Strontium-90 content of the stratosphere.
D011847:Radioactive Fallout; D011851:Radioactivity; D013324:Strontium; D013326:Strontium Radioisotopes
D011847:Radioactive Fallout; D013326:Strontium Radioisotopes; D013324:Strontium
RADIOACTIVE FALLOUT; STRONTIUM/radioactive