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  • Section 7 Radiation Effects on the Developing Embryo and Fetus Answers and Feedback

  • Section 7 Radiation Effects on the Developing Embryo and Fetus Answers and Feedback 

    1. ANSWER: A
    FEEDBACK: The risk estimate for the hereditary effects of radiation, based on a doubling dose of 1 Gy, plus an allowance for multifactorial diseases, is estimated by the ICRP to be 0.2%/Sv. (For x-rays, sieverts and grays are interchangeable units, since the radiation weighting factor for x-rays is unity.) The risk for a hereditary effect from an exposure of 0.1 Gy is therefore 0.2/100 × 0.1 = 2 × 10–4, a risk of 2 in 10,000. The correct option is A, less than 1 in 1,000. 

    2. ANSWER: A-FALSE, B-FALSE, C-TRUE, D-TRUE
    FEEDBACK: Radiation-induced abortions after a 2-Gy exposure are very likely during weeks 0–2 of gestation, but are unlikely during weeks 8–15. Option A is False. During weeks 0–2, radiation-induced abortions are likely, but congenital abnormalities are unlikely to occur until weeks 2–6. Option B is False. Although not high, the risk of mental retardation may occur during weeks 15 –25 (a risk level of about 10%/Sv). Option C is True. The risk of mental retardation is as much as 40%/Sv during weeks 8–15. During the period of organogenesis (2–6 weeks of gestation), congenital abnormalities are likely after a dose of 2 Gy. Option D is True. 

    3. ANSWER: 1-B, 2-A, 3-C
    FEEDBACK: Animal experiments indicate that exposure to radiation during organogenesis leads to a wide spectrum of malformations. B matches with 1. During pre-implantation, radiation appears to have an all-or-nothing effect; either the newly fertilized egg is killed, or it develops normally. Growth retardation and malformations do not result from irradiation at this time. A matches with 2. There is an increased risk of cancer due to exposure in utero. C matches with 3. 

    4. ANSWER: A-FALSE, B-FALSE, C-TRUE, D-TRUE, E-FALSE
    FEEDBACK: An accident situation in which injuries are possible justifies the small risks associated with diagnostic x rays. Option A is False. A therapeutic abortion would not be justified. Option B is False. On the basis of the Japanese survivors’ data, 8–15 weeks is the sensitive period for reduced head diameter and mental retardation. The doses are not large enough for this to be very likely, but if a radiation-induced defect occurred, it would involve the central nervous system. Option C is True. On the basis of the case-control studies of Stewart et al, even a few radiographs during pregnancy increase the risk of leukemia and childhood cancer. Option D is True. The dose to the fetus would be considerably less than 0.1 Gy. Option E is False. 

    5. ANSWER: A-FALSE, B-FALSE, C-TRUE, D-TRUE
    FEEDBACK: Intrauterine death occurs as a result of irradiation during pre-implantation (0–10 days), and neonatal death (i.e., death at or about the time of birth) occurs because of irradiation during organogenesis (10 days to 6 weeks). Irradiation at 18 weeks is too late for either of these. Options A and B are False. The data from persons exposed in utero at Hiroshima and Nagasaki show that irradiation to a sufficient dose may produce microcephaly (reduced head diameter) and mental retardation. The most sensitive time interval for these effects was 8–15 weeks. There was a less sensitive interval at 15 –25 weeks. Option C is True. The case-control studies of Stewart et al showed that even a few obstetric radiographs could lead to an elevation of risk of leukemia and childhood cancer. Option D is True. 

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Discounted Dues: Eligible North American Countries 
Belize
Costa Rica
Dominican Republic
El Salvador
Grenada
Guatamala
Haiti
Honduras
Jamaica
Netherlands Antilles
Nicaragua
Panama
St.Lucia
St. Vincent & Grenadines
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Albania   Guatemala   Papua New Guinea
Algeria   Guinea   Paraguay
Angola   Guinea-Bissau   Peru
Armenia   Guyana   Phillippines
Azerbaijan   Haiti   Rwanda
Bangladesh   Honduras   Samoa
Belarus   India   Sao Tome & Principe
Belize   Indonesia   Senegal
Benin   Iran   Serbia
Bhutan   Iraq   Sierra Leone
Bolivia   Jordan   Solomon Islands
Bosnia & Herzegovina   Jamaica   Somalia
Botswana   Kenya   South Africa
Bulgaria   Kiribati   South Sudan
Burkina Faso   Korea, Dem Rep (North)   Sri Lanka
Burundi   Kosovo   St Lucia
Cambodia   Kyrgyzstan   St Vincent & Grenadines
Cameroon   Laos\Lao PDR   Sudan
Cape Verde   Lesotho   Swaziland
Central African Republic   Liberia   Syria
Chad   Macedonia   Tajikistan
China   Madagascar   Tanzania
Colombia   Malawi   Thailand
Comoros   Maldives   Timor-Leste
Congo, Dem. Rep.   Mali   Togo
Congo, Republic of   Marshall Islands   Tonga
Cote d'Ivoire   Mauritania   Tunisia
Djibouti   Micronesia, Fed. Sts.   Turkmenistan
Dominica   Moldova   Tuvalu
Domicican Republic   Mongolia   Uganda
Ecuador   Montenegro   Ukraine
Egypt   Morocco   Uzbekistan
El Salvador   Mozambique   Vanuatu
Eritrea   Myanmar   Vietnam
Ethiopia   Namibia   West Bank & Gaza
Fiji   Nepal   Yemen
Gambia, The   Nicaragua   Zambia
Georgia   Niger   Zimbabwe
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