The following excerpts are quoted directly from a National Institute of 
Justice Research in Brief pamphlet January 1993 :

Testing Hair for Illicit Drug Use
by Tom Mieczkowski, Harvey J. Landress, Richard Newel, and Shirley D. 
Coletti

Urinalysis testing
Immunoassay technology, whether based on radioisotopes, enzymes, or 
fluorescence, enhanced our ability to measure illicit drug use.  
However, use of urine as the test meduim imposes practical limitations 
on the frequency of collection when these techniques are applied.  
Opiates and cocaine are water-soluble and quite rapidly excreted, 
generally within 48 to 72 hours.  Only marijuana, whch is fat-soluble, 
has a slow, relatively long-term urine excretion rate (regular, heavy 
users can test positive for several weeks).

Use of Hair Testing
Use of hair as a test medium avoids the limitations of infrequent urine 
testing.  Hair testing is relatively well established and uses a number 
of the same technologies as urine-based tests, including enzyme, 
radioisotope, and fluorescent immunoassays.  The methodologies are 
identical; the distinction is in the medium.

Hair has several advantages over urine in testing for drugs of abuse:
-Hair greatly expands the time window for the detection of an illicit 
drug.  Urinalysis of a single specimen generally can detect the presence 
of drugs for a period of several days to a week or two, depending on the 
drug.  Hair analysis can detect drug use for several months or more, 
depending on the length of the hair.
-Brief periods of abstinence from drugs will not significantly alter the 
outcome of hair analysis.
-Contaminating or altering a sample to distort or manipulate test 
results is much more difficult with hair than with urine.  Preliminary 
research shows that even treating hair with a variety of strong 
compounds will not completely eliminate traces of illicit drugs. -Hair 
is relatively inert, easy to handle, and requires no special storage 
facilities or conditions.  Compared with urine samples, it presents 
fewer risks of disease trasmission.
-Collecting comparable samples for repeat testing is easier with hair 
than with urine.

Some practical difficulties may occur in collecting specimens from 
individuals with short or no head hair.

Scientific basis for hair testing
Scientifically, the radioimmunoassay of hair (RIAH) rests on the fact 
that growing hair absorbs drugs and their metabolites into its structure 
from the circulatory system.  Metabolites are the biochemical products 
of the breakdow of drugs within the body.  For cocaine, both urine 
testing and hair testing detect the drug metabolites rather than the 
illegal drug itself.

Once a drug metabolite is embedded in the hair shaft, a process which 
appears to occur while the hair is being formed in its follicle, the 
metabolite is very nearly permanent.  As the hair shaft grows, it forms 
a longitudinal record of the compounds it has absorbed, including drugs 
of abuse.

Drug metabolites appear in detectable levels in hair approximately a 
week after ingestion.  Hair grows at an average rate of about half an 
inch every 30 days.  The hair shaft can be cut into various lengths, 
allowing a "time line" analysis of drug consumption.  Like a tape 
recording, a hair specimen can allow an analyst to construct a history 
of drug use.  This "tape recording" presents an expanded time-monitoring 
window in contrast to single urine specimens collected at widely spaced 
intervals.

Additional research is needed to better understand such issues as the 
biochemical processes of the absorption of drugs and their metabolites 
into hair, dose-related cutoff levels, and the influence of external 
contamination.  NIJ is currently conducting studies on these issues.

References:
W. Baumgartner, V. Hill, and W. Blahd, 1989. "Hair analysis for drugs of 
abuse." Journal of  Forensic Sciences 34, 6: 1433-53.
E. Cone, 1990. "Testing human hair for drugs of abuse: Individual dose 
and time profiles of morphine and codeine in plasma, saliva, urine, and beard compared to 
drug-induced effects on pupils and behavior." Journal of American Toxicology 14: 1-7.


                               -transcribed by Rod Serling 1-96