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What Is Thimerosal and Why Are Some People Worried About it?

By April 14, 2016 3 Comments

“I don’t wanna put mercury in my baby, Doc; it’s poison.”  After Robert DeNiro’s anti-vaccination massive misstep Tuesday, I’m yet again, dreading hearing these words.

This is where, as a pediatrician, I grit my teeth (sorry, dentists).  I know that when I parent tells me this,  that science has lost another battle with fear in the race to inform families first. Since the race has been lost, I know I’m going to have to work from behind to get this child protected from deadly diseases.

There will likely be a lot of questions for me.  Questions based on faulty premises and that question my integrity as a doctor, as a dad and as a person.  I will put my pride aside and try to help these parents make the right choice for their kid.

I will explain that thimerosal is not mercury (although it contains very small amounts of it).

I will explain that even though there was no evidence that thimerosal was harmful, that it was removed from early childhood vaccines in 2001.

I will try to communicate with evidence-based information.

I will bring up the fact that Andy Wakefield, the man behind the current anti-vaccine movement and the movement has had his medical license revoked after the General Medical Council in the UK found he committed professional misconduct and acted dishonestly and irresponsibly. I will remind them that they don’t know many people that sleep in iron lungs because of Salk’s polio vaccine.

Reluctantly, I may even have to go into my personal life and divulge that my entire household (my wife, two girls and I) is fully vaccinated. These things may or may not sway the family.The conversation may end in an awkward stalemate. There could be a conversion that occurs over months.

I hope not, though, “because deadly diseases ain’t waitin’ on you to decide.” I get colloquial once we’re all good friends.

Sometimes people change their hearts and minds right away when I reassure them; those conversations are more fun, but I am usually wary of the spurious information that is just outside the hospital doors, or sometimes in the room with me on their smart phones.  I know once I’m done talking to them, there’s a whole lot of noise outside waiting to undo what I just did.

Robert DeNiro Appeared on NBC's Today Show on Tuesday

Robert De Niro Appeared on NBC’s Today Show on Tuesday

Like Tuesday, during The Interview Heard Around the Internet, when one of the greatest (the greatest?) screen actors of all time went full anti-science on the Today Show. Robert DeNiro, in explaining why he regrets the pulling of the movie “Vaxxed: from cover-up to catastrophe” from his Tribeca Film Festival, made some dangerously inaccurate statements about vaccines and autism.

In case you missed the discussions from a few weeks ago, here’s the skinny: Big-time festival announces the screening of a pro-disease (or, anti-vaccination) motion picture, the scientific community loses our collective mind and lets them know it’s a dangerous choice, Big-time festival pulls the movie, anti-vaxxers go up in arms. The science community was FINE with this result (you know, the support of actual scientific fact), even tentatively giddy.

Bobby D pulled no punches in his NBC interview, citing most of the tried-and-true tropes of the antivax movement: he stated that vaccine science is not “settled,” claimed “overnight” changes in children after immunizations, talked about mercury in vaccines and even gave the ol’ “I’m not anti-vaccine” speech, which is pretty much only said by people that are.

I’d love to make a reference to the classic “Just when I thought I was out, they pull me back in”… but that was Pacino’s line.

As a parent, if someone told you the nonsense that De Niro spouted on the Today Show, it would sound terrifying. No one wants to cause harm to their own child (or someone else’s). As a doctor I can tell you I’ve dedicated my life to helping parents keep their kids safe.  I don’t want to see your kid hurt either.  So let me break down De Niro’s claims starting with thimerosal.

The reality is that if De Niro got his information from better sources and actually talked to real scientists he’d know that a lot of what he just said isn’t true. He’d know that thimerosal hasn’t been in early childhood vaccines for 15 years, and he’d know that it was never in the MMR vaccine, the one that his boy Andy Wakefield falsely claims causes autism.

