A reader writes:
The Register had this story; it paraphrases a study from Pediatrics but includes this paragraph:
The incidents are no laughing matter, as a swallowed button cell can generate sufficient current to burn a hole in a child's oesophagus, from the inside, without the child displaying any obvious symptoms. Acid can also injure. Even batteries that appear depleted, inasmuch as they can no longer power electrical devices, can inflict these injuries.
Is it just me, or is the claim that a mostly-depleted button cell can "burn a hole in a child's esophagus" via electrical current a complete and obvious impossibility? By leaking strongly acidic or basic electrolyte I can buy, but by electrical action?
In brief: Yes, the problem here is burning, and it can be very serious. But it's not electrical burning, it's chemical burning, specifically as a result of electrolysis of tissue fluids. And if a battery makes it to the stomach, the swallower is likely to be OK; it's only if it lodges in the oesophagus that big trouble is likely to result.
Well, that's what I learned in the course of writing the following Wall O' Text, anyway.
("I would have written a shorter letter, but I did not have the time.")
Whenever you find yourself wondering about some oddball medical news, you should proceed directly to PubMed.
(This is particularly important if you got the news from a newspaper or TV show, many of which can be relied upon to get almost all science news solidly wrong. Mass-media science reporting is sometimes good, but it's very often terrible, for surprisingly complex reasons. Whenever I hear some interesting-sounding science report on TV news, I try to remember the first five seconds of the report and expunge the rest of it from my consciousness, so I can look up what, if anything, has really been discovered, without wasting any neuron-connections on what some attractive ignoramus thinks is going on. See also, jazzed-up, dumbed-down reality shows, some of which make a real effort to get things right, and some of which don't.)
PubMed lets you search the Medline, and some other, medical research databases. You'll generally only get the abstract of each paper (and not even that, for some), and you're not tremendously likely to be able to find the whole paper for free anywhere (a situation which should change, and actually may). But a quick PubMed search will nonetheless give you a rough idea of the state of research on a subject.
If you lean on PubMed for evidence when you're having an argument with someone, the two of you are likely to end up playing what I call Duelling Abstracts, in which neither of you knows how good any of the research you're citing is, so you both just end up Bullshitting for Victory. All research is not of the same quality, and PubMed will cheerfully present you with numerous papers in support of almost any nutty idea you like. (This is largely because Medline indexes many dodgy journals along with the respectable ones.)
Assuming you're not using the science for support, rather than illumination, you need to see how well a given piece of research was done, and how often it's been reproduced by other researchers, before you should cite it in a serious discussion. (At least few bad papers are the result of outright fraud. Unfortunately, though, a paper often has to be blatantly and quite famously fraudulent before it'll actually be withdrawn, though this situation is improving.)
But if you're just trying to see whether there's any research on, say, kids swallowing batteries, and you don't need more detail than you get from paper abstracts or letters written to medical journals (PubMed doesn't only index research papers), a couple of minutes on PubMed is all you need.
I was surprised to discover that there's actually quite a bit of literature on the subject of kids eating small batteries. I suppose it's the result of more and more consumer items that run from these tiny batteries. In 1980 you might have had a lithium coin or an alkaline LR44 in your calculator or wristwatch, or a silver-oxide cell if you were fancy, or a zinc-air battery in your hearing aid and maybe a mercury battery in your camera. But plenty of people didn't have one button cell in their house.
Nowadays, small remote controls, key-ring flashlights, laser pointers and umpteen other glowing tchotchkes run from miniature batteries, and it's easy to get the batteries out of most of these items. The only other thing you need to guarantee many tiny-battery-ingestion events is firm instruction from a parent that children must most emphatically not eat said batteries.
However it happens, kids are eating batteries, and the results can be quite serious.
I initially thought some danger might be posed by lithium batteries, which really do contain metallic lithium...
...which isn't as excitable as its relatives further down the leftmost column of the Periodic Table, but which is still not something you want running around loose in your stomach. Lithium salts: Mood stabiliser. Metallic lithium: Mood ruiner.
In theory, stomach acid could eat through the casing of a battery, but in practice this doesn't seem to happen. Especially not with lithium cells, which are deliberately made very resistant to corrosion specifically to stop them from starting fires all over the place. The same goes for pretty much every other tiny battery; I don't know which of them have stainless-steel casings, but it seems they can be expected to pass through the gastrointestinal system pretty much intact, even if they do some damage on the way.
