Radioactivity is everywhere, including us humans. So technically, even our smiling faces spread ionizing radioactivity to the surroundings. Our bodies are radioactive because of radioactive isotopes we get for example from our food and drink. But how radioactive are we? Where does our daily radioactive dose come from?

Nuclear power is often associated with radiation[i], as radioactive materials are both used in and result from the nuclear power sector. People often don’t know very much about radiation, and hence they tend to fear it – often disproportionally. This fear of radiation is then associated with nuclear power[ii], becoming a fear of nuclear power. Let’s put things into perspective and learn that this fear is largely misplaced.

The place of residence affects the amount of radiation

The average Finn gets a lifetime (80 years) dose of about 250 millisieverts[i] (mSv), or 3.2 mSv per year. Globally, the dose is slightly less, at around 240 mSv and 3 mSv, respectively. These are averages, and often people get much higher doses. If one lives in an area with a lot of radon, the dose can be ten times higher, or even more[ii]. In our book “Musta Hevonen[iii]” (currently only available in Finnish, English version estimated in 2018) we used a radiation dose unit called “Pispala”. It corresponds to the dose one can get by living one year in the area of Pispala in Finland, which has a high background radiation level due to radon. One “Pispala” equals 35 mSv.

The single largest source of radiation is radon

Radon is the single largest source of radiation for the average person, representing 41 % of total dose. Other natural sources make up another 39 %, leaving 20 % for artificial (man-made) radiation. This is overwhelmingly due to medical procedures. When these are all added up, we have over 99.5 % of the total accounted for.

The rest, about 0.4 % of the total dose, is due to atmospheric nuclear weapons tests (0.16 %), occupational radiation mainly from mining activities (0.16 %), Chernobyl nuclear accident (<0.1 %) and nuclear fuel cycle (<0.01 %). The part of radiation that gets the most press, meaning the part resulting from civilian use of nuclear power, is also by far the least significant part. It is not even noticeable from statistical background noise.


The Chernobyl accident increased the average global radiation dose by less than a tenth of a percent. In Finland, the average lifetime additional dose was almost ten times larger, at roughly 2 mSv. This equals the additional dose from a three week visit to Pispala or working as a flight attendant for a year[vi]. Compared with the press and the subsequent fear of Chernobyl (and nuclear power in general), the actual average doses have been a bit underwhelming.

The individual doses we get from different sources vary greatly. Some of the common and uncommon radiation sources can be found table below. For example, by smoking two packs a day for a year gives comparable radiation dose the survivors of the initial blast of Hiroshima atomic bomb got on average. And radiation is not even the biggest health hazard from smoking! In my next article, I will discuss the actual health effects from radiation a bit more closely.

Source of radiation Pispalas Millisieverts
Smoking 2 packs a day for a year 5 – 6 years in Pispala 160 – 200 mSv
A year of loitering around at Guarapari beach in Brazil 5,5 years in Pispala 175 mSv
A combined medical PET and CT scan. About 8 months in Pispala 20 – 25 mSv
A year as a flight attendant or the dose a Finn gets on average from Chernobyl accident during lifetime. 3 weeks in Pispala 2 mSv
Estimated additional dose for 170 front line emergency workers in Fukushima. 3 years in Pispala 100 mSv
Additional average dose for those who survived the blast from the atom bomb in Hiroshima 6 years in Pispala 200 mSv



[i] Radiation exists in many forms. In this article, by “radiation” I mean ionizing radiation, which can cause cancer.

[ii] Usually with the help of anti-nuclear activists.

[iii] Sievert (S), and the smaller units like millisievert (0.001 S), are used to measure the health effects of a radiation dose over time. Sievert aims to take into account the variability between types of radiation and exposure.

[iv] It could be roughly 30 times more. International Commission on Radiological Protection (ICRP) has been planning for changes in how we calculate the dose-effect from radon. While it has not yet been published, the latest draft (as seen on summer 2017) would increase the dose from Radon significantly.

[v] Musta Hevonen – Ydinvoima ja ilmastonmuutos, Rauli Partanen and Janne M. Korhonen, Kosmos 2016.

[vi] In high altitudes cosmic radiation is stronger, so those who spend a lot of time in aeroplanes tend to get a higher dose from it.