Toxins and tanks: could your fishtank really be deadly?

Could a deadly poison be lurking in your fish tank?

A few days ago I came across a news story: “Fish owner tells how cleaning out tank released deadly palytoxin that poisoned family and led to closure of entire street“. Now you have to admit, as titles go that’s pretty compelling.

To begin with, for some reason, I had it in my head that this happened in Australia (in my defence, that is where most of the really deadly stuff happens, right?). But no, this happened in the U.K. Not only that, but it was even in Oxfordshire, which is my neck of the woods.

The fish tank owner, a man named Chris Matthews, was actually an experienced aquarist. He knew about palytoxin – a poisonous substance which can be released by corals – and he was aware that it can be deadly if ingested. He also knew that it can cause serious skin irritation.

What he didn’t realise was that taking his pulsing xenia coral out of the tank could cause it to release the toxin into the air.

But before I talk about palytoxin, let’s just look at the word “toxin” for a moment. It has a specific meaning, and it’s often misused. As in many, many adverts. Here’s a recent one, but these easy to find – just put “toxin free” into the search engine of your choice.

In a way, this is quite funny. You see, “toxin” specifically refers to “a poison of plant or animal origin“. In other words, a naturally occurring poison*. There are lots and lots of naturally occurring poisons. Plants make them all the time, generally to ward off pests. Most essential oils can, at a high enough dose, be toxic. The hand cream in that picture contains peppermint oil. Peppermint is, of course, pretty safe – we’ve all eaten mints after all – but guess what? Take huge dose of it and it becomes a real problem. Now, I’m not for one second suggesting that hand cream is dangerous or harmful, but technically, it’s not “toxin free”.

Beauty products which contain only synthetic ingredients are, by definition, toxin-free.

Yes, the irony or this sort of marketing is that beauty products made out of entirely synthetic ingredients definitely will be toxin-free. Nothing natural = no toxins. Whereas anything made out of naturally occurring substances almost certainly isn’t, regardless of its spurious labelling.

Anyway, back to the palytoxin. It’s naturally occurring. And incredibly dangerous. More proof, as if we needed it, that natural doesn’t mean safe. Very often, in fact, quite the opposite. The human race has spent millenia working out how to protect itself from nature and all her associated nastiness (bacteria, viruses, extreme temperatures, poor food supply, predators…. the list is long and unpleasant) and yet for some reason it’s become fashionable to forget all that and imagine a utopia where mother nature knows best. Honestly, she doesn’t. Well, maybe she does – but being kind to human beings isn’t on her agenda.

Palytoxin is especially unpleasant. Indeed, it’s thought to be the second most poisonous non-protein substance known (there are some very impressive protein-based ones, though – botulinum toxin for one). The only thing which is more toxic is maitoxin – a poison which can be found in striated surgeonfish thanks to the algae they eat.

Palytoxin is a large molecule.

Palytoxin is a big molecule, technically categorised as a fatty alcohol. It has eight carbon-carbon double bonds, 40 hydroxy groups (phew) and is positively covered in chiral centres (don’t worry students: your teacher isn’t going to expect you to draw this one. Probably). Bits of it are water-soluble whilst other parts are fat soluble, meaning it can dissolve in both types of substance. Because it’s not a protein, heat doesn’t denature it, so you can’t get rid of this toxin with boiling water or by heating it. However, it does decompose and become non-toxic in acidic or alkaline solutions. Household bleach will destroy it.

It’s mostly found in the tropics, where it’s made by certain types of coral and plankton, or possibly by bacteria living on and in these organisms. It also turns up in fish, crabs and other marine organisms that feed on these things.

In fact, story time! There is a Hawaiian legend which tells that Maui villagers once caught a Shark God with a hunger for human flesh whom they believed had been killing their fishermen. They killed the Shark God and burned him, throwing the ashes into a tide pool. The ashes caused ugly brown anemones to grow. Later, the villagers discovered that blades smeared with these “limu” would cause certain death. So the anemones came to be known as “Limu Make O Hana” or Seaweed of Death from Hana. We now know that those brown ‘anemones’ are zoanthid corals, and the ‘certain death’ was due to palytoxin poisoning.

Zoanthids are a source of palytoxin.

