Expert response from Bruce M. Chassy
Professor Emeritus of Food Safety and Nutritional Sciences, Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign
Friday, 14/11/2014 13:43
The claim is not substantiated in the Kruger et al. 2014 paper, and no relationship is shown between glyphosate in urine and health. The design, conduct, analysis and conclusions of the research are all so flawed that one wonders how the paper was accepted (in 20 days) even in a journal with a low impact factor (0.6). This is just another in a growing series of flawed papers designed to incite fear. The reasoning that underlies this conclusion is briefly explained in the following paragraphs.
We often read on the net or see on TV that a new research paper claims some new risk or harm. The question asked here shows why it’s really important to consider the source before accepting new claims and, if at all possible, to read the original paper. The alternative, if the paper is unavailable or is too complicated to understand — which happens often with research papers written in fields with which we are unfamiliar — is that we end up relying on the opinion of experts. It’s fair to say that whom we believe determines what we believe.
Let’s start with a little background information. Glyphosate has been used for decades with no evidence of having had adverse effects on people, including those who are frequently exposed to large quantities of glyphosate (e.g., farmers and farm families). Chances are good you have used it around your own house. Toxicologists have found that glyphosate is about as toxic to us as baking soda, so we have to consume enormous amounts to see any evidence of harm. There is also substantial scientific literature that documents the relative safety of glyphosate, so much so that switching from other herbicides to glyphosate is considered beneficial for the environment. Regulators at the Environmental Protection Agency have approved its use in agriculture and have conservatively set safe levels of consumption in foods. The World Health Organization, the European Food Safety Authority and expert regulatory bodies around the world are in agreement and have set similar safe levels of intake.
Since it’s a key issue to this discussion, it’s worth taking a moment to examine what a safe level of intake really means to us. Toxicology is sometimes called the science of poisons, but toxicologists prefer to think of it as the science of how to avoid getting poisoned. Take note on what this really means. It is impossible to avoid consuming chemicals that could poison us if we consumed too much of them. We encounter dozens, if not hundreds, of potentially toxic compounds in our food and water every day; it is impossible to avoid them, but when consumed in small amounts, these chemicals cause no harm. The key questions toxicologists seek to answer are how much does it take to hurt us and how often do we consume a potentially toxic compound. Toxicologists like to say “the dose makes the poison.” Toxicologists have developed rigorous testing systems in animals that allow them to determine the amount of a material we can consume every day for a lifetime without doing any harm. And just to be careful, they set recommended levels of intake 100- or 1,000-fold below the highest safe intake level. All of this is done so that we don’t have to test high doses of compounds in humans; it’s generally accepted that deliberately exposing humans to uncharacteristically high doses would be unethical. One downside of this approach is that it allows opponents of chemicals to claim that “this compound has never been tested in humans.”
The paper in question claimed glyphosate was found in urine. This comes as no surprise, since with today’s highly sensitive methods we can detect trace amounts of thousands of environmental chemicals in biological fluids. The question we must answer is whether the observed levels were high enough to cause us to be concerned that they might cause harm. This is important, since the paper claims that sick people have higher levels of glyphosate in their urine than healthy people and clearly implies that glyphosate may be contributing to their illness. Before we become alarmed, we need to carefully examine the paper.
It’s hard to believe that this paper received an adequate peer review in the short time between submission and acceptance. It contains many typos and is sketchy and incomplete in many important points normally expected to be detailed in a paper. There are serious shortcomings in experimental design, the experimental groups and procedures are not adequately described and key statistical analysis is missing. One could not replicate this paper with the information provided. This is a key requirement for all research papers.
