The “EPA Mercury Limit” Canard
February 5, 2010 by Do'C 
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If there’s one thing typical of anti-vaccination trolls on the internet, it’s that they are fairly predictable. Amidst tons of logical fallacies, they’ll persistently ignore evidence, cite things that don’t say what they think they say, provide supporting information in the form of links to conspiracy theory stories, repeat things that have already been pointed out as incorrect, and pretty consistently ask for proof of a negative wherever they can. In addition to all that usual fare, it’s fairly common, that they’ll jump right into something about “evil toxins” when advocating against vaccination. A perfect example of this is persistent use of what I’ll call “The EPA Mercury Limit” canard.
In a recent article by Trine Tsouderos at the Chicago Tribune, the anti-vaccination brigade infested the comments like fleas. There was relatively little actual commentary on the article itself, the intersting points it raised, or the subject of the article - Boyd Haley’s new “dietary ingredient“ - OSR, that’s apparently being given to autistic children by parents who believe their childrens’ autism diagnoses are the result of some condition that is mecury-induced. Instead, anti-vaccine commenters turn the dialogue to vaccines, pharmaceutical industry conspiracy, and seem to spend more time attempting to appeal to fear than anything else.
One of the pervasive appeals to fear from vaccine rejectors is of course mercury in flu shots. They have to bring up flu shots most of the time, because they know (or should know) that mercury (ethylmercury specifically, present in the preservative Thimerosal, in multi-dose vials of injectable flu vaccines) has essentially been removed from the routine childhood vaccines that used to contain it. It’s been greatly reduced, or has been pretty much gone for seven or eight years now. The “Flu shots” is pretty much all they’ve got.
Nevermind that the anti-vaccination advocates never provide data about pediatric uptake of flu shots that actually contain Thimerosal. Nevermind that they don’t acknowledge the general availability of Thimerosal-free flu shots for pediatric patients. It seems like they’d pretty much prefer that others buy in to mercury fear. How do they fan the flames of fear? With misinformation. Here’s a fairly typical scare quote:
“And finally consider the fact that the Environmental Protection Agency HAS established a maximum daily dose of one tenth of a microgram per day per 2.2 pounds of body weight. The means a single flu shot with thimerosal would require a child to weigh 550 pounds in order to NOT exceed the USEPA DAILY amount per body weight.”
Holy crap, my kid doesn’t weigh 550 pounds! It seems that the author of this comment would have readers believe that kids being vaccinated for influenza are being overdosed with mercury - but, although it may appear scary on the surface, there’s more than one problem with this argument.
Here’s what this commenter’s argument would look like if it were factually correct:
“And finally, consider the fact that the Environmental Protection Agency has established a daily oral intake reference dose for methylmercury of one tenth of a microgram per 2.2 pounds of body weight. This means a thimerosal-containing flu shot given every single day of a child’s life for 75 years, would require a child to weigh 550 pounds in order to not to exceed the EPA’s oral RfD for methylmercury“
In case you’re wondering, thimerosal-containing flu shots don’t contain methylmercury, and children don’t get them every single day of their lives for 75 years.
The EPA’s RfD (Reference Dose) For Mercury
What is it really, and why does the EPA even have an Oral RfD for methylmercury? The answer is pretty simple. The EPA provides standardized guidance for exposure to methylmercury from seafood consumption to enable other federal, state, and local health agencies to make appropriate health advisories about seafood consumption.
Guidance for Assessing Chemical Contaminant Data for Use in Fish Advisories
Lot’s of additional links to information from the EPA can be found at this link, and information (including citations of the supporting science) from the EPA about the .1µg/kg body weight RfD can be found at http://www.epa.gov/iris/subst/0073.htm. Yet more information is available from the National Academies Press(free to read online).
Two Big Problems With The Thimerosal-Containing Flu Shot Comparison
The first and perhaps most noticeable thing about this .1µg/kg body weight RfD is that it is for methylmercury, which has absolutely nothing to do with Thimerosal in Flu Shots. Methylmercury and ethylmercury are not the same substance. Methylmercury is not used in any vaccine - it typically finds it’s way into humans via the consumption of seafood. The half-life of ethylmercury and methylmercury in the blood of humans appears to be markedly different too (with ethylmercury clearing much more rapidly than methylmercury).