People don’t suffer palytoxin poisoning very often. Most cases have been in people who’ve eaten seafood and, as here, aquarium hobbyists. In a few cases people have been exposed to algae blooms.

It’s really nasty though. Palytoxin can affect every type of cell in the body (yikes) and as a result the symptoms are different according to the route of exposure. Eat it and you’re likely to experience a bitter taste in your mouth, muscle spasms and abdominal cramps, nausea, lethargy, tingling and loss of sensation, slow heart rate, kidney failure and respiratory distress. It can damage your heart muscle; in the worst case scenario, it causes death by cardiac arrest.

On the other hand, if you inhale it, the symptoms are more likely to revolve around the respiratory system, such as constriction of the airways which causes wheezing and difficulty breathing. It can also cause fever and eye-infection type symptoms. Over time, though, the result is the same: muscle weakness and eventually, death from heart failure.

The respiratory symptoms from palytoxin are easily misdiagnosed: it looks like a viral or bacterial infection. In fact, our fish tank owner initially thought he had flu. It was only when everyone in the family got ill, even the dogs, that he realised that it must be poisoning. Fortunately, the emergency services took it seriously and sent both ambulance and fire crews to his house, as well as police. They closed the street and ensured that the poison was safely removed.

There is no antidote, but the symptoms can be eased by, for example, treatment with vasodilators. If the source of exposure is removed the victim is likely to recover over time. You’ll be pleased to hear that Chris Matthews, his family, and the firefighters who attended the scene, were checked over at hospital and appear to be okay.

If you’re an aquarium owner, how to you avoid getting into this kind of predicament? As Chris Matthews said, the coral he had, pulsing xenia, was “not expensive and a lot of people have it.”

Click the image to read safety guidelines from the Ornamental Aquatic Trade Association.

According to the Ornamental Aquatic Trade Association, the most important piece of safety advice is to only handle your marine creatures underwater and fully submerged. Don’t take them out of the tank unnecessarily, and if you do need to move them, use submerged plastic bags or a bucket, so that they stay underwater at all times. You should also wear strong rubber gloves, ideally gloves specifically designed for aquarium use (such as these). If you need to dispose of a rock which contains soft coral species, soak it in a bleach solution – one part household bleach to nine parts water – for several days before you intend to dispose of it. Leaving an untreated rock outside to dry will not make it safe – it could still be highly toxic. Finally, whilst activated charcoal can help to keep palytoxin out of the water, it may not be able to cope with large quantities, and it needs to be changed frequently.

Fish tank owner Chris also said: “The information is not readily available online in a way people can easily understand” and “I want to use this experience to educate people about the risks and the measures people need to take.” Hopefully this blog post (and all the associated news coverage) will help with that. Be careful with your corals!


* Note that while ‘toxin’ specifically refers to poisonous substances from plants and animals, this restriction doesn’t extend to the word “toxic”. The definition of that is “containing or being poisonous material” (regardless of whether it’s a naturally-occurring substance or not). So “non-toxic” labels are fine, if a little bit meaningless – no matter what the woo-pushing sites say, your hand cream really isn’t poisonous.


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What’s all the fuss about glyphosate?

Glyphosate, the key ingredient in Monsanto’s weedkiller Roundup, has been in the news recently. A few weeks ago it was widely reported that a UN/WHO study had shown it was ‘unlikely to pose a carcinogenic risk to humans‘. But it then emerged that the chairman of the UN’s joint meeting on pesticide residues (who, incidentally, has the fabulous name of Professor Boobis) also runs the International Life Science Institute (ILSI). Which had received a $500,000 donation from Monsanto, and $528,500 from an industry group which represents Monsanto among others.

And then it transpired that there was going to be an EU relicensing vote on glyphosate two days after the (since postponed) UN/WHO report was released, which resulted in another outcry.

Glyphosate molecule

A molecule of glyphosate

So what is glyphosate, and why all the fuss?

It was first synthesized in 1950 by Swiss chemist Henry Martin. It was later, independently, discovered at Monsanto. Chemists there were looking at water-softening agents, and found that some of them also killed certain plants. A chemist called John E. Franz was asked to investigate further, and he went on to discover glyphosate. He famously received $5 for the patent.

