Quick Radiation Reference Guide

Recommended Yearly Limit

(we get 240 to 300 millirems per year from natural background radiation)

25,000 millirems for astronaut missions

5000 millirems for adults

500 millirems for childrenA useful comparison to get an idea of reported radiation levels is the fact that the average dose that all humans on the planet get yearly from natural background radiation is 2.4 mSv per year

ave dose per person per year is 2.4 mSv = 2.4 milli Sieverts = .0024 Sieverts

240 millirems

Quote from Leslie Corrice page:

1. Radiation occurs everywhere as a natural part of the world…everyone and everything is naturally radioactive.
2. The no-safe-level theory of radiation only applies to enormous exposures (above 100 REM) absorbed over a short period of time.
3. Low levels of radiation exposure over long periods of time, up to 500 times typical natural background levels, are not harmful.
4. Low level radiation is beneficial to human health, improves damage recovery, and is essential to the functioning of the immune system.
5. Way too much or way too little of a good thing can be deadly.


To answer how radioactive something is we use Becquerels or Curies

To answer what effective dose somebody has received we measure in millirems or milli Sieverts

To answer what actual dose somebody has received we measure in rads or grays

At Fukushima a total of 11 kilograms of material (out of approximately 60,000 kilograms of fuel per unit) escaped from the reactor pressure vessels

Metric prefixes in everyday use
Text Symbol Factor
tera T 1000000000000
giga G 1000000000
mega M 1000000
kilo k 1000
hecto h 100
(none) (none) 1
deci d 0.1
centi c 0.01
milli m 0.001
micro μ 0.000001
nano n 0.000000001
pico p 0.000000000001

Zetta (Z) (1021)

Eta (E) (1018)

Peta (P) (1015)

Tera (T) measured in Trillions (1012)

Giga (G) measured in Billions (109)

Mega (M) measured in Millions (106)

Kilo (K) measured in Thousands (103)

milli (m) measured in thousandths

micro (μ) measured in millionths

nano (n) measured in billionths

pico (p) measured in trillionths


Some useful diagrams