Beverages leave 'geographic signatures' that can track people's movements

Lesley Chesson and colleagues explain that the body removes hydrogen and oxygen atoms from water (H2O), and beverages containing water, and incorporates them into proteins, including the protein in hair. Hydrogen and oxygen exist in different forms, or isotopes. The proportions of those isotopes vary in a predictable way geographically, with higher values in low-latitude, low-elevation, or coastal regions, for instance, and lower values elsewhere. Since manufacturers usually use local or regional water sources in producing beverages, isotope patterns in hair could serve as a chemical "fingerprint" to pinpoint the geographic region where a person has been.

The scientists analyzed isotope patterns in bottled water, soda pop, and beer from 33 cities and found that patterns in the beverages generally matched those already known for the tap water. They noted that the isotope pattern in beverages tends to vary from city to city in ways that give cities in different regions characteristic "iso-signatures." A person who drinks a beer or soda in Denver, Des Moines, or Dallas, for instance, consumes a different isotope signature than a person in Las Cruces, Las Vegas, or Laramie. The finding may help trace the origin of drinks or help criminal investigators identify the geographic travels of crime suspects and other individuals through analysis of hair strands, the study suggests.