The second thing about the RfD that stands out as incongruous between the 550lb-kid canard and reality is that a flu shot is a one-time annual event. The RfD is clearly based on a reasonable expectation of safety with daily exposure, even by sensitive subgroups, over an entire lifetime. It’s not a simple one-day limit as implied by the canard.
The oral Reference Dose (RfD) is based on the assumption that thresholds exist for certain toxic effects such as cellular necrosis. It is expressed in units of mg/kg-day. In general, the RfD is an estimate (with uncertainty spanning perhaps an order of magnitude) of a daily exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime.
[Emphasis mine].
It’s probably makes sense to most readers that understanding RfD in terms of daily exposure over a lifetime, paves the way for meaningful and standardized comparison to average weekly seafood consumption. It’s fairly straightforward for other agencies to adjust advisories (and make adjustments - for things like local contaminant levels, or variability of mercury levels among different fish species). It doesn’t take a PhD to understand that seafood consumption advice expressed as .1µg/kg body weight, daily, over a lifetime is probably less useful for most consumers than say, specific guidance on number of meals per week for different types of fish [example].
For most readers, it won’t be terribly difficult understand that EPA RfD for MeHg really isn’t relevant to thimerosal-containing flu vaccines at all. There are those who will claim in some form or another, “but it is relevant, the government says so”. We’ll get to that in a minute, but first, let take a look at a real live example.
The Canard/Comparison In Action
To look for an example of this canard in action (other than in blog comments by people with likely anti-vaccination leanings), one need look no further than the NVIC.org website (Barbara Loe Fisher, Co-Founder and President, and Kathi Williams, Co-Founder and Vice President). The NVIC website, which claims a title of “America’s Vaccine Safety Watchdog”, prominently displays a large graphical link to a “Vaccine Ingredients Calculator” dead center of its main page (as of this writing).
A quick visit to the calculator, entry of data for an average 12-month old, and selection of a Thimerosal-containing flu shot, reveals some interesting “RESULTS”.
There are problems with these “RESULTS”.
For now, disregard the fact that when Thimerosal-containing Fluzone was chosen there was no mention that the thimerosal-free version is the recommended, specifically packaged and labeled, and noted in the Fluzone dosing table for pediatric patients: 6-35 months (although a thimerosal-free version is listed in the vaccine choices of the Vaccine Ingredients Calculator). There are the two big problems with the comparison of a thimerosal-containing flu shot to the EPA’s RfD, that make this a perfect example of the canard.
1. Step 5 (Calculate mercury exposure) states, “Based on EPA standard of 0.1 mcg/kg/day.”
It should be clear that the EPA establishes no such standard for the ethylmercury in Thimerosal in a vaccine. Remember, the EPA’s reference dose is for methylmercury.
2. “RESULTS:” states, “Mercury amount the EPA says a 12 month-old can handle today: 1.0 mcg”.
If you’ve read any of the EPA reference materials linked in previous paragraphs, you should have no trouble recognizing that this is misleading! The EPA says no such thing. The EPA does say how much methylmercury a 12 month-old could ingest every day for 75 years (how a “lifetime” was defined), even if the 12 month-old is the most sensitive in the population, with a reasonable expectation of safety. Additionally, even if we were talking about ingested methylmercury, the EPA guidance is for daily exposure over a lifetime - it does not say anything about a single day event (e.g. “can handle today”).
Here’s the bottom line - The EPA reference dose is for the ingestion of methylmercury (primarily to provide scientific guidance for seafood consumption). The reference dose is an evidence-based guideline for a reasonable expectation of safety, expressed in a daily exposure amount, standardized to body weight, over a person’s entire life. There’s a 10-fold safety factor built-in, and it’s intended to protect the most sensitive in the population.
The EPA RfD for oral MeHg has absolutely nothing to do with vaccines!
But wait… ”The Government Compared Thimerosal In Vaccines To The EPA’s Oral RfD for MeHg!”
It’s true. The FDA did consider ethyl- and methyl- mercury as if they were “equivalents” in its risk evaluation - of 1999.
