Energy Mix
Project
This pamphlet is written and
produced as part of Civic Exchange’s
Energy Mix Project. We have invited
scholars and experts locally and internationally to help
frame some key issues relating to Hong Kong’s energy mix.
These papers and pamphlets are aimed at enriching
community understanding and deliberation on energyrelated issues in Hong Kong.
Other pamphlets in the series can be downloaded at
http://www.civic-exchange.org/wp/energyproject_en/. For
more information about Civic Exchange’s Energy Project,
please visit Civic Exchange’s website at http://www.civicexchange.org.
Radiation
and public
health
Other pamphlets in this series
Other pamphlets in this series can be
downloaded from http://www.civicexchange.org/wp/energyproject_en/.
1. Deconstructing radiation basics.
2. Radiation and environment.
3. Health effects of ionizing radiation.
4. Ionizing radiation from nuclear power plants.
Useful
references
Environmental Protection Department
(2009).
Radon
and
You.
http://www.iaq.gov.hk/pamphlets/2009
11/Radon%20And%20you.pdf.
Wong T. W. & Yip S. T. (2013). Radiation and Public Health.
http://www.civic-exchange.org/wp/wp-content/uploads/
2013/04/energy04_en.pdf.
World Health Organization (2009). “Radon and cancer”. Fact
Sheet N°291. http://www.who.int/mediacentre/factsheets/
fs291/en/index.html.
Actions: What can we do to minimize
our exposure to ionizing radiation?
As inhalation of radon constitutes the major source of
radiation for an individual, except for those undergoing any
medical radiation procedure, the most important thing to
do is to reduce exposure to radon in home and workplace:
Do not smoke.
Radionuclides (210Po and 210Pb) are
present in cigarette smoke. They cause
lung cancer in addition to all the other
cancer-causing chemicals in cigarette smoke. Moreover, the
presence of radon in the environment enhances the risk of
lung cancer from cigarette smoking.
Maintain good air quality and
circulation in your living environment.
Radon will accumulate when the
windows are closed with no artificial
ventilation or if fresh air intake and exhaust are not
installed correctly when artificial ventilation is in place.
Also, cracks on the floor and permeable walls will lead to
the seepage of radon into the building. Cracks should be
repaired and less permeable wall covering such as wall
paper should be applied.
Avoid drinking water from untreated
groundwater sources such as springs
and wells, which usually contains higher
radon levels than surface water from
rivers and lakes.
Spend leisure time outdoors in
places with good air quality, such as
country parks.
Property owners and employers
should prevent radon problems in the
premises.
Concerned parties can seek advice from
environmental professionals. The Indoor Air Quality Information
Centre’s website provides a list of service providers:
http://www.iaq.gov.hk/second.asp?page=iaqlist&sub=&
content=&number=0&language=en
You should also avoid unnecessary man-made radioactive
exposure:
Avoid unnecessary exposure to x-rays.
This applies to some x-ray examinations
for
non-medical
purposes
(e.g.,
employment, legal, insurance), and one
should ask if the risk of exposure to a radiation dose is worth
the benefit, if any, of that examination. The harm and benefits
of routine x-rays for screening purposes should be discussed
with your doctor. The use of radiation in the treatment of
cancer also produces harmful effects. However, the benefit of
treating cancer generally outweighs the harm of radiation.
Beware of products that may use
radioactive materials unnecessarily.
Some of these items may even claim to
have health benefits. All ionizing radiation
produces some risks. Beware of the presence of radioactive
materials added into food and other consumer products. E.g.,
radioactive thorium has been used as a long lasting deodorant
in socks and underwear. Thorium has also been used in
pain-relief pads and in some water purifiers with
unsubstantiated miraculous effects.
40 km
Cover design by DesignNORM
Layout by Carine Lai
Radiation and
public health
Frequently asked questions
about radiation
Wong Tze Wai and Yip Sung Tat
April 2013
Basics
Q1. What is radiation?
A: Radiation is energy carried through
space in the form of waves or particles. Heat, light and
lower-energy ultraviolet rays are non-ionizing radiation,
while X-rays and gamma rays are ionizing radiations.
‘Ionizing radiation’ is sufficiently energetic that it can
remove electrons from (‘ionize’) atoms or molecules.
Q2. What is background radiation, and is there a normal
level for background radiation?
A: Background radiation refers to the highly energetic
ionizing radiation from both natural and man-made
sources which is present everywhere, and which the
general population is exposed to at all times. However
there is no such thing as a ‘normal’ level since some places
are naturally high in background radiation level, and others
are naturally low, due to rock composition or altitude.
Q3. Is there ‘good radiation’ and ‘bad radiation’?
