In article <19971003132501.JAA23295 at ladder02.news.aol.com>,
JimLavL <jimlavl at aol.com> wrote:
>>ian at ilm.mech.unsw.edu.au wrote, among other things:
>>>Many new blends contain components whose toxicology is now uncertain.
>>The only replacement refrigerants known to be non-toxic are blends
>>consisting of pure saturated hydrocarbons only, for example HC-12a
>>(tm).
To see the other things I wrote, point your browser to URL:
http://ilm.mech.unsw.edu.au/pub/archive/HC/news/toxicity.html
>1. The "new" refrigerants are probably the most toxicologically tested
> chemicals on earth. It took over 7 years of long term exposure testing to get
> 134a approved for some applications, including metered dose inhalers for
> asthma patients. This is much more testing than R-12 ever was subjected to.
Exposures to R-134a in air longer than a minute at concentrations
of 0.4% by volume possible from car air conditioner leaks have
previous to Vinegar et al (1997) only been on rodents and
dogs. Vinegar et al (1997) is available electronically at the URL
above.
The concentration in the lung from a metered dose inhaler (MDI) is
under 0.3% by volume for only a single breath. Approval for MDIs in no way
implies safety as a refrigerant for car air conditioners.
For a discussion of the toxiciology of R-134a relative to R-12 see
Dekant (1996) (abstract follows).
>2. Hydrocarbons have not been tested nearly as much as the HFC alternatives,
> and many commercial grade hydrocarbons are not pure by any means. They
> ususally contain several percent of "unknowns", many of which are toxic. To
> get them all out, the cost of the hydrocarbon goes way up.
The hydrocarbons used as refrigerants are the same as those used in
aerosol cans except most have ethyl mercaptan odorant added at 0.0025%
by volume as used in natural gas. Consumers who use modern grooming
products are exposed to hydrocarbons every morning at concentrations
higher than resulting from a typical car air conditioner leak. They
are exposed to odorant when they cook with gas.
Yes, hydrocarbon refrigerants and propellants are several times more
expensive than LPG as a result of purification and quality control.
>3. I wouldn't want to be tooling down the highway at 65 mph, lighting a
> cigarette, when my AC full of HC 12a blows in my face. KABOOM.
Physically impossible when recommended safety precautions are
followed. No such event has occurred despite over 10 million user
years of hydrocarbon refrigerant in car air conditioners.
See URL http://ilm.mech.unsw.edu.au/ for more information.
Toxicology of Chlorofluorocarbon Replacements
Wolfgang Dekant
Department of Toxicology, University of Wurzburg, Wurzburg, Germany
_________________________________________________________________
Abstract
Chlorofluorocarbons (CFCs) are stable in the atmosphere and may reach
the stratosphere. They are cleaved by UV-radiation in the stratosphere
to yield chlorine radicals, which are thought to interfere with the
catalytic cycle of ozone formation and destruction and deplete
stratospheric ozone concentrations. Due to potential adverse health
effects of ozone depletion, chlorofluorocarbon replacements with much
lower or absent ