Washington, DC -- Occasional airline travel by pregnant women generally poses little risk of radiation exposure to developing fetuses, but pregnant pilots, flight attendants, air marshals, couriers, and frequent business travelers can receive radiation exposures that exceed current recommendations if they do not modify their work schedules, according to a current commentary in Obstetrics & Gynecology.
In the US, the National Council on Radiation Protection and Measurements recommends a maximum annual exposure limit of 1 millasievert (mSv) for members of the public, as does the International Commission on Radiological Protection. For pregnant women, the maximum exposure limit is 1 mSv over a 40-week pregnancy. In Europe the 1 mSv guideline is the law, but it is only advisory in the US. While the exact threshold isn't certain, radiation exposure to the fetus may increase the risk of developing cancer, such as leukemia, during childhood.
At airline altitudes, cosmic radiation levels are greater than at sea level because the earth's atmosphere absorbs much of the radiation before it reaches the ground. The magnitude of in-flight exposure depends strongly on altitude. For instance, the radiation dose received on a short, low-altitude flight between two US states would be far lower than a long, inter- or intra-continental flight at high altitude. A round-trip flight between New York and Tokyo would amount to 15% of the maximum exposure allowed (1mSv), whereas a round-trip flight from New York to Seattle would deliver 6% of the limit.
According to the commentary, physicians can assure pregnant women who are concerned about radiation risks during flight that during casual travel under normal solar conditions the radiation risk to the fetus is negligible. However, there is an irregular space-weather phenomenon called a solar-particle event. These are infrequent and usually short-lived, but they can significantly change the radiation dose while in flight to levels that can easily surpass the 1 mSv exposure limit, even for a single trip. The US Federal Aviation Administration (FAA) and the Space Environment Center have recently introduced an alert system that sends airlines a warning at the start of a significant solar-particle event. The alert is specifically intended to limit the radiation dose received by pregnant women who are already in the air by redirecting the aircraft to a safer altitude.
Pregnant women also can check the website of the Space Environment Center of National Oceanic and Atmospheric Administration (http://www.sec.noaa.gov/rt_plots/pro_3d.html) immediately before their flight departure to see if there is a solar-particle event warning. If so, they should consider a brief postponement of their trip until the peak-dose period has passed.
Pregnant pilots, flight attendants, air marshals, couriers, and business travelers should be more cautious about tracking their radiation exposure due to their increased exposure. These women may calculate their radiation dose on a trip-by-trip basis using software available from the FAA and accessible on the Internet (http://jag.cami.jccbi.gov/cariprofile.asp).
