Radiologic or Nuclear Event

Potential health effects of prenatal radiation exposure:²⁹ Exposures at less than 5 rads appear to be safe for the developing fetus. About 5% of the energy from a nuclear explosion is released as radiation. The prompt radiation from a Hiroshima-sized explosion would expose people within about 1.3 miles (2 km) of ground zero to a 500-rad dose of radiation. For 2 days after such an explosion at ground level, anyone within about 1.7 miles (2.75 km) of ground zero could be exposed to a 500-rad radiation dose from fallout.

Before about 2 weeks’ gestation (i.e., the time after conception): The health effect of concern from an exposure of more than 10 rads is the death of the embryo. If the embryo survives, however, radiation-induced noncancer health effects are unlikely, no matter what the radiation dose. In all stages of gestation: Radiation-induced noncancer health effects are not detectable for fetal doses below about 5 rads. From about 16 weeks’ gestation to birth: Radiation-induced noncancer health effects are unlikely below about 50 rads.

Potassium iodide (KI)30: After a ra­diologic or nuclear event, local public health or emergency management officials will tell the public if KI or other protective actions are needed.

Infants (including breastfed infants): Infants need to be given the recommended dosage of KI for babies. The amount of KI that gets into breast milk is not enough to protect breastfed infants from exposure to radioactive iodine. The proper dose of KI given to a nursing infant will help protect it from radioactive iodine that it breathes in or drinks in breast milk.

Pregnant women: Because all forms of iodine cross the placenta, pregnant women should take KI to protect the growing fetus. However, pregnant women should take only one dose of KI following internal contamination with (or likely internal contamination with) radioactive iodine.

Breastfeeding Women: Should take only one dose of KI if they have been internally contaminated with (or are likely to be internally contaminated with) radioactive iodine. Because radioactive iodine quickly gets into breast milk, the CDC recommends that a woman internally contaminated with (or likely to be internally contaminated with) radioactive iodine stop breastfeeding and feed her child baby formula or other food if it is available. If breast milk is the only food available for an infant, nursing should continue.