Does radiation from dental X-rays cause thyroid cancer?

Does radiation from dental X-rays cause thyroid cancer?


It wasn’t long after the discovery of radioactivity that we also discovered its health effects.

The Nobel Prize-winning discoverer of radioactivity, Marie Curie, died of aplastic anemia at age 66.

Then you have the case of Eben Byers.

He used a form of quack medicine called radium patent medicine back in the 20s.

Not only did it cost him his life, but he had to be burned in a lead-lined casket to protect the surrounding area.

And the health effects of ionizing radiation even led to the creation of OSHA

It started after dozens of workers who painted glow-in-the-dark radium paint on watch dials became severely ill.

They realized that a safety organization needed to watch out for workers exposed to radiation.

So, you can see how dangerous radiation is.

Still, we use radiation in our medical practice.

We use it for cancer and diagnostic treatments.

But, what both radioactive elements and X-rays have one thing in common is that they both produce ionizing radiation.

What exactly is ionizing radiation, though?

Ionizing radiation is the process that ionizes molecules without the use of iron, and it creates free radicals.

These free radicals can then go on to create many different hazards in the body.

It leads to lipofuscin, DNA mutations, cross-linked proteins, and fibrosis.

And they can cause DNA chain breaks directly by directly ionizing DNA.

Studies show these effects conclusively.

With this information, we wonder, can X-rays give you cancer?

A doctor in Kuwait analyzed the amount of X-rays received by 313 patients with thyroid cancer.

He matched them against 313 controls of the same age and location.

And he found that people with thyroid cancer had received more X-rays in their past than the controls.

This doctor also found that people who had dental X-rays were more than two times more likely to get thyroid cancer.

And this side effect of dental X-rays was dose dependent — people who had over ten X-rays were nearly five and a half times more likely to get thyroid cancer.

Dental assistants know about this problem, and it is probably why they leave the room during each exposure.

The thyroid gland is highly susceptible to radiation carcinogenesis and exposure to high-dose ionising radiation is the only established cause of thyroid cancer.

A Swedish study calculated the odds ratio for thyroid cancer and dental assistants as 13.1.

And the Swedes also noticed a trend with increasing dose.

In this study, researchers matched 186 subjects against 426 controls.

The association between ionizing radiation and thyroid cancer […] has been known for several decades.

They also noticed that people under 50 had higher odds of developing thyroid cancer.

This finding could be the result of the increased cell division rate in younger people.

But even young thyroid cells don’t divide very quickly compared with other cell types.

So, there is a long latency period of about five years from exposure to finding cancer.

The excess number of thyroid cancer cases has been know to start 3–7 years after irradiation.

Researchers also noticed this latency period in a study on children.

These children received X-rays for ringworm of the scalp

With 10,834 subjects and 10,834 controls, this was a statistically-powerful study.

They found a risk ratio of 4.0 between irradiated and non-irradiated subjects.

They also estimated the total radiation exposure.

The researchers found the highest risk in the highest X-ray group.

The researchers also estimated the total radiation absorbed and found a very high-risk ratio (8.0) in the highest dental X-ray exposure group.

Now, in a study done in Belarus on thyroid cancer.  They performed it after the Chernobyl incident.

And they noted a minimum latency period of four years.

It’s easy to logically explain these latency periods by DNA damage, which we know X-rays cause.

Cancer becomes evident only long after the first damage is done, following a period of latency. Leukemia first appears at least 2–5 years after exposure while solid tumors appear after at least 10 years.

Although the cell can repair minor damage to the DNA can, double-strand breaks in the DNA can lead to loss of information.

And it doesn’t take much dental x-ray radiation to cause damage.

Scientists measure X-ray radiation using a gray.

The measurement equals the absorption of one joule of radiation energy per kilogram of matter.

And it takes just one gray of X-ray radiation to cause quite a bit of DNA damage within one cell.

Some of this damage can be countered by antioxidants, but not all of it.

Researchers estimate that only 65% of the damage is caused by free radicals.

The rest is caused by direct hits to the DNA.

OH radicals are responsible for 65% of the strand breaks (single and double), 65% of cell killing, and 65% of chromosomal aberrations produced by low LET ionizing radiation.

Many studies show that antioxidants increase the survivability of X-rayed cells by safely quenching free radicals.

Some antioxidants, such as glutathione, are particularly helpful.

One thing to do to help avoid these issues is to avoid polyunsaturated fatty acids.

PUFAs can sustain free radical chain reactions, causing more and more damage.

The thyroid gland is one of the most radiosensitive organs.

The thyroid is particularly sensitive to X-rays, probably because of its unusually high iodine content.

Here’s a complicated, but pretty interesting way to look at it.

Scientists know that an atom’s ability to absorb radiation is proportional to their nuclear cross section.

And iodine atoms have very large nuclei.

They found that iodine has an X-ray absorption similar to that of lead.

Here is how it measures up.

  • Carbon = 3.519
  • Oxygen =5.168
  • Iodine = 1621.083
  • Lead =1676.868

The iodine gives the thyroid the ability to capture more X-ray radiation than surrounding tissue.

And the irradiated iodides in the thyroid can then produce oxygen free radicals.

The probability that an absorber (atom of a given species in a given excitation state and ionization level) will interact with an incident photon of wavelength λ is quantified by the absorption cross section.

Or it can re-emit the absorbed X-ray energy as radiation of a lower frequency.

Getting an X-ray is a lot like rolling dice, hoping that no X-rays will hit a crucial DNA segment.

Researchers know that mutations in the genes coding for cytochrome c oxidase can cause cancer.

Cytochrome C is an essential enzyme in the electron transport chain, and the X-rays disrupt it.

Without this enzyme, the cell has to rely on glycolysis alone to survive.

You may recognize this symptom of the well-known Warburg Effect.

In any case, you want to avoid routine yearly X-Rays for this reason.

If you do need to have a dental X-ray, you can dose yourself with glutathione, vitamin E, and vitamin C.

And in the meantime, hope that the development of dental ultrasound moves fast!

 

 

 

 

 


Matt Cook is editor-in-chief of Daily Medical Discoveries. Matt has been a full time health researcher for 26 years. ABC News interviewed Matt on sexual health issues not long ago. Matt is widely quoted on over 1,000,000 websites. He has over 300,000 daily newsletter readers. Daily Medical Discoveries finds hidden, buried or ignored medical studies through the lens of 100 years of proven science. Matt heads up the editorial team of scientists and health researchers. Each discovery is based upon primary studies from peer reviewed science sources following the Daily Medical Discoveries 7 Step Process to ensure accuracy.
Compilation of X-Ray Cross Sections 
http://cars9.uchicago.edu/~newville/mcbook/mcbook-l.pdf 

Dental x-rays and the risk of thyroid cancer: A case-control study 
http://www.tandfonline.com/doi/abs/10.3109/02841861003705778 

DNA Damage Produced by Ionizing Radiation in Mammalian Cells: Identities, Mechanisms of Formation, and Reparability 
http://www.sciencedirect.com/science/article/pii/S007966030860611X 

Diagnostic X-ray Exposure and Female Papillary Thyroid Cancer: A Pooled Analysis of Two Swedish Studies 
http://journals.lww.com/eurjcancerprev/Abstract/1997/12000/Diagnostic_X_ray_exposure_and_female_papillary.10.aspx 

Thyroid Neoplasia following Low-Dose Radiation in Childhood 
http://www.rrjournal.org/doi/abs/10.2307/3577801 

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