Far more toxic than glyphosate: Copper sulfate, used by organic and conventional farmers, cruises to European reauthorization

Over the past months, the European Union and several member nations have vigorously debated re-authorizing glyphosate, the herbicide maligned by anti-GMO and pesticide activists.

Recently, the European Union — without anything near the debate surrounding glyphosate decided to reauthorize the fungicide copper sulfate, a popular pesticide among organic farmers that has a more toxic rap sheet than glyphosate.

The European Commission and its member states reauthorized the use of copper sulfate, a widely used pesticide in organic farming but which also is used in some conventional applications, although the European Food Safety Authority (EFSA) and European Chemicals Agency (ECHA) considered toxicity risks for farmers, birds, mammals and soil organisms, and the chemical’s overall environmental impact. This decision extended permission for the use of copper sulfate in the EU, against bacteria and fungus.

Copper sulfate is used a great deal in organic farming, especially with potatoes, grapes, tomatoes and apples. In comparison, glyphosate one of the world’s most popular herbicides is focused on weed control and is not used in organic farming. Instead, it has attracted the attention of anti-GMO activists and members of the EU because it works hand-in-hand with genetically modified crops bred to resist it.

But which is safer?

According to the European Chemical Agency (ECHA), Copper Sulfate “is very toxic to aquatic life, is very toxic to aquatic life with long lasting effects, may cause cancer, may damage fertility or the unborn child, is harmful if swallowed, causes serious eye damage, may cause damage to organs through prolonged or repeated exposure.”

In addition, the European Food Safety Authority (EFSA) pointed to risks to farmers, birds, mammals and soil organisms. Both the EFSA and the US Environmental Protection Agency say more data is needed on the potential health effects on consumers.

copper sulfate 3 14 18 2
Copper sulfate.

While organic food does not contain as much pesticide residue as conventionally grown food, copper sulfate is the most common pesticide residue in organic food, according to a 2015 European Parliament research report. It is bio-accumulative, meaning it can build up to toxic levels in the soil and possibly even animal tissue. In fact, many organic wine growers, in the US and in Europe (including France) have opted out of their organic designation in order to use alternatives to copper sulfate fungicide. Their fears? Accumulation of the chemical in soil.

The European Commission, when it extended copper sulfate use in 2014, did so on the condition that its use would be reduced and other environmental studies would be carried out. In 2015, the EU listed the same chemical as a “candidate for substitution” due to concerns over its effects on health and the environment. It was this extension that expired in January, and was re-extended by the EC.

So far, however, no realistic organic alternatives have been created. According to the European Parliament report: “Some promising alternatives include potassium bicarbonate (which is safe for humans and the environment) and milk by-products. In the meantime, restrictions limit the use of copper salts.”

Meanwhile, glyphosate has shown no bioaccumulation, and next to no toxicity, except for possible health problems among workers who are exposed to very high doses of the pesticide. Only one agency — the International Agency for Research on Cancer — has connected glyphosate to health problems (in this case, cancer), through a methodology that is not risk-based, and through a process that has gathered accusations of unrealistic results to outright corruption.Screen Shot at PM

This comparatively healthy profile did not prevent the European Commission and member states from seriously considering banning glyphosate in Europe. Eventually, the herbicide’s use was re-authorized, although the European Parliament has vowed to re-evaluate pesticide approvals in the wake of criticism from certain member states (which themselves have moved to ban glyphosate) and anti-GMO groups that have long opposed glyphosate’s existence as a legal agricultural chemical.

Glyphosate also does not have an alternative that possesses the same ability to kill weeds as well as the same low toxicity profile. Copper sulfate, meanwhile, can be used by conventional farmers, though they tend to prefer other fungicides.

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Copper sulfate has a history. Steve Savage, a San Diego, California-based geneticist, remarked that “copper sulfate was a state-of-the-art fungicide, in 1885!” Its use began in the early 1880s in Europe, as wineries began noticing downy mildew in their plants. This raised more than a little fear, because it was the same type of infestation that resulted in the great Ireland potato famine, just 40 years previous.

Savage talks more about this history in his webcast, “Plants Get Sick, Too:”

There was a fellow named Pierre Millardet who was a professor of botany at the University of Bordeaux. In October of 1882 he was driving his carriage along a road in St.-Julien. The vineyards he passed were a sad sight, and as a Frenchman and a plant scientist, he was concerned about the future of the crop. But Then he noticed one vineyard by the road that looked much healthier than the rest. The vines still had leaves. He stopped and looked closer. The leaves and fruit looked good, but were covered with a powdery blue substance.

