Sources of Natural Radiation

Uranium 238 - Uranium Series
99.2745% of all natural uranium, 4.7 ppm in common rocks
4.47 billion years half life

Uranium-238	4.47 billion years	alpha, x-rays
Thorium-234	24.1 days	beta, gamma, x-rays
Protactinium-234m	1.17 minutes	beta, gamma
Uranium-234	245,000 years	alpha, x-rays
Thorium-230	77,000 years	alpha, x-rays
Radium-226	1600 years	alpha, gamma
Radon-222	3.83 days	alpha
Polonium-218	3.05 minutes	alpha
Lead-214	26.8 minutes	beta (700 keV), gamma, x-rays
Bismuth-214	19.7 minutes	beta (0.5, 3 MeV), gamma
Polonium-214	164 microseconds	alpha
Lead-210	22.3 years	beta, gamma, x-rays
Bismuth-210	5.01 days	beta
Polonium-210	138 days	alpha
Lead-206	Stable

Thorium 232 - Thorium Series
1.6 to 20 ppm in common rocks
14.1 billion years half life

Thorium-232	14.1 billion years	alpha, x-rays
Radium-228	5.75 years	beta
Actinium-228	6.13 hours	beta, gamma, x-rays
Thorium-228	1.91 years	alpha, gamma, x-rays
Radium-224	3.66 days	alpha, gamma
Radon-220	55.6 seconds	alpha
Polonium-216	0.15 seconds	alpha
Lead-212	10.64 hours	beta (335 keV), gamma, x-rays
Bismuth-212	60.6 minutes	alpha, beta, gamma, x-rays
Polonium-212	0.305 microseconds	alpha
Thallium-208	3.07 minutes	beta, gamma
Lead-208	Stable

Potassium 40
1-30 pCi/g in soil, 0.0117% of all Potassium
1.28 billion years half life

Potassium-40	1.28 billion years	beta (1.3 MeV) , gamma
Argon-40	Stable
Calcium-40	Stable

Rubidium 87
2 pCi/g in soil
4.7 billion years half life

Rubidium-87	4.7 billion years	beta (282 keV)
Strontium-87	Stable

Carbon 14
0.00000000010% of all carbon
6 pCi/g (0.22 Bq/g) in organic material, produced by Cosmic-ray interactions
5730 yr half life

Carbon-14	5730 years	Beta (156 keV)
Nitrogen-4	Stable

Tritium 3
0.032 pCi/kg, produced by Cosmic-ray interactions
12.3 yr half life

Hydrogen-3	12.3 years	Beta (19 keV)
Helium-3	Stable

Beryllium 7
0.27 pCi/kg, produced by Cosmic-ray interactions
53.28 day half life