Calculating your own natural radiation dose in context

26 06 2012


Traditional Radiation Trefoil Hazard Symbol. (Image credit: ORAU)

A Dose of Radiation Information

How much radiation is normal?

In light of Fukushima, sensationalized media, political fear-stoking, and rampant misinformation regarding radioactivity, consider this post an easy-to-reference tool/resource.  With it, you can be armed to understand and quickly make sense of this over-mystified, natural aspect of reality when it comes up.

For starters, here’s the simple reality about how much radiation you receive in a year just for standing on Planet Earth:

The average natural annual radiation dose for a U.S. resident is about 300 millirem, and when including man-made commercial products and medical procedures (MRI scans, etc.), the average dose jumps up to 600 millirem per year.  This is what we all get every year and bears no known, measured relationship to developing cancer.

  • Note: For the international units, divide all “millirem” numbers by 100, (i.e. 3.6 millisieverts.)  Or, an online converter can be found here.

However, what does that mean?  I’m completely aware that unless you’re a professional in the field of health physics, (as I am,) this number has no context.  So, allow me to explain just what this really means using things we can all identify with.

Hold on to your hats.

So, What’s My Dose?

For context, below is a list of the amount of radioactivity you receive in a year from very familiar items/sources:

  • Cosmic radiation  = 26-96 millirem (higher with altitude)
  • From standing on the Earth itself (geology) = 20-90 millirem (higher nearer igneous mountains)
  • From your own brick/stone/concrete building = 7 millirem
  • From your own body (food/water!) = 40 millirem
  • From breathing (naturally-produced radon) = 200+ millirem
  • For flying 1,000 miles in an airplane = 1 millirem
  • From having a dental/chest/normal x-ray = 50 millirem each
  • From having an annual mammogram = 75 millirem
  • From having a single CT scan = 150 millirem
  • From smoking a pack of cigarettes a week (polonium) = 200 millirem
  • From consumer goods = 10 millirem

Just add these up to produce your own, custom average annual radiation dose.

Wait.  My house/food/body/atmosphere is radioactive?

Yes.  Not to fear.  Just like the small amounts of chemicals that we can reliably tolerate, (e.g., trace arsenic, lead, etc.,) so too are trace amounts of radioactivity completely tolerable.

Fukushima in Context

Now, as you can see in the above plot of the radioactivity measured at the entrance of Fukushima nuclear powerplant as the disaster happened, it looks pretty dramatic.

  • (Note: The numbers are reported in “micro”sieverts per hour, which are admittedly reading a much smaller span of time, (hours versus years,) but are in units 1,000 times smaller than the “milli”sievert international units described above.  This is important.)

However, instead of running for the hills just yet, let’s take a look at what the numbers actually say.

The March 15th hydrogen explosion at the plant, which occured roughly 84 hours after the earthquake, shows the largest spike of activity: for a brief period upwards of nearly 12,000 microsieverts per hour.

But let’s take this apart.  What does that mean?  12,000 microsieverts is the same as 12 millisieverts.  12 millisieverts is the same as 1,200 millirem.

Now, compare this to the above list of natural radiation values, with an eye toward the annual average does of 360 millirem.

Yes, if reading correctly, this implies that simply standing on planet Earth every year nets everyone the same external radiation dose that would have been received if standing at the gates of the Fukushima Daichi powerplant during the worst part of the disaster for a full 15 minutes.

With these, even worst-case numbers, it becomes obvious that one could stand at the entrance to Fukushima during the worst period of the disaster for a full three minutes and have earned only the equivalent radiation dose of… an average chest x-ray.

Granted, this isn’t something one would necessarily want.  This is upwards of 15% of your natural average dose.  -But your biology wouldn’t ever notice the difference.  And one could go many orders of magnitude more than that before there would be any reasonable expectation of an acute health effect.

More realistically, even standing at the Fukushima gates during the unprecedented event of external venting from the internal containment of reactor number 2, (with an exposure rate of 0.5 millisievert per hour), it’s a full hour of loitering there before one would rack up the external exposure of simple set of dental x-rays.

Funny how the perception and the reality differ, eh?

Unwanted radioactive material is serious, just as a leak from underground gasoline storage tanks that could contaminate drinking water is serious.  But that seriousness must be given honest context.


Hopefully this has provided a window into the reality of radiation protection, and it is my sincere wish that this was and will continue to be a useful go-to when radiation numbers come up in the media.

Feedback is welcome, and if desired, I would be happy to put other radiation values in context… (Chernobyl, Three Mile Island, going to the Moon, etc.)

Go forth and combat radiation misinformation!

[Sources for the above information: American Nuclear Society, the National Council on Radiation Protection and Measurement, the U.S. Department of Energy.]


Columbia shuttle disaster board supports commercial spaceflight

6 09 2010

A short note today on welcome news.  While it isn’t necessarily new news at this point, it’s something that didn’t get a lot of play when it came out, and in my view it really should have.

CAIB members examine Columbia space shuttle debris in 2003. (Credit: Rick Stiles)

So, what is it?  It’s a sigh of relief for everyone rooting for the success of commercial spaceflight:  Former members of the Columbia Accident Investigation Board (CAIB) released a statement in early July announcing their support for the commercialization of low-Earth-orbit space travel.

Yep – those responsible for ensuring that the safety lessons of the Columbia space shuttle disaster are incorporated into all future NASA space activities have endorsed contracting astronaut flights to commercial aerospace firms.

To quote a portion of the statement, which was in the form of a letter to senatorial science subcommittee chairwoman Senator Mikulski, the former board members write:

  • “The new strategy will task an array of companies, including both established industry stalwarts with decades of experience as well as newer service providers, to build simple spacecraft that are exclusively focused on the mission of sending crews to low Earth orbit. By using existing launch vehicles that are already accumulating extensive track records to launch these spacecraft, NASA will ensure that crews would not be risked on a vehicle that has not repeatedly demonstrated its safety and reliability.”

For everyone who feels that “private industry” will somehow sacrifice safety when compared to NASA initiatives, this is in my view a much-needed blast of cold water.  Using the launch vehicles that have been putting satellites in orbit for nearly half-a-century leverages much tried-and-true experience that normally flies under the radar.

So, just a reminder.  Commercial space will likely be safer than any new NASA launch vehicles.

The people who investigated our most recent space disaster say so.

The art of emergency response

24 06 2010

I spent this past weekend on a training exercise with the Nevada-1 Disaster Medical Assistance Team, or NV-1 DMAT.  On a part-time, voluntary basis, I serve as a Logistics Officer for the federal emergency response team (currently under NDMS instead of FEMA), which involves monthly meetings and periodic training in preparation for deployment to the next Katrina disaster, for example.

Me training with the Nevada-1 Disaster Medical Assistance Team. June 19. Credit: NV-1 DMAT

This particular Saturday, we partnered up with the FEMA’s Urban Search and Rescue (US&R) Nevada Task Force One (NV-TF1) and spent time practicing the rapid set-up of emergency shelters (and associated electrical and communications equipment) that will be used as portable hospital rooms, triage areas, command posts, sleeping quarters for the responders, etc.

The take home message for me is that emergency response is an art, and one that must be practiced.  Familiarity with equipment is key.  It’s hard enough to set these things up in a warehouse, and it was immediately obvious that every second more proficient we became was one fewer future second spent standing in the sweltering humidity of a tropical depression in a cloud of blood-sucking insects.

In short: Be prepared.

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