Helium-3 of the airway tree, locate unventilated defects, measure the alveolar oxygen partial pressure, and measure the ventilation/perfusion ratio. This technique may be critical for the diagnosis and treatment management of chronic respiratory diseases such as chronic obstructive pulmonary disease (COPD), emphysema, cystic fibrosis, and asthma. Production, sales and distribution of helium-3 in the United States are managed by the US Department of Energy (DOE) Isotope Program. Virtually all helium-3 used in industry today is produced from the radioactive decay of tritium. Tritium is a radioactive isotope of hydrogen and is typically produced by bombarding lithium-6 with neutrons in a nuclear
Tritium 65 nuclear sites in the US. In one case, leaking water contained of tritium per litre, which is 375 times the EPA limit for drinking water. The US Nuclear Regulatory Commission states that in normal operation in 2003, 56 pressurized water reactors released of tritium (maximum: 2,080 Ci; minimum: 0.1 Ci; average: 725 Ci) and 24 boiling water reactors released (maximum: 174 Ci; minimum: 0 Ci; average: 27.7 Ci), in liquid effluents. According to the U.S. Environmental Protection Agency, self-illuminating exit signs improperly disposed in municipal landfills have been recently found out to contaminate waterways. The legal limits for tritium