Deuterium-depleted water is water which has a lower concentration of deuterium than occurs naturally on Earth. DDW is also known as light water, although that term is also used in reference to normal water.
Chemistry
Deuterium-depleted water has a lower concentration of deuterium than occurs in nature. Deuterium is a naturally-occurring, stable isotope of hydrogen with a nucleus consisting of a single proton and a single neutron. The nucleus of ordinary hydrogen consists of a single proton. Deuterium atoms are about twice the atomic mass of normal hydrogen atoms as a result. Heavy water consists of water molecules with two deuterium atoms replacing the two normal hydrogen atoms. The hydrogen in normal water consists of about 99.98% of normal hydrogen. In Vienna Standard Mean Ocean Water that defines the isotopic composition of the ocean water, deuterium occurs at a concentration of 155.76 ppm. For the SLAP standard that determines the isotopic composition of natural water from the Antarctic, the concentration of deuterium is 89.02 ppm. The production of heavy water involves isolating and removing deuterium containing isotopologue within natural water. The by-product of this process is deuterium-depleted water. Various technologies have been developed for the production of deuterium depleted water, such as electrolysis, distillation, desalination from seawater, Girdler sulfide process, and catalytic exchange. Due to the heterogeneity of hydrological conditions natural water in its isotopic composition varies around the globe. Distance from the ocean and the equator and the height above sea level have a positive correlation with water deuterium depletion. Snow water especially from glacial mountain meltwater is significantly lighter than ocean water. The weight quantities of isotopologues in natural water are calculated on the basis of the data collected using molecular spectroscopy: According to the table above the weight concentration of heavy isotopologues in natural water can reach 2.97 g/kg, thus, there are about 300 milligrams of deuterium containing isotopologues in each liter of water. This presents a significant value comparable, for example, with the content of mineral salts.
Positive biological effects of deuterium-depleted water were registered during experiments with non-human animals and in vitro. Harriet Hall investigated health claims being attributed to drinking DDW, which has been sold for as much as $20 per liter. In a July 2020 article published at Skeptical Inquirer online, she reported that the overwhelming majority of DDW studies did not involve humans, and the few that did did not verify any human efficacy. She concluded "I don’t see any good science-based evidence that would make me fear deuterium. I’ll stick to tap water, thank you."