FDA has been actively addressing the issue of thimerosal as a preservative in vaccines. Under the FDA Modernization Act (FDAMA) of 1997, the FDA conducted a comprehensive review of the use of thimerosal in childhood vaccines. Conducted in 1999, this review found no evidence of harm from the use of thimerosal as a vaccine preservative, other than local hypersensitivity reactions (Ball et al. 2001).
As part of the FDAMA review, the FDA evaluated the amount of mercury an infant might receive in the form of ethylmercury from vaccines under the U.S. recommended childhood immunization schedule and compared these levels with existing guidelines for exposure to methylmercury, as there are no existing guidelines for ethylmercury, the metabolite of thimerosal. At the time of this review in 1999, the maximum cumulative exposure to mercury from vaccines in the recommended childhood immunization schedule was within acceptable limits for the methylmercury exposure guidelines set by FDA, ATSDR, and WHO. However, depending on the vaccine formulations used and the weight of the infant, some infants could have been exposed to cumulative levels of mercury during the first six months of life that exceeded EPA recommended guidelines for safe intake of methylmercury.
As a precautionary measure, the Public Health Service (including the FDA, National Institutes of Health (NIH), Center for Disease Control and Prevention (CDC) and Health Resources and Services Administration (HRSA) and the American Academy of Pediatrics issued two Joint Statements, urging vaccine manufacturers to reduce or eliminate thimerosal in vaccines as soon as possible (CDC 1999) and (CDC 2000). The U.S. Public Health Service agencies have collaborated with various investigators to initiate further studies to better understand any possible health effects from exposure to thimerosal in vaccines.
The FDA has also noted newer science that demonstrates a lack of equivalence between ethyl- and methyl-mercury since then, such as Pichichero et al., 2002:
Blood levels of mercury did not exceed safety guidelines for methyl mercury for all infants in these studies. Further, mercury was cleared from the blood in infants exposed to thimerosal faster than would be predicted for methyl mercury; infants excreted significant amounts of mercury in stool after thimerosal exposure, thus removing mercury from their bodies. These results suggest that there are differences in the way that thimerosal and methyl mercury are distributed, metabolized, and excreted. Thimerosal appears to be removed from the blood and body more rapidly than methyl mercury.
A Final Note On The “EPA Mercury Limit” Canard
The EPA’s oral RfD for MeHg has nothing to do with vaccines. Just because the FDA used it as a basis for comparison (considering it an “equivalent” for a study, but not claiming it was actually equivalent) to estimated ethylmercury exposure from vaccines in 1999, does not mean the EPA has said anything about ethylmercury in vaccines, let alone that it has set a “maximum daily dose”. To state or imply that the EPA has (such as in the case of the blog commenter), is inaccurate. To imply that the EPA guideline is a valid comparison, only to justify the validity of such a comparison by claiming the FDA drew such a conclusion is misleading. The FDA did compare exposure to ethylmercury to the guideline for methylmecury intake in their review in 1999, but did so in the lack of “existing guidelines for ethylmercury”, not because the two forms of mercury are equivalent.
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Comment by Squillo — 6 February, 2010 @ 10:18 am
Beautifully done, D’oC. One of the best and most accessible explanations of this canard I’ve seen.
Comment by isles — 7 February, 2010 @ 1:36 am
You really sort of have to wonder whether the dedicated antivaxers really don’t understand this by now - because surely it’s been explained in more than a few of the comment threads they pounce on so eagerly - or whether they enjoy the shock value of the image of a 550-pound baby so much that they simply can’t help themselves from repeating it.
My kids had more restraint by the time they were four years old, and they were able to understand concepts like “same vs. different” too.
Comment by Bill — 7 February, 2010 @ 6:57 am
I’m trying to make sense of this…. where do you get everyday for 75 years from?
Comment by Do'C — 7 February, 2010 @ 8:35 am
Hi Bill,
The 75 years is in the age-weight tables in section 3 of the first linked EPA document in the article.
You can also find it in the Glossary under “Lifetime” of the National Academies Press book on the subject.
Here’s a quick link to that page.
http://books.nap.edu/openbook.php?record_id=9899&page=341
The “every day” is noted consistently throughout the documents.
