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There is a common pro-vaccination argument that attempts to equate the amount of formaldehyde injected into the body when receiving a vaccine, with the amount of formaldehyde ingested into the GI tract when eating a pear.

Here is a classic example:

  • Refutations to Anti-Vaccine Memes

    120 times

    A 200g pear contains up to 12,000 μg of formaldehyde naturally.

    Vaccines contain up to 100 μg, or 0.83% of the formaldehyde in a pear.

    i.e. A pear contains 120 times more formaldehyde than a vaccine.

I loathe this argument mainly as a non-sequitur factoid, but also because it is often parroted without references in a hypocritical argument to tell people not to believe everything they are told.

For example, it is not hard to find (repeated) examples of similar claims with different numbers:

  • Science Alert: Six myths about vaccination – and why they’re wrong

    there’s 600 times more formaldehyde in a pear than a vaccine.

  • Just the Vax: The Toxin Gambit Part 1: Formaldehyde

    Put another way, the amount contained within a vaccine is more than 50 times less than what is in a pear.

  • I found this image on a Mothering.com forum

    600 times image

    The difference is subtle, but notice it is 600 times as much (a factor of 5 increase), and the level of blue has changed by maybe 10%.

  • Vaxplanations repeat the 120 times claim, but I give them credit for also addressing the ingestion versus injection difference.

  • Gizmodo says a 220 g pear contains 8,600 to 13,200 µg of formaldehyde, putting the original 12,000 µg for a 200 g pear at the upper end.

  • This forum commenter seems to have lost a percentage sign:

    A typical vaccine may contain up to 100 ug, or 0.83 of the formaldehyde available in a typical pear.

So what is the real ratio of formaldehyde between a typical pear and a typical vaccine? 50:1, 120:1, 600:1, 1:0.83 or a different number?

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Oddthinking
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    *The dose makes the poison*. Does either side of the argument even address the formaldehyde dose that would matter to a human baby (in comparison to how much vaccine or pear contains)? – user5341 Apr 19 '16 at 16:47
  • The cartoon-pear that says "60,000 ug" doesn't specify the mass of pear, while the one that says "12,000 ug" specifies 200g. So it's very likely the "60,000 ug" value comes from disregarding "/kg" in the 60 mg/kg value that is the upper end of the 38.7-60 mg/kg range in the HK government document, which seems to be a typo with respect to the 6.0-38.7 mg/kg reported in German by primary researchers Moehler and Denbsky. – DavePhD Apr 19 '16 at 17:48
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    This comparison would only make sense if one could inject himself with a pear. – Dmitry Grigoryev Apr 20 '16 at 11:13
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    What's really galling here is that it's comparing apples and oranges, vaccines are injected straight into the flesh while pears will go through the stomach where a lot of components just won't survive the acid and enzymes. – ratchet freak Apr 20 '16 at 11:50
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    @ratchetfreak: Yes, I had hoped I had got that across with "non-sequitur factoid" and the GI tract. I didn't want to focus on this too much and make it into an opinionated rant. – Oddthinking Apr 20 '16 at 12:58

2 Answers2

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No. The amount of formaldehyde in 200 grams of pear is about 7 times the maximum that an infant would receive from a single vaccine, as explained below:

According to Determination of formaldehyde in foods, biological media and technological materials by headspace gas chromatography Chromatographia December 1996, Volume 43, pages 625-627:

Sample: Pears

Formaldehyde content: 7.4 mg/kg

Number of samples: 18

Given 200 grams of pear, 7.4 mg/kg corresponds to 1.48 mg (1480 μg) of formaldehyde

According to Children's Hospital of Philidelphia's page Vaccine Ingredients – Formaldehyde

The average quantity of formaldehyde to which a young infant could be exposed at one time may be as high as 0.2 mg

It lists the formaldehyde concentrations (or upper limits) of various vaccines. It lists Japanese encephalitis vaccine as having up to 0.2 mg (200 μg) of formaldehyde.

So the proper ratio is 1480:200 or 7.4:1.

