Radon was discovered by Friedrich Ernst
Dorn, a German chemist, in 1900 while
studying radium’s decay chain.
Originally named niton after the Latin word
for shining (nitens) radon has been known
as radon since 1923.
Today, radon is still primarily obtained
through the decay of radium.
Atomic number: 86
Atomic Weight: 222
Atomic mass: 222 u
Melting point: 202 K (-71°C or -96°F)
Boiling Point: 211.45 K (-61.7°C or -79.1°F)
Density: 0.00973 grams per cubic
Phase at Room Temperature: Gas
Chemical series: Noble gas
Element Classification: Non-metal
Period Number: 6 Group Number: 18
Radon is formed as one intermediate step in
the normal radioactive decay
chains through which uranium (u), thorium
(Th) and slowly decay into lead (Pb) .
radon itself decays, it produces new
radioactive elements called radon daughters
or decay products.
Unlike the gaseous radon itself, radon
daughters are solids and stick to surfaces,
such as dust particles in the air.
Half-life (t1⁄2) is the amount of time required
for the amount of something to fall to half its
initial value. The term is very commonly used
in nuclear Physics to describe how quickly
unstable atoms undergo radioactive decay.
If such contaminated dust is inhaled, these
particles can stick to the airways of the lung
and increase the risk of developing lung
The most common forms of radon decay
through alpha decay.
Alpha decay usually isn't considered to be a
great radiological hazard since the alpha
particles produced by the decay are easily
However, since radon is a gas, it is easily
inhaled and living tissue is directly exposed
to the radiation.
Although it has a relatively short half life,
radon decays into longer lived, solid,
radioactive elements which can collect on
dust particles and be inhaled as well.
For these reasons, there is some concern as
to the amount of radon present within
Radon seeps into houses as a result of the
decay of radium, thorium or uranium ores
underground and varies greatly from location
On average, the earth's atmosphere is
If the gas is trapped in dwelling enclosure,
radon and its daughter nuclides can attach to
dust particles and then be inhaled in to lungs.
Where the decay radioactively and increase
lung cancer risk.
The radioactive decay of radon is by far the
single greatest source of human radioactive
Radon mostly enters a home directly from the
soil through the lowest level in the home that
is in contact with the ground.
Radon concentrations in the same location
may differ by a factor of two over a period of
1 hour. Also, the concentration in one room
of a building may be significantly different
from the concentration in an adjoining room.
Typical entry points of radon into homes are,
Cracks in solid foundations.
Cracks in walls.
Gaps in suspended floors.
Gaps around service pipes.
Cavities inside walls and
Source of cell damage in lungs.
Short lived products most significant.
Have static charges.
WHO presented in 2009 a recommended
reference level (the national reference level),
100 Bq/m3, for radon in dwellings.
The actionable concentration of radon
varies depending on the organization for
example, the United States Environmental
Protection Agency encourages that action
be taken at concentrations as low as
74 Bq/m3 (2 pCi/L).
The becquerel (symbol Bq) is the IS derived unit of radioactivity.
One Bq is defined as the activity of a quantity of radioactive
material in which one nucleus decays per second.
The European Union recommends action be
taken when concentrations reach
400 Bq/m3 (11 pCi/L) for old houses and
200 Bq/m3(5 pCi/L) for new ones.
On 8 July 2010 the UK's Health Protection
Agency issued new advice setting a "Target
Level" of 100 Bq/m3whilst retaining an
"Action Level" of 200 Bq/m3.
The same levels (as UK) apply to Norway
from 2010; in all new housings preventative
measures should be taken against radon
• Alpha particles
from the Radon
can damage lung
• Lung cancer is
the main health
• Alpha energy
directly to cells.
• Alpha particles
strike Lung cells
damage to DNA
* One picocurie/Liter is 2.22 disintegrations within that Liter.
This comes from the fact that one curie is 37 billion disintegration per second (dps).
One picocurie is one trillionth of a curie (0.037 dps).
There are 60 seconds in a minute (60 x 0.037 = 2.22)
Safe level: < 2.0pCi/L
Because the half-life of radon is only 3.8
days, removing or isolating the source will
greatly reduce the hazard within a few weeks.
Another method of reducing radon levels is
to modify the building's ventilation.
Generally, the indoor radon concentrations
increase as ventilation rates decrease.
In a well ventilated place, the radon
concentration tends to align with outdoor
values (typically 10 Bq/m3, ranging from 1 to
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