Cosmic Radiation and Frequent Flyers
Abstract & Commentary
Synopsis: There may be a cancer risk associated with exposure of airline crews to cosmic radiation.
Source: Aw JJ. J Travel Med. 2003;10:19-28.
This intriguing article explores the issue of occupational exposure of airline crews and the risk of cancer. Various programs attempt to estimate the radiation equivalence dose of cosmic radiation (the naturally occurring galactic ionizing radiation) on skeletal tissue and bone marrow. While most cosmic radiation comes from outside the solar system, periods of solar flare can also significantly contribute to cosmic radiation by a factor of 100. Cosmic radiation was officially deemed an occupational risk for airline crews in 1991; that year, a landmark decision established recommended limits of 20 mSV units per year for airline crews and 2 mSV units per year for pregnant workers. The general public, it was suggested, should receive no more than 1 mSV unit per year. Current estimates of mean annual exposure are 0.2 to 9.1 mSV for 950 hours of flight time; higher flying crews may be exposed to up to 9 mSV annually. NASA was previously using the Concorde as a model for exposure data.
A few studies have examined the cancer risk of airline crews with variable, but not statistically significant, results, although larger epidemiological studies of US military aircraft crews have found excess risks of cancer. Aw and associates examined a group of 1690 cabin attendants from 1955 to 1997, comparing their rates of cancer to the Iceland Cancer Registry. The mean employment time was 8 years, the mean age at start of employment was 23, and the mean age at the time of follow-up in 1997 was 40. Cancers among men were infrequent (n = 2), and there were too few male flight attendants to draw any statistical conclusions. However, women had a statistically significant increased risk of malignant melanoma, as well as a trend toward an increased risk of breast cancer and other cancers. There was no increased risk for leukemia, and lung cancers were absent. This association was strongest in women employed after 1971, when new long-haul higher-flying aircraft were introduced (there was also a period of solar flare in 1974). A dose relationship was identified when the woman was employed for more years and the lag time to assessment was 20 years or more.
Comment by Carol A. Kemper, MD, FACP
Ongoing monitoring of radiation effects and air travel is continuing. It was suggested that frequent flyer business travelers who log more than 200 hours per year of flight time take note of this data and should be classified as radiation workers. Women who are in their childbearing years, or who are pregnant and travel frequently, should also be aware of the potential risks. One potential factor overlooked by this study was the effect of irregular working hours or more frequent nighttime flights on cancer risk. Recent data suggest that nurses who work more night shifts have an increased risk of breast cancer, possibly as the result of an adverse effect on daily hormonal shifts. Airlines might wish to review these data for relevance to female cabin attendants.
Dr. Kemper is Clinical Associate Professor of Medicine, Stanford University, Division of Infectious Diseases; Santa Clara Valley Medical Center; Section Editor, Updates Section Editor, HIV