He found the vineyard manager and asked what was going on. The manager explained that he and other growers in the area had grown tired of having people come along the road and steal their grapes. So, they had come up with a mixture of copper sulfate and hydrated lime to spray onto the grapes by the road to make them look unappealing.
What Millardet realized was that in an effort to prevent theft, these growers had accidentally discovered a “medicine” for the vines – what we now call a fungicide.

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Italian vineyard. Image credit: Decanter

Since, copper sulfate has  been used in organic farming as an allowed synthetic substance (most modern copper comes from reusing non-iron scrap metal in a factory and then precipitating the compound from sulfuric acid), as well as in conventional growing. In California, the largest agricultural region in the United States, 54 different variants of the chemical are used, largely for fungal disease control. Some of these uses include rice production, fighting walnut blight, and in aquatic control of algae (this is a big part of its use in rice, too).

According to a 2015 USDA technical report on copper sulfate, it is registered with the EPA for these uses:

  • As an algicide, copper can control or eliminate algae and invasive aquatic weeds from aquaculture facilities, drainage systems ponds, crop and non-crop irrigation canals, and sewage lagoons and potable water lines.
  • As a molluscicide, a dilute solution of copper sulfate can be used to remove snails from an aquarium, and control freshwater snails that may be a vector for harmful trematodes. Copper sulfate and has been used to control invertebrates, specifically tadpole shrimp, in rice production.
  • An estimated 9-11 million pounds of elemental copper in the form of copper sulfate pentahydrate are applied each year solely for algae and weed control.
  • As a footbath antiseptic to help control and prevent infectious hoof disease problems that affect the skin adjacent to the claw horn of dairy cattle and sheep i.e., digital dermatitis (DD) (hairy heel warts), foot rot lesions (interdigital area and invading the subcutaneous tissue), and heel erosions.

Copper compounds also have run into organisms that developed a resistance to them. This is similar to the common accusation by organic activists against glyphosate is that weeds have developed resistance to the herbicide. In tomatoes in the Southeastern US, copper compounds have been used for decades to combat bacterial leaf spot. Today, however, Xanthomonas, the microbe behind the spot, has developed resistance to copper compounds. Researchers are now looking to genetics for an alternative to copper compounds, focusing on two genes that confer disease resistance in tomatoes. However, given popular attitudes toward GMOs and aggressive lobbying and public opposition by anti-GMO organizations, its future is hazy, at best.

Andrew Porterfield is a writer and editor, and has worked with numerous academic institutions, companies and non-profits in the life sciences. BIO. Follow him on Twitter @AMPorterfield.

48 thoughts on “Far more toxic than glyphosate: Copper sulfate, used by organic and conventional farmers, cruises to European reauthorization”

  1. This is not the end of the story. The re-authorization procedure has spilled over the the current authorization deadline. The extension has thus been granted for one year ony, pending completion of the process.

  2. Both should NOT be used! As long as we do not know how a cell exactly works (we are just scratching the surface there) we cannot allow these (and a lot more) substances. There are so many examples of the past.

    • Nope, we know enough to make improvements to agriculture. The 40 plus year safety record of glyphosate shows that. Also, as copper is a minor mineral. that can also be used with caution. For example when I first bought my place the soil had a copper deficiency. I needed to apply some copper. So, why not kill 2 birds with one stone and try to fight the bacterial leafspot on my peppers.

      • So how do you determine the ‘safety record’ when you don’t know all the cauuses of many diseases and when you don’t know all the molecular effects of the substances?

        • Same way I determine the safety record of sleeping. even though I don’t know all of the molecular effects of sleeping. Many repetitions and no ill effects. Same as glyphosate. Except with glyphosate we had many safety studies done as well. Actually, statistically glyphosate use just might be as low a risk as sleeping. Why don’t you run a comparison on those while trying to think up another goofy question designed to raise needless fear. BTW, we do know most of the causes of diseases. And you don’t get “all” There is risk in this world. After all, I might not wake up in the morning .But, I know that spraying glyphosate tomorrow will not kill me.

          • Remarkable comparison between sleeping (which is a natural thing) and a herbicide (which is not invented by nature).
            But it is like as difficult to discuss the existence of a god with a true believer ;)
            Future will tell for sure.

          • You are aware that the EPSPS enzyme used to generally give resistance to glyphosate was derived from Agrobacterium sp. CP4, and was the result of natural mutations within the genome of the bacteria, right?