He’d also know that thimerosal is a mercury-based substance used in multi-dose vials of vaccines as preservative. It kills bacteria and prevents the growth of fungus in the vial, to help keep it sterile and safe for injection. It’s also a substance found in tattoo ink in concentrations thousands of times higher than what is found in vaccines. The compound breaks down into ethylmercury, half of which is broken down and rendered “ineffective” by the body in about a week. Then, we poop it out!

He’d know that in term of quantities, the amount of mercury given in a yearly flu vaccine is 25 micrograms (mu). The amount needed to kill 50% of living organisms (LD50) is 98 milligrams (mg) per kilogram (kg) of body weight. Remember, 1 milligram is equivalent to 1,000 micograms – so this means that, for a 10 kilogram (about 22 pound) child to have life-threatening effects, the child would need to have 980,000 micrograms of mercury. At one time.

He’d contrast this with methylmercury, which is found in tuna and industrial waste or elemental mercury which used to be found in old school thermometers (You may have even played with spheres of it as a kid if you’re an old fogey, like me). These are the types of mercury that we really worry about.  With methylmercury there are so many ways we are exposed and with elemental mercury we’re usually exposed to a lot when we’re exposed (like playing with broken thermometers).

Methylmercury is the one that makes us warn pregnant women about salmon intake.  Elemental mercury is the kind was used when making felt hats, giving the makers neurological damage centuries ago, i.e. The Mad Hatter. It takes about six weeks for the body to break this substance down to its ineffective state. In the meantime, the compound binds strongly to fat and neurological tissue; it finds its way to the brain, where it causes intellectual deficits.

This is why it’s important for people like De Niro to know the difference between mercury compounds, but he didn’t (or he doesn’t).

How did we get to this point? Why are parents distrusting of the scientists and physicians they chose, and continue to choose to listen to celebrities and snake oil salesmen?  Why are we still discussing something that’s not even in early childhood vaccines any more?  Why are we talking about “mercury” that was never even in the MMR vaccine to begin with?

I believe that three, nearly concurrent events happened almost twenty years ago that set this phenomenon in motion:

1) The FDA Modernization Act of 1997 required vaccine manufacturers to give detailed information to the government about all mercury-containing products. At the time, jabs for Hepatitis B, DTaP (diphtheria, tetanus and pertussis) and inactivated Polio had trace to small amounts of thimerosal (a mercury-based preservative) in their ingredients.

2) In 1998, Andrew Wakefield, a UK gastroenterologist published his infamous study in the Lancet that claimed a link between the MMR vaccine and autism (that’s since been retracted – more on that in a moment).

3) After vaccination rates declined because parents were so concerned about Wakefield’s study and lots of talk about thimerosal the CDC recommended the FDA order thimerosal removed from early childhood vaccines (except for the flu shot).  We’re still talking about this 15 years later, so pulling thimerosal from the vaccines didn’t work.

After the FDA Modernization Act, and widespread fears about autism following the paper published by Wakefield, there was quite a bit of public outcry for changes to be made in vaccines. In spite of good scientific evidence that there was no link between thimerosal and autism, government agencies and vaccine manufacturers decided to make all childhood vaccines thimerosal free. This decision placated some, but many pediatricians feel that it served as a capitulation to non-science. Thimerosal, at this point, only exists for children in certain flu vaccines. There is no thimerosal in the dose for children from 0 to 3 years-old.

In terms of Wakefield’s claim, his paper stating that a combined MMR vaccine was linked to autism was retracted in 2010 and his license to practice medicine was stripped in the same year. In the eyes of many health professionals, however, the damage had already been done. Vaccine rates dropped in several Western nations in the early 2000s, leading to multiple outbreaks of diseases that had been on a steady decline or even eradicated from some countries.

In spite of the overwhelming, worldwide, scientific evidence that vaccinations are safe and effective, claims of “toxins” and “poisonings” continue on the internet and at family gatherings. I won’t link to them here, but trust me. My job, as I see it, is to continue to fight the good fight against vaccine misinformation. The more people understand what we are giving their children, the more vaccine uptake and suffering prevented.