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DavePhD
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  • What about vaccines? – Oddthinking Apr 19 '16 at 16:25
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    @Oddthinking I will add, but up to 200 micrograms – DavePhD Apr 19 '16 at 16:28
  • @Oddthinking actually, looking at the original Moehler and Denbsky paper, it says in the English summary "2-8 mg/kg in fruits (apples and pears)", but in German in table 3, it says "Birnen: 6,0 - 38,7", so using the 38.7 mg value you could have as high as 7780 ug of formaldehyde in 200 grams of pear. But 600 times is still quite an exaggeration. "Zur Bestimmung des Formaldehyds in Lebensmitteln" http://link.springer.com/article/10.1007%2FBF01292437 – DavePhD Apr 19 '16 at 17:02
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    According to this document: http://www.cfs.gov.hk/english/whatsnew/whatsnew_fa/files/formaldehyde.pdf a pear can have 38.7-60 mg/kg. They say this is from WHO. Those levels are almost a factor of 10 higher than your answer quotes. – JasonR Apr 19 '16 at 17:03
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    Also, can we keep prefixes to the units consistent? Most Americans couldn't convert 1,000,000 micrograms to a gram. ;) – JasonR Apr 19 '16 at 17:05
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    @JasonR I think the Hong Kong document has a typo and it should be 6.0 to 38.7 mg/kg, which is what Moehler and Denbsky say in German. – DavePhD Apr 19 '16 at 17:07
  • Ah, I can't read German. – JasonR Apr 19 '16 at 17:20
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    Pear does not contain as much formaldehyde as meme says, but **still** vastly more than a vaccine. So meme is correct, just numbers are bit off. – Peter M. - stands for Monica Apr 19 '16 at 18:03
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    The first line should be changed to **"No (but it still contains more, just not by that margin)"** or something similar, for the sake of future readers who might only give a casual glance. Otherwise this answer could be misinterpreted by an anti-vaccination advocate as "look, the answers was a clear NO, so the claim that pears contain more formaldehyde was a silly lie, pears contain much less than vaccines". – vsz Apr 19 '16 at 23:16
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    The question doesn't talk about the "highest dose of [formaldehyde in a] vaccine" though, but the dose in vaccines, plural. If this is understood to be an average, I suspect it is quite a bit less than 0.2 mg, and I wouldn't find it improbable that the meme makers even used a value lower than the average for making the comparison - maybe even the lowest amount of formaldehyde found in a vaccine? – eirikdaude Apr 20 '16 at 08:01
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    @eirikdaude it does talk about highest dose by saying "Japanese encephalitis vaccine as having up to 0.2 mg" which is the highest value in the Children's Hospital of Philadelphia list. – DavePhD Apr 20 '16 at 08:27
  • I first see that figure in your answer, but it is possible it was included in a previous edit of the question. Anyway my point was that it is not likely that it is the highest dosage of formaldehyde the makers of the meme have compared against. Rather I think it is likely they compared against vaccines with a low amount of formaldehyde in them, in order to make the figure in their meme as high as possible. I.e. is there no vaccine which contains 1/200th of the maximum amount of formaldehyde found in 200g of pear? Or; there is one case where the meme is untrue, is it untrue for all cases? – eirikdaude Apr 20 '16 at 09:21
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    If a pear contains 7 times the amount in a vaccine, that means that it contains 600% more formaldehyde than a vaccine contains. Perhaps someone confused 600% more with 600 times. – Matt Malone Apr 20 '16 at 13:24
  • That the first line starts with **No** is appropriate. A pear does not contain 600 times more formaldehyde than a vaccine. Yes, someone could link here and spin it to suit their agenda. But that's true of a more circumspect answer: "Look, this answer said the 600x is basically correct, so let's keep using it." – Hugh Apr 21 '16 at 04:52
