Deuterium is a rare but naturally occurring stable isotope of hydrogen. Only 1 in 6500 hydrogen atoms are deuterium. Deuterium levels in drinking water vary with approximately 95% of the global potable water ranging between 143-157 ppm. Lowest deuterium water levels are found at the north and south poles and on top of glacial mountains. The highest levels are found along the equator at sea level and in desert groundwater.