Or: "Hair today, yer gone tomorrow!"
For years I have read loads of arguments about clean and cleaner water, how tap water is becoming better and finally, how paying $1 for tap water will change the world. In any case, drinking ANY tap water will certainly change your world, most likely for the worse. Dig.
(For those folk unable to subscribe to The Economist, or whose sub expired over a year ago, read on:
"Telltale hairs"
Feb 28th 2008 (From The Economist print edition)
You can tell where someone has been from his hair
POLICE now have a new test to help catch criminals and verify
alibis. By analysing the chemical composition of human hair,
researchers can determine the source of the water someone has been
drinking in recent months. And that can indicate where he has been.
The technique depends upon studying isotopes. These are naturally
occurring variants of elements, which share the same chemical
properties but have different weights because their nuclei contain
different numbers of neutrons. James Ehleringer and Thure Cerling, at
the University of Utah in Salt Lake City, and their colleagues
collected human hair from barbers' shops in 65 American towns. They
report in the Proceedings of the National Academy of Sciences that isotopes in hair closely match the hydrogen- and oxygen-isotope ratios found in the local water.
This
research has obvious implications for law enforcement and is being used
by Salt Lake county sheriffs to help identify a murdered woman. Isotope
analysis of her hair revealed that she spent the years before she died
in America's western mountains, which helps detectives concentrate
their search. The new method may also help anthropologists understand
more about the history and migration of ancient humans at sites where
bits of hair are preserved.
The technique works because when water evaporates at sea, a
combination of hydrogen and oxygen isotopes rise to form a cloud, which
then releases rain when it moves inland. Heavier isotopes tend to fall
sooner. So those living close to the sea, or in corridors suffering
frequent storms, will tend to absorb more of the heavy isotopes in
their hair.
For that reason, however, it is not perfect. In America, storms can
come from the Pacific or the Atlantic. This creates regions with
geographically similar isotope values. So, if a murder took place in
Los Angeles and a suspect claimed to have been in San Diego all the
time, hair analysis could not help, because the cities have similar
isotope signatures. But if the suspect were in Las Vegas, which has a different signature, he could find himself nicked.
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