  • Aren't there different kinds of formaldehyde? The one your body synthesizes is not the same as the one used as a preservative, I'm under the impression. –  Apr 21 '16 at 06:31
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    @fredsbend formaldehye is a very simply molecule, there is only one formaldehyde, no matter the source. – Mad Scientist Apr 21 '16 at 11:56
  • @eirikdaude the makers of the meme are comparing to 100ug from the vaccine, so that only accounts for a factor of 2 difference. Also, I believe that the meme creators themselves corrected the 600x version and replaced it with the 120x version. http://www.vaccinews.net/2013/03/a-pair-of-pears-putting-into-perspective-the-amount-of-formaldehyde-in-a-vaccine/ – DavePhD Apr 21 '16 at 14:34
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    Japanese encephalitis vaccine is not part of a regular vaccine schedule. – JasonR Apr 21 '16 at 20:18
  • @JasonR The manufacturer of this influenza vaccine also says up to 200 micrograms formaldehyde http://www.fda.gov/downloads/BiologicsBloodVaccines/Vaccines/ApprovedProducts/UCM112836.pdf , and the meme just says vaccines, not vaccines in a particular schedule of a particular country. – DavePhD Apr 22 '16 at 11:30
  • @fredsbend The liquid used in labs as a preservative is a 37% aqueous solution of formaldehyde, not pure formaldehyde. Pure formaldehyde is a gas at room temperature. The numbers in my answer are based upon pure formaldehyde, not the diluted liquid used to preserved stuff. – DavePhD Apr 22 '16 at 11:36
  • @Dave So, when they say formaldehyde it could actually include other things? My understanding is that it's use in vaccines is for a preservative function. –  Apr 22 '16 at 15:27
  • @fredsbend It's not a preservative function in vaccines. It is to inactivate virus, so it is only in vaccines which are inactivated virus. For example http://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0004167 where they try to achieve a 0.05% final formaldehyde concentration by adding formalin. "Formalin" is the technical term for formaldehyde aqueous solution. – DavePhD Apr 22 '16 at 15:36
  • @Dave So this formalin, which is in the vaccine, is not just formaldehyde. It includes other stuff. So in a simplified explanation, yes, the "formaldehyde" in vaccines is different from the formaldehyde in your body. –  Apr 22 '16 at 15:40
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    @fredsbend no, that would be like saying sugar from sugar solution is different from ordinary sugar. My point was, if you are going to dissect a frog and say this frog is preserved in formaldehyde, the liquid that it is preserved in isn't pure formaldehyde (which is a gas) but instead a solution of formaldehyde, which is mostly water. – DavePhD Apr 22 '16 at 15:45
  • @Dave Ok, so it's water and formaldehyde only? If yes, I understand. If no, then there's an issue. What's the other stuff? –  Apr 22 '16 at 15:57
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    @fredsbend Duke Univ. says "Beware though, that some solutions have methanol in them to stop polymerization but this could have a negative effect on your sample." http://microscopy.duke.edu/sampleprep/formaldehyde.html So possibly methanol. – DavePhD Apr 22 '16 at 16:04
  • @Dave Conversely, I'd bet the formaldehyde in the pear is naturally occurring. "No strings attached" as it were. –  Apr 22 '16 at 16:09
  • Let us [continue this discussion in chat](http://chat.stackexchange.com/rooms/38790/discussion-between-fredsbend-and-davephd). –  Apr 23 '16 at 19:27
  • Given that the formaldehyde present in your body is present in your body water, etc., - formaldehyde in water (formalin) in a vaccine is not different. – Darwy Sep 29 '16 at 20:25
  • @Darwy potassium chloride is present in your body, and injection of potassium chloride in water stops the heart in lethal injection death penalty https://en.wikipedia.org/wiki/Lethal_injection#Potassium_chloride – DavePhD Sep 29 '16 at 21:02
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No, the maths on these memes don't quite add up, but it is fair to say that a pear does still contain quite a bit more formaldehyde than any vaccine by at least a factor of 10.