Yet we still have neighbors, family members, and very high-profile celebrities who are against or that “question” the safety of vaccinations. You know the ones: they show up on your Facebook timeline once a week with a story about “the medical industrial complex” or tell you that Big Pharma is out to make money by “making our kids zombies.” These folk often have a dubious story to share about a medical catastrophe or grand claims about medical marijuana curing cancer along the lines of “it also raised my cousin Scott from the dead.”

They seem to be proliferating and we’re seeing these diseases come back: an intentionally unvaccinated child recently died of diptheria in Spain, the first case seen there since the 1980s.  Then there was the measles outbreak that began in Disneyland last year, largely fueled by families that had refused to vaccinate their children.

While unrelated scientifically (do I need to repeat myself, MMR vaccines never had thimerosal as an ingredient), these three events became the bedrock of the modern anti-vaccination movement. The headlines falsely claiming that vaccines cause autism spread quickly throughout the Western world, and vaccine rates plummeted.  Once it’s out there you can’t get the genie back in the bottle.

The reality is that vaccine programs have been heralded as the greatest medical innovation of the last hundred years. We have drastically decreased deaths from vaccine preventable diseases. Even cervical cancer is getting its butt kicked. We need to keep it that way.

Editor’s Note 2.16.17 | This post was updated to better reflect the difference between the historic uses of elemental mercury.

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Categories: Disability + Disability Advocacy, Infectious Disease + Vaccines, Science 101 + Mythbusting

Celebrity Moms Who Side With Science

By April 15, 2015 1 Comment

Who has two thumbs and sides with science?


As a mom, vaccines are always on my mind. Just this morning, I found myself touring a prospective school for my toddler and asking about the vaccination rates of his potential classmates.

While the anti-vaccine celebrities get (too much) press, I’d like to give a shout out to the celebrity moms who side with science and passionately advocate for vaccination. I first wrote about this topic in 2013 when I was pleasantly surprised to see the TDAP vaccine being promoted on an episode of “Keeping Up With The Kardashians”.

With celebrity moms having such a public platform, I became curious about how closely their messages align with the barriers that we know stand between children and their vaccinations. In a nice review of patient barriers to immunizations, Hendriksz et al describe three types: (1) miseducation and misconceptions of patients, (2) fear and anxiety of immunization pain, and (3) lack of access (perceived and real) to immunizations.

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Categories: Infectious Disease + Vaccines, Policy, Politics, + Pop Health

A Rejection of Eva Mendes H1 and a Confirmation of the Gosling Sweatpants Null Hypothesis

By March 22, 2015 No Comments

According to Eva Mendes sweatpants are the number one cause of divorce after the birth of a baby. We’d like to live in Eva Mendes’ world (hello Gosling!) wherein one can comfortably wear jeans and flouncy summer dresses immediately after giving birth, but that’s not the norm for most women. If you’ve become a mother by giving birth, your body needs time to heal and the cotton and stretch offered by yoga pants, pajamas, leggings and yes, the dreaded sweatpants is often doctor recommended.

Even if your path to parenthood came through different means, soft, cotton clothes for those first few months are often a necessity. A friend who became a mother through surrogacy swore by her comfy cotton clothes after she and her husband brought their son home, “yoga pants, tees and always a pony tail. I could rest comfortably without changing and they’re spit-up proof, and [our son] spit-up a lot … and my husband didn’t cheat on me.”

But my friend’s claim is what we call anecdotal evidence and it doesn’t hold a lot of scientific weight, so let’s test the substance of Mendes’ claim: New mothers’ use of sweatpants postpartum is the primary cause of divorce in America. We’ll set aside the gender norms and implications of her statement and put only her hypothesis to the test.

Divorce is a complex subject and not one that can be neatly summed up in a few paragraphs. For now I’m going to focus on data surrounding first marriages ending in “irreconcilable differences” divorces, meaning those where violence, substance abuse, adultery or incarceration were not factors. I’m also going to look at the broad strokes of the issue, because with everything, the data is nuanced once by age and socioeconomic status.

