OH-92-1 Acceptable Exposure Limit for HCFC-123 Lowered
                           OFFICE OF HEALTH
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                          HEALTH HAZARD ALERT 
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       Assistant Secretary for Environment, Safety and Health
U. S. Department of Energy                           Washington, DC 20585
Issue 92-1                                                 September 1992
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Acceptable Exposure Limit for HCFC-123 Lowered

On June 21, 1991, the DuPont Corporation announced results of a 2-year
toxicity study involving the chemical 2,2-dichloro-1,1,1-trifluoroethane
(HCFC-123), a chlorofluorocarbon (CFC) substitute.  The HCFC-123 is used
as a refrigerant in chillers that generate low temperature brines, as well
as in the blowing agent FORMACEL, which is used for generating insulating
foams.  The CFC substitutes were developed because CFCs are linked
to the reduction of the earth's ozone layer. 

The DuPont animal toxicity studies showed the development of nonmalignant
(not cancer-producing) tumors in rats.  As a result, DuPont lowered their
Acceptable Exposure Limit (AEL) for HCFC-123 to 10 parts per million (ppm)
for an 8 to 12 hour workday--a level far below the limit formerly allowed
for CFCs.  Field experience at DuPont facilities shows that
HCFC-123 levels have been as low as 8 ppm and as high as 20 ppm when
making or breaking hose connections and during routine maintenance
procedures. 

The CFC substitutes, such as HCFC-123, may not always adapt to, or be
compatible with, the existing machinery.  Some plastics or rubbers
deteriorate or decompose on contact with CFC substitute products.  DuPont
advises that a check for compatibility between new CFC substitutes and
existing machinery and equipment be made before the new CFC products are
used.

DuPont advised that worker exposure to HCFC-123 should be controlled and
recommended several forms of engineering controls for work with this
product.  These include air monitors, alarm systems, air dischargers,
ventilation exhausts, and strict maintenance standards (American Society
of Heating, Refrigeration and AirConditioning Engineers Standard 15-1989).

These forms of  engineering controls do not lessen the potential toxicity
of HCFC-123, but rather reduce and monitor HCFC123 exposures.

For further information, please contact Carlos Coffman, Industrial
Hygienist, Industrial Hygiene Programs Division, EH-412, (301) 903-6493.