CR3 News Magazine 2020 VOL 3: MAY Medical - Radon vs Covid-19 | Page 10

EPA Facts about Radon
During the decay process, radiation is released
in the form of alpha particles, beta particles, and
gamma rays. Alpha particles can travel only
short distances and cannot penetrate human
skin. However, when inhaled, they can
penetrate the cells lining the lungs. Beta
particles penetrate skin, but cannot pass
through the entire body. Gamma radiation can
travel all the way through the body. The health
risk associated with each type of radiation is a
function of how and what parts of the body are
exposed.
What is radon?
Radon is a naturally occurring radioactive gas
without color, odor, or taste that undergoes
radioactive decay and emits ionizing radiation.
Radon comes from the natural (radioactive)
breakdown of uranium and thorium in soil, rock,
and groundwater and is found all over the U.S.
The largest fraction of the public’s exposure to
natural radiation comes from radon, mostly
from soil under homes. (There are three forms
of radon, but this document refers primarily to
radon-222 and its progeny.)
The time required for a radioactive substance to
lose 50 percent of its radioactivity by decay is
known as the half-life. The half-life of uranium-
238 is about 4.5 billion years. The half-life of
radon is 3.8 days.
How does radon change in the
environment?
The primary source of radon is from uranium in
soils and rocks and in groundwater. Over time,
uranium decays into radium, which then decays
directly into radon. (See EPA Facts about Radium
and Uranium.) Uranium is present naturally in all
soil, although quantities differ from place to
place. Because radon is a gas and chemically
unreactive with most materials, it moves easily
through very small spaces, such as those
between particles of soil and rock, to the soil
surface. Radon is also moderately soluble in
water, and it can be absorbed by groundwater
flowing through rock or sand. Radon undergoes
radioactive decay, when it releases ionizing
radiation and forms “daughter” elements,
known as decay products. It is the release of
radiation from this decay process that leads to
exposure and health risks from radon.
How are people exposed to radon?
Outside air typically contains very low levels of
radon (about 0.4 picoCuries per liter [pCi/L] of
air). But it can build up to higher concentrations
in indoor air from soil under foundations of
homes, schools, and office buildings, where it
can seep into buildings. EPA estimates that the
national average annual indoor radon level in
homes is about 1.3 pCi/L of air. However, more
than 6 percent of all homes nationwide have
elevated levels at or above EPA’s voluntary
action level of 4 pCi/L. Levels greater than 2,000
pCi/L of air have been measured in some homes.
Although radon in indoor air from soil gas
typically accounts for the bulk of the total radon
risk to individuals, people may also be exposed
to radon and its daughters through use of
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