Answer to Question #11887 Submitted to "Ask the Experts"

Category: Pregnancy and Radiation — Flying

The following question was answered by an expert in the appropriate field:


Could the cosmic ray exposure detailed below have had any effect on the brain of my unborn child?

Home country: United States

Exposure: Cosmic rays while flying one-way, trans-Pacific, from Dallas to New Zealand. Three flight segments on the trip: 3 hours + 13 hours + 1 hour. The online calculator I used gave a total value of 57.6 microsieverts (µSv).

History: Two children, both normal.

Pregnancy stage: Second trimester.

Could this trip in any way have affected the fetus' IQ or rate of brain development? I read that during certain weeks, the fetus' brain is especially sensitive to radiation. What if the trip was during those weeks? Note that this trip happened a long time ago, and I don't remember which week of my pregnancy it was.


A radiation dose of 57.6 µSv is well below the radiation dose level known to cause brain development effects. In fact for comparison, during the nine months of gestation, the baby receives about 2,300 µSv of radiation dose from natural background radiation sources alone. The radiation dose limit in the United States for a person who is exposed occupationally to radiation is 5,000 µSv (in addition to natural background radiation dose).

As reported in scientific literature, the radiation exposure that could cause possible developmental effects on the brain would occur from 8 to 15 weeks of embryonic age at radiation doses above 200,000 µSv. This is orders of magnitude above the dose your baby received from the flight.

In summary, radiation doses received while flying are well below the radiation doses reported in literature that would cause a deleterious effect.

Kelly Classic
Certified Medical Health Physicist

Hall EJ, Giaccia AJ. Radiobiology for the radiologist. 6th ed. New York: Lippincott Williams & Wilkins; 2006.

Ask the Experts is posting answers using only SI (the International System of Units) in accordance with international practice. To convert these to traditional units we have prepared a conversion table. You can also view a diagram to help put the radiation information presented in this question and answer in perspective. Explanations of radiation terms can be found here.
Answer posted on 3 March 2017. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.