This weekend, my attention was drawn towards what looked a straightforward toxicological problem: Antifreeze kills.
Antifreeze is mostly used to prevent your engine coolant from freezing in winter. It lowers the freezing point of water (and, incidentally, raises the boiling point), so you can still use your car when winter hits. It’s also used as an additive to a lot of other products such as paint or window cleaner, but in far lower concentration than the concentrate you need for a car..
Most antifreeze products use organic substances to obtain the necessary properties of the anti-freeze product. The two most popular components of antifreeze are ethylene glycol (EG) and propylene glycol (PG). While PG is a harmless substance used in food and drinks with extremely low toxicity and does not form a health hazard, EG is completely the opposite. The Environmental Protection Agency files EG as hazardous, and the list of effects in humans is quite long. The estimated toxic dose lies around 1 mL / kg body weight in humans (for a 50% EG solution), and most likely similar for animals. which means that a 10 kilo pet could die after ingestion of 10 millilitres of antifreeze product.
But before we move on to pets, let’s get one thing off the table straight away: EG and PG get confused. A lot. And while it is easy to confuse two substances so much alike in form (and antifreeze use) as those two, their completely different toxicology should be enough to keep them apart. And yet. Confusing two compounds on purpose can be a very efficient strategy to spread wrong information, and pushing people towards so-called ‘natural’ solutions.
Take, for example, this site. At first, it looks like an valid information sheet on PG, but if you look closer, things go wrong. First of all, compare it with the ATSDR toxicity report to which I linked above. The information on the ‘good human’ website is rubbish. But wait, you might say. Didn’t they just confuse it with EG? Not really. Because they go on to cite numerous products that contain PG. Including skin care products. And by coincidence, there are links to ‘natural’ (more expensive) solutions without PG. It’s interesting to read the comments below the article. All the sensible comments were completely ignored. One person mentions the confusion with PG, and is ignored completely. And that’s just one example of deliberate false information. While many good articles on the facts are available on the internet (like this one).
Where safety is concerned, people want to believe whatever truth looks scarier. Hold that thought.
What about pets?
But let’s just look at the big killer, EG, and concentrate on pets.
And what’s better to get an idea about what’s happening than to google it? A quick search on “Ethylene glycol pets” gives 710,000 results, “Antifreeze pets” gives 1.4 million. Those results can be put into two categories: scientific reports or hazard warnings on the one side, and what i would call ‘concerned citizens’ on the other. The scientific reports usually consist of a list of lab tests that where done to see how toxic EG really is. Most of them on small mammals. Which is how we know it kills animals too.
The other group, the vast majority of the hits, consists of the vast and treacherous wasteland where fact and fiction blend: “common knowledge”. Half of those hits are discussions, either under articles such as the one mentioned above, on facebook, or on forum threads about pet care. The other half is a blend of pet care websites, kennels websites and petitions (like this one called “Blue Death”, which mixes up EG and PG. More on them later)
Looking for the facts
So what do these people talk about? Why is EG a concern for pets?
From the noise and clutter of the conversations, the following reasoning can be distilled:
1.Antifreeze is poisonous
2. Sometimes antifreeze leaks or spills onto the ground during a refill
3. Dogs and cats are attracted to antifreeze because they like the sweet taste
4. Dogs and cats will drink antifreeze, even if water is around.
As to the death toll, most cite 10,000 pet deaths every year (in the US) as a result of EG poisoning through antifreeze. None of the sites cite a source for that, but let’s just assume that they are right. To be on the safe side, let’s double that. 20,000 dogs and cats every year in the US. There are approximately 80 million dogs and 90 million cats in the US. A quick calculation learns us that it’s 1 pet in 10,000. By comparison, most websites on pets cite 1.2 million dogs run over by cars per year (in the US). That’s one in a hundred.
On all of the sites I’ve consulted (50 or so), on EVERY single one, those 4 statements were stated as solid fact. None of them, not a single one, made references to the basic science to prove those fairly simple statements. All they did was copy the exact same text from somewhere else, adding some comments about how sad and cruel poisoning is (it is. it really is. I’m not disputing that). If this goes on for a while, you end up with thousands of webpages (1 million, in this case) blurring out the same unreferenced statements as facts.
But it can’t be that difficult to check the facts, can it?
Let’s do some science!
If we have a look at statements 1 to 4, it’s immediately obvious that 1 and 2 are true. EG is poisonous, as we have proven before. No doubt about that. It’s poisonous to mammals in very low doses. No problem there. And of course sometimes EG spills onto the ground when you refill the car. So far, so good.
Statement 3, however, is a problem. From a biological, human point of view, sweetness is a good thing . Sweetness attracts us, because it signals the presence of sugars. Energy. But is the sweetness I taste the same as the one you taste? and is sweetness to us also sweetness to cats? Or dogs? To avoid philosophical discussions about sensory input, let’s just assume that the concept (and the meaning of) sweetness is a universal thing among mammals. That’s the reason why statement 3 consists of both the attraction and the preference for sweetness. We assume they like sweet things because we do.
Fair enough. But wrong.
