Are children more at risk from LDR?
It has been generally accepted by the medical community that children are more susceptible to radiation-induced cancers than adults. This is based on the increased risk of cancers reported in atomic bomb survivors who were exposed to radiation at a younger age, e.g. as indicated in the graph below:
However, please note that the excess cancers observed were for children who received high radiation doses, and only by LNT extrapolation these curves can be used for low-dose radiation. Considering the vast amount of evidence against the LNT model, the use of the above graph for low doses is not justifiable.
Another reason usually given for the higher radiosensitivity of children is that they have a higher proportion of dividing cells which are more susceptible to mutations due to radiation. This argument ignores adaptive protection. Low-dose radiation adaptive protection reduces overall mutations and enhances the immune system (see Figures below) and so would reduce cancers.
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The reduction of cancers following low-dose radiation exposure to children has been observed in the incidence of second cancers in childhood cancer survivors who have undergone radiation therapy to the primary tumor. When high dose radiation is given to the primary tumor site, other parts of the body receive lower radiation doses. In a study by Tubiana et al., the authors compared the incidence of second cancers per kg of tissue in such patients as a function of radiation dose to the tissue. What they found was that the parts of the body that received low radiation doses (~20 cGy) had lower incidence of second cancers per kg of tissue than the parts of the body that received no radiation dose (see Figure below), demonstrating that radiation hormesis is effective for children also.
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Thus, there should be no concerns at all regarding low-dose radiation exposures such as CT scans for children.
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