The mechanism for said damage does seem to be electrical, but not directly. Even a brand new button cell doesn't have a lot of power to deliver, and the harder you load a battery the less capacity you'll get, but swallowing a battery will give it a quite nice low-resistance pathway from one terminal to the other, and button cells all have terminals separated by only a millimetre or two. This means something close to the battery's full short-circuit current could flow through a quite small amount of tissue. The relatively large circumference of a coin cell will spread out the affected area a bit, unless the battery lodges in such a way that only part of its circumference has a good contact.
To see how much current that actually is, I threw together a battery-torturing apparatus...
...in which the twenty-amp current range of a multimeter, with about one ohm of resistance including the wires, stood in for the conductive lining of a human gut. I think one ohm is a pretty good figure to go with, here; human tissue is often not very conductive at all (put multimeter probes next to each other on your tongue and you can get a surprisingly high reading; more invasive test techniques are discouraged), but I think the internal mucous membranes, plus stomach acid or one or another salt, are both pretty conductive and pretty easy to damage.
My first victim was a tiny LR754 alkaline button cell, 7.9 by 5.4 millimetres in size, which had been sitting in my miscellaneous-battery drawer for a while but still had an open-circuit voltage above 1.5 volts. At the moment when I clicked the magnetic contacts onto the cell it produced more than 0.2 amps, but this fell to 0.1 amps after 30 seconds, 0.07 after a minute, and so on down the line until it was 0.01 amps at five minutes.
(Because I was using the super-low-resistance 20-amp range on the meter, the lowest current I could measure was 0.01 amps, and I wouldn't bet my life on the meter's accuracy either.)
Next I tried a CR2016 lithium coin cell, 20mm in diameter and 1.6mm thick. These cells are commonly used in Photon-type key-ring flashlights; red key-ring lights can run from one double-thickness CR2032, but blue, green and white LEDs need more voltage and so run from a series stack of two 2016s.
(Modern computer motherboards usually have a 20-series coin cell as their BIOS-setting backup battery. It'll probably be a CR2032, but in a pinch you can substitute a 2025 or 2016; the thinner cells should still fit the contacts. Don't stack thinner cells to fill the holder, though!)
The 2016's initial open-circuit voltage was 3.25V, but it managed less than 0.01 amps from the outset.
I thought I might have picked a defective or very old CR2016, but who cares, if the ceiling performance of shorted lithium coins isn't high enough to be a worry anyway? So I next tried to establish where that ceiling is by testing a beefy (by coin-cell standards) CR2430 (24mm wide, 3mm thick), which had also been on the shelf for rather a while and only started at 3.16 volts open-circuit, but which still should be able to easily beat any of the more common 2016s or 2032s.
The 2430's initial current was up around half an amp, but that lasted less than a second. It managed 0.16 amps after 15 seconds, 0.12 amps after a minute, 0.09 after two minutes, and kept going strongly (again, by coin-cell standards); it still managed 0.08 amps after four minutes, 0.06 after seven minutes, and was still managing 0.03A after thirty minutes, which was when I unshackled the prisoner from the wall and consigned him to eternity in the rubbish bin.
OK, so this cell managed to deliver something in the neighbourhood of a tenth of an amp for at least a few consecutive minutes. Voltage equals current times resistance, so if the current is 0.1 amps and the resistance is one ohm, there must be only 0.1V across the battery. (Voltage sag is normal in overloaded batteries.) Power equals voltage times current; 0.1 volts times 0.1 amps gives a miserable ten milliwatts of power, which even if it were concentrated in one small spot probably wouldn't, I think, directly singe even a baby's oesophagus.
My last victim was an alkaline LR44. I think this is the button battery most likely to end up inside a child, because it's both conveniently pill-shaped and very widely used. The one I chose started out at 1.57 volts open-circuit, and initially managed to deliver more than 0.3 amps into the short circuit. This, again, fell very rapidly, to 0.23 amps at 15 seconds, 0.21 at 30 seconds, 0.18 after a minute, and so on. At five minutes it was 0.12 amps, and just before ten minutes it suddenly fell from 0.07 amps to only 0.01, perhaps because of some internal failure caused by the short.
(The LR44 didn't get hot or leak, though. Modern batteries are extraordinarily good at not leaking, and only partly because we now use a lot of alkalines instead of carbon-zinc cells which corroded away their zinc casing as part of their normal operation. Un-leaking batteries are one of those things, like un-popping tyres, that now give so little trouble that people fail to even notice them any more.)
