T IRITIUM, an isotope of hydrogen with an atomic mass number of three, is produced in nuclear reactors in substantial quantities. Although tritium is one lof the least hazardous radioactive nuclides, its continued production and long half-life for radioactive decay may lead to increased levels in the environment. Because tritium is an isotope of hydrogen, it can be metabolized in the form of tritiated water and incorporated into body fluids and tissues. This source of population exposure requires that public health agencies be cognizant of the significance of tritium as an environmental contaminant. The nuclear power industry has expanded rapidly during the past few years, and the U.S. Atomic Energy Commission predicts that this high rate of growth will continue during the next decade. Nuclear power reactorsuand fuel reprocessing plants release tritium to the environment under normal operating conditions. Due to the stratospheric fallout from previous atmospheric testing of nuclear weapons, measurable levels of tritium are already present in the environment. An analysis of the effect of