Comment by Bill — 7 February, 2010 @ 10:56 am
Hi Do’C,
I’m sorry, having a really hard time finding the exact reference. Maybe its that I just don’t understand it… can you specify that exact page? Section 3 doesn’t have the word “lifetime” in it at all. There is one ref to it on 2-58 and another on 5-56. I’m looking at Guidance for Assessing Chemical Contaminant Data for Use in Fish Advisories. Is that the correct doc?
What I’m trying to reconcile is that the calc site is talking about exposure per day and you are talking about exposure per lifetime.
Thanks!
Comment by Do'C — 7 February, 2010 @ 11:39 am
It is referenced many times in several of the docs. Open the “Guidance for Assessing…” doc, do a CTL-F and enter the search term “lifetime”.
See pages 2-14,2-15
It’s also in this doc very early on.
http://www.epa.gov/iris/subst/0073.htm
It’s also in the National Academies Press book.
I also placed it for readers, right in the post.
The last age group the age-weight tables I mentioned previously is probably not as helpful, but it’s clear that the calculations are through age 75.
Bill,
The calc site does seem to be talking about exposure per day, doesn’t it? But it references the “EPA Standard”.
Step 5 of the calculator states an “EPA standard of 0.1mcg/kg/day”.
In referencing the EPA standard, they are referencing a standard that is clearly stated as:
I’m not talking about daily exposure per lifetime, the “EPA standard” is.
Aside from the fact that the EPA standard is for methylmercury, do you see the problem now?
Comment by Bill — 7 February, 2010 @ 4:44 pm
Well, this might be a dumb question but if what you are saying is correct, why does it matter if pregnant women consume fish with mercury? Pregnancy does not last for 75 years.
The EPA states: “Outbreaks of methylmercury poisoning have made it clear that adults, children, and developing fetuses are at risk from dietary exposure to methylmercury. During these poisoning outbreaks some mothers with no symptoms of nervous system damage gave birth to infants with severe disabilities and it became clear that the developing nervous system of the fetus may be more vulnerable to methylmercury than is the adult nervous system. Mothers who are exposed to methylmercury and breast-feed their babies may also expose their infant children through their milk.”
http://www.epa.gov/mercury/exposure.htm
I don’t understand how your explanation fits with EPA guidance. How would you explain this?
Comment by Do'C — 7 February, 2010 @ 4:59 pm
Bill,
I’m sorry, but I’m not terribly interested in discussing maternal seafood consumption guidance further than noting its existence and documentation (by the EPA).
My explanation is not intended to “fit with EPA guidance”. What I’ve offered is the explanation of a canard that attempts to align with EPA guidance where a. it does not exist, and b. what the actual available guidance is (for methylmercury) seems poorly understood at a very basic level.
Comment by MJ — 7 February, 2010 @ 7:06 pm
Doc,
Just a few minor things -
“Nevermind that they don’t acknowledge the general availability of Thimerosal-free flu shots for pediatric patients. ”
It has been my experience that the thimerosal-free flu shot is not readily available, at least in my area. Of the parents that I talk to, the majority are told that this verion is simply not available and only given the option of the thimerosal version.
Regarding the thimerosal vs methylmercury you did not mention that the delivery path is different between the two. Methylmercury is normally injested and processed via the stomach whereas thimerosal in shots is (presumably) absorded directly into the bloodstream.
Third, for children receiving the flu shot for the first time they would normally receive two shots, one month apart. If they elected for the H1N1 shot, they would have as few as 3 shots or as many as 4 shots in a one month time. That changes the short term max dose by a factor of 3-4, at least for this year.
” even by sensitive subgroups”
Where in the EPA limits is this stated? I have never seen anything that claimed the guidelines were for senstive subgroups.
The last thing that you seem to be glossing over in your description is that while the guideline is intended to be a daily intake limit it is also designed to keep the body burden of mercury beneath a certain level on an ongoing basis.
These single events (flu shot) can push that burden up, and all else being equal, the value would come back down fairly quickly. That is assuming that there isn’t any other substantial source of -mercury intake and a normal functioning of detoxification pathway.
“The EPA RfD for oral MeHg has absolutely nothing to do with vaccines”
It would be a good thing if the EPA did evaluate what the “safe” exposure to ethyl-mercury was - that way this whole debate would be over quicker. Not that I have an hope that they will.