Chemically, glyphosate is a fairly simple molecule. It’s similar in structure to amino acids, the building blocks of all proteins, in that it contains a carboxylic acid group (the COOH on the far right) and an amine group (the NH in the middle). In fact, glyphosate is most similar to the smallest of all amino acids, glycine. Where it deviates is the phosphonic group (PO(OH2)) on the left. This makes it a (deep breath) aminophosphonic analogue of glycine. Try saying that when you’ve had a couple of beers.

As is usually the way in chemistry, changing (or indeed adding) a few atoms makes a dramatic difference to the way the molecule interacts with living systems. While glycine is more or less harmless, and is in fact a key component of proteins, glyphosate is a herbicide.

This probably bears stressing. It’s a herbicide. Not an insecticide. A herbicide.

Crop spraying

Glyphosate is a herbicide, not an insecticide.

I say this because people often conflate the two – after all, they’re both chemicals you spray on plants, right? – but they are rather different beasts. Insecticides, as the name suggests, are designed to kill insects. The potential problem being that other things eat those creatures, and if we’re not careful, the insecticide can end up in places it wasn’t expected to end up, and do things it wasn’t expected to do. This famously happened with DDT, a very effective pesticide which unfortunately also had catastrophic effects on certain predatory birds when they ate the animals that had eaten the slightly smaller animals which had eaten the insects that had eaten the other insects (and so on) that had been exposed to the DDT.

Herbicides, on the other hand, kill plants. Specifically, weeds. They’re designed to work on the biological systems in plants, not animals. Often, they have no place to bind in animals and so are simply excreted in urine and faeces, unchanged. Also, since plants aren’t generally known for getting up and wandering away from the field in which they’re growing, herbicide sprays tend to stay more or less where they’re put (unless there’s contamination of waterways, but this can – and should, if the correct procedures are followed – be fairly easily avoided).

Nicotine pesticide

Nicotine is an effective insecticide. It’s also extremely toxic.

Now this is not to say we should be careless with herbicides, or that they’re entirely harmless to humans and other animal species, but we can cautiously say that, in general, they’re rather less harmful than insecticides. In fact, glyphosate in particular is less harmful than a lot of everyday substances. If we simply look at LD50 values (the amount of chemical needed to provide a lethal dose to half of a test population), glyphosate has an LD50 of 4900 mg/kg whereas, for comparison, table salt has an LD50 of 3000. Paracetamol (acetaminophen) has an LD50 of 338, and nicotine (a very effective insecticide, as well as being the active ingredient in cigarettes) has an LD50 of just 9.

Of course, there’s more to toxicity than just killing things, and that’s where it gets tricky. Yes, it might take more than a third of a kilo to kill you outright, but could a smaller amount, particularly over an extended period of time, have more subtle health effects?

But before we go any further down that rabbit hole, let’s take a look at that ‘smaller amount’. Certain campaigners (they always seem to have some sort of stake in the huge business that is organic food, ahem) would have us believe that food crops are ‘drenched’ in glyphosate, and that consumers are eating significant quantities of it every day.

Here’s a great graphic, made by Sarah Shultz of the Nurse Loves Farmer blog (reproduced with her kind permission), that answers this question nice and succinctly:

How much glyphosate?

How much glyphosate is sprayed on crops? (Reproduced with permission of Sarah Shultz)

It’s about 1 can of soda’s worth per acre. Or, if you find an acre hard to visualise, roughly ten drops for every one hundred square feet – the size of a smallish bedroom.

In other words, not a lot. It’s also worth remembering that although there is some pre-harvest spraying – particularly of wheat crops – no farmer is spraying their crops five minutes before harvest. What would be the point of that? Farmers have margins, just like any other business, and chemicals cost money. If you’re going to use them, you use them in the most efficient way you can. The point of spraying pre-harvest is to kill any weeds that might be present so that they don’t get into your harvest. This takes time to happen, so it’s done seven to fourteen days before harvesting takes place. It’s also carefully timed in the growing cycle. Once wheat turns yellow, it’s effectively dead – it’s neither photosynthesising nor transporting nutrients – so if it’s sprayed at this point, glyphosate isn’t moved from the plant into the grain of the wheat. Which means it doesn’t make it into your food.

The long and short of all this is that if there IS any glyphosate in food crops, it’s in the parts per billion range. So is that likely to be harmful?

