from news.bbc.co.uk (http://news.bbc.co.uk/hi/english/health/newsid_963000/963334.stm)
The risk that airline passengers and staff face from cosmic and solar radiation is to be measured by scientists.
Radiation from the sun and other sources, is mainly absorbed by different layers of the atmosphere when it hits the earth.
However, at higher altitudes, the atmosphere is thinner and offers less protection.
Previous studies into the potential health effects of frequent exposure have been contradictory.
Now British scientists are linking up with Virgin Atlantic to fit aircraft with equipment to measure radiation within the cabin.
The study is being backed by the Civil Aviation Authority, whose medical director Robert Hunter said: "We need a better understanding of the factors that may cause the radiation dose rates in aircraft to vary.
"In particular we need to determine the influence of solar activity. The radiation dose from a transatlantic flight is similar to the dose from a chest x-ray."
'Poorly understood'
Project scientist Dr Bob Bentley, of the Mullard Space Science Laboratory at University College London, said: "We know that cosmic radiation at aircraft altitudes is several orders of magnitude more intense than that experienced at ground level, because there is less protection from our atmosphere.
"But the extent and nature of the risk to aircraft and aircrew is poorly understood."
Increased air travel is thought to be responsible for a jump in the overall amount of radiation to which the average Briton is exposed.
Figures from the National Radiological Protection Board show that the average annaul dose is 2.6 milli Seiverts - the equivalent of 13 chest x-rays.
Some studies have linked a career on high-altitude aircraft with an increased cancer risk.
Danish pilots who had clocked up more than 5,000 flying hours in their careers had a slight increase in the risk of one type of leukaemia.
Another suggested a higher incidence of bone and breast cancer among female cabin crew who had been flying for more than 15 years.
However, a British Airways study suggested that pilots and flight engineers could actually be at less risk of cancer.
The effect of regular medicals and better levels of general fitness may well be either disguising or outweighing the increased risk of cancer.
The health effects of frequently disrupting the body's natural clock by crossing time zones has also never been fully assessed.