides and pesticides on my roses, no more, zip, zero. For the last few years, inside the house I use vinegar and water to clean, and outside for weeds I use my gloves. I will say that it was hard to make the switch to thinking more critically and questioning product content. ” title=”herbicide

    • Erica Rowell
      Jul 15, 2008

      Dr. Bill Chameides responds – Stephany, Thanks for your cautionary tale; many of us have similar stories to tell. I hope you are doing ok now.” title=”Cautionary tale

  2. Geoffrey Mock
    Jul 15, 2008

    I don’t have a comment as much as a question: I’ve been hearing different things about Roundup — which allegedly has less toxic events. I use it sparingly, but my yard is prone to poison ivy so I have used it for that. What is the evidence as to whether Roundup is an endocrine disrupter?” title=”herbicides and Roundup

    • Erica Rowell
      Jul 15, 2008

      Dr. Bill Chameides responds – Roundup is a problem because it contains glyphosate, which studies suggest has toxic properties (see, also linked to above). Whether you want to take the chance or not is up to you. I don’t use it. I rip up my weeds instead, not unlike the character wary of Roundup in Barbara Kingsolver’s novel PRODIGAL SUMMER. “Earlier in the day she’d showed Rickie how to use a sharpened spade instead of Roundup to cut out the field-apple saplings planted by accident in the lawn.” — PRODIGAL SUMMER, Barbara Kingsolver, p. 440″ title=”Pulling out weeds is an effective alternative

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