Unnatural Fear of Roundup – Understanding Small Numbers

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Robert Pavlis

If you spend time understanding the science behind Roundup and glyphosate, it’s active ingredient, you soon realize that this is a safe chemical compared to many other chemicals, even ones liberally used in the home. Why is it then that so many people fear Roundup?

Probably the biggest reason is great promotion by the anti-Roundup and anti-Monsanto crowd. That is one powerful force, that brings one misleading article after another to the attention of a lot of people.

I think that another reason for this fear is our inability to understand very small and very large numbers. A recent research study found glyphosate in natural water systems and I have seen it posted by several people as proof of a real problem that needs to be feared. If these people simply understood small numbers, they would not fear the report or Roundup.

Unnatural fear of Roundup in drinking water - Understanding small numbers
Unnatural fear of Roundup in drinking water – Understanding small numbers, Source; Aqua Mechanical (photo modified)

Glyphosate in Our Water

A recent study found that 41% of the 140 ground water samples tested in Spain contained glyphosate.

The abstract title is “Determination of glyphosate in groundwater samples using an ultrasensitive immunoassay and confirmation by on-line solid-phase extraction followed by liquid chromatography coupled to tandem mass spectrometry.”

Soil Science for Gardeners book by Robert Pavlis

The author of the quoted reference took the data of the study and came up with this title, “Glyphosate, despite its low mobility in soils, is capable of reaching groundwater. 41% of 140 groundwater samples from Catalonia, Spain contained high levels, technically beyond the limit of quantification.” Note the “contained high levels, technically beyond the limit of quantification”

The levels are in the ng/L range – that is not high levels.

What does “technically beyond the limit of quantification” mean? It certainly does not mean the levels were too high to measure – you simply dilute the sample. And if the levels were so low they could not be detected – then they are certainly not high levels.

More gobbledygook to help convince people of the terrors of glyphosate.

They did find glyphosate in 41% of the samples. That means 59% had no glyphosate – a much more positive way to report things.

I don’t have the actual paper, only the abstract, but that is enough for this discussion. I’ll assume the work was well done, and the data is accurate.

Understanding Small Numbers

The average glyphosate in the 41% of positive samples, was 200 ng/L. A number like 200 sounds like a lot and we humans really can’t visualize a ng (nano-gram), so this seems like a lot. But how much is it?

200 ng/L = 0.000,000,2 g/L

You might know that a gram is about the weight of a paperclip, but that does not really help to understand this number because it is so small.

Building Natural Ponds book, by Robert Pavlis

“The EPA Allowable Daily Intake (ADI) for glyphosate is set at 1,750 µg (1.75 mg) per kg of body weight. The EU ADI is just 0.3 mg per kg body weight.” (ref 2). I’ll go with an average of 1mg/Kg.

The daily safe intake for someone weighing 70 Kg (150 pounds) is 70 mg. If you were drinking the average contaminated water in Spain you would need to drink 350,000 L before you would reach this safe level. Or putting it in terms everyone understands – 1,000,000 beer-sized bottles. And that is the daily allowance.

How Toxic is Water?

The above calculation is informative, but I left out one very important detail. Water is also toxic with an LD50 of 90 mL/Kg body weight. The 70 Kg person discussed above would have a 50% chance of dying after drinking just 6.3 L of water. They would almost certainly be dead long before they could drink the 350,000 L of glyphosate-laced water from Spain.

Interesting, probably only to a biochemist, is the fact that water would never kill you. By drinking water your body would get its sodium/potassium levels out of whack and that kills you. The water itself is not toxic.

Glyphosate in Cheerios

The same kind of arguments have been made for food products, especially Cheerios. With claims that they are laced with Roundup.

The truth is that all food products contain some glyphosate. Even organic caged chicken eggs contained it. But the levels in food are extremely low. “Fourteen of the twenty-four food items tested contained less than 75 ppb of glyphosate, which is equivalent to 75 µg of glyphosate per liter of testing solution. This is well below the ADI of 1,750 µg per kg of bodyweight per day”.