Mendes’ claim pertains to women of childbearing years that were married at the time of their child’s birth. This accounts for approximately 59.5% of all births in the United States.

Within that age bracket, approximately 42% of those marriages entered into during childbearing years will result in divorce, by the end of the individuals’ childbearing years, according to the U.S. Bureau of Labor Statistics. The average length of a marriage that ends in divorce is 9.2 years.

What the data seems to support is that across Western nations, the number one cause of divorce oscillates between communication issues (‘we grew apart,’ ‘we never talked,’ ‘we became strangers’) to financial problems/differences in spending and saving. Note, sweatpants are not mentioned. That’s not to say that the birth of a child is a smooth transition for married couples, with about 20% reporting that the birth of their child caused a crisis in their marriage. With that said, the “crisis” appears to be additional strain added to preexisting stressors in the marriage.

Postpartum depression also seems to be an additional risk factor for divorce, however, the correlation doesn’t appear to be clear: does the divorce exacerbate the postpartum depression, or does the postpartum depression exacerbate the end of a marriage?

But what’s important to note is that sweatpants are not mentioned in any of the literature as being a cause of divorce. What we can say now is that we have confirmed Eva Mendes’ null hypothesis, meaning that there is no correlation between divorce and sweatpants.

Now, this is a subject I feel passionate about. I am Canadian and grew up in the same area as Ryan Gosling at around the same time. Just as there was an audible gasp when Gosling and Rachel McAdams split up, I also heard the gasp from this land when we saw that Gosling’s wife criticized sweatpants. This is a land where sweatpants are just shy of being our official national costume, so we come to their defense rather quickly. It’s been great to see that Gosling hasn’t forgotten his roots (pun intended) and also came to their defense.




Martinez, G., Daniels, K, and Chandra, A. Fertility of Men and Women Aged 15-44 Years in the United States: National Survey of Family Growth, 2006-2010. National Health Statistics Reports. April 12, 2012. Retrieved 3.22.15.

Bodenmann, G., Charvox, L., Bradbury, T. et al. The role of stress in divorce: A three-nation retrospective study. Journal of Social and Personal Relationships. pp 707-728. October 2007. Retrieved 3.22.15

Dakin, J. and Wampler, R. Money doesn’t buy happiness but it helps: Marital satisfaction, psychological distress and demographic differences between low- and middle-income clinic couples. The American Journal of Family Therapy. pp 300-311

Michaels, G. The Transition to parenthood: Current Theory and research. Cambridge University Press, New York. 1988.

Hawkins, A., Willoughby, B. and Doherty, W. Reasons for divorce and openness to marital reconciliation. Journal of Divorce and marriage. pp 453-463, August 13, 2012. Retrieved 3.22.15.

Gigy, L. and Kelly, J. Reasons for Divorce: Perspectives of Divorcing Men and Women. Journal of Divorce and Marriage. pp 169-188. October 18, 2008. Retrieved 3.22.15.

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Categories: Science 101 + Mythbusting

The Science of Kelly Clarkson’s Baby Fat, Because We Apparently Need to Talk About It.

By March 12, 2015 No Comments

Let’s talk about something that’s none of our business: Kelly Clarkson’s postpartum body. We’re not going to talk about her third number one album on the billboard charts, her awesome duet with Jimmy Fallon or her adorable baby girl. We’re going to put her recent accomplishments aside and talk about her postpartum body because she had the nerve to have a baby in June and not be “skinny again” by March, and that’s what really matters.</sarcasm>

Before we talk about Clarkson specifically, let’s talk about what’s average and what’s recommended in terms of pregnancy and postpartum weight gain. The American College of Obstetricians and Gynecologists (ACOG) recommends a gestational weight gain (GWG) of 25-35 pounds for a

Trends in Gestational Weight Gain 1990-2005 via

Trends in Gestational Weight Gain 1990-2005 via

woman that began her pregnancy with a body mass index of 18.5-24.9 and is pregnant with a single fetus. In reality what we’re seeing is an increasing trend in women gaining both less than and more than the recommended GWG. This is because more women are beginning their pregnancies with a BMI considered overweight or obese.