Looking specifically at the data in question reveals that the authors do not present the actual data for analysis of glyphosate in the urine or “clinically diseased” humans. The observed differences are small, and without the data we can’t verify for ourselves if the differences are significant. Actually, it isn’t even necessary to check the numbers, because the researchers didn’t collect the right data. The reported concentration of a compound in urine is only half the story; without knowledge of the urine volume, we can’t calculate how much of the compound being measured is present in our bodies. It’s really pretty simple: Urinary Volume x Urinary Concentration = Total Compound Excreted. The authors don’t bother to tell us what illnesses and diseases the sick subjects were suffering from, which is important because illness has direct effects on urine flow and concentration. For that matter, the subjects’ food and fluid intakes were also not reported. Obviously, if one person drinks twice as much water a day as another, his or her urine will be more dilute, and in this case that person would have half the glyphosate concentration in his or her urine. Sick people are often dehydrated and thus excrete more-concentrated urine. Looking at the data for people who consume organic foods, we could ask if the more health-conscious organic consumers also are careful to follow the healthy advice to consume plenty of water every day and thus have more dilute urine due to greater volume of urine flow. In other words, it is impossible to confirm that there really is a difference between the control and experimental groups in this study. And, to return to the concept that the dose makes the poison, none of the observed levels raises any cause for concern, because they are far below the level required for glyphosate to do harm over long-term exposure.
The paper commits a serious logical fallacy. Even if it were factually true that levels of glyphosate are higher in sick and diseased subjects than in healthy people, that does not demonstrate any cause-and-effect relationship. Simply put, there is no way to determine whether glyphosate caused the illness, whether higher glyphosate in urine was caused by the illness, or whether there is no relationship between glyphosate and illness. Of course, since urine volume was not measured and the primary data are not provided in the paper, it is actually illogical to conclude that there is any relationship whatsoever between glyphosate and disease.
There are in fact so many flaws in this paper, this review could go on for pages and pages, but let's try to get to the bottom line by looking at the authors’ conclusions:
“Glyphosate residue could reach humans and animals through feed and excreted in urine. Presence of glyphosate in urine and its accumulation in animal tissues is alarming even at low concentrations. Unknown impacts of glyphosate on human and animal health warrants further investigations of glyphosate residues in vertebrates and other non-target organisms.”
Well, it’s certainly true that if glyphosate is used in agriculture, one might reasonably expect to find trace amounts of glyphosate in food and feed. The question is, are those levels of concern? The answer to that is no, but the authors want you to believe that any chemical is of concern, no matter how little of it is present. In the second sentence of the conclusions, they state that the mere presence of glyphosate is alarming, even when expert medical toxicologists and hundreds of other research papers have concluded that they are of no concern. Moreover, although the authors use the word “accumulation,” glyphosate has not been shown to accumulate in this paper. Glyphosate is very water-soluble, is rapidly excreted in urine and does not accumulate in the body. The authors chose that word because they know we are all concerned about chemicals that accumulate in our bodies. They are trying to scare us. The authors conclude by forecasting “unknown impacts,” but this statement ignores 30-40 years of safety research on glyphosate that demonstrates its low toxicity and relative safety. The conclusions are, however, a perfect scary sound bite for a reporter who doesn’t bother to read the fine print.
To boil all of this down, this is a very flawed paper that makes unsubstantiated claims. This journal is a favorite publication place for environmental advocates. One of the authors has published several other papers that question the safety of glyphosate and has actively campaigned against glyphosate and GM crops. This is a very clear bias. One author claims to be an environmental toxicologist; however, the paper ignores basic principles of toxicology. There have been a number of similarly flawed papers published in recent years that question the safety of glyphosate.
It is important in science and for public safety to constantly question and reexamine the safety of chemicals to which we are all exposed. It is equally important, however, that we hold all papers to standards of quality, accuracy and thoroughness. The recent trend of publishing papers solely intended to discredit chemicals or technologies distracts us from paying attention to real risks and diverts science from doing relevant risk research. They waste scarce resources, since regulators and scientists must analyze and respond to their claims. Papers such as the one in question are being published for the sole purpose of scaring consumers and should be ignored.
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