In March 2015 the International Agency for Research on Cancer (IARC) – the cancer-research arm of the World Health Organisation – announced that glyphosate was ‘probably carcinogenic to humans’, or category 2A. It needs to be pointed out that this outcome was controversial, as this post by The Risk Monger explains. But even that controversy aside, lots of things fall into category 2A, for example smoke from wood-burning fires, red meat, and even shift work. The IARC did note that the evidence mainly involved small studies and concerned people that worked with glyphosate, not the general public, and that recommendations were partly influenced by the results of animal studies (really, go and read that Risk Monger post). The one large-cohort study, following thousands of farmers, found no increased risk.

And by the way, alcohol has been classified as a Group 1 carcinogen, meaning it’s definitely known to cause cancer in humans. If you’re worried about glyphosate in wine and beer, I respectfully suggest you have your priorities the wrong way round.

So, the tiny traces of glyphosate that might be on food definitely aren’t going to poison you or give you cancer. Are there any other health effects?

Gut bacteria

Glyphosate isn’t interfering with your gut bacteria (image: microbeworld.org)

One thing that the health campaigners like to talk about is gut health. Their logic, such as it is, follows that glyphosate passes though our body largely unchanged. Now, you might imagine this would be a good thing, but according to these particular corners of the internet, it’s exactly the opposite. Glyphosate is known to be anti-microbial, and since it’s not changed as it passes through the body, the argument goes that it gets into our guts and starts wiping out the microbes in our digestive system, which have been increasingly linked to a number of important health conditions.

It sort of makes sense, but does it have any basis in fact? Although glyphosate can act as an antimicrobial in fairly large quantities in a petri dish in a laboratory, it doesn’t have a significant effect in the parts per billion quantities that might make their way to your gut from food. Glyphosate prevents bacteria from synthesising certain essential amino acids (it does the same thing to plants; that’s basically how it works) but in the gut these bacteria aren’t generally synthesising those amino acids, because they don’t need to. The amino acids are already there in fairly large quantities; bacteria don’t waste energy making something that’s readily available. In short, glyphosate stops bacteria doing something they weren’t doing anyway. So no, no real basis in fact.

I have so far avoided mentioning GMOs, or genetically-modified organisms. “GMO” often gets muttered in the same breath as glyphosate because certain crops have been modified to resist glyphosate. If they weren’t, it would damage them, too. So the argument goes that more glyphosate is used on those crops, and if you eat them, you’ll be exposed to more of it. But, as I said earlier, farmers don’t throw chemicals around for fun. It costs them money. Plus, not-really-surprisingly-if-you-think-about-it, farmers are usually quite environmentally-conscious. After all their livelihood relies on it! Most of them use multiple, non-chemical methods to control weeds, and then just add the smallest amount of herbicide they can possibly get away with to manage the last few stragglers.

Ah, but even a little bit is too much, you say? Why not eat organic food? Then there will be absolutely no nasty chemicals at all. Well, except for the herbicides that are approved for use in organic farming, and all the other approved chemicals, famously copper sulfate and elemental sulfur, both of which are considerably more toxic than glyphosate by anyone’s measure. And, of course, organic food is much more expensive, and simply not a feasible way of feeding over seven billion people. Perhaps, instead of giving farmers a hard time over ‘intensive’ farming, we should be supporting a mixture of sustainable methods with a little bit of, safe, chemical help where necessary?

In summary, the evidence suggests that glyphosate is pretty safe. Consuming the tiny traces that might be present in food is not going to give you cancer, won’t cause some sort of mysterious ‘leaky gut’ and it’s definitely not to poison you. There is a lot of fuss about glyphosate, but it’s really not warranted. Have another slice of toast.


EDIT 2nd June 2016

After I wrote this post, a very interesting article came my way…

  • Petaluma city suspended use of glyphosate in favour of alternatives. Notable quote:“Having used the alternative herbicides over the past two months, DeNicola said crews have needed to apply the treatments more often to achieve similar results. The plants are also likely to regrow, since the root remains alive underground.The treatments are also said to be extremely pungent during application, with several workers complaining of eye irritation and one experiencing respiratory problems, DeNicola said. Those attributes have required the use of new protective equipment, something that was not required with Roundup.“It’s frustrating being out there using something labeled as organic, but you have to be out there in a bodysuit and a respirator,” he said.”

