Hello everyone.
In this video, we will continue to discuss radon.
As mentioned in our previous video, the decay chains show that radon is mainly produced
by the decay of uranium.
Radon is one of the common elements in soil and rock.
The radon released from soil and rock may spread to the air and surrounding water source.
So it is possible to find radon in the water supply.
Diffusion and pressure induced flow are the main ways for radon to flow from underground
to the surface.
Building materials made of concrete also emit radon to the indoor environment.
Besides, burning fossil fuels, like natural gas release radon to the surrounding environment.
Radon can enter buildings through several ways.
As mentioned, water supplied to the buildings may contain radon.
Besides, radon can release from the building materials when there are cracks on the walls,
and ceilings.
Moreover, radon from the air and soil can flow into the buildings by windows, drains,
and even via ventilation systems.
After getting into a building, radon stays inside the building and accumulates, so it
is important to remove radon from buildings.
Radon will not cause acute health effects, but exposure in an environment with radon
for a long period of time can increase the risk for lung cancer.
It is the second leading cause of lung cancer while the first one is smoking.
In US, about 20 000 deaths per year are estimated to be caused by radon.
As mentioned in the previous video, radon in the air disintegrate into other radionuclides
called radon daughters.
When we breathe, those radon daughters enter our lungs and perform disintegration processes,
releasing radiation there.
That radiation, such as alpha particles, reacts with lung cells and damages the DNA, eventually
causing lung cancer.
To evaluate the radon concentration, Becquerel per cubic meter and picocurie per liter are
used depending on which unit system you use.
1 Becquerel is equal to 1 disintegration per sec. 1 curie is equal to 37 billion disintegrations
per sec.
So 1 picocurie per liter is equal to 37 Becquerel per cubic meter.
This table shows the number of non-smokers per 1000 people that are estimated to suffer
lung cancer under different radon concentration.
The data comes from the United States Environmental Protection Agency.
It is obvious that increasing the radon level, the possibility to suffer lung cancer is increased.
The optimal condition is to keep the radon level in the environment below 2 picocuries
per liter.
We measure radon in an indoor environment by detecting the emissions of alpha, beta
or gamma during the radioactive decay of radon.
There are four common measurement methods suggested in this video, continuous radon
monitor, alpha-track detector, grab sampling, and charcoal canister.
The radon measurements can be analyzed either at home or at a laboratory.
For the measurements taken at home, the continuous radon monitor is one of the choices.
It is a real time sampling and real time analysis instrument.
It measures the radon concentration by monitoring the electric pulse caused by the radon decay
process.
Alpha track detector is another instrument that can be used at home.
The alpha particles emitted by the radon during decay while air diffuses through the filter
in a container can be detected.
The radon concentration is calculated by the amount of alpha particles detected and the
sampling time.
It needs longer sampling times in order to obtain a more accurate result.
Grab sampling is one of the radon measurement methods that need to be analyzed at a lab.
To perform the sampling, air is drawn into a container filled with activated charcoal.
Then, the container will be transported to a lab for analysis.
For charcoal canister, there are charcoal granules in a container to adsorb radon.
It takes several days for sampling.
It also needs to be analyzed in a lab.
To mitigate and control the radon concentration in an indoor environment, so as to minimize
the effect of radon, several methods are recommended.
First, building materials with concrete that can emit radon as mentioned.
It is suggested to use materials emitting no or less radon for building construction.
Besides, some coatings, such as epoxy resin on the surface of walls and ceiling materials,
can reduce radon emission from the materials.
Sealing the cracks in the walls can also reduce the emission of radon from the building materials.
In addition to source control, to reduce the radon concentration in an indoor environment,
the ventilation rate can be increased to extract radon from the buildings.
The use of air cleaners can also help to filter the radon to reduce its concentration in an
indoor environment.
To conclude, we have introduced the indoor and outdoor sources of radon, and discussed
the health effects of radon.
In addition, we have listed some radon measurement methods.
Finally, we have suggested some methods to reduce the radon concentration in buildings.
Christopher ChaoAdjunct Professor
