Here is an obvious statement – radiation is dangerous. You should limit your radiation exposure because in large doses it negatively affects your cells. Here at Astrophysics Inc, we work with X-ray systems on a daily basis and understand the importance of proper radiation safety.

Now here is a more complicated statement – your body is exposed to radiation every day. Activities as harmless as eating a banana, flying in an airplane, or living in a brick building all expose your body to radiation. Not harmful doses, but doses nonetheless.

You are likely thinking, I know radiation is dangerous, but I don’t fly all the time so I’m probably fine. You might be right, but radiation absorption is less cut and dry than you might think. In fact certain activities, such as passing through X-ray security, expose you to less radiation that other activities that seem far less notorious (such as living in those brick buildings mentioned earlier). Lucky for you, Randall Munroe (of xkcd) created a helpful radiation chart that provides context to these different activities. Before we dive into the chart though, we need to better understand how radiation doses are measured.

Radiation Safety and Dose Chart

Radiation Dose Chart (courtesy of Randall Munroe)

Sieverts and Radiation Safety

Absorbed radiation is measured in sieverts (Sv). From a technical perspective, different forms of radiation affect cells in different ways so the sievert accounts for this relative biological effectiveness (RBE). There are also other ways of measuring radiation exposure (rems, rads, and grays) but we will stick with sieverts to stay consistent with Mr. Munroe’s chart.

1 Sv is a dangerous radiation dose; 2 Sv causes severe poisoning and may even be fatal. Few people are ever exposed to those levels of radiation though, so we will limit our focus to more common exposure levels. The majority of your daily radiation exposure comes from natural background radiation (radon gas and cosmic rays) and medical scans. If we ignore medical scans, the average person absorbs about 10 microSieverts (μSv) of radiation each day. This dose is 100,000 times smaller than the dangerous 1 Sv dose mentioned earlier.

Now you are probably thinking, Doing some quick math, doesn’t that mean I’ll absorb 1 Sv worth of radiation before my 28th birthday? Thankfully that is not the case, and Mr. Monroe explains why:

One sievert (all at once) will make you sick…but we safely absorb small amounts of natural radiation daily.

So the good news is our amazing human bodies can safely absorb most of the radiation we are exposed to each day. And that daily exposure is still much less than the radiation absorbed from an X-ray security scanner. As we explore Mr. Munroe’s chart in more detail we will gain a better understand for how these activities compare to one another

Putting It All in Perspective

Let us explore how the radiation exposure chart relates to an Astrophysics Inc. X-ray unit. The HXC-320 vehicle scanner inspects passenger cars and trucks at borders and checkpoints. The system utilizes a powerful X-ray generator for inspecting vehicles, and it is designed to limit passengers’ radiation exposure. During an average scan, passengers absorb less radiation than they ingest while eating a banana! Mr. Munroe’s chart provides additional context for how little radiation is absorbed during an HXC-320 scan:

  • You absorb on average 100 times more background radiation each day
  • Passengers flying from New York to Los Angeles absorb 400 times more radiation
  • Living for a year in the brick building we mentioned earlier includes 700 times more radiation exposure
  • Patients getting a head CT scan absorb 20,000 times more radiation

Mr. Munroe’s chart has many more exposure examples that provide perspective on how much radiation your body can safely absorb. It is a great reference tool for radiation safety, but this chart should not be treated like a science textbook. In fact, measuring exposure and its effects on the body is an imperfect practice because it is unethical to expose human beings to large radiation doses for scientific experiments. It is best to keep Mr. Munroe’s own words of warning in mind as you explore his chart:

If you’re basing radiation safety procedures on an internet PNG image and things go wrong, you have no one to blame but yourself.