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Flight crews get scheduled for a month at a time, with an upper limit on the number of hours per year they are allowed to fly. A round trip flight between New York and Tokyo is about 26 hours. On average flight crews working the New York to Tokyo route make somewhere around 2-3 trips a month, which would be equivalent to about 52-76 hours of flying. This makes sense when you consider that for health and safety reasons, the upper limit of flight hours for a crew member is set at about 80 hours per month.
US Government standards for radiation protection are established by the National Council on Radiation Protection and Measurement (NCRP). Based on this, the individual states, the Nuclear Regulatory Commission (NRC), and the Department of Energy (DOE) regulate the maximum permissible dose of radiation to which people should be exposed in their work. Those recommendations are generally adopted as the maximum limits permitted by law.
The NCRP-recommended annual limit for occupational radiation exposure is 5000 mrem. The exposure limit for workers are 20 to 50 times greater than those established for the general public. Workers are assumed to accept their increased exposure and risk as a trade-off in exchange for the benefits of their employment.
The FAA estimates that a one-way trip between New York and Tokyo involves radiation exposure levels that are equivalent to that of having several chest x-rays (about 1000 mrem). However, occasionally magnetic fields increase in force due to radioactive particles from the sun during a solar storm. This may increase radiation exposure by 10 times or more. In addition, radioactive material may be transported on some flights. This also increases the levels of exposure. Health problems are most likely to occur for crew members when there is increased exposure to radiation over time.
The principal health concern from radiation is the increased risk of cancer and negative effects on mortality rate. To give some perspective on relative exposure levels, see below.
Rem is the term used to describe the dose of radiation absorbed in human tissues and the ability of that radiation to cause damage. . In the International System of Units, the sievert (Sv) is used to measure radiation dosage. One Sievert is equal to 100 rem.
Exposure to between 1000 to 10,000 mrem (.01 to 1 Sv) is safe and usually causes no observable health effects. Although at the higher end of these numbers,the chance of getting cancer does increase slightly.
Exposure at the level of 100,000 mrem (10 Sv) over a short period of time will likely cause some observable health effects. However, the body can recover fairly well from this short-term exposure to radiation. Exposure at this rate over a long period of time, may result in increased cancer rates.
Exposure to 1,000,000 mrem (100 Sv) of radiation, whatever the period of exposure, will cause immediate health effects which are eventually likely to be fatal.
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