How does Radon cause Cancer?

When people say radon is a carcinogen, what they technically mean is that radon decay products cause cancer.  Radon itself isn’t the carcinogen: I’ll get to that in a bit.  Radon is a noble gas, which means it’s chemically inert. It does not react with other elements.  Radon is, however, radioactive, which means that its atomic structure is unstable.  Radon decays naturally.  It is part of the Uranium 238 decay chain.  See the full chain below.

Decay chain

Radioactive decay is a technical term for shedding energy.  This energy can be in the form of photons (gamma rays), protons/neutrons (alpha particles) and electrons/positrons (beta particles).  The radioactive decay we’re concerned with is alpha decay.  An alpha particle consists of two protons and a two neutrons combined (basically a helium nucleus).  It’s the largest of the radioactive particles.  Sometimes it’s referred to as an “atomic cannonball”.  The alpha particle is jettisoned from the radioactive element at incredible speeds in a straight ray.  It collides with whatever is in its path.  It can be stopped by something as simple as a piece of paper.  The trouble begins when this particle gets inside our lungs.

Cloud Chamber

Rn222 is an ionized gaseous particle.  Ions mean there is an energy imbalance or a charge to the particle.  These charged particles get stuck to other particles in the air.  Occasionally, we breathe them in.  Since radioactive elements are always decaying, a non-zero number of these decays happen while the radon ion is in our lungs.  This alpha decay now travels at incredible speeds until it collides with lung tissue.  

On occasion, these particles collide directly with our DNA.  Yes that’s right, radon alters your DNA.  The alpha particle rips through your DNA strand like an atomic cannonball.  Now your body has to repair the DNA damage.  This is occurring constantly.  The rate at which it’s occurring depends on how radioactive your air is (we’ll get to that soon).

If your body cannot repair your DNA properly, then you can get a genetic mutation.  This is the process by which lung cancer begins.  

Linear risk, no threshold model

This is why radon’s cancer risk is modeled on the linear risk, no threshold model.  Every time radon decays in your lungs there is a risk of lung cancer.  It’s Russian roulette with atomic particles as the bullets.  This is why international health groups say there is “no safe level” of radon exposure.  You could be the unlucky case that gets lung cancer with very little exposure, or you could be the lucky person that lives with high radon levels your entire life and gets away scot-free.  Similar to smoking, we’ve all heard these anecdotes of the unlucky and the lucky.  Just like with smoking, they’re anecdotes.  Empirical evidence proves high-risk with a great degree of certainty.

EPA action level

The EPA action level of 4.0 picocuries per litre was not chosen because it is safe.  Some experts estimate that over half of all radon-induced lung cancers occur below this threshold.

The action level was chosen because it was a technically-achievable reduction in radon levels with the technology at the time (early 1990s).  Nowadays, many radon professionals guarantee levels below the WHO action level of 100 Becquerels per cubic meter or 2.7 pCi/L.  What do these numbers really mean?

Radioactive Measurements

pCi: stands for picocurie, a unit of radioactivity equal to one-trillionth of a curie.  Named after Nobel Prize winner Marie Curie who discovered radium, the Picocurie is the most frequently used term for radioactivity in the US.  Picocuries per litre (pCi/L) equals the number of picocuries of radioactive material per liter of air or water.  At 4 pCi/L, there are approximately 12,672 radioactive disintegrations in one liter of air over a 24-hour period.  

The standard unit (SI) of radioactivity is measured in becquerels.  Like with the metric system, the US doesn’t use this standard.  However, I wish we did.  The conversion numbers cause the appropriate amount of alarm.  4 pCi/L doesn’t sound like a lot, only because any toddler can count to four.  However, 4 pCi/L is equivalent to ~148 Bq/m3.  So if you get the same radon reading in Canada, you may find that 148 is a more alarming number than four even though the exposure and risk is the same for the two units.

Again, these units themselves don’t mean much to most folks, so CDPHE came up with a conversion rate.  At the average radioactivity level for a Colorado home (6.2 pCi/L) you are getting the equivalent exposure of 200 chest x-rays per year or over one dozen “low-dose” CT scans.  Another comparison is 12-16 cigarettes per day.  That’s a lot of needless radioactive risk exposure.

Protect yourself

Just like any amount of smoking is risky and dangerous, so is any amount of radon exposure.  Luckily, radon is easily mitigated with contemporary technology.  Be sure to only use NRPP/NRSB certified or state-licensed radon professionals.  Pick up a test kit from your local health department or buy one today.  Don’t delay!

What to read next: what does a radon system cost?

Thanks for reading!

Bonus section: why doesn’t the government clean it all up?

A lot of folks wonder why there isn’t more government action regarding radon.  I have a few reasons.  First, radon is part of the Uranium 238 decay chain.  Uranium is a very plentiful element on earth (google estimates over 6 million tones on earth).  It would be completely infeasible to simply “clean it all up”.  It’s been here since the big bang and it’s part of our earth’s crust.  It’s going to be here another few billion years; it’s not going anywhere.

Uranium 235 is the isotope of uranium that can more easily be turned into nuclear power systems or weapons.  This isotope is much more highly sought after and the government does control its mining and supply.  It’s estimated that this isotope is less that 1% of all uranium on earth.  A much more feasible supply to control by the federal government.

If radon is so dangerous, then why doesn’t the government at least mandate radon testing?  A few reasons that can all comfortably fit under the umbrella of: “politics & money”.  Radon is not part of a building material that was put into homes by profit-seeking corporations.  Lead and asbestos both have storied histories surrounding amoral corporations and the naive general public.  These materials were kept in homes even after their risk was determined.  Cover ups became class action lawsuits with huge payouts that still pay for late night TV ads and billboards to this day!

Radon is naturally-occurring.  It’s part of your soil, not your building materials*.  I often joke, who are you going to sue, God?

This means that all consumer protection laws were based on very little lobbying monies.  No class action lawsuit regarding radon has been settled (at the time of this writing**).  The protections that have been written have been done so with sweat-equity from hard-working and caring scientists, citizens, and politicians.

Write your congressperson today and ask for more radon consumer protections at the state and federal level.  Spread the word at the dinner table, at school, and at book club.  Now you have the knowledge, go forth and spread radon awareness.

*Radon is sometimes found in concrete aggregate.  Be sure to ask for the radon report at your local concrete plant before spec’ing it in your build.

**There are specific, known radon contaminated areas in this country; places that were once uranium mines.  I believe these places should never have homes built on them, however, some profit seeking builders continue to build on them.  These are the builders that should face judicial repercussions.

Again, thank you for reading and spreading radon awareness