          • Yes….but what is your point?…..Do you want to say that because that there is a natural resistence (because of the natural mutation which is now used in GMO /crops) against the used compound the compound is completely safe?
            Very strange way of providing evidence.
            We know that glyphosate has effect on morphology and behavior of zebrafish:

          • …you didn’t bother to read that did you?

            The dosages that were required to see an effect are significantly higher than MCL for aquatic systems.

            Wow, look at that! It’s almost like people have already worked out the baseline toxicology for these things.

            …which is exactly what they did, and your citation actually shows that the MCL in the US is already well below the NOAEL.

            Just a tip for the future, before you reach from pitchforks and torches, see if the exposure levels required to see a adverse effect are above the MLC. If they are, you’re only providing evidence of glyphosates excellent safety record.

          • I did read it of course. The only point I am making here that the substance is toxic not to (not modified or resistant) plants only which is a socalled ‘Unique Selling Point’ of glyphosate/Roundup.

            Of course there are ‘normative levels’ but how safe are these levels?
            Exposure levels vary tremendously.

            I don’t even take in account potential stack effects and the effects of the many different substances together.

          • Most of the pesticides you eat are produced by the plants. All of the effects are not known, and all the effects of eating foods is not known. Perhaps you should quit eating.

          • Plants produce natural pesticides yes to protect themselves, those are even healthy (polyphenols, flavonoids anti-oxidants).
            That is something different.

          • No, it is not different. Dry drinking to much caffeine or eating some Jicama leaves. Again, appeal to nature fallacy.

          • Yes I agree! Even drinking to much water can kill you!
            I am not saying that everything in nature is healthy (e.g. snake venom kills you).

          • So your point was that, in a study where an the adverse effects were only seen when the researchers exposed zebra fish to a level of Roundup or glyphosate to levels far, far higher than both what is seen in the wild, as well as being over the legal limits permitted for water, that this somehow implies that glyphosate is unsafe?

            The maximum concentration for glyphosate is determined as part of the acute and chronic toxicity evaluations. Some key metrics that are used to determine the acceptable daily intake are the LD50 (Lethal Dose 50%), Lowers-Observed-Adverse-Effect-Limit (LOAEL), and No-Observered-Adverse-Effect-Limit (NOAEL).

            For determining the ADIs, the NOAEL and LOAEL are directly used, and as a general rule, the limits are set by taking 1% of the LOAEL or NOAEL, thus allowing for the levels to exceed the ADI by 100X…and that’s for the levels to reach a point where we can start to see an effect.

            These aspects of toxicology are all well established, and as your citation showed, they work. At the limits set, based upon the acute and/or chronic toxicity studies, there is no cytotoxic effect.

            Quite literally, everything is toxic under the right (or wrong) conditions. Drink too much water, or inhale it, and you die. Try breathing 100% oxygen at a depth greater than 10m underwater, and you die. Want to have an eating contest between you and a friend where you eat table salt, while they eat glyphosate, you both die, but you do so first.

            Oh, and one final point to make, take a look at the materials that the researchers used for this study. Do you see where the made a critical error?

            What formulation of Roundup did they use?

            They used the original Roundup formulation…which is not meant to be used in aquatic environments. Do you know why?

            The surfactants, which are basically soap, and have been shown to have a much greater cytoxic effect than the glyphosate on its own. Then again, you also see this if you introduce any soap into the water. This is why different formulations, like Roundup ProVantage, or Roundup ProActive exist.

          • Then you are choosing to ignore the overwhelming safety data out there. No one, not even the individuals who have jumped on board with this letter have been able to show cytotoxic effects at the levels found in the environment. Additionally, no causative mechanism for how ANY effect could be seen at the ADI levels has ever been validated.

            That letter runs contrary to every major regulatory and science body out there, and conveniently ignores the the little problem that, once again, no causative relation has been observed. Additionally, saying many researchers have serious concerns” isn’t quite accurate, as it ignores the discrepancy between the actual numbers involved.

            Put bluntly, there are orders of magnitude more scientists who do not ascribe to the fearmongering perpetuated by a tiny minority of the research community. Once again, none of the individuals in that opinion piece can actually show a causative relationship at the ADI levels.

            …and I had to laugh when I saw the 2015 date. You might want to revise your criteria, as there were just a few big reports issued from 2016 to the current date.

          • .? Lose….Is this a game of chess? It is not a matter if winning or losing for me.
            I think we have to consider the fact that we are not sure of all the possible effects just because we don’t understand the way a cell works.

