Are Dental X-rays Causing the Boom in Thyroid Cancer?

A few years ago, I was turning 40 and figured it’d be a good idea to have a routine physical exam. I hadn’t been to the doctor in years and wasn’t really using that nice health care insurance I had access to. The doctor discovered a lump in my throat. One biopsy later and bam! I had cancer.


Xelfie: The bright dots are a couple cancerous lymph nodes, which absorbed the radioactive iodine post-surgery.

I was of course shocked and freaked-out. I had a thing growing inside of me which didn’t belong there. What followed was a furious bit of googling, a series of appointments, a 3-hour surgery, radioactive iodine treatment (complete with a few days of isolation), and a lifetime of pills to substitute for my now-missing thyroid gland. As cancers go, they call Thyroid Cancer “the good one”. Screw that – no cancer is good. Granted survival rates are pretty high when caught early, and since the cancer is made of thyroid cells, it’s fairly easy to isolate and treat (thyroid tissue soaks-up iodine, so just make the iodine radioactive and blamo – you’ve poisoned the cancer). But thyroid cancer is often asymptomatic, going undetected until it’s spread and caused all kinds of serious complications. Mine was a 5cm tumor – about as big as they get before spreading. I consider myself incredibly lucky to have caught it just in time, and I’m immensely grateful to my doctor, who may have saved my life by simply feeling my neck.

Thyroid Cancer Types

There are four types of Thyroid Cancer

As soon as I learned I had thyroid cancer, of course, I scoured the internet looking for answers. In addition to concern about my prognosis, I wanted to know how this happened. Was this just random chance? or did something specific cause this? What I found was alarming. Thyroid cancer has tripled in prevalence over the past 30 years. While some of this may be due to improved detection, that doesn’t account for all of the increase. Something is certainly causing it – something that has changed in the recent past.

The only certain cause of thyroid cancer is exposure to radiation – especially in one’s youth. Even moderate exposure can dramatically increase the risk of developing cancer when you’re older. There have been many studies to show this link, such as this one. The onset can be decades after the exposure, which makes linking cause and effect difficult. Did I wander past some radioactive facility when I was young? Maybe… Was the basement of my childhood home filled with radon gas? Possibly (in fact, this might be an interesting thing to investigate). Or perhaps I was just randomly unlucky; even without a distinct cause, thyroid cancer still happens. But, my concern is more than just personal. This didn’t just happen to me. Something is happening throughout our society – and in fact, throughout all developed societies.

If exposure to radiation is the most certain cause of thyroid cancer, what are the most common exposures to radiation? And have any of these changed dramtically in the past few decades? While there are many possible sources of radiation exposure, from radon gas to nuclear test fallout, one thing immediately jumps out – x-rays. In particular, dental x-rays. Since the 1950s, access to professional dental services has grown exponentially in the US, and throughout the developed world. As a child in the 1970s, I was subjected to dozens of x-rays during my regular visits. Either my teeth were crappy, or the family dentist was “drilling for dollars”. I had a lot of cavities, and a lot of x-rays.

Thyroid Cancer Rates - from NIH

Thyroid Cancer Rates – from NIH

My suspicions got a serious jolt when I learned this fact: The use of x-ray equipment in the US is virtually unregulated. That’s right, your dentist could be blasting you with any level of x-ray radiation, and nobody cares or knows. Nobody is measuring machines to see if they’re operating as expected. Sure, we know that excessive exposure to x-rays are incredibly harmful, but you can’t see them, and the harmful effects are only apparent years later. Who would know if you’re being blasted with the equivalent of a nuclear explosion at every exam? The dentist might not have a clue either. For all I know, my childhood dentist got his x-ray machine from the army surplus dump after WWII, and it had the level set to maximum. Why not? If it makes for easier operation, and clearer x-rays, who was to care?

What makes this particularly concerning is that dental x-rays are directed at an area very near the thyroid gland (which sits right about at your collar bone). Sure, x-ray operators will cover your chest and neck with a lead vest, but this is hardly a rock-solid protection, and I have no memory if or how this was done when I was a kid. Vests are not always situated properly, and the x-ray beam can be directed such that it bypasses the vest altogether & goes straight to the neck.

The good news is that modern digital x-ray machines use far lower levels of radiation, and are certainly a lot safer. But, there are still plenty of older machines in service. New equipment is expensive… and the older equipment doesn’t go to the dump, it goes to the third world, who are just getting on-board the dental hygene train and all that comes with it.

How can we figure out if this is more than just speculation? A couple studies have looked at this. This is a particularly good one, and quite striking too – the conclusion is that there is indeed a measurable link. However, this is looking at broad population. The challenge is that dental practices & patient experiences vary widely. A dentist who used x-rays sparingly, was very careful with neck shielding, and had a low-emission x-ray machine would have given their patients very low exposures. Some patients may have received a lot of x-rays as a youth, others only a few. A study comparing the outcomes of patients of specific dentists ~30-40 years on would be far more interesting. I’m hopeful there are epidemiologists with ideas of how this might be accomplished. The data exists, the challenge is combing through it – ultimately looking at groups of people treated by specific dentists, and see if some groups have a higher incidence of thyroid cancer ~30-40 years later than others. Dentists keep good records, and one might be able to determine which equipment they were using, and which patients had how many x-rays. There are likely issues with privacy though, I’m not sure how you get around that one.

