Radiation is everywhere
We live in a sea of radiation…
Cosmic
Inhaled Radon
RocksRadioactive Elements
PlantsBodies
DNA RepairBasic mechanism living cells
Enormous intensity10 per second per cell10 x 50.1012
500 billion/second
500.000.000.000.000
Incomplete or erroneous repair of DNA damage
misrepair
leads to mutations
→ defects/diseases
→ evolution / life
→ cancer
Doses
1Sv = 100rem
1mSv = 0.1 rem100 mrem
10 mSv = 1 rem(1000 mrem)
100 mSv = 10 rem/rad
1000 mSv = 1Sv,1Gy100 rem/rad
General population: 1 mSv / year
Professional exposure: 20 mSv / year
Permitted annual additional doseabove background
SOURCES OF BACKGROUND RADIATION IN BELGIUM
Isotopes in bodyThoronRadonNuclear energyMedicalCosmicEarth/Buildings
Total average dose in Belgium: 4.3 mSv / year
Ref RUG
Regions with high / very highbackground
2 - 4 mSv/y France (Massif Central)6 - 7 mSv/y Finland-Sweden
>30 mSv:Ramsar, Iran: 260 mSvKerala, India: 35 mSvGuarapari, Brasil 35 mSv
High mountains 0.6 – 6 mSv/year
Transcontinental flights
0.1 mSv America0.25 mSv Australia
Smoke (one pack/day)
20 to 80 mSv per year
Doses diagnosticsRadiology
Thorax 0.02 tot 0.1 mSvBarium investigation 3 à 10 mSvCT brain 2 mSvCT abdomen/thorax 10 mSv
ref. fda.gov
Doses thyroidDiagnosis
Thyroid gland: Iodine 123: 100 mSvIodine 131: 1000 mSv
Total body (I131) 4 to 10 mSvTherapy
- Hyperthyroidism(usually 10 mCi) thyroid gland: 5 à 15… Sv
total body 20 to 100… mSv
- Cancer (per dose of 100 mCi) thyroid gland/tissue : 50 à 150… Svtotal body 400 to 1500… mSv
(high doses may disappear slower per unit of dose)
EffectsAcute exposure >>> effective than chronicalPart of body ≠ total body irradiation
Part of body (radiotherapy)20-100 Gy (20 000 to 100 000 mSv)
Total body irradiation (TBI)in therapy (with bone marrowtransplantation)
8 to 10 Gy ( 8000 – 10 000 mSv)
Acute effects TBIClinical / hematological
– Under 250 mSv nihil
– 250 – 1000 mSv decrease white blood cells
– 1000 – 2000 mSv strong decrease blood elements
– 2000 – 5000 mSv death by marrow depression
– Above 6000 mSv death by gut mucosa necrosis
– Above 10 000 mSv no recuperation possible
“Deterministic” effects
- in all irradiated subjects- skin, mucosae, organs
bone marrow …- from treshold dose 250 mSv- severity depends on organ/dose
A) results acute (deterministic) reactions
B) “stochastic” ( random/probabilistic effects) cancer / genetic abnormalities
- all or-nothing effects
- probability increases with dose(not severity)
- very low dose possibly harmfull
Chronic, late effects
STOCHASTIC EFFECTSWell known above 100 to 200 mSv
Increase of already high incidences:only statistically evaluable
• Cancer (data Japan, accidents, after radiology/therapy …)
spontaneous incidence 33 to 50 %
• Congenital defects (dataJapan, …)
spontaneous incidence 3 % defects at birth8 to 10% genetic defects
Under 100 mSvvery controversial
Legal maxima in Belgium1 mSv population/pregnants
20 mSv professionally exposed
Why so strict?
Under 100 mSv
LNT (Linear no treshold)
vs.
Treshold hormesis?
Heavy debate
Ref.illusration: web Berkeley Nuc science:lbl.gov
Extrapolation
Working hypothesis ICRP (International Commission for Radiation Protection)
“every doseis potentially harmful”
illustration:ref uic.com
.01 .05 .1 101.0 4.0 100
The “Gold Standard” --A-bomb Survivors
5-10% Cancer Risk
Low Dose Extrapolations
Dose (Sv)(from Hall)DOE Low Dose Program
• Epidemiological models use human population exposures and outcomes
• Models confirmed to an extent by animal research
• Molecular and cellular data are not fully utilized
Radiation protection standards are currently based on human exposure data
(LNT: a testable hypothesis)
Effects according to extrapolation model(“linear” scenario- ref ICRP)
On cancer incidence: 0.6 % per 100 mSv
1 in 17 000/mSv, or “8501 i.s.8500…”
On congenital defects: not under 100 mSv
above 100-200 mSv
probability x 2 per 1000 mSv
Guidelines pregnant womenICRP
• Under 100 mSvno action
• 100-200 mSvgrey zone
• Above 200 mSvindividual counseling
Controversial dataEpidemiologic
Cancer incidence not increased in regionswith high background
Cancer incidence lowerlow dose irradiated persons Japanin “mountain states” U S
Effects low dose ControversyEpidemiologic data
Cancer incidence not increased in regionswith high background
Cancer incidence lowerlow dose irradiated persons Japanin “mountain states” VSirradiated persons in Taiwan/Ural
Longer life/lower mortality in low doseirradiated (Japan)
Effects low dose-controversialExperimental- cell biology
“Unorthodox data”Adaptive response
low dose induced
Adaptive Response
0102030405060708090
0 0.5 150 0.5 + 150
ObservedExpected
Shadley and Wolff 1987
Abe
rrat
ions
Dose cGy
Intervention
Effects low dose-controversialExperimental- cell biology
“Unorthodox data”Adaptive response
low dose inducedBystander effect
other than hit cells show- mutation- genome instability- cell death
“Cancer is a problem of cell interaction”
Effects low doseRole Tissue
- more efficiënt DNA-repair
- apoptosis harmed cells
- inhibition stable mutants
Effects of doses up to 100 mSv on top of background are
- too small to be demonstrated bystatistical methods (LNT)
or
- not existent up to a treshold(T)
Maurice Tubiana
…prevailing assumption … any dose… possibility of risk …
… there is no scientific evidence of risk at doses below about 50 millisieverts in a short time or about 100 millisieverts per year.
At lower doses and dose rates, up to at least 10 millisieverts per year, the evidence suggeststhat beneficial effects are as likely as adverse ones.
Eric Hall
Discussion on effects low doses
Enormous financial and economicalconsequences
Radioprotection is a science in crisis
Media “awareness”
1974-1978 New York Times
50 items on industrial accidents
12 000 deaths (240 /item)
200 items on nuclear incidents
0 deaths
Chernobyl
Doses : - at start: workers on reactor order of Sv, up to 2028 deaths acute, 19 later
- later on reactor: thousands of workersdoses a few hundreds of mSv
- contaminated region: 10 tot 50 mSv
Thyroid doses up to 50 Gy by drinking of contaminatedmilk
4000 cases of cancer, children and adolescents; 16deaths
Influence on other cancers: unknown, probablyimpossible to distinguish
LNT is a safety norm, not a prediction method
Risk of dying 1 per million/year
- 90 km driving- 2500 km train- 4000 km flying- 3 hrs work on fishing boat- 1.5 hrs skiing- 6 min canoeing- 1.5 cigarette- 2 days New York (air)- 33 hrs at home
or once 1 mSv