Aoki’s Science Corner: Cosmic Radiation
Radiation Exposure During Commercial Airline Flights
Q: What radiation doses do people receive from flying commercially?
A: We have summarized the following information from the articles referenced:
Feng YJ et al. Estimated cosmic radiation doses for flight personnel. Space Med Med Eng 15(4):265-9; 2002.
The average effective dose rate of all flights of Xinjiang Airlines from 1997 to 1999 was 0.238 mrem (millirem) per hour.
The average annual cosmic radiation dose for flight personnel was 219 mrem.
Annual individual doses of all monitored flight personnel are well below the limit of 2,000 mrem per year recommended by the International Commission on Radiological Protection (ICRP).
Bottollier-Depois JF et al. Assessing exposure to cosmic radiation during long-haul flights. Radiat Res 153(5 Pt. 1):526-32; 2000.
The lowest dose rate measured was 0.3 mrem per hour during a Paris-Buenos Aires flight.
The highest rates were 0.66 mrem per hour during a Paris-Tokyo flight and 0.97 mrem per hour on the Concorde in 1996-1997.
The corresponding annual effective dose, based on 700 hours of flight for subsonic aircraft and 300 hours for the Concorde, can be estimated at between 200 mrem for the least exposed routes and 500 mrem for the more exposed routes.
Waters M et al. The National Institute for Occupational Safety and Health/Federal Aviation Administration (NIOSH/FAA) working women’s health study: Evaluation of the cosmic-radiation exposures of flight attendants. Health Phys 79(5):553-559; 2000.
Radiation dose levels represent a complex function of duration of flight, latitude, and altitude.
Based on data collected for this study, radiation dose levels that would be experienced by a flight crew are well below current occupational limits recommended by the ICRP and the FAA of 2,000 mrem/year.
The National Council on Radiation Protection and Measurements (NCRP) recommends a monthly equivalent dose limit of 50 mrem. The ICRP recommends the radiation limit during pregnancy be 200 mrem.
Only flight crew flying both a large number of hours during pregnancy (for example, 100 hours per month) and strictly the highest dose-rate routes (typically global routesUnited States to Buenos Aires or United States to Tokyo, etc.) would exceed the NCRP monthly guideline.
Friedberg W et al. Radiation exposure during air travel: Guidance provided by the FAA for air carrier crews. Health Phys 79(5):591-5; 2000.
Seattle to Portland: 3 mrem per 100 block hours
New York to Chicago: 39 mrem per 100 block hours
Los Angeles to Honolulu: 26 mrem per 100 block hours
London to New York: 51 mrem per 100 block hours
Athens to New York: 63 mrem per 100 block hours
Tokyo to New York: 55 mrem per 100 block hours
Oksanen PJ. Estimated individual annual cosmic radiation doses for flight crews. Aviat Space Environ Med 69(7):621-5; 1998.
In this study, crew members averaged 673 block hours and pilots 568 block hours.
Average annual cosmic ray dose for cabin crews was 227 mrem.
Average annual cosmic ray dose for long-distance flight captains was 219 mrem.
Q: We plan to bring our 15-month-old grandson to Sicily for vacation, flying a commercial airline from the Philippines. Will the radiation while flying during our 12-hour trip plus the return flight be dangerous to his health?
A: There is no evidence to indicate that the low-level exposure which will be received on the single round-trip flight you have described will pose any harm to your grandson. The total dose from such a trip is only a few percent of the naturally occurring differences in background radiation that exist from one place to another on the Earth. People live healthy lives in areas where exposures over their entire lifetimes are differentially much greater than the in-flight exposure you have described.
Q: I work in the airline industry as a crew member and want to know if there is a way to find out what my radiation exposure might be.
A: There are several commercial firms that can provide individual dosimeters to interested passengers or crew members. It is extremely important to know that there are several types of radiation that contribute to a person’s dose at flight altitudes. Any dosimeter that will be useful in this application must contain a suitable neutron measurement system. To locate current vendors of these products, one can search on the Internet for “radiation dosimetry services,” “radiation dosimetry, or personnel radiation monitoring.”
Q: I understand that the radiation dose while flying diminishes as you get closer to the equator. Is this true?
