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Ernest Rutherford: 1898-99 Ernest Rutherford 1898-99

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Ernest Rutherford: 1898-99 Ernest Rutherford 1898-99 November 1895: Roentgen discovers x rays February 1896: Becquerel discovers radioactivity Ernest Rutherford: 1898-99 Ernest Rutherford 1898-99 1 The Electromagnetic Spectrum Interaction of Charged Particles with Matter: Interaction of x or γ rays (photons) with matter Ionization Relevant Quantities & Units How does ionizing radiation damage DNA? – for Individuals UNITS QUANTITY DEFINITION New Old Absorbed Dose Energy per unit mass Gray (Gy) rad Equivalent Dose Average dose X radiation Sievert (Sv) rem weighting factor Effective Dose Sum of equivalent doses to Sievert rem organs and tissues exposed, each multiplied by the appro- priate tissue weighting factor Committed Equivalent dose integrated Sievert rem Equivalent Dose over 50 years (relevant to incorporated radionuclides) Committed Effective dose integrated Sievert rem Effective Dose over 50 years (relevant to incorporated radionuclides) 2 Principal Hazards of The Carcinogenic Effects Ionizing Radiation of Radiation ( Genetic effects ( Carcinogenic effects ( Effects on the developing embryo/fetus Radiation and Cancer Radiation and Cancer ( Ionizing radiation does cause How does radiation cancer cause cancer? ( Parts of the mechanisms are understood ( The full picture is still very unclear Chromosomal Deletions Radiation and Cancer Ionizing radiation is quite efficient at inducing chromosomal aberrations such as deletions and translocations 3 Chromosomal Translocations Links between chromosomal aberrations and cancer Loss of tumor Deletion suppressor gene Translocation Activation of an or oncogene or creation Inversion of fusion gene Radiation and Cancer: Radiation and Cancer Sources of Information What do we know ( Extrapolation from animal quantitatively about the data risks of radiation-induced cancer in humans? ( Relevant human cohorts ( Mechanistic information Radiation and Cancer: Radiation and Cancer Are animal data useful? ( Useful for indicating relative What are the problems in patterns (dose, dose rate, estimating the risks of radiation quality) radiation-induced cancer in ( Not useful for assessing humans? absolute risk 4 Problems estimating cancer risks Problems estimating cancer risks 9 Dose reconstruction 9 Statistics Many! 9 Controls 9 Latency Problems estimating cancer risks The BIG caveat 9 Dose extrapolation Radiation risk estimates at 9 Dose rate extrapolation low doses are based on plausible assumptions, but are 9 Age and time dependencies estimates nevertheless. 9 Transfer models They are not, and can never 9 Neutrons at Hiroshima be, direct measurements! Radiation and Cancer: Radiation and Cancer Relevant Human Cohorts Emerging Human Cohorts 9 A bomb survivors 9 Chernobyl 9 TB patients (multiple fluoroscopies) 9 Mayak 9 Tinea Capitis children 9 Airline personnel 9 Ankylosing Spondylitics 9 RT patients 5 Radiation and Cancer: Radiation and Cancer A-bomb survivors Most of our information ( 87,000 survivors followed comes from studies of ( 7,800 cancer deaths observed A-bomb survivors ( 7,400 expected ( Therefore 400 excess cancers Extrapolating from High to Low Doses A Linear Extrapolation from High to Low Doses? ( At low doses the Japanese dose- response relations are consistent with a linear relation between dose and cancer risk. ( Although controversial, a linear model (implying no low-dose threshold for risk) is most likely valid. Solid Cancers – A-Bomb Survivors Radiation and Cancer Can low-dose risks be estimated directly from groups exposed to low doses of radiation? Recent study of 120,000 nuclear workers exposed to ~40 mSv consistent both with: • Zero risk • A risk appropriately extrapolated from A-bomb s u r v i v o r d a t a . Pierce et al 96 6 Estimated excess fatal cancers (ICRP) % / Sv The Nuclear High Dose / Low Dose / Worker Study High Dose Rate Low Dose Rate General population 10% 5% Cardis et al 1995 Working population 8% 4% Lifetime cancer mortality risk Distribution of uncertainties in as a function of age at exposure radiation risk Radiation and Cancer Non-Cancer Radiation Risks Individual Susceptibility to Radiation Carcinogenesis … are not quantified as well as the cancer risks ATM: Ataxia Telangiectasia 7 Radiation Risks Gene Mutations Single Dominant 9 Polydactyly Teratogenic risks 9 Huntindon’s chorea 9 Retinoblastoma Order of magnitude larger than Recessive 9 Sickle-cell anemia Carcinogenic risks 9 Tay-Sachs disease 9 Cystic fibrosis Order of magnitude larger than Sex-linked 9 Color blindness Hereditary risks 9 Hemophilia Radiation-Induced Mutations Radiation does not produce new, unique mutations, but simply increases the incidence of the same mutations that occur spontaneously We are heavily reliant on animal Heritable Effects data for hereditary risk estimates Children of the survivors of the A-bomb attacks have been studied for: ( Untoward pregnancy outcomes ( Death of live-born children ( Sex chromosome abnormalities ( Electrophoretic variants of blood proteins But no statistically significant effects have been observed 8 IN UTERO EFFECTS Hereditary Effects - ICRP OF RADIATION Probability / caput of severe hereditary disorder (working population) 0.6% / Sv Teratogenic Risks The principle effects of radiation on the (i.e., to the embryo/fetus, if relevant) developing embryo and fetus are: ( Growth retardation Moderate doses of radiation can ( produce catastrophic effects on Embryonic, neonatal, or fetal death the developing embryo and fetus. ( Congenital malformations and functional impairment, such as mental retardation. A-bomb survivors irradiated in-utero, with microcephaly Factors Influencing Probability of Teratogenic Effects 9 Dose to embryo/fetus 9 Stage of gestation at time of exposure 9 Microcephaly at Hiroshima Dose Incidence of microcephaly for exposure (rad) during 6 to 11 weeks gestation period 0 4% 31/764 1-9 11% 2/19 10-19 17% 4/24 20-29 30% 3/10 30-39 40% 4/10 50-99 70% 7/10 100 100% 7/7 In utero exposure & mental retardation Radiation Risks Severe mental retardation, after in-utero exposure Teratogenic risks (8-15 weeks gestation period) order of magnitude larger than Carcinogenic risks Risk: 40% / Sv order of magnitude larger than Hereditary risks Typical sources of exposure to Stanley Watras at the ionizing radiation Limerick nuclear power plant, 1984 10 Stanley Watras and family, Number of articles about Boyertown, PA, 1985 radon in the New York Times The uranium-238 decay chain The Reading Prong: A granite formation Radon, polonium and basal cells in the lung Radon: From Rocks to Lungs 11 Radon risks are estimated by Estimated lung cancer risks from studying uranium miners lifetime exposure to radon Percent risk Percent risk of lung cancer of lung cancer in smokers in non smokers 1 pCi/l 0.7% 0.05% 4 pCi/l 3% 0.2% 20 pCi/l 14% 1% Testing houses for high radon Estimated lung cancer deaths per year in the US due to radon levels In the range 15,000 to 22,000 (~1 in 8 of all lung cancer deaths) About 85% of these deaths are attributable to radon + smoking Radon remediation: 1-800-SOS RADON Sub-slab ventilation 12.
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