RADON
The biggest single source
Radon is a colourless, odourless gas from the uranium in all rocks and soils. In the UK it gives an average dose of 1.3 mSv a year, about half the total.
Compare dosesWHAT THE NUMBERS SAY
A little radiation,
all the time.
Radiation is all around us, every day.
Compare doses
2.6 mSvUK average a year
Most of it is natural: radon gas from the ground, rocks, food and rays from space. The units can be confusing, so here is what a rad, a gray and a sievert mean, and how everyday doses compare.
At a glance
- Mostly natural
- Radon is the biggest part
- Testing is the only way to know
- Clear units, calmer reading
2.6 mSv
Average radiation dose per person per year
The largest part is natural radiation in homes and workplaces, from radon and building materials, with further contributions from natural radioactivity in food and from medical exposures.
UK AVERAGE · UKHSA
100 rad
Rads in one gray
Absorbed dose is energy per kilogram. One gray is 1 joule per kilogram; one rad is 0.01 joules per kilogram, so 1 gray equals 100 rad.
UNITS · US EPA
TWO NUMBERS WORTH KNOWING
What a dose is,
and where it comes from.
One figure for the UK's yearly dose,
one to translate the old and new units.
The rad and rem are US units. The gray measures absorbed energy; the sievert, like the rem, adjusts that for the type of radiation and how sensitive each part of the body is. 1 sievert equals 100 rem.
A QUICK DOSE CHECK
How big
is that dose?
Pick a source to see its typical dose in millisieverts (mSv), from UKHSA's comparison table. The bar shows how big the dose is compared with the others.
Figures are typical or average doses from UKHSA. Individual doses vary.
THE SHORT ANSWER
Mostly natural,
mostly radon.
Everyone gets a small background dose.
Where you live makes the biggest difference.
General information only, not medical advice. For advice about your own health, speak to a doctor, pharmacist or other qualified health professional.
COSMIC
Higher up, a bit more
Cosmic radiation rises with altitude because there is less atmosphere above you. A transatlantic flight gives about 0.08 mSv.
See the numbers
TESTING
Only a test can tell
UKHSA says the only way to know if a building has a high radon level is to have it tested, and recommends a test in radon-affected areas.
What you can do
FOUR THINGS TO KNOW
Know your home,
know your numbers.
Most everyday radiation is natural, but radon is one part of it you can find out about for your own home.
Check the radon map
UKHSA publishes a map showing where high radon levels are more likely, based on the type of ground.
Test if you are in an affected area
Levels vary from building to building, so UKHSA recommends a test if you live or work in a radon-affected area.
Treat basements as higher risk
UKHSA says basements, cellars and underground sites should be treated as having an increased chance of high radon, wherever they are.
Read the units carefully
mSv measures effective dose, while a gray or rad measures absorbed energy. Check which one a figure uses before comparing.
WHAT RADON IS
A gas you
cannot sense.
Radon forms when the small amounts of uranium found naturally in all rocks and soils decay. It has no colour or smell. Outdoors, and indoors in many areas, levels are low. It is measured in becquerels per cubic metre of air, and the average UK home has about 20.
When radon decays, the products can be breathed in and give off alpha particles inside the lungs. UKHSA says studies in many countries have shown that more exposure to radon increases the risk of lung cancer, which is why it suggests finding out the level in your home.
Questions
Questions people ask
What is a rad?
A US unit of absorbed radiation dose: the energy deposited per kilogram. One rad equals 0.01 joules per kilogram, and 100 rad make one gray, the international unit.
What is the difference between a gray and a sievert?
A gray measures the energy absorbed. A sievert adjusts that for the type of radiation and how sensitive different organs are, giving an indicator of long-term health risk.
How much radiation do people in the UK get each year?
About 2.6 millisieverts on average, according to UKHSA. The US average is 6.2 millisieverts.
Is flying a big radiation dose?
A transatlantic flight gives about 0.08 mSv, according to UKHSA. Cosmic radiation increases with altitude because there is less atmosphere above you.
What is the average radon level in UK homes?
About 20 becquerels per cubic metre. UKHSA says that for levels below 100, individual risk remains relatively low, though risk rises as the level rises.
Sources
Where the facts come from
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