Report Urges Action on Ionizing Radiation Exposures in Commercial Aviation
A report published in June by the National Academies of Sciences, Engineering, and Medicine on ionizing radiation exposure in commercial aviation urges the Federal Aviation Administration (FAA) to require airlines to implement radiation safety programs for flight crew members and “improve the accessibility and usability of existing dose-estimation tools.” According to the report, flight crews are regularly exposed to naturally occurring ionizing radiation but lack regulatory protections like those that cover workers exposed to radiation in other industries. While the radiation dose that pilots, cockpit crew, flight attendants, and cabin crew receive per commercial flight is “relatively small,” these workers may “accumulate significant dose with no centralized record or cap” over the course of their careers, the report states. So far, studies of flight crews have been inconclusive as to whether their occupational radiation exposure is associated with adverse health effects. However, the National Academies report stresses that ionizing radiation “is known to cause certain cancers and other adverse health outcomes.”
Variables such as flight altitude, latitude, duration, and solar activity can affect radiation dose. Flight crews are exposed to ionizing radiation from both solar and cosmic sources. The report describes two sources of cosmic radiation: galactic cosmic radiation, which is continuously present, and rare solar energetic particle events, which are associated with solar storms. These events can temporarily increase radiation exposure during certain flights but are “unlikely to affect total career dose relative to [galactic cosmic radiation] substantially,” the report explains. FAA has no regulatory limits, but the agency recommends internationally accepted occupational limits for ionizing radiation exposure, including the International Commission on Radiological Protection’s (ICRP’s) five-year-averaged dose limit of 20 millisieverts per year.
However, occupational dose limits are more conservative for pregnant workers, who the report notes are among the most likely to potentially exceed these limits. ICRP’s current guidance, which FAA recommends, states that pregnant flight crew members should limit exposure to 1 millisievert for the duration of the pregnancy. The National Academies report stresses that solar energetic particle events “approach dose levels of concern for pregnant flight crew.”
“If a pregnant worker is caught in a solar storm, the conceptus could receive a dose on the order of several hundreds of [microsieverts] in a single flight,” the report explains.
Flight crew members currently must track their own exposure to ionizing radiation. The report describes the tools available for determining radiation exposure as “difficult to use” and notes that flight crews lack training “to track the accumulating radiation doses received during their careers.” FAA has an effective tool for estimating radiation dose from galactic cosmic radiation during flight called the CARI7 model, the report states, but it is impractical for individuals use. Aspects of the model that make it less accessible include the need to download and install software, review technical documentation, and manually enter parameters like route, altitude, and timing of flights.
“Interpreting model outputs and converting them into cumulative exposure estimates requires familiarity with radiation dose concepts,” the report says. “In addition, individuals must independently maintain records over time if they wish to track cumulative exposure.”
The report recommends that FAA improve the usability of the CARI7 model to allow flight crews to track individual dose until a more comprehensive dose-tracking system is developed. It stresses that individuals should not remain responsible for tracking their radiation dose in the long term but encourages FAA to increase accessibility to dose estimation for flight crews in the near term by developing a user-friendly, web-based application for this purpose.
The report mentions NIOSH as an agency FAA should work with to establish a dose-tracking system to allow both airlines and individual flight crew members to monitor and make decisions to manage radiation doses. The authors of the report envision that this dose-tracking system “would also facilitate epidemiologic research by providing standardized dose information for study participants” and “would support assessment of the population health of flight crew.”
The report, “Assessing Radiation Exposure, Health Outcomes, and Mitigation Strategies for Flight Crewmembers,” was congressionally mandated and sponsored by the U.S. Department of Transportation. It can be accessed via the National Academies website.