Postpartum trends also show that a year after giving birth, women that began their pregnancy at a “normal” weight and gained the recommended amount retained three pounds of their pregnancy weight a year later. Those that gained more than the recommended weight retained about 10 pounds. Within some weight ranges the retained gestational weight can become problematic, putting women at risk for the development of type 2 diabetes post-pregnancy.

Postpartum GWG by week via

Postpartum GWG by week via

Retained gestational weight gain can compound with subsequent pregnancies, increasing a woman’s pre-pregnancy BMI and putting them at risk for gestational complications such as gestational diabetesHELLP syndrome and preeclampsia.

A major assumption in previous research (and it seems by society in general) is that postpartum “baby weight” serves no purpose, but that assumption is being challenged by evolutionary biologists.  Research in this field over the last decade has posited that postpartum weight retention plays an important role in lactation, providing nursing mothers with energy reserves should their baby’s need for milk outpace the mother’s energy (food) intake.

Pregnancy is hard, recovering from childbirth is hard, new motherhood is hard and in the West we do an abysmal job of supporting new mothers. One of the unspoken rules of new motherhood is that if you’re not pregnant anymore, you have to look like you never were. That’s an incredibly powerful but negative message to send to a woman.  This is where we get Tori Spelling’s “Just Keep Your [Bleeping] Mouth Shut and Eat Air [postpartum] diet,” which is incredibly dangerous, new mother or not.

I’m glad that we can now put Kelly Clarkson in the category of women who have openly taken a healthy approach to postpartum weight loss, along with Tia Mowry, Hilary Duff, Jenna Fisher and Bryce Dallas Howard.  At the end of the day, what Kelly Clarkson’s postpartum body matters only to herself and her doctor, new album or not.


Institute of Medicine (US) and National Research Council (US) Committee to Reexamine IOM Pregnancy Weight Guidelines; Rasmussen KM, Yaktine AL, editors. Weight Gain During Pregnancy: Reexamining the Guidelines. Washington (DC): National Academies Press (US); 2009. 2, Descriptive Epidemiology and Trends. Retrieved March 11, 2015.

Centers for Disease Control and Prevention. Pediatric and Pregnancy Nutrition Surveillance System (PNSS). Updated December 17, 2014. Retrieved March 11, 2015.

Centers for Disease Control and Prevention. Infant Feeding Practices Study II and its Year Six Follow-Up. Updated August 26, 2014. Retrieved March 11, 2015.
Weight gain during pregnancy. Committee Opinion No. 548. American College of Obstetricians and Gynecologists. Obstet Gynecol 2013;121:210–2.

Leahy-Warren, P., McCarthy, G. and Corcoran, P. First-time mothers: social support, maternal parental self-efficacy and postnatal depression. Journal of Clinical Nursing. March 25, 2011. Retrieved March 11, 2015.

Bedor, E. and Tajima, A. No Fat Moms! Celebrity Mothers’ Weight-Loss Narratives in People Magazine Journal of Magazine & New Media Research Summer 2012. Retrieved March 11, 2015.

American Pregnancy Association. Pregnancy Complications: HELLP Syndrome. Retrieved March 11, 2015.

Mayo Clinic. Preeclampsia Risk Factors. Retrieved March 11, 2015.

Mayo Clinic. Gestational Diabetes Risk Factors. Retrieved March 11, 2015.

Dufour, D.L. and Sauther, M.L. Comparative and evolutionary dimensions of the energetics of human pregnancy and lactation. American Journal of Human Biology. August 21, 2002. Retrieved March 11, 2015.

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Categories: Pregnancy, Birth + Family Planning