According to the WHO (World Health Organization), (PDF File) a Pear can contain 6 to 38.7 mg/kg of formaldehyde. That would mean for a 200 gram pear, we have anywhere from 1.2 to 7.74 mg.(1)

According to the Children's Hospital of Philadelphia, the vaccine with the highest amount of formaldehyde is the Japanese Encephalitis vaccine at a whopping 0.2mg. However, that vaccine is not on the standard CDC schedule (PDF File). The highest amount in a regularly scheduled vaccine is actually 0.1mg.

So at a worst case scenario for a regularly scheduled vaccine, a 200g pear may have 77 times the formaldehyde that type of a vaccine. At best, we are talking 12 times the amount. So pear is greater than vaccine. However, that doesn't really matter.

This is all a non-sequitur argument as Oddthinking points out (injection versus ingestion for instance). I think the really important point comes from the Children's Hospital website (emphasis mine):

Formaldehyde is essential in human metabolism and is required for the synthesis of DNA and amino acids (the building blocks of protein). Therefore, all humans have detectable quantities of natural formaldehyde in their circulation (about 2.5 ug of formaldehyde per ml of blood). Assuming an average weight of a 2-month-old of 5 kg and an average blood volume of 85 ml per kg, the total quantity of formaldehyde found in an infant's circulation would be about 1.1 mg, a value at least five times more than the amount an infant would be exposed to in vaccines.

That right there should put a nail in the coffin of that bad argument. As a human adult, you will have 4.5 to 5.5 liters of blood. This means you have 11.25 to 13.75 mg of formaldehyde in your body anyway (maths in comments below didn't scale properly apparently).

(1) - Please note, there does seem to be a systematic typo that exists in the documentation. The original German document lists 6 - 38.7 mg/kg. This figure has been turned into 38.7 - 60 mg/kg. For the purposes of this answer, I am using the original citation of MÖHLER, K. & DENBSKY, G. (1970) [Determination of formaldehyde in foods.] Z. Lebensm. Unters. Forsch., 142: 109-120.

NOTE: With the above referenced typo, the first meme would be considered mostly correct (i.e. 60 mg/kg does indeed give an answer of 12,000 micrograms, or 12mg as an answer at the upper end. So while not 600 times, the 120 times is an understandable mistake). Another mistake is that 7 times anything is about 600%, so a percent symbol getting dropped could be another cause of that confusion. This is all "below the line" speculation though, as tracing the origins of mistakes is probably beyond the scope of this site.

