All data used by US EPA and foreign agencies determining acceptable and "safe levels" of radiation are based upon the size and weight of a grown man.  Although the US EPA has known for years and recently recognized that children are more vulnerable to hazaradous and toxic substances, the EPA has not issued a separate determination of "safe" levels for children. 

"Thyroid cancer for sure. Leukemia, probably. Too much radiation can raise the risk of developing cancer years down the road, scientists agree, and the young are most vulnerable.

Children are the ones at risk for radiation's most obviously related cancer - thyroid. Radioactive iodine collects in the thyroid gland in the neck. Potassium iodide pills can block its absorption and minimize harm, but they must be given within 12 hours of exposure to do much good."