AI both chemical and radioactive contuminants. Current population body burden ’ levels of the common radiocontaminants are generally considerably less " / than one ten-thousandth of the levels listed in Table II. — The highest * relative level is for potassium-40 which is present at a level of about one thousandth that estimated to produce severe long term éffects. hus been a part of all individuals since the origin of life. Potassium-40 It is a. ‘naturally occurring form of potassium and makes up 0.01% of the potassium of the earth. It may be that some chemical agents are present in the body at levels much closer to that expected to produce severe long term effects.