Air Plane Travel - Factors which affect Health and Safety 2

Risks to Health

                                                                                                                                                                                    Research References (Air Risk Factors)

(4) In the Air - after take-off

RADIATION:

• Cosmic Radiation
• Terrestrial Gamma Radiation (TGR)
• UV Radiation (UVA)

• FACTOR: Cosmic Radiation Exposure. Cosmic radiation (a form of high energy ionizing radiation) is severe form of radiation which directly attacks cells and DNA. Since cosmic radiation penetrates the metal of the plane, it is difficult to protect against.The amount of cosmic radiation exposure while flying is a function of three factors: Altitude, Latitude, Time of Day. Cosmic radiation penetrates the metal of the plane and traveler. It is estimated that 3.5 hours at cruising altitude is equal to one chest x-ray. Using this as a base line, it can assumed that most flight crews (and many frequent fliers) are exposed to approximately 300 chest x-rays per year. Ionizing radiation damage is cumulative.

• Altitude  - the higher the altitude the more exposure to cosmic radiation .At higher altitude, Cosmic radiation from the sun becomes much higher as the plane  reaches cursing altitude (approximately 30,000 ft).   
• Latitude - earth's magnetic field, which deflects cosmic radiation (and acts as a natural radiation shield), is weakest at the polar regions. Therefore, by flying over the polar regions increases your level of radiation exposure by a factor of 2-3 times versus flying over equator where the magnetic field strongest. Therefore, radiation shielding is strongest at the equator and diminishes as travel extends north or south from the equator.  
• Time of Day - Night time flying lowers exposure to cosmic radiation. 

Note: solar flares, whereby a significant increase in ionizing radiation is generated from the sun, can create extremely greater exposure levels

• Cancer Risk -  Cosmic radiation is known to cause defects in the DNA in any part of the body, which is a precursor to cancer development.  Prostate cancer, for example, is twice as likely in pilots.⁷ Also, flight crews have been shown to have a higher mortality rate of CNS cancer (brain or spinal cord) resulting from cumulative radiation exposure ⁸
• How much ionizing radiation exposure is harmful? Expert opinion is split. However, many experts believe that THERE ARE NO SAFE LEVELS OF IONIZING RADIATION (this also being the stance of the International Commission on Radiological Protection). The contention is that even low doses of ionic radiation can cause DNA damage. In the case of air travel, the amount of exposure is additive. Exposure starts at security screening and continues through the duration of the flight until exit from the destination airport. While the security screening exposure is small, when combined with the flight exposure the amount becomes more significant.

• FACTOR: Terrestrial Gamma Rays (TGR) - In thunderstorms, at the altitude of airplanes, short bursts of high energy gamma rays may be generated, and the amount of gamma radiation can be significantly higher than levels of cosmic radiation exposure. Airplanes in the vicinity of these thunderstorms may expose passengers to very high levels of radiation. Also known as "dark lightning" because gamma ray burst is invisible (there is no light like normal lightning) The amount of radiation from TGR is about equivalent to a full body CT scan - a tremendous amount of radiation.⁹  While this phenomena has been known for a decade, there is still much scientists do not understand, including the potential harm to airline passengers. ALL TYPES OF STORMS APPEAR TO GENERATE GAMMA RAY BURSTS - REGARDLESS OF THE STRENGTH OF THE STORM. Gamma rays are a type of ionizing radiation and are more powerful than X-rays. ¹⁰

• FACTOR: UVA / UVB radiation exposure. Increased Incidence of Melanoma (Skin Cancer) in pilots and flight attendants. UVA can penetrate the windows in an airplane, whereas UVB is blocked by window. UVA can penetrate deep into tissue, damaging to DNA and damaging collagen in the skin. As such, it is a primary factor in aging of the skin and causing wrinkles due to a breakdown of the underlying collagen support. UVA is equally intense at all daylight hours throughout the year. Melanoma is believed to be caused by a combination of UVA and cosmic radiation. Pilots in the cockpit and passengers in window seats would be most susceptible to UVA rays.
• Altitude - As with cosmic radiation, UV radiation becomes significantly stronger at higher altitudes.
• Melanoma Risk - Airline pilots and cabin crew have twice the incidence of melanoma as compared to the general population.¹¹
• Exposure Levels - Research indicates that a pilot spending 56 minutes in the cockpit at 30,000 feet is the equivalent of 20 minute absorbing UVA radiation on an average strength sunbed.¹²

OZONE:

•  FACTOR: Ozone levels increase with altitude and may affect health. Most modern planes deploy ozone catalytic converters as part of the ventilation system - required in long haul planes. However, over time, the converter ages and become only 60% efficient before being replaced. Ozone is a component of the air quality of the cabin, and higher levels of ozone may affect eyes and create breathing problems and other stress to the respiratory system (oxidative stress). Long term exposure may also cause lung problems due to chronic inflammation. Domestic flights without converters experienced higher levels of ozone.^13-14

 CIRCULATION: Deep Vein Thrombosis (DVT)

•  FACTOR: DVT is the formation of a blood clot in a vein deep in the body. Common DVT's in air plane travelers occur in the lower leg or thigh. It becomes extremely dangerous if the clot breaks off and travels to the lung (known as a pulmonary embolism). Sitting for long periods during the flight affects blood flow and raises blood sugar levels.
• Your risk increases for DVT if you have had any of the following:¹⁵
• Have had recent surgery (generally within 3 months)
• Have been on prolonged bed rest or hospitalization
• Have heart failure
• Have a blood clotting disorder
• There is a direct correlation between long duration flights and DVT.
• Additional risk factors:  age over 40 years, gender (female), women who use oral contraceptives, varicose veins in lower limbs, obesity and genetic thrombophilia.¹⁶
• Muscle contraction is important for moving blood through the body. An immobile passenger is unable to contract muscles, making blood more sluggish. Circulatory issues such as Deep Vein Thrombosis (DVT) is one such manifestation.
• Suggestion: It is important to stay hydrated and avoid prolonged sitting. For those at high risk, the wearing elastic stockings may provide added support. Always consult with your doctor if you feel that you are at risk for DVT.  

(5) Oxidative Stress Load - the Additive Effect of Radiation

Many of these health issues presented create oxidative stress to the cells. The effect between all of these may be additive, meaning that the total health effect will be much more serious than any individual effect. For example, the combined effects of all forms of radiation places tremendous stress on the DNA genome. At lower levels of exposure the DNA repair mechanism of the body can make most repairs. However, this ability can be easily overwhelmed. An additive effect of radiation damage may happen not only during the same flight but accumulate over many flights. 

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