It is long past time for the autism world to move past these debates.
Comment by Do'C — 7 February, 2010 @ 8:14 pm
Hi MJ.
I think it’s fairly self-evident from several clue words like:
“Flu Shots”
“Oral RfD”
“Seafood Consumption”
What “short term max dose” are you referring to? Did you read the post and reference materials?
The EPA hasn’t published “limits”. Read all the EPA documents, including the linked National Academies Press book, and you will have your answer - more than once.
If you want the shortcut, you could start by reading just the IRIS doc for methylmercury from the EPA (linked in the post). You could even use the CTL-F and search “sensitive” to have your browser highlight it on that first page you’ll already be looking at.
I think most people who read the post, and skimmed some of the provided EPA docs understand this part:
“The oral Reference Dose (RfD) is based on the assumption that thresholds exist for certain toxic effects such as cellular necrosis. It is expressed in units of mg/kg-day. In general, the RfD is an estimate (with uncertainty spanning perhaps an order of magnitude) of a daily exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime.”
If they don’t, well there is more than ample information - tons of it - in the reference sources I provided.
Yeah, cause having the EPA evaluate ethylmercury exposure safety makes a whole lot of sense when the childhood immunization schedule (minus some flu shots) is essentially Thimerosal-free.
Comment by MJ — 7 February, 2010 @ 8:52 pm
DoC,
“I think it’s fairly self-evident from several clue words like”
Yes, but it does change how the mechanisms that the body has available to rid itself of the substances, which is not obvious.
“What “short term max dose” are you referring to? Did you read the post and reference materials?”
Yes, I read the post and I have skimmed the EPA docs. I am referring to the fact that while the EPA guidelines talk about a daily dose, the shot delivers a greater dose directly which take a certain about of time to clear.
You state that the flu shot is a one time a year event and I am pointing out that they is not always the case. Children receiving the flu shot for the first time receive 2 doses, one month apart. In the worst case, if you added in the H1N1 shot this year you had 2 shots and then another 2 shots a month later.
So the idea is that at any point in time you have a certain burden from the shots - if you have 1 shot, wait 30 days, then potentially some of the mercury from the original shot has not been cleared so the second shot adds to that amount and pushes the entire burden higher - hence what I was calling the “short term max dose”. As in the highest burden generated in a short time period from multiple shots.
“The EPA hasn’t published “limits””
Sorry, the, the EPA “estimate of a daily exposure to the human population that is likely to be without an appreciable risk of deleterious effects during a lifetime”. I would call abbreviate that phrase to “limit”, but you are correct in that it isn’t a limit per se.
“Yeah, cause having the EPA evaluate ethylmercury exposure safety makes a whole lot of sense when the childhood immunization schedule (minus some flu shots) is essentially Thimerosal-free.”
Plus the tetanus shot and the Rhogam given to pregnant women. Then there is the fact that shots provided to other countries still have the full dose of thimerosal. Add to that some doctors are calling for thimerosal to be added back into the shots since it has been “proven” not to have a relation to autism.
But really, the best way to put the debate behind us all is to acknowledge the facts of the matter - admit that while it is likely there are no harmful since effects from the thimerosal in the flu shot that there are still potential questions about its safety so it is better to get the shot without it, and move on.
Comment by Bill — 7 February, 2010 @ 9:56 pm
Well, my friend, you’ve been making some pretty big claims about your understanding of the EPA seafood consumption guidance, and now you back down from applying your own logic? If you refuse to answer, I cannot accept that its because you are “not interested.” I can only conclude that it is because you **cannot** apply your sloppy logic to EPA guidance without getting tangled in the mess of your own flawed thinking.
You can’t have it both ways, Do’C.
Comment by Do'C — 10 February, 2010 @ 1:15 pm
Bill,
As indicated by most of your comments in this thread, I’m not sure you understood what was communicated by this post, the linked reference materials, or my comments. Conclude whatever you like.
Comment by What is Autism? — 14 February, 2010 @ 10:48 pm
Thanks for educating the ignorant public about the fear-mongering anti-vaccine crowds who trip over themselves in their irrational rants of who’s at fault for autism.