We live on a planet full of natural radiation. It is present in soil, rocks, the air we breathe,
the water we drink, and even in our own bodies. This natural radiation makes up the bulk
of the total radiation we are exposed to every day.
But we're also exposed to artificial radiation, including medical tests like x-rays,
and small amounts of radioactive material -
called "radionuclides" - from licensed releases from nuclear facilities.
I'm Julie and I work for the Canadian Nuclear Safety Commission.
We can't see, hear, smell, touch or taste radiation.
Until 1895 we didn't even know it existed! But we've come a long way in our understanding
about what ionizing radiation is and how it affects our bodies and our environment.
For example, we can measure the amount of radiation
in the environment with radiation detection devices -
like Geiger counters. They count the energy deposited
in the detector by the radiation. Listen to the sound of naturally occurring
uranium in this rock sample.
[clicking sound intensifies] That count can then be used to calculate a
dose. A dose is the quantity we use when we talk
about the potential health effects of radiation.
A dose takes into account the type of radiation you've been exposed to and the organs in your
body which have been exposed.
It is expressed using the unit "sievert" or more commonly "millisievert" which is 1,000 times smaller.
On average, Canadians receive a dose of 1.8 mSv every year
from natural background radiation coming from
radioactive materials found in soil, rocks, some foods and cosmic radiation.
This number can range from 1 to 4 mSv depending on where you live in Canada.
For example, the cosmic radiation is more intense
for people living at higher altitudes or further from the equator.
Likewise, terrestrial radiation is higher for people
living in areas where rocks and soil contain more natural radioactive elements.
So what are the health effects caused by radiation? Certain types of radiation have enough energy
to penetrate our bodies. When it passes through tissues in the body,
electrically charged atoms, called ions, can change or destroy cells.
The body is a pretty amazing organism and most of the time,
these cells repair themselves. This can happen millions of times every day!
If however the DNA or other critical parts of the cell
receive a large dose of radiation all at once, the cell may die or be damaged beyond repair.
If this happens to a large number of cells, "tissue effects" can occur.
Examples of these effects include cataracts, which can happen at around 500 mSv,
and acute radiation syndrome symptoms like nausea
and skin burns that can be seen at doses well over 1,000 mSv.
Extremely high levels of radiation in the range
of 4,000 to 5,000 mSv can be fatal. This level of exposure is very rare.
If the cell incorrectly repairs itself, but continues to live,
then "stochastic effects" could occur. This type of damage could develop into cancer
over time. The higher the radiation dose,
the more likely a cancer will occur. In population studies, we generally don't
observe health effects appearing at doses lower than
about 100 mSv. Most importantly, our understanding of how
cells can be damaged by radiation allows us to use
that same knowledge to target and kill cancer cells.
We know what happens once radiation enters the body,
but how does it get inside you in the first place?
When we talk about radiation exposure, we are talking about "pathways";
there are various pathways radiation can take to get inside the body - including the air
we breathe and the food we eat - all of which contribute
to our radiation dose. Did you know a brazil nut naturally contains
trace amounts of the radionuclides potassium-40 and radium-226? Delicious!
Our bodies can't distinguish between natural and artificial radioisotopes.
One source of artificial radiation is the small,
controlled quantity of radionuclides permitted to be released from licensed nuclear facilities
into the environment. These radionuclides could be carried in the
air and deposited in a farmer's field.
Animals eat grass and grains from that field and then provide food that people eat and
drink. Understanding that chain of events - that
one pathway - makes it possible to begin estimating a dose
to the person who consumes that food. Overall, the amount of radionuclides in foods
are extremely small and do not affect your health.
For major facilities, a similar assessment is done
to look at the impact of radiation on the environment itself,
including wildlife and vegetation. Since radiation has the potential to cause
harm, it must be strictly regulated.
That's where the Canadian Nuclear Safety Commission comes in; our mandate is to regulate
the use of nuclear energy and materials to protect health, safety, security and the
environment. The Radiation Protection Regulations
define the dose limits used to protect the health of the public and nuclear energy
workers. Members of the public are limited to 1 mSv
of exposure per year from licensed activities;
this is in addition to all other sources of radiation,
like naturally-occurring or medically-related radiation.
Workers are limited to 50 mSv in one year and 100 mSv over 5 years.
Nuclear energy workers can wear small devices called "dosimeters" that measure and track
their radiation doses as one way to make sure they don't exceed these limits.
These can be worn on different parts of the body
depending on the kind of work they do. It's important to note that these dose limits
are regulatory limits, and not health limits. As a result of our strict regulations and
oversight, we are happy to report that these dose limits
are rarely reached. I've given you a lot of information.
Let's put some of the numbers in perspective. Members of the public living near a major
facility typically receive 0.001 mSv a year from licensed nuclear
activites, which is less than a typical chest x-ray (0.1
mSv). The public dose limit is 1 mSv per year.
This is on top of the dose received through natural background radiation which in Canada
is nearly twice that high, at an annual average of 1.8 mSv.
Workers are limited to 50 mSv in one year or 100 mSv in 5 years.
In fact they typically get far smaller doses. Health effects like cataracts can happen at
500 mSv and acute radiation syndrome symptoms
can be seen at doses well over 1,000 mSv. I know radiation doses can sound scary,
but you can rest assured; the Canadian Nuclear Safety Commission is
there, overseeing the nuclear sector to protect
your health and safety, as well as that of the environment.
The Canadian Nuclear Safety Commission: the answers you need, from a source you can
trust! Visit our website, Facebook page or Youtube
channel.