Health effects of nuclear accidents– providing facts not fiction
Professor Gerry Thomas

G Thomas

Japan 25/4/13

• Effect of any toxic substance depends on theamount received by the body’s tissues• We have developed very sensitive methods
for detecting radiation• Just because we can measure radiation does
not necessarily mean that it is dangerous• We live in a world that is full of naturalradiation – yet our species thrives. Therefore
we must have developed mechanisms tocope with the biological effects of radiation
G ThomasJapan 25/4/13

Where does our background radiation
come from?

Fallout/nuclear discharges – A-bombs, nuclear accidents
e.g. Chernobyl and Fukushima
G Thomas

Japan 25/4/13

Relative radiation doses
Source of Exposure
Dental X‐ray
135g of Brazil Nuts
Chest X‐ray
Transatlantic flight
Nuclear Power station worker, average annual dose
UK average annual radon dose
CT scan of the head
UK average annual dose
CT scan of the chest
Whole body CT scan
Annual limit for nuclear radiation workers
Level at which increased cancer incidence seen
LD50 (within a month of exposure)Dose
0.005mSv
0.005mSv
0.02mSv
0.07mSv
0.18mSv
1.3mSv
1.4mSv
2.7 mSv
6.6 mSv
10 mSv
20mSv
100mSv
5000mSv

http://www.hpa.org.uk/Topics/Radiation/UnderstandingRadiation/UnderstandingRad
iationTopics/DoseComparisonsForIonisingRadiation/
G Thomas

Japan 25/4/13

Facts about radiation – types of radiation}

particles

waveG Thomas

Japan 25/4/13

• For radiation to cause damage to cells, it
must come into contact with them.
• Mechanism of contact depends on type ofradiation – wave (, X-ray) or particulate ().
• Radiation exposure can come fromoutside of your body () or inside (), if
you breathe in or eat radioactive particles

G Thomas

Japan 25/4/13

Biological effect of radiation
depends on the amount of time
the radioactive isotope stays inthe body (biological half-life)
and the frequency with which
the isotope emits radiation(physical half-life)• Long physical half-life, short biological half-life – littleeffect• Short physical half-life, long biological half-life – big
problem
G Thomas

Japan 25/4/13

Health effects of nuclear accidents– where do we get our facts from?
• Atomic bomb (Hiroshima and Nagasaki)– large population exposed to high doseradiation close to explosion site
– low doses to population further away
– mainly gamma, but some  and • Chernobyl accident– Large dose to small numbers of people– Low dose to majority of population– Mainly  from isotopes of iodine and caesium
G Thomas

Japan 25/4/13

Health effects of the A‐bomb• Many people (120,000) were killed by theheat energy from the A-bombs• Some people received very high doses ofradiation and died of radiation sickness(20,000) within a few weeks• Most people were exposed to smaller
amounts of radiation.
• Radiation has resulted in 5% more
cancers over 70 years• No health effects for many people
G Thomas

Japan 25/4/13

Health effects from Chernobyl• Explosion and fire in reactor number 4• Large amount of 131-I and 137-Cs released• 131-I has a half-life of 8 days and 137-Cs of 30years• 3 people died in the explosion• 28 firemen were exposed to large amounts ofradiation and died of radiation sickness within afew months• 10 million children in Belarus, Ukraine andRussia exposed to radioactive fallout
G Thomas

Japan 25/4/13

Radiation effects on health
Two types of health effects of radiation:•Deterministic – effect is certain under specificconditions e.g. high dose/ARS•Stochastic – may or may not occur. Difficult topredict on an individual level but effects seen at
a population level e.g. cancer after radiation
exposure

G Thomas

Japan 25/4/13

Chernobyl ‐ deterministic•••

134 cases of ARS, 28 fatalities.
19 further deaths up to 2006 –but none thought to berelated to radiation.
Increased incidence of
cataracts in those with highest
doses

14 normal, healthy children born to ARS survivors within
5 years of the accident
www.unscear.org/docs/reports/2008/11‐80076_Report_2008_Annex_D.pdf

