PROGRAM TITLE:	Human Health Effects of CFC Replacement 
SCIENCE ELEMENT:	Human Interactions


DESCRIPTION:  The most often mentioned near term replacement 
chemicals for the chlorofluorocarbons (CFCs) are the 
hydrochlorofluorocarbons (HCFCs).  The presence of a hydrogen atom in 
their molecular structure makes them degrade more rapidly in the lower 
atmosphere, thus reducing the possibility of migration into the stratosphere 
and depletion of the  ozone layer.  In addition, their degradation in the lower 
atmosphere removes a very strong absorber of infrared (IR) radiation emitted 
from the earth's surface.  CFCs in the lower atmosphere are also very strong 
absorbers of IR radiation making them important green house gases as well as 
ozone layer depleting chemicals.  
There is a paucity of toxicity information about these chemicals and their 
degradation products.  Chronic toxicity studies are required because of the 
similarities of many of the HCFCs to the cardiotoxic anesthetic halothane and 
because they are more chemically and biologically active than the CFCs.
The National Institute of Environmental Health Sciences (NIEHS) funds 
research on the metabolism and toxicity of the HCFCs, including HCFC 22, 
HCFC 123, HCFC 124, HCFC 125, HCFC 132b, HCFC 134a, HCFC 141b, AND 
HCFC 142b.  Specifically, the studies investigate the metabolism of HCFCs in 
rat hepatocytes and rat liver subcellular fractions and the toxicity of HCFCs 
and their metabolites.
All NIEHS grants are subjected to four levels of review before funding:  an 
initial review by NIEHS staff to determine if the proposal is relevant to an 
NIEHS research objective; a rigorous and very competitive peer review by 
experts in the area resulting in a priority score; review by the institute's 
advisory council to determine priority among all areas of research funded by 
NIEHS; a final review and decision by the NIEHS director.
STAKEHOLDERS:  The international environmental health community 
relies on NIEHS research for a substantial portion of the scientific results that 
affect prevention and health care policies and strategies.  The primary 
beneficiary is Homo Sapiens, but as decisions are made to protect human 
health other vulnerable species benefit.
POLICY RELEVANCE:  This research provides part of the health science base 
on which policymakers must rely in regulating the use of CFC chemical 
PROGRAM CONTACT:  Mary Gant, NIEHS, Bldg. 31, Room B1-CO2, 
Bethesda, MD  20892, (301) 496-2919