A classic example of almost-certainly unfounded fear leading to bad decision-making.


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Elements, compounds and misleading mercury

Elemental mercury isn't the same as mercury in compounds.

Elemental mercury isn’t the same as mercury in compounds.

Today I read an interesting article about some recent research carried out at the University of Illinois where they demonstrated that the best way to convince parents to vaccinate their children might be to show them the results of the diseases the vaccines prevent. (This, by the way, contradicts some research published in 2014 which showed that this tactic didn’t work. For an excellent discussion of the two, see here.)

Then, because I am just one of those people who can’t resist poking at ulcers with my tongue (you know what I mean) I had a quick look at some of the comments regarding that article. Reassuringly, most people were weighing in on the “yeah, vaccinate!” side of the argument. But not surprisingly there was also a small group of people posting the traditional anti-vaccine arguments. And then, this appeared:

mercury ppm

This is thoroughly silly, and I’ll tell you why.

Well, it did make be go “hmmmmm”, but for the reason you might imagine.

No, you see, what I thought was: “hmmmmm, someone else who has, possibly deliberately, failed to understood the difference between elements and compounds, and how chemical bonding changes properties.”

Allow me to start at the beginning. If you went to a school in the UK (and I would hope it’s similar elsewhere in the world) you learned about elements, compounds and mixtures when you were about 13 years old – if not before. You might have forgotten it since, but I can absolutely, categorically guarantee you that lesson happened. In fact, it was probably a few lessons.

iron sulfide experiment

The much-loved reaction between iron and sulfur.

One experiment much beloved of chemistry teachers since year dot is to take a mixture of sulfur (a yellow powder) and some iron filings (grey) and show that they can be separated with a magnet. Then heat the mixture up so that the two react, with a rather beautiful red glow, to form iron sulfide. This is a blackish solid which is in theory not magnetic (but in practice almost always is) and demonstrate that now the two elements cannot be separated.

Thus we have demonstrated that elements (the iron and the sulfur) have different properties to the compound they formed (iron sulfide), and also that mixtures can be separated fairly easily, whereas breaking compounds up into their constituent elements is much harder. Lovely. Job done.

And yet… so many people seem to have been asleep that day. Or perhaps just didn’t grasp it well enough to continue to apply the principle to other things.

pouring mercury

Elemental mercury

For example, mercury. Mercury, the element (the runny, silvery stuff that you used to find in thermometers) is a heavy metal. Like most of its compatriots, such as cadmium, lead and arsenic, it’s toxic. It can be absorbed through the skin and mercury vapour can be inhaled, so containers need to be tightly sealed. The increasing awareness of the toxicity of mercury is why older readers might remember seeing it ‘in the flesh’, so to speak, at school, whereas younger ones will not – these days it’s rarely even used in thermometers for fear of breakages.

That said, it does occur naturally in the environment, particularly as the result of volcanic eruptions – and very low levels aren’t considered harmful. The dose, as they say, makes the poison. It also occurs as the result of industrial processes, particularly coal-fired power plants and gold production, and occupational exposure is a genuine concern. In particular, chronic exposure is known to cause cogitative impairment. It might the source of the ‘mad dentist’ myth. It’s almost certainly the origin of the phrase ‘mad as a hatter‘.

So in summary, don’t mess about with elemental mercury; it’s not good for your health.

However, as I took some pains to establish, elements and compounds are different things. So what about compounds which contain mercury?

The compound thiomersal

The compound thiomersal

This is where vaccines come in. There is a substance that used to be used as a preservative in (some) vaccines called thiomersal (or thimerosal, in the U.S). You may have heard its name; it comes up quite a lot. Incidentally, it hasn’t just been used in vaccines, but also in various other things including skin-test antigens and tattoo inks.

Now, to be clear, thiomersal IS potentially toxic, however it’s quickly metabolised in the body to ethyl mercury (C2H5Hg+) and thiosalicylate and, although ethyl mercury does, clearly, still contain atoms of mercury, it does not bioaccumulate. In other words, your body gets rid of it. At very low doses (such as those in vaccines) there is no good evidence that thiomersal is harmful.