JasonR
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    Just because I have 5×x of a substance in my body does not mean that ingesting me with a quantity of 1×x is harmless. Suppose I have 40 litre water in my body. If I am suddenly ingested with 8 litre, I would be not happy. I don't dispute that ingestion of a small amount of formaldehyde is safe, but the fact that we have a 5× larger quantity in our body already is not itself sufficient evidence to support that. – gerrit Apr 19 '16 at 17:39
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    @gerrit, the word you're looking for in this case is injected or inject, "ingesting me" implies that someone is eating you. However I agree with your overall argument. – Ryan Apr 19 '16 at 17:50
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    I would indeed be interested in the injection vs ingestion difference, with injection, it all ends up in the bloodstream, whereas with ingestion a significant portion might be degraded or not absorbed. In the absence of measure about how much formaldehyde from a pear makes into the bloodstream when eating said pear, this is all pretty inconclusive. – Matthieu M. Apr 19 '16 at 17:52
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    @gerrit See the quote in the answer. I DO address the difference in that our blood contains 2.5 ug of formaldehyde per ml naturally. A 5kg infant has 1.1mg. An adult weighing 70kg (155lbs) has 15.4mg or so of formaldehyde if the maths scale. – JasonR Apr 19 '16 at 18:17
  • @JasonR So the answer is probably that not much of the ingested formaldehyde from a pear makes it into the bloodstream? – pydsigner Apr 19 '16 at 18:47
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    @pydsigner I would say it's irrelevant since it's comparing "apples to pears" as it were. :) – JasonR Apr 19 '16 at 19:18
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    Is the lowest amount in a regularly scheduled vaccine less than 1/200th of the highest amount of formaldehyde found in a pear? I suspect that is the ratio that'd be used for making the meme, not highest amount vs. highest amount. – eirikdaude Apr 20 '16 at 07:57
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    @MatthieuM. When have you been vaccinated the last time? Vaccines are injected into muscle, not the bloodstream. Sure, it ends up in the blood eventually, but the same is true for digestion (that's kind of how digestion ultimately works). – Luaan Apr 20 '16 at 08:12
  • @Luaan: A long time ago... I might have mistaken vaccination for perfusion indeed. In any case, the question remains: two different modes of administration are unlikely to yield the same "penetration rate". – Matthieu M. Apr 20 '16 at 08:30
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    @MatthieuM. Yeah, definitely. The "natural blood content" (and natural in-body production) is a much better argument ceteris paribus. But, well, it's most likely a counter-argument to an even more ridiculous claim. I'm guessing the guys using formaldehyde content as an argument against vaccination have no idea how formaldehyde works in the body, how it is produced and that quite a bit of it is produced whenever you drink alcohol, for example. This kind of meme is targeted *precisely* on people like that - thinking that formaldehyde is un-natural or that natural means desirable or healthy. – Luaan Apr 20 '16 at 08:37
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    In Pediatric and adolescent environmental health, Volume 2, in "TABLE 44.2 : Level of formaldehyde in foods Food source Formaldehyde content (mg/kg)" it also says "Pears 6.0-38.7 mg/kg" https://books.google.com/books?id=i9UhAQAAMAAJ&q=pear+formaldehyde+mg/kg&dq=pear+formaldehyde+mg/kg&hl=en&sa=X&ved=0ahUKEwiz8pbi55zMAhXKPCYKHXb8CjU4ChDoAQhMMAc – DavePhD Apr 20 '16 at 08:41
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    @JasonR You say "The argument is a non-sequiteur". Well that goes even more so for the original argument. The leap from "Vaccines (may) contain some formaldehyde" to "Don't vaccinate your kids" is a **giantic** NS. In order for this argument to work the proponents have made some impliped assumptions that fill the gap. The counter-argument "Pears contain it too" kills those assumptions. –  Apr 21 '16 at 06:27
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    Assumption that a 20% increase is blood concentration is too small to be harmful isn't sound. For example: "The normal concentration of sodium in the blood plasma is 136-145 mM. Hypernatremia is defined as a serum sodium level over 145 mM. Severe hypernatremia, with serum sodium above 152 mM, can result in seizures and death." http://medical-dictionary.thefreedictionary.com/hypernatremia – DavePhD Apr 21 '16 at 19:16
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    While the cited web page gives the blood level of formaldehyde, that does not mean blood is the only part of the body where formaldehyde is found. Particularly, if it is needed for DNA and amino acid synthesis, it does make sense to assume that there is some more formaldehyde there. Which would mean that the injected amount leads to less relative increase than the guesstimate from the blood compartment only suggests. – cbeleites unhappy with SX Apr 21 '16 at 19:17
  • @DavePhD See second statement on the Philadelphia Children's Hospital: "Quantities of formaldehyde at least 600 times more than the amount contained in vaccines have been given safely to animals." Sodium isn't formaldehyde, so not sure what the comparison is there. – JasonR Apr 21 '16 at 19:20
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    @DavePhD: while it is true that the guesstimated increase of 20 % per se doesn't allow any conclusions about toxicity, neither can you easily draw conclusions from toxicology data of totally different substances. – cbeleites unhappy with SX Apr 21 '16 at 19:20
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    Given that the adult liver metabolizes on average 22 mg of formaldehyde per minute, and that over the course of the day, an adult will produce nearly 55 grams of endogenous formaldehyde, the amounts in a vaccine are not an issue. An infant will also have around 9000 ug of formaldehyde in their blood (alone) at any given time. Every mammalian cell produces it, and they all can metabolize it via FDH. It's gone in minutes. – Darwy Sep 29 '16 at 20:27