G Thomas

Japan 25/4/13

Chernobyl – population radiation doses• Evacuees – thyroid dose 500mGy• Not evacuated but resident in contaminatedareas ‐ thyroid doses 100mGy• Whole body doses to 6M residents = 9mSv– 80% of lifetime dose delivered by 2005• 150,000 people living in most contaminatedareas – 50mSv over 20 years (natural radiation
average 1‐2 mSv per year)
G Thomas

Japan 25/4/13

Chernobyl – health effects• Consequences of exposure to radiation dependon the dose of radiation you are exposed to, andthe type of radiation• 131-I concentrates in the thyroid and is boundthere – short physical half-life, long biologicalhalf-life• Child’s thyroid is small, and drink a lot of milk –higher dose than adults• Child’s thyroid still growing – higher risk ofdamage to cells, increases cancer risk
G Thomas

Japan 25/4/13

Chernobyl – health effects• The only cancer to be increased is thyroid cancer inthose who were young at exposure• Thyroid cancer easy to treat and low death rate(estimated16,000 cancers in 50 years = 160deaths)• Thyroid cancer incidence falls back to normal inthose born after radiation had gone
• Unlikely to see rises in other cancers – 137-Cs
does not concentrate in the body, dose for mostpeople less than one CT scanLong physical half-life, short biological half-lifeG ThomasJapan 25/4/13

Chernobyl 25 years on– 28 from ARS– 15 deaths from thyroid cancer in 25 years– 1% death rate overall predicted for thyroid cancer.
Predicted total death rate thus far approx 60– No (scientific) evidence of increased thyroid cancer
outside 3 republics– No effect on fertility, malformations or infantmortality– No conclusion on adverse pregnancy outcomes or stillbirths– Heritable effects not seen and very unlikely at thesedoses
G Thomas

Japan 25/4/13

Chernobyl vs Fukushima• Move population away from source• Limit inhalation by staying insideand keeping windows and doors
shut• Stop ingestion of contaminatedfoodstuffs• Block uptake of radionuclides (e.g.
stable iodine prophylaxis)
G Thomas

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Japan 25/4/13

Fukushima radiation doses
On site•19,594 workers, 167 received doses of >100 mSv(6 >250mSv)•No ARS, no radiation related deaths
Population at large•150,000 people evacuated, sample of 1700
showed 98% <5mSv, only 10 >10mSv•Mean thyroid dose 4.2mSv in children (3.5 mSvadults) compared with 500mSv in Chernobylevacuees
G Thomas

Japan 25/4/13

Health effects of Fukushima• No radiation related deaths compared with 761
who died as a result of the evacuation, and20,000 in tsunami• Unlikely to be any increase in thyroid cancer atthe doses received• Psychological harm due to evacuation andradiophobia – very likely. Economic effects also
likely to have health effects• Results of health survey must be put into
context for general public
G Thomas

Japan 25/4/13

Thyroid cancer incidence in Japan (2005)
（歳）

90‐99

男

80‐89
637例女2792例70‐7960‐6950‐59
40‐49
30‐3920‐29
10‐19（0）800 700 600 500 400 300 200 100（Japan Thyroid Surgery Asso.2007）
G Thomas（0）

0‐900

PTC

100200 300

FTC400 500 600 700 800

MTCATCCourtesy S Yamashita
Japan 25/4/13

Comparative risks

Smith BMC Pubic Health 2007 7:49
G Thomas

Japan 25/4/13

Comparative risks

NB Radiation doses from nuclear accidents much lower than from A-bomb,
so risk even lower

G Thomas

Japan 25/4/13

What do the general public think?

How many people died as a result of the Chernobyl and Fukushimaaccidents?
All Russia omnibus 24.10.12
G Thomas

Japan 25/4/13

Public communication• Public communication is key• Clear message given by independent scientists• Important to tame sensationalist media• Put risk into context with other common risks
that public expose themselves to• Persuade media to produce factual programmes
based on science aimed at all sections of thepopulation• Communicate sensitively and put facts intocontext
G Thomas

Japan 25/4/13

Take Home Messages• Health consequences of a Nuclear Power plant
accident may not be as bad as we first thought• We must separate fact from fiction to decide ourfuture energy policy• Effects of climate change likely to kill more (est.
150,000 per year) than nuclear accidents• Don’t believe everything you read on the internet
or in the media• Politics gets in the way of good science
G Thomas

Japan 25/4/13