          • We do understand the way a cell works. You are just trying to fear monger using speculative claims. If “we” used your standard we would have zero crop protectant chemicals, much higher food prices and more people hungry. You lose because you not only rely on a fallacy. but are not reasonable.

          • Sorry but …”you lose” is a strange way of trying to end a discussion.
            The fact is there is so little knowledge about e.g. the total genome, epigenetics, gene-expression, ribosomal biogenesis and translation.
            This list is nearly endless.
            There is still so much what we don’t know about the functioning of a living cell.
            It is too easy to say: ‘it is safe’ without knowing everything. DDT was also ‘safe’. Once we learned more we know more of the risks.

          • And we have since realized that DDT is safe and effective when used correctly against malaria. We consider cars safe and yet many die. Airplanes, same thing, baseball has killed. Yet we don’t ban it. The list of what we do know is what is nearly endless. Marc is scared is not a reason to declare a product unsafe.

          • The Riskmonger:
            David (Zaruk) is an adjunct professor at Université Saint-Louis Brussel and KUL Brussel (Odisee) where he lectures on Risk Communications, EU Lobbying, Corporate Communications and PR. He also does training and public speaking , formally under Risk Perception Management. In the past, he has been employed by Solvay, Cefic and Burson-Marsteller, retiring from “active work” in 2006.(from his own website).

            I put more trust (above one riskmonger) in the extensive list of scientists in the mentioned article in zeit.de

            There are a lot if lobbyists on the pay-roll of Monsanto. I will not be surprised if David Zaruk is one of them.

          • The American Council on Science and Health (ACSH) is a pro-industry[2][3][4] science education nonprofit organization founded in 1978 by Elizabeth Whelan. Its stated mission is to “support evidence-based science and medicine.”

            Not very ‘independent’ as well.

            I think it is now just a matter of time for more confirming evidence.

            Like the pollution of ground water:

          • What in the Sam Hill can you possibly find wrong with that statement. That is exactly the ideal that all journalists should follow regarding science. They are thus only [pro-industry when the facts indicate that the proper reaction is to be pro-industry. Thus this comment is nothing but another shill gambit. And an extremely poor one at that.

          • Nonsense. I have read their funding sources. You can as well. they are a nonprofit and have to file accordingly. You need to deal with the fact that you are wrong and doubling down on the shill gambit in the name of Monsanto only confirms that you are a partially educated fool.

          • Is it proper to start ‘naming’ me a fool? Not so polite.

            Their funding sources are of course not so transparent as they seem.

            GLP is also an ‘industry partner’.

            Maybe you are as well?

          • And the partially educated fool adds a few more shill gambits to his attempt to prove lack of knowledge and integrity. Once one uses the gambit and doubles down. One gets no respect from me.

          • It is all so obvious. I must admit, you seem to be good in your vigorous way of defending somebody else his interests (all over the place). But too good and too close on the ball. It worries me. Time for a démasqué…

          • Sheesh, so now you are claiming that being competent is a bad thing. First off I am not good at this. It is just that those who oppose reality make errors that are easy to spot. Then when opposed with vigor. they react with the shill gambit, by trying to move the goalposts or a fallacy. It is really very simple.

          • I do not oppose reality. There is at least a lot of controversy. I see enough studies with evidence that glyphosate is negatively affecting more (life) than it is supposed to do. I also see that the stakes are very high (multi-billion turnover business), so it is worthwhile paying (educated) people and foundations to work on a positive ‘scientific’ and public opinion.

          • Incorrect, you are in the same mental boat as a flat earther. The so-called studies you refer to have been either debunked or had the highly speculative clams made afterwards exposed. Then the fool resorts to yet another shill gambit. The millions of farmers who buy and use the glyphosate know what they are doing. I know what I am doing. I don’t want to get cancer and neither do the others. If glyphosate were a carcinogen. we would have realized it. Chelator binding minerals causing deficiencies. We would notice. Damaging spoil. Guess what? Us again. Go back to your armchair.

          • The closer I come to the truth and or to the interest you defend the more insulting you get.
            The farmers and you are depending on (addicted to) it. It is so easy (and profitable) to farm with killing the weeds but not your (GMO) crop.
            Do they really know what they are doing?
            I don’t think so.

            There are harmless alternatives.

          • You have not budged your position one iota. So that was a false claim. Not farmers and me. Just farmers, although I am a very small one. And yes, we know what we are doing. We also know that if there was a better alternative. we would quickly be using it in rotation with glyphosate. The other herbicides available are more risky and mechanical control burns more diesel, increases labor and causes more wind and water erosion. We would love to have even an equivalent product as rotating modes of action slows resistance build up.