Roundup and Glyphosate

Bayer, owner of Monsanto, has been releasing numerous products using the Roundup brand name. These do not all contain glyphosate, while others contain glyphosate and much more toxic herbicides. One type of Roundup now contains vinegar and no glyphosate. Gardeners need to clarify which product they are talking about when they use the word Roundup. This post is about the traditional product containing glyphosate.

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Robert Pavlis

I have been gardening my whole life and have a science background. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

63 thoughts on “Unnatural Fear of Roundup – Understanding Small Numbers”

    • Government bans are implemented by politicians. Politicians do what people want. If they have to chose between being popular and following science – they select being popular. The general public believes glyphosate is harmful so they create bans. But …. bans and lost court cases tell us nothing about the safety of a product – it only tells us about peoples opinion. Science tells us about safety.

      I use almost no herbicides anywhere in the garden. In the veg garden, I mulch with straw, which eliminates 99% of the weeds.

      Here is an important point. On this blog I am reporting the science. Roundup is safe, but that does NOT mean I recommend that everyone use it everywhere. In general, I am against the use of chemicals except in cases where they are the only good tool. I use Roundup of my thousands of buckthorns. But I don’t use perfumes, household air fresheners and many other chemicals found in the home because they are not needed.

  1. I most certainly enjoy your work. I have long believed that much of gardening was actually a collection of superstition, wives tales and “common sense”.

    Perhaps someone might apply your vigor to the new (old) realm of sourdough baking.

    But never mind. I am, however, troubled by your apparent insistence that “the dose makes the poison” and by extension small doses can or do have little effect.

    Perhaps I missed the reference to hormones or hormone like chemicals.

    A pleasant blog on the point of trace amounts.


    • Your link starts off with a serious error – “The phrase “The dose is the poison,” carries with it the implication that if something is toxic, then less will be less toxic. And a lot less is safe.”

      That is not what people are saying. When we say the dose is the poison we are saying that you have to understand the dose and its effect, before you can reach any kind of conclusions.

      Nobody, at least nobody who understands science, believes that ” half as much is half as toxic”.

      • The saying is “the dose makes the poison,” not “the dose is the poison.” In other words, whether something is poisonous is dose-dependent.

  2. I dismissed concerns about glyphosate because I understood that its half-life was on the order of a day in open air. It decomposes to carbon dioxide and water. Recently I was asked some questions that made me reevaluate my position. First, glyphosate does not necessarily decompose in the soil. In fact, its solubility in water allows it to be flushed deeper, and in permeable soils it is plausible that it reaches ground water. Given its virtually universal use, it means that if glyphosate does not fully decompose, it is likely to be in potable water sources world-wide. If so — and not a lot of research has been done on this — then it means there are concerns. An MIT researcher, Dr. Stephanie Seneff noticed the similarity of glyphosate to glycine, the amino acid found in virtually all proteins. The difference, of course, is the presence in glyphosate of a phosphate side group. There is limited — very limited, I might add — indication that some of the glyphosate consumed by lab animals remains in them, primarily in the epiphyses, or the growing portion of long bones. Alarmingly, glyphsate has been found to inhibit spermatogenesis in test animals. If there is a connection between Roundup use and spermatogenesis inhibition, this may be why fertility in young men today is decreased and — from my perspective — why we have so many effeminate males. It is also possible that masculization of women is occurring as well. Studies to-date have involved C14 labeled glyphosate. I think radioactive labeled phosphorus in the molecule is needed. Trouble is, P-32 only has a half-life of a couple of weeks, meaning tests could only be run on very rapidly dividing tissues such as cell culures and embryos. Still, this needs to be done. If cellular damage is confirmed, then Roundup needs to be banned.

    • Re: ‘its half-life was on the order of a day in open air” – I doubt that very much – do you have a reference to support this?
      Re: ‘glyphosate does not necessarily decompose in the soil” – that is not true. It does decompose in soil, but that does not mean some might not end up in the water systems.
      Re: ‘it is likely to be in potable water sources world-wide. If so — and not a lot of research has been done on this” – actually there has been a lot of research on this. That is how we know it is not an issue.


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