Cats, it seems, can’t taste sweets. The full story can be found in this “Strange but true” feature in Scientific American. Cats exclusively eat meat, and lack the ability to taste the rich sugars present in plants. They even lack key enzymes to digest them.
At least for cats, statement 3 is false. For dogs, the situation is more complex. This article in the Journal of Nutrition states that dogs lack the ability to taste some sugars, but still respond to most sugars. Dogs are partly omnivore (mostly carnivore), so there’s no real evidence that EG wouldn’t taste sweet to them.
But there’s another problem. The attraction. Let’s assume dogs like the taste of EG. If they can smell it, perhaps they can be attracted to it. EG does not evaporate that easily (it has a high heat capacity), but dogs have sensitive smell, so perhaps it might be true. However, and this is crucial, there is NO evidence whatsoever to believe that dogs (or cats) are attracted to EG puddles. Nada. None. Everything is based on the assumption that pets will eat anything sweet they come across. Which for cats isn’t true because they can’t taste it, and for dogs highly unlikely, as most of them are overfed.
Hold the (Word)press!
There is a 2006 study on rats and dogs (both of which can taste sweets) which rejects the hypothesis that animals are attracted to anti-freeze.
It’s an interesting read, and it points to the impact of water content and water deprivation, which I discuss below.
Ethylene Glycol (EG), main component of anti-freeze
An inconvenient truth?
But let’s just, for the sake of argument, proceed to statement 4. That animals will prefer EG over water. They might. But there we come to a point that, on all those websites, is plainly ignored. Why, in an environment where dozens of water sources are available to every single pet, would they happen to stumble upon the tiny puddle of EG that lies near a car? Unless you spill enormous amounts of the stuff, which would be plain stupidity, the amount of antifreeze that ends up on the ground is minimal. Most of those websites and petitions will let you believe it’s an extremely common thing.
But think about it. Imagine that by some accident you spill antifreeze liquid on the ground, outside or in your garage. What are the chances that it will form a puddle on the ground? It’s my guess, but an educated one, that 9 out of 10, a spill of EG (and how common is a spill of EG on the ground, anyway? doesn’t it all end up on the engine block?) will hit the ground, splatter in all directions, and form tiny droplets that will be absorbed by the soil or surface.
So chances for encounter are small, the chances to have deadly puddles of EG even smaller. Will a cat, not attracted to antifreeze, really stumble upon deathly amounts of EG every time she puts a paw outside her sleeping basket (or box)? Unless she’s forced and deliberately poisoned, Not really.
The only logical reason I can think of to increase the accidental probability for an animal to stumble upon antifreeze is when all other sources of water are not available. It’s just a hypothesis, but it seems obvious to me that the two moments when this could be the case is during heat of summer, when antifreeze avoids boiling of the engine and water sources are more scarce, and during winter when antifreeze avoids freezing and all the water outside is frozen. That’s a testable hypothesis. Checking cat behaviour and liquid source preference can’t be that hard.
One last thing about the US death toll of 10,000 each year. Allow me to doubt those numbers. When I read a number like that without a source, alarm bells start ringing in my head. Deliberate antifreeze poisoning (by animal-hating neighbours for example) is quite common (and sadly, efficient), but remember: those 10,000 deaths are supposed to be accidental. How did they count that? Is there any source among vets that can confirm this? If so, please put it in the comments, and I will gladly stand corrected.
I’m not an animal hater, as many of the chief defenders of the EG-sweetness will probably throw me in the face after they read this (if they read this at all)
One more thing…
Why did I start my short research into EG in the first place?
Well…because of Blue Death Org UK (the people from the petition mentioned above). They have a Facebook page where every voice of reason is blocked and removed from the webpage, dismissed as “trolls”. The admin of the page uses violent measures to remove every other (scientific) argument that dares to contradict the 4 statements I discussed here. What’s more, other related issues are wiped off the table as well.
Rock salt, another antifreeze for road surfaces, is much more dangerous to animals than EG. The risk at poisoning is actually much higher (it get’s mixed with snow). But dare to suggest it, and you’re forever denied the right to discuss the issue.
This is, in my opinion, appalling. These people have started a petition to force the EU/UK to add bitterant additive to anti-freeze. That, in itself, is a noble cause. It helps avoid poisoning of children, and might in its wake also avoid the occasional pet poisoning. In fact, the US has just approved a decree that forces bitterant additives in most states two days ago.
Where they go wrong, however, is their basic understanding of science, and most of all, their attitude. The motivation texts for the petitions are a mix of urban legend (people died after their drinks were spiked with EG!), insufficient knowledge (mixing up EG and PG), and exaggerated reasoning based on a very emotional reaction.
And I can understand that people get emotional when their pet dies. I really do. And i would sign any petition based upon solid facts. But this? A combination of hoaxes and confusion? No. Emotions are not a good indicator of scientific value. Especially when that means refuting every scientific evidence to the contrary.
Remember, these people are backed by several charities, have a website, gather money. And the EG debate is just one of the examples. Many more can be found. And in every case, the underlying science is dodgy. How can you hope to convince EU officials when your basic facts are wrong? Emotion? Think again.
Think again. Then Act.