There are a number of articles raising this issue. And there are a number of articles telling people not to worry about it. Those downplaying the link essentially conclude “It hasn’t been proven, so don’t worry about it”. They claim that dental x-ray radiation is “low”, without mentioning that it’s unregulated, unmeasured and widely inconsistent from dentist to dentist. They claim that the increase in thyroid cancer incidence is primarily due to increased awareness. That might certainly contribute, but don’t we owe it to ourselves to do an actual detailed study? There’s a lot of vested interest in maintaining the status-quo. Can you imagine the costs involved to replace all the aging x-ray equipment still in use? What if people get irrational and panic, eschewing all x-rays? X-rays have saved millions from serious dental problems, but that doesn’t mean they’re 100% good.

So, that’s where things sit. I have no tools to take this much further. It’s my hope that this blog post will find its way to someone who has more experience or resources and can look into it. I’m not a conspiracy nut, but this is a problem craving for more study. Thyroid cancer is a huge cost to society – in dollars, in time, and in quality of life. Maybe the answer isn’t dental x-rays, maybe it’s something else? But, we simply don’t know. One thing is completely unacceptable – denial of a potential problem simply because we don’t have the data. All I’m asking is that it’s thoroughly studied, and proper regulations are put in place so we know what our x-ray equipment is emitting. Everyone should be in favor of that. Something is causing this, and we owe it to ourselves & our children to figure out what it is.

If you’re reading this as a newly diagnosed Papillary thyroid cancer patient, don’t panic. You’re not alone, and your prognosis is likely pretty good. This is unfortunately a common cancer, and treatment is almost like a formula. It goes something like this:

  1. Someone feels a lump in your thyroid. Perhaps this is precipitated by some symptoms of low Thyroid levels (sluggishness, fatigue, etc), or you just happen upon it. Thyroid cancer is often asymptomatic – even the lump may not be noticable.
  2. You get a biopsy. Even if this doesn’t show cancer, your doctor might treat it as such. Thyroid nodules (semi-solid growths) are fairly common, and while many of these are benign, they can grow and turn cancerous.
  3. Surgery to remove your thyroid. It’s a delicate surgery, though common. Mine took about 3 hours, plus a day in the recovery room. Risks are damage to the parathyroid (a completely different gland that sits snuggly against the thyroid), and damage to other things in your throat (my vocal nerve got nicked, and I couldn’t talk for a week afterwards). Recovery is anywhere from a few days to a week or so. You’ll likely acquire a 2-3 inch scar on your neck.
  4. Radioactive Iodine treatment (RAI). Since thyroid tissue soaks-up iodine, they can feed you radioactive iodine, which any remaining thyroid tissue soaks up. The first step in this to give you a low dose followed by a full body scan to see if you have any hot spots. In my case, the cancer had just started spreading to a nearby lymph node. They missed this during the surgery, but it showed-up like a beacon in the scan. So, I did the high-dose treatment a few weeks later. (this involes going on a low-iodine diet beforehand, and stopping thyroid replacement medication). After a year, I had another scan, which showed the hot spot was gone,and there was no other uptake – I was clear.
  5. A lifetime of pills. Your thyroid gland does one thing – produce thyroid hormone. Thyroid hormone essentially enables your cells to metabolize energy. Luckily this hormone is easy to synthesize, and cheap. It’s also one of the most common prescribed medications. Many people get T4, which is what the thyroid produces… it’s most commonly known by the brand Syntheroid, but there are generic equivalents. T4 breaks down into T3 in the body (and it’s the T3 which actually does the work). You might also get prescribed a T3 replacement (most commonly known by the brand Cytomel). Personally, I take 125 micrograms of T4 and 10 micrograms of T3 every day. Your dosage may vary depending on many factors, such as your weight and how well your body uptakes the medication.
  6. Monitoring your thyroid levels. It’s a good idea to get your thyroid levels checked every year to make sure your doseage is correct. If you have symptoms of low thyroid levels (fatigued muscles, tiredness, chills, fuzzy thinking) see a doctor. Too much thyroid hormone can be a problem as well.
  7. Checking for Thyroglobulin. Your thyroid gland also produces thyroglobulin, which is a fatty very of thyroid hormone. A few months after surgery & RAI treatment, you should have zero thyroglobulin. If you have any, it might mean there are rogue thyroid cells (i.e. cancer) in your body somewhere. It’s good to get a thyroglobulin check every 5 years or so.

One thought on “Are Dental X-rays Causing the Boom in Thyroid Cancer?

  1. I feel the same way about my medical conditions. Why am I the only one in our extended family that has Type 1 Diabetes? And breast cancer? Really – no one else has this – we have 40 cousins and a dozen aunts/uncles. Well, 1 aunt had breast cancer and 1 had ovarian. Sometimes things just happen to people. I do worry about radiation though and am careful about exposing myself to any more than necessary. Cancer sucks. P.

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