TABLE 1.

Natural radioactivity in the body of a typical 70-kg (150-pound) adult human^*

Nuclide	Approximate Total Mass	Disintegrations per Day
Uranium isotopes	90 micrograms	95 thousand
Thorium isotopes	30 micrograms	9.5 thousand
Potassium-40	17 miligrams	380 million
Radium isotopes	31 picograms	95 thousand
Carbon-14	22 nanograms	320 million
Tritium	0.06 picograms	2 million
Polonium isotopes	0.2 picograms	3.2 million

^*Based on information from Idaho State University’s web site (ISU 2008).