Foolosophy wrote on Apr 2
nd, 2011 at 11:38pm:
Cesium137 is linked to brain tumours.
It also bioaccumulates in vegetation, animals, fungi etc.
Also need to multiple the half life by at least a factor of 10 so that they decayed level reaches something close to normal background level.
These facts are correct, but dose is everything. A Cesium 137 source produces beta and gamma radiation (the latter through its daughter Barium-137 which decays in a few minutes.)
Radon gas is a natural source of radiation that accounts for about 80% of the total dose for the general population. It's produced from the decay of Uranium. Whenever we engage in mining activities eg coal, Uranium etc, we release radon. Whenever we burn coal, we release radon. Whenever we burn natural gas, we release radon, sometimes in the home. It's a prime cause of sick building syndrome. Actually the Darwin Gas pipeline has probably the highest Radon concentration I've come across. It also has a helium content measured in the percent range.
Those people who live in high altitude cities, and who fly long distances are subjected to a higher level of cosmogenic radiation, but the effects are exactly the same.
I posted a map of background radiation in the US earlier and somebody asked the question - what was it like in the 1930's before atmospheric detonations of nuclear weapons. Well if you want the correct answer, it was not much different to today. The combined fallout from all nuclear accidents and weapons to date accounts for maybe 1/8 of natural background radiation, less so in higher altitudes.
Of course we can detect the man-made stuff quite easily CS-137 Sr-90 and I-131 didn't exist on Earth before nuclear power.