RE: Calling all laser experts

[Sliney David H <David.Sliney@APG.AMEDD.ARMY.MIL>]

Dear Ms. Algutifan:

    The CDRH of FDA has issued a warning statement on laser pointers, and
more recently, the International Commission on Non-Ionizing Radiation
Protection (ICNIRP) prepared a statement for publication next year in Health
Physics journal regarding laser pointers.   Unfortunately, there has been
much published in the press which is at least partly in error and some
exposed persons have even thought that they had endured permanent injury.
Here are the facts as we in the laser biophysics community know them.

1.  Many of us in laser safety feel strongly that laser pointers should not
be in the hands of children and should not be sold as novelty items.  While
the actual risk of permanent injury is exceedingly small or virtually
non-existent, the risk of causing an accident because someone is dazzled and
unable to see for a short time (generally at night) is very real.  There
have been many instances reported of laser pointers directed at passing
motorists, police helicopter pilots and law enforcement officers.  They take
this very seriously.  The Laser Institute of America (LIA) has issued
warning information as well.

2.  The laser pointers are generally Class IIIA (3A) between 1-5 mW.  This
level is just above the 1 mW level which is safe for momentary viewing and
known to all of us as Class II (or Class 2 in ANSI Z136.1-1993).  Visible
lasers of this power will produce intense disability glare and an afterimage
and produce an aversion response (about 180 ms, standardized in laser safety
as 0.25 s)to limit exposure to that moment. Even if the entire beam entered
the eye, it would not produced a permanent injury that could be detectable
to the exposed person or to an ophthalmologist.  The actual ED-50 threshold
exceeds 10 mW for barely detectable injury for 0.2-0.3 s.  The MPE for
lasers has a "safety factor" of about 10 built into it.  I personally have
had equivalent powers directed into my eye and know that permanent effects
do not exist and there is a large research literature on this (e.g., see
Sliney DH and Wolbarsht ML, "Safety with Lasers and Other Optical Sources,"
New York, Plenum, 1980).

3.  There are two instances where retinal injury detected by retinal
specialists have been reported by the American Academy of Ophthalmology.
These were both youngsters who stared into the pointer for tens of seconds
either as a "science experiment" or on a dare.  This is the situation where
the threshold for injury can really occur.  We are hopeful that eventually
they will recover to full visual performance, since the injuries were so
close to threshold.  This gives added impetus to assure that children do not
obtain these laser pointers. 

4. Laser pointers have been used by instructors for two decades without
concern; however, once the cost of red diode lasers crashed and they were
incorporated into novelty items, the number of LASER HARASSMENT incidents
has exploded.  I hope you and other health physicists will do your best to
provide accurate information to all concerned.  It is critical that
officials understand that forbidding use of these Class 3A lasers and allow
only the use of Class 2 (1 mW or less) lasers will not eliminate the problem
of laser dazzle.  The Class 2 lasers, while of lower power, generally have
shorter wavelengths with more visual impact; thus laser harassment will not
be affected.  Such a move would at least greatly reduce the risk of injuries
from lengthy staring into the source by children.

Sincerely 

David H. Sliney, Ph.D.
Manager, Laser/Optical Radiation Program
US Army Center for Health Promotion and Preventive Medicine
Aberdeen Proving Ground, MD 21010-5422

Chair, Hazard Evaluation Subcommittee, ANSI Z136
Chair, ICNIRP Subcommittee IV on optical radiation biophysics
etc.  
     




__________________________________
Subject: Calling all laser experts 
Author:  <radsafe@romulus.ehs.uiuc.edu > at internet-mail
Date:    10/29/98 7:42


Hey Radsafers,
     
I took my kids to the mall here in St. Charles last night.  My older son had

been begging me for a week to get him a "cool laser" to use on Halloween
night 
("All the other kids have one, Mom," he pleaded).  The first gift shop we
came 
to had some key chains hanging near the cash register.  My son immediately 
recognized them as laser key chains, so I picked one up and looked at it.
It 
had a warning label that said it was a Class IIIa, red laser in the 660-680
nm 
wavelength range.  It said "Keep out reach of children" (not my typo; an
import 
I guess) and "Do not point directly in the eyes" (well, yeah, that makes
sense!)
 It was selling for $14.99.  I did not buy it for him (because I know
someone
will ask).  Of course, I know that these key chains are becoming very
popular 
among school children, as are laser pointers and other types of laser
devices 
that are sold over the counter in some retail stores.  Our local school
district
has just made a rule forbidding children to bring any type of laser devices
to 
school under any circumstances.  A child at my kids' school was just
suspended 
for bringing a laser pointer to class (a third grader).
     
Now, my question is, isn't a Class IIIa laser a pretty severe ocular hazard?
And
what can we as health physicists do about it?  I'm no expert in this field,
but 
the bits and pieces I've read from studying for the CHP exam indicate to me
that
it's an immediate ocular hazard if intrabeam viewing occurs.  I'd like
others' 
thoughts on this issue; I was so upset last night about these things being
in 
plain view in retail stores (and at a child's eye level) that I was thinking

about calling up the FDA.  This seems to be a significant acute radiation
issue 
to me, that you folks will be interested in.  I hope I'm not overreacting,
and I
think I am not.  Thanks for the help and advice.
     
Elizabeth Algutifan,
Environmental Health Physicist
WSSRAP
St. Charles, MO
Elizabeth_Algutifan@wssrap-host.wssrap.com
     
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