A: Radiation can be ‘good’ or beneficial in the right amount
and and at the right energy level. Radiation is ‘bad’ if it is
harmful to health. E.g. Ultra violet (UV) rays are necessary
for the synthesis of vitamin D in our body, but excessive
exposure to UV can lead to skin cancer. So, UV can be ‘good’
and ‘bad’. High-level ionizing radiation such as X-rays are
very useful in medicine, and gamma rays are also used in
treating cancers, in surgery, and in sterilising equipment, but
ionizing radiation can also damage our organs and tissues,
and may produce changes in our cells resulting in cancer or
genetic changes that can be passed to the next generation.
Exposure
Q4. What are safe levels of radiation?
A: The measuring unit for biological
damage resulting from radiation exposure is sieverts
(Sv). The International Commission on Radiological
Protection (ICRP) recommends a limit of 0.001Sv per
year on top of background radiation for the general
public. The health risk for exposure beyond this limit is
not acceptable under normal conditions. For your
information, 1-year background radiation in Hong Kong
is approximately 0.0024Sv.
Q5. How do I get exposed to radiation?
Background radiation
is everywhere, there
is no way to avoid it.
Additional doses of radiation
can also come from...
Outer space
Living at high
altitudes or flying
frequently
Air
Staying in a poorly-ventilated room:
Radon gas from the soil below the
house or from building materials will
accumulate over time.
Food and drink
Rocks, soil and building
materials (especially granite)
Q6. Do home appliances emit radiation?
A: Heaters, light bulbs, microwave ovens, mobile phones…
emit non-ionizing radiation; usually no ionizing radiation is
emitted from home appliances unless you have gadgets with
radioactive materials in them (such as some smoke
detectors, some luminous watches/clocks).
Q7. Can I travel to Japan after the Fukushima incident?
A: Yes, you are safe to travel to most areas in Japan because
the risk of exposure to extra radiation in the aftermath of
Fukushima incident is very small. You will actually be
exposed to a higher level of radiation during your flight to
Japan. However, you should avoid entering/staying in the
evacuated area in Fukushima, as the radiation level is still
higher than normal background level.
Q8. Where is Daya Bay nuclear plant located? Will Hong
Kong be affected if there is an accident?
A: Daya Bay is located in Guangdong Province, China, about
50km northeast from urban areas of Hong Kong. According to
IAEA’s recommendation, the high risk zone radiation exposure
after a nuclear incident typically covers the area within 3 -5km
of the nuclear plant. The UK Atomic Energy Authority report
suggests countermeasures against the plume exposure
Medical sources, e.g. radiotherapy
for cancer, X-rays, CT scans
exposure pathway for a distance of 10-16 km from the plant.
Hong Kong has established an Emergency Planning Zone 1
(EPZ1) of 20km radius from the plant for plume exposure
pathway countermeasures. Only Ping Chau falls within EPZ1.
Still, Hong Kong people should get prepared and follow
instructions when an emergency occurs. For more information
please visit the contingency plan’s website: www.dbcp.gov.hk.
Health
impacts
Q9. Is there a cumulative effect?
A: Yes, cumulative effects are observed for
high exposure received over a period
—some people have been accidentally exposed to radiation
sources (such as those used in radiotherapy) and the
damage done depends on how long the exposure lasted.
For low level exposures, it is agreed that there is a
cumulative effect that builds up over time, increasing the
risk of cancer, and the protection/control measures should
take this into account.
Q10. Is there a health difference amongst radiation from
a CT scan, a cell phone, and background radiation?
A: Radiation from a mobile phone consists of non-ionizing
radio waves, while radiation from a CT scan and background
radiation are ionizing. Thus the health effects from different
sources can be very different. Ionizing radiation can also
exert different health impacts. E.g., naturally occurring radon
is an inhaled gas that irradiates the lungs from inside the
body, which is rather different from cosmic radiation
received in a plane that will affect people from outside.
Q11. Are there different health effects based on different
pathways through which we are exposed to radiation (e.g.
through the skin, inhalation)?
A: Yes. It depends on the radiation emitted by the
radioactive materials and the physiological properties of the
affected tissues. E.g., radon emits alpha particles that
cannot penetrate the layer of dead skin cells on the surface
of your body. Therefore, radon has limited health effects on
skin but it can cause lung cancer by inhalation. On the other
hand, tritium (a radioactive form of hydrogen that is
produced in the upper atmosphere by cosmic rays) emits
beta particles which can be absorbed through skin in
addition to being inhaled or ingested.
Q12. Is the health impact larger on vulnerable populations, such as babies and the young?
A: Yes. Foetuses (in pregnant women), babies and the young
are considered to have higher risk in their life-time because
after the exposure to radiation, they have a longer time
period for the probabilistic occurrence of cancer. Moreover,
their cell division rate is higher than that of adults and the
old.
Q13. Should we stock up and use iodine to counter
radiation effect?
A: Stable (non-radioactive) iodine preparations will only be
useful under particular circumstances. When radioactive
iodine is released (such as during a nuclear accident), the main
radioisotope (iodine-131) only lives for a short time, so stable
iodine will only be effective if taken at a specific time. In any
case, iodine should only be taken if instructions are given to do
so in particular quantities, since it could be harmful otherwise.