![]() Greatest probability of malformation in a specific organ system (critical period) exists when the radiation exposure is received during the period of peak differentiation of that system May occur if the embryo irradiated during organogenesis (3rd-8th week), especially at 20-40 days Poses little risk of congenital malformations, but CNS abnormalities (reduced intelligence quotient (IQ) is the main risk at 8-25 weeks) 2, growth retardation and risk of childhood cancer (main risk after 25 weeks) can be significant Growth retardation can also occur if irradiated >4 weeks gestationĭeterministic effect with a probable threshold of >100 mSvīegins after the end of organogenesis (>8 weeks) and continues until term Risk of fetal death decreases substantially, whereas the risk of congenital malformation coincides with the peak developmental periods of various organ systems either intrauterine death and resorption (usually undetected) or normal fetal risk Pre-conception radiation of either parents' gonads has not been shown to result in an increased risk of malformations or cancer in children ![]() The risks are most significant during organogenesis and the early fetal stage. Radiation risks to the fetus are dependent on the developmental period the embryo/fetus is at upon exposure. Radiation effects related to the stage of development ![]() Stage of development at the time of exposure Total dose, dose rate and radiation quality The response after exposure to ionizing radiation depends on: Additionally, as with ionizing radiation exposure in children compared to adults the potential time available for stochastic effects to manifest is typically greater. Guarapari, BrazilĮffects on embryonic and fetal developmentĭue to rapid cell proliferation, migration and differentiation, the developing embryo is extremely radiosensitive. Populations with high natural background exposures, e.g. Patients who received significant diagnostic exposures: multiple fluoroscopies for tuberculosis (Massachusetts, USA and Nova Scotia, Canada), prenatal diagnostic x-rays ankylosing spondylitis (UK), acute post-partum mastitis, hyperthyroidism, cancer treatment Patients who received radiation treatment for neoplastic and non-neoplastic conditions, e.g. ![]() Marshall Islanders who inhaled/ingested iodine-131 following US nuclear weapon testing Other data on carcinogenic effects of ionizing radiation exposure: The Life Span Cohort Study is ongoing and continues to publish updates that can better inform our understanding about long term risks of radiation exposure. This has faced criticism in some of the interpretations of the literature 5, which suggest a non-linear dose-response relationship, and there is some evidence of a potential protective effect at very low doses 6,7. The BEIR report supports the linear no-threshold model, which extrapolates directly observable effects of exposure at higher ionizing radiation doses, to suggest that all radiation exposure is harmful. Although several updates have been issued in light of further research and continued cohort follow-up, these studies initially estimated lifetime cancer risk by considering accumulated data to 1985 and making projections to lifetime risk by a multiplicative model for high dose and dose rate exposure. Radiation effects related to the stage of developmentĭata on the effects of ionizing radiation on humans is predominately from studies (Life Span Cohort Study) of Japanese survivors of the 1945 atomic bomb blasts and their assessments by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) 3,8 and National Academy of Sciences Biologic Effects of Ionizing Radiation (BEIR) 4.Effects on embryonic and fetal development.Alpha particles, however, are the most damaging if their source is inside the body because internal tissues absorb all of their energy. (CC BY-SA-NC anonymous)īecause of their great penetrating ability, γ rays are by far the most dangerous type of radiation when they come from a source outside the body. Gamma rays, which have no charge, are stopped by only very dense materials and can pass right through the human body without being absorbed. In contrast, β particles do not interact as strongly with matter and penetrate more deeply. Because α particles interact strongly with matter, they do not penetrate deeply into the human body. The depth of penetration of alpha, beta, and gamma radiation varies with the particle. \): Depth of Penetration of Ionizing Radiation.
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