BACKGROUND: Law enforcement officials are enthusiastic about a new tool for alcohol testing that uses near-infrared absorption spectroscopy to determine a person's blood-alcohol content more swiftly, and in a more sanitary and less invasive way, than current methods. The TruTouch 1100 system can also function as a biometric identity-verification system for prison work-release programs or airline pilots, for example.
HOW IT WORKS: The TruTouch 1100 system introduces very low power light (in the near-infrared wavelength portion of the spectrum) into the skin of the forearm. The light that returns to the tissue surface by reflection and is collected by a detector. The light reflecting from each type of molecule (water, alcohol, etc.) is unique. This allows the spectrum of alcohol to be discriminated from other molecules that are commonly present in the body. The entire process takes about one minute, compared to 30 minutes or more for a standard breathalyzer test.
ABOUT BLOOD ALCOHOL LEVELS: The amount of alcohol in the blood stream is referred to as Blood Alcohol Level (BAL). It is recorded in milligrams of alcohol per 100 milliliters of blood, or milligrams percent. For example, a BAL of .10 means that 1/10 of 1 percent (or 1/1000) of the total blood content is alcohol. When a person drinks alcohol it goes directly from the stomach into the blood stream. This is why people typically feel the effects of alcohol quite quickly, especially if drinking on an empty stomach. BAL depends on the amount of blood (which increases with body weight), and the amount of alcohol consumed over time. Drinking fast will quickly raise a drinker's BAL because as the liver can only handle about a drink per hour--the rest builds up in your blood stream. With a BAL of .02, you may experience an increase in body warmth, and a lowering of inhibition; at .05, you are less alert and begin to experience impaired coordination. A BAL of .08 is the legal limit for drunk driving in most states. With a BAL of .15, you experience impaired balance and are noticeably drunk. Many people lose consciousness with a BAL of .30 or higher, and breathing can stop with a BAL of .50, at which point many people die.
WHAT IS SPECTROSCOPY? Spectroscopy is a technique used by astronomers and physicists to study the make-up of an object based on the light it emits. Anything that produces light or radiates energy, whether a light bulb or a star, is telling us about itself and anything between us and the source. This is possible because each chemical element has a unique signature, emitting or absorbing radiation at specific wavelengths. For example, sodium, used in street lights, emits primarily orange light. Oxygen, used in neon lights, emits green light. By passing the light from a star or other object through a special instrument, called a spectrograph, the light is "spread" into a spectrum in much the same way visible light is spread into its colors by a prism. By carefully studying how the spectrum becomes brighter or darker at each wavelength, scientists can tell what chemical elements are present.
The Optical Society of America contributed to the information contained in the TV portion of this report.