          • It is all about the money. Meanwhile we are destroying nature and the future of others. More and more farmers do see and use the alternatives. They don’t want to be dependent and feel more responsible, that is a good thing.
            We have to move further into this transition towards a real sustainable way of treating our planet. For me it is not a question of who is right or wrong. We are in (and on) this together.

          • All about the money? Aaahhh, I see you are also ignorant enough to have a pro-leftist bias. Farmers have been improving of late and without profitable farms you become a hunter/gatherer. You have no clue what farmers see and no proof for your claim.

          • Did you read the paper?

            Ecotoxicol Environ Saf. 2018 Mar 15;156:216-222. doi: 10.1016/j.ecoenv.2018.02.075. [Epub ahead of print]
            Toxicity of atrazine- and glyphosate-based formulations on Caenorhabditis elegans.

            García-Espiñeira M1, Tejeda-Benitez L2, Olivero-Verbel J3.

            In the discussion..

            “It is also noteworthy that in terms of legislation, according to the Environmental Protection Agency of the United States (EPA), the per- mitted Atrazine and Glyphosate concentrations in drinking water are 3 ppb (0.014 μM) and 700 ppb (4.14 μM), respectively (USEPA, 2009). These values are below the LOAEL reported in this study for both pesticides, and indeed generate small but significant effects on the C. elegans model. Although the adjuvants in the formulation could be adding some toxicity to the herbicides, further detailed analysis should be performed on these environmental health criteria.”


            “Atrazine- and Glyphosate-containing herbicides induce dose-de- pendent toxic effects on C. elegans. The toxic response was evident in survival, locomotion, fertility, and changes in gene expression. Glyphosate-based formulation was proved to be more toxic than that with Atrazine, given the lower dose required to induce biological and biochemical changes. Interestingly, both pesticides induced some bio- logical changes at concentrations similar to those recommended by drinking water standards. Together, Atrazine and Glyphosate formula- tions work additively, mostly involving an oxidative stress-related mechanism of action.”

  3. pol/healthcare/glyphosate/it’s not about gmo:
    . this author pretends the reason for hating glyphosate
    is because they really hate gmo;
    the reverse is more true:
    one major reason for hating gmo
    is that it’s been mainly used for
    increasing the amount toxins we’re exposed to.
    . author also pretends glyphosate is not a toxin,
    when in fact glyphosate kills probiotics
    and increases the risk of dysbiosis.
    . however the main source of it is not gmo,
    but desicating crops that are not resistant to it.

    • Care to share the study that was able to show an inhibitory effect in vivo at exposure levels consistent with dietary exposure?

      I ask because the dose is what makes the poison, and studies such as Nielson et al.,(2017) clearly showed that inhibition of the gut microflora required exposure about 50X the ADI limits. This is particularly true in an environment like the chyme present in the stomach and small intestine, and was a major issue with the earlier in vitro studies.

      On the bright side, data such as this also eviscerates the hypotheses of Samsel and Seneff.

      Finally, or your erroneous regarding toxins in general; literally everything can be toxic under the right conditions, even things that we require to live.

      Think oxygen is safe? Try breathing 100% oxygen 10m underwater (don’t do this, at that partial pressure, oxygen acts effectively like a neurotoxin).

      How about water? Well drink too much, and you can end up dead from water intoxication, to say nothing about the effect of inhaling water.

      You might want to take a look at some of the basic biochemistry and toxicology principles, because you appear to be sorely lacking when it comes to these topics.

      • This data does nothing to eviscerate Seneff or anybody else regarding glyphosate. A couple of mentions in paragraphs and a table of dubious information does nothing at all to put this argument to rest.

        And if the dose makes the poison take some mercury, let us all know what dose it was that poisoned you.

        • Actually, as Seneff and Samsel have yet to perform any experiments to support their hypotheses, any data will eviscerate their position.

          Let’s make this easy, provide a citation for an OECD-compliant chronic toxicity study (452 or 453 if a combined tox and carcinogenicity), that shows a dose dependent causal elationship between glyphosate exposure and adverse health effects. As shown in Nelson et al. (2017), there are no harmful effects seen at levels until they reach 50X the ADI.

          BTW this does completely gut Samsel’s hypothesis.

          The dose does make the poison, and we are all exposed to mercury from our environment. The average exposure is about 50ng/kg/day. As these levels are far below the ADI, it’s not an issue.

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