Almost all parents at some point during their children’s lives will need to take their child to the hospital for some sort of illness. Whether it is a cough, fever, broken bone, or abdominal pain, a visit to the emergency room or urgent care will include some sort of radiology study and often that radiology study will expose the child to radiation. This brings to light an important question I often get from parents. It usually comes in the form “Will my child get cancer from this xray?””How much radiation is my child being exposed to during this CAT scan?” And these are important questions. Parents have every right to be concerned about their children’s radiation exposure.

Are children more sensitive to radiation than adults?

The short answer is yes.

When given equal radiation doses, the risks for children and adolescents are greater than for adults. Children grow quickly, and their cells are more sensitive to radiation. Since effects of radiation take years to develop, their youth extends the time for any potential effects from ionizing radiation to occur. But, the radiation doses required to obtain pictures of children are much lower than adult levels. Therefore, the risk associated with a diagnostic medical examination for a child need not be greater than that for an adult, and is often much less.

As adults age, radiation exposure becomes less of a concern. The body tissues of older patients are less sensitive to the effects of radiation.

What are children more at risk for than adults when exposed to radiation?

The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) presented a report to the UN General Assembly as part of the Report of the 60th session of UNSCEAR to the General Assembly in 2013 detailing the differences in risks of radiation exposure in children and adults. “Because of their anatomical and physiological differences, radiation exposure has a different impact on children compared with adults,” said Dr. Fred Mettler, Chair of the Expert Group on the UNSCEAR Report on Effects of Radiation Exposure of Children.

The report highlights some important issues. For instance, for a given radiation dose, infants and children are more at risk than adults of developing a variety of tumors. This risk is, generally, not always immediate but extends later into life. In all, the Committee reviewed 23 cancer types in their report, some of which are highly relevant for evaluating the radiological consequences of nuclear accidents and of some medical procedures. Children were found to be more sensitive than adults for the development of about 25 per cent of tumor types including leukemia, and thyroid, brain and breast cancer. The risk can be significantly higher, depending on circumstances. On the other hand, for about 15 per cent of cancer types such as colon, children were found to have the same radiation sensitivity as adults, and for 10 per cent of cancer types, such as those affecting the lungs, children were less sensitive than adults. Data were too weak to reach any conclusions for 20 per cent of cancers such as those affecting the esophagus and there was a weak or non-existent link between exposure and risk at any age for 30 per cent of cancers such as those of the prostate, rectum and uterus or Hodgkin’s disease.

For tissue effects that may occur soon after very high doses, the Committee concluded that as seen with carcinogenesis, there are some instances in which childhood exposure poses a higher risk than adult exposure (e.g. for effects on the brain, and for cataracts and thyroid nodules). There are other instances where the risk appears to be about the same (e.g. neuroendocrine system and on the kidneys) and there are a few instances where children’s tissues are more resistant (lung, marrow and ovaries).

“It is not recommended to use the same generalizations used for adults when considering the risks and effects of radiation exposure during childhood,” said Dr. Mettler. “The specifics of the exposure and situation play a significant role,” he added.

The Report also concluded that no heritable effects in offspring due to radiation exposure of their parents as children themselves had been explicitly identified in humans – including in the offspring of people who survived the atomic bombings as children.

It also pointed out that health effects are also dependent on a number of physical factors. For instance, when it comes to internal exposure to radiation, there are differences in the doses received by children and adults from exposure to the same distribution of radioactive material in the environment. For example, children may receive higher doses from radioiodine in the environment due to higher intake of milk compared to adults.

Similarly, as infants and children have smaller body diameters, and their organs are less shielded by overlying tissues, with the same exposure the doses to their internal organs is higher than that to an adult. In addition, both metabolism and physiology vary with age, which also affects the concentrations of radionuclides in different organs and thus the dose to those organs for a given intake.

Infants and children can also receive significantly higher doses than adults in situations such as medical exposure if the technical settings are not adapted appropriately.

Reference:

Sources, effects, and risks of ionizing radiation. UNSCEAR 2013 Report