OK, let's suppose we've got a very beefy LR44 that manages to deliver 0.3 amps into one ohm for a significant amount of time. V equals IR, once again, I is 0.3, R is 1, therefore V is 0.3V, and V times I is a pathetic 0.09 watts. Again, this doesn't seem to me to be very dangerous.
And the medical literature mostly agrees.
If a button battery lodges in the oesophagus then you have a problem. A neck-lodged battery can cause a tracheo-oesophageal fistula (a hole between the trachea and the oesophagus); one did in this unfortunate one-year-old, who recovered, and in this toddler, who didn't.
Interestingly, there's a two-page guide to "Management of children who have swallowed button batteries", which was published in 1986 in Archives of Disease in Childhood, in PDF format here. It agrees with the newer papers that it's lodgement in the oesophagus that's the problem, but says thin lithium coin cells don't seem prone to lodge at all. And it also speculates that an increase in pH (an increase in alkalinity around the battery's anode) is what causes tissue burns, not simple electrical heating or leaking chemicals from inside the battery.
A swallowed battery is essentially electrolysing water wherever it comes to rest. That'll produce hydrogen bubbles on one terminal and oxygen bubbles on the other, but the salts that make saliva, gastric juices and tissue conductive will electrolyse too. Sodium chloride in water, or hydrochloric acid from the stomach, could give you chlorine bubbles along with the others, which would be bad news. Perhaps it's that, along with mechanical damage from the child trying to swallow the battery or cough it up, that causes fistulas and their life-threatening consequences.
Given the feeble numbers I got by short-circuiting miniature batteries, I agree that there really doesn't seem to be any electrical burning going on there. You'd just need more watts per conductive length than 1.5V and 3V miniature batteries can deliver. A twelve-volt A23 battery might do it; A23s have a stack of tiny button cells inside them, and used to be ubiquitous in small radio transmitters like car central-locking key-fobs and wireless doorbells, but are now being replaced by lithium coins. I bet a standard rectangular nine-volt battery could do it too, in the unlikely event that even a full-grown adult, let alone a child, somehow managed to ram one down their throat. There are rechargeable button cells as well, which like other rechargeables have a lot more current capacity than non-rechargeables of the same size, but they're rare enough that no child may ever actually have swallowed one.
There are various other individual case reports, ranging from the benign to the fatal, in the face of which one should remember that surely for every kid who ends up in hospital for battery-eating there must be a few who ate and later excreted a battery without any adult noticing. Or, at least, without any adult noticing until they changed that nappy.
Saving the best for last, here we have "an analysis of 8648 cases", the full text of which is available for free. The authors conclude, and also say in this slightly later paper (also online for free), that the severity of battery-swallowing injuries is getting worse, because of proliferation of 20mm-plus coin cells, which (in contradiction of the 1986 management guide) now seem to be the most dangerous. Misdiagnosis seems to be a major part of the problem, though, which shouldn't be too hard to fix since batteries show up loud and clear on an X-ray. Oh, and kids do manage to swallow AAA and AA batteries too; more than 5% of the 8648 cases involved "cylindrical cells".
These authors also say it's alkalinity - formation of hydroxide ions in tissue fluids next to one terminal of the battery - that "is now appreciated as the most important mechanism" in batteries damaging flesh.
So yes, swallowed batteries can "burn" the swallower, but chemically, not via resistive heating, which barely happens at all because these batteries can't deliver much power.
In the absence of complications like swallowed magnets, there only seems to be a danger if the battery lodges in the oesophagus. But 20mm and larger lithium coin cells are a good size to do exactly that, and if one does, there appears to be a good chance of very bad results. The authors of those two meta-analyses says there's a 12.6% chance that a child younger than six swallows a 20mm-plus coin cell will "experience serious complications or death", but they base that primarily on the records of the US National Poison Data System and National Battery Ingestion Hotline (who knew?), which of course don't get to hear about battery-consumption that doesn't cause any problems and passes unnoticed.
Still, in the million-item list of things for parents of young children to freak out about, this doesn't seem like a silly one. I think parents could do worse than scan their house for remote controls, kitchen scales, toys and so on that have small and easily-removed batteries.
And then commenters will, I hope, correct at least the most obvious flaws in my answer.