Being the #hygienenerds that they are, #fletcherandbest were thinking about the hazards that they might encounter during their trip to Texas for #AIHce2014. They tell me that they might have gotten a little side tracked consuming some G&T’s in the Qantas lounge before their flight…especially when they were sitting next to Tim Cahill! ….But they did get back to business and thankfully bring us their first blog post on the hazards of cosmic radiation that they were exposed to during their long-haul flight!
Firstly, some background: The electromagnetic spectrum includes a variety of radiation types, dependent on their wavelength, for example, radio waves, microwaves, infrared, ultraviolet, x-rays and gamma rays. Low frequency, long wavelengths are considered non-ionizing, whereas higher frequency, shorter wavelengths are classed as ionizing radiation. Ionizing radiation has enough energy to cause chemical changes by breaking chemical bonds. X-rays and gamma rays have very high frequencies and very short wavelengths, and have enough energy to remove electrons from an atom. This process is referred to as ionisation.
On earth, we are constantly exposed to radiation from space; this invisible ‘shower’ of radiation contributes to our background radiation dose. These cosmic rays consist of both low and high energy charged particles. When we are on the earth’s surface, we are protected by these rays by the earth’s atmosphere, which acts as a shield. Those who live in high altitude areas are exposed to higher levels of cosmic radiation than those at sea level.
Exposure to ionising radiation can increase when travelling in an aircraft, as the earth’s atmosphere provides less protection from cosmic radiation at altitudes around 7000 – 12000 metres – the usual travelling altitudes of commercial aircraft. The exposure depends on the altitude of the flight and the latitude of the flight from the equator, the further the flight path is away from the equator, the higher the exposure.
The dose limit of 1 mSv/year applies for all members of the public. Occupational exposures have a dose limit of 20 mSv/year; in this case, this would include people such as pilots and aircrew. ARPANSA report that studies undertaken to determine cancer risk to pilots and aircrew, show that there is no significant increased risk of cancer due to radiation exposure.
We were lucky enough to borrow Tracerco Personal Electronic Dosimeters (PEDs) to use during our flight from Sydney to Dallas to measure our gamma radiation exposure.
The results measured our dose to be 23.57 µSv, or 0.024 mSv for the duration of our flight (well, the time we were allowed to have electronic equipment operating – about 14 hours). This equates to about 2.5% of the annual dose limit of a member of the public. To reach the dose limit for the public, someone would need to fly this route 42 times in a year!
In comparison, a chest CT provides a dose of 8 mSv, a mammogram (four views) 0.7mSv, chest x-ray 0.1 mSv, or dental x-ray 0.01 mSv.
So, in the scheme of things, radiation exposure from flying, does not result in a concerning risk, however, if you were concerned, you could apply the three radiation protection principles of 1) time; 2) shielding; and 3) distance. You could choose to fly more flights over shorter distances, thereby reducing your exposure time and increasing your shielding, as shorter haul flights fly at lower altitudes, or spend shorter amounts of time at altitudes of concern.
The Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) provides further information regarding radiation basics and cosmic radiation. Radiation doses for medical procedures can be found at the Health Physics Society Fact Sheet.
Thanks #fletcherandbest for going to the effort of measuring and assessing your dose of exposure to cosmic radiation!