Still, due to continuing public health concerns, thiomersal has been phased out of most U.S. and European vaccines. In the UK, thiomersal is no longer used in any of the vaccines routinely given to babies and young children in the NHS childhood immunisation programme. And at the moment, all routinely recommended vaccines for U.S. infants are available only as thimerosal-free formulations or contain only trace amounts of thimerosal (≤1 than micrograms mercury per dose).

Let me just say that again. The evidence suggests it’s safe, but it’s been removed anyway as a precaution. If you live in the UK, it’s not in your child’s vaccines, and that includes the new nasal-spray vaccine for flu which has been rolled out over the last few years. If you live in the U.S. it’s probably not, and thimerosal (thiomersal) free versions exist. It does turn up most often in flu vaccines (hence the meme image at the start) but thiomersal-free versions of those also exist in the U.S.

So chances are it’s not in your vaccines. Not in there. Got it? Ok.

ethyl vs methyl mercury

methyl mercury (left) is not the same as ethyl mercury (right)

Now, you may have heard about mercury in seafood. It is an issue, particularly for women who are pregnant, trying to become pregnant or breastfeeding, and is the reason such women are advised not to eat shark and swordfish, and to keep their tuna consumption low. But here’s the thing: it’s a different kind of mercury. In this case, it’s methyl mercury (remember, thiomersal breaks down to ethyl mercury, which is not the same).

Methyl mercury is more toxic than ethyl mercury. Methyl mercury binds to parts of amino acids much more readily than its ethyl cousin, and it’s able to pass through the blood brain barrier and into nerve cells where it causes damage. In addition, ethyl mercury is much more quickly eliminated from the body than methyl mercury. Because of all this, methyl mercury does bioaccumulate (build up in the body), and that’s why large top-of-the-food-chain fish like shark and tuna can have significant levels of it, and why certain groups of people should be careful about eating them.

The FDA’s action level (the limit at or above which FDA will take legal action) for methyl mercury in fish is 1000 ppb (1 ppm). But remember, that’s for the much more dangerous methyl mercury, not ethyl mercury. I’ve been unable to find an equivalent figure for the UK, but I’d imagine it’s similar.

So, where does the 200 ppb mercury figure in the image at the top come from? Well the Environmental Protection Agency does indeed set a ‘maximum contaminant level goal’ for inorganic mercury of 0.002 mg/L or 2 ppb in water supplies. Methyl and ethyl mercury are not inorganic mercury; compounds that fall into this category include mercuric chloride, mercuric acetate and mercuric sulfide, which largely get into water as the result of industrial contamination.

In summary, that meme image at the start is basically comparing apples and oranges. The EPA limit isn’t relevant to vaccines, because it’s for inorganic mercury, which the substance in vaccines isn’t. While we’re about it, the levels applied to fish don’t apply either, because that’s methyl mercury, not ethyl mercury. They’re not the same thing. And all that aside, it’s highly unlikely (if you live in the UK, no chance at all) that there are 50,000 ppb of ethyl mercury in your flu vaccine anyway. AND, let’s not forget, there’s no evidence that the tiny quantities of thiomersal used in vaccines are harmful in the first place.

Phew.

You may note that I’ve studiously avoided the word ‘autism’ in this post so far. But yes, that’s the big concern; that exposure to thiomersal in vaccines could cause autism. Despite multiple, huge, studies in several countries looking for possible links between vaccines and autism, none have been found. Vaccines don’t cause autism. It’s time we stopped wasting enormous amounts of time and resources on this non-link and spent it instead on finding out what does cause it. Wouldn’t that be far more useful and interesting?

Now… if you’re hardcore anti-vaccine and you’ve read this far, and you’re about to hit the comment button and tell me that all this research is just Big Pharma covering things up so they can make money from the ‘million(/billion/trillion) dollar vaccine industry’, just wait a moment.

Stop.

Think about this: how much money could the medical industry make from people actually catching measles, mumps, polio, TB, whooping cough and all the others? Just think of all the money they could make selling antivirals and antibiotics, all the money to be made from painkillers, antipyretics, drugs to treat respiratory symptoms of one kind or another, and everything else? Believe me, it would be much, much more than they make from a single 2 ml dose of vaccine. Why ‘cover up’ research that’s, if anything, reducing their profits?

All these diseases are horrible, and some can be fatal or have genuinely life-changing consequences. That’s proven. Please vaccinate your children, and yourself.

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