A: Because incoming cosmic radiation particles are deflected by the Earth’s magnetic field, the intensity of in-flight radiation is a function of both altitude and latitude. In general, radiation shielding by the geomagnetic field is greatest at the equator and decreases as one goes north or south. At typical flight altitudes of 30,000 to 40,000 feet, the difference between the cosmic ray dose rates at the equator and at high latitudes is about a factor of 2 to 3, depending on where one is in the approximately 11-year solar cycle. So if all your flying is in the equatorial zone, you would expect that the dose rates at altitude are 2 to 3 times lower than for your colleagues flying more northern or southern routes. Of course, your total exposure will be a function of the hours you spend at altitude. In any case, your annual radiation burden will be well within the limits considered acceptable for occupational exposure by such organizations as the ICRP.
Q: Have there been studies of long-term, low-level exposure to radiation during commercial flights and the effects for flight crew?
A: At present, the Airline Pilots Association is conducting dosimetry studies for its membership and NIOSH is engaged in a study of reproductive disorders among flight attendants. Several studies have already been published; some show an increase in various malignancies among crew members while others show no increased risk. The following references all present data showing an increase in malignancies among flight crew members with the exception of the second British Airways paper which, as discussed above, reevaluates data published in the earlier reference. These papers can be obtained through your local library.
1. Pukkala E, Auvinen A, Wahlberg, G. Incidence of cancer among Finnish airline cabin attendants, 1967-1992. British Medical Journal 311:649-652; 1995.
2. Lynge E, Thygesen L. Occupational cancer in Denmark. Cancer incidence in the 1970 census population. Scandinavian Journal of Work, Environment and Health 16 (Sup 2):3-35; 1990.
3. Band PR, Nhu DL, Fang R, Deschamps M, Coldman AJ, Gallagher RP, Moody J. Cohort study of Air Canada pilots: Mortality, cancer incidence, and leukemia risk. American Journal of Epidemiology 143(2):137-143; 1996.
4. Grayson JK, Lyons TJ. Cancer incidence in United States Air Force aircrews 1975-1989. Aviation Space and Environmental Medicine 67(2):101-104; 1996.
5. Vagero D, Swerdlow AJ, Beral V. Occupation and malignant melanoma: A study based on cancer registration data in England and Wales and in Sweden. British Journal of Industrial Medicine 47(5):317-324; 1990.
6. Irvine D, Davies DM. The mortality of British Airways pilots, 1966-1989: A proportional mortality study. Aviation Space and Environmental Medicine 63:276-279; 1992.
7. Irvine D, Davies DM. British Airways flightdeck mortality study, 1950-1992. Aviation Space and Environmental Medicine 70:548-55; 1999.
8. Gundestrup M, Storm HH. Radiation induced acute myeloid leukaemias and other cancers in commercial jet cockpit crew: A population based cohort study. Lancet 354:2029-2031; 11 Dec 1999.
9. Reynolds P, Cone J, Layefsky M, Goldberg D, Hurley S. Cancer incidence in California flight attendants. California Department of Health. In Press.
Q: For pilots flying below 6,000 feet for 200 hours a year is there any danger from cosmic radiation?
A: Even at ground level, cosmic radiation is part of our normal environment. The Earth’s atmosphere absorbs this radiation, so its intensity is least at ground level. The altitude of interest in this question6,000 feet (1,800 m)is, of course, ground level in many places. Using the CARI-6 program available from the FAA, the calculated cosmic-ray dose rate at this altitude at high geographic latitude is about 0.0001 millisievert per hour. It would, therefore, require 10,000 hours of flying at this altitude to reach the 1 millisievert annual limit recommended as a maximum for members of the public exposed to ionizing radiation. It should also be noted that exposures well above this 1 mSv limit are not “dangerous.”
Q: Is there any specific limit for air travel for children?
A: An annual radiation dose limit of 1 mSv (100 mrem) for members of the public has been recommended by both the NCRP here in the United States and by its overseas counterpart, the ICRP. In June 2003 the Health Physics Society, the organization of radiation protection professionals that sponsors this website, reaffirmed that these limits are appropriate. This recommended limit, unchanged for more than 10 years, has generally been adopted into law or regulation by the government agencies that mandate radiation protection programs. No distinction is made between the exposure of adults or minors. However, radiation exposure to the flying public (versus someone who works as a crew member) is not regulatedit is considered a voluntary activity. So at least as far as any legal limits are concerned, there are none for this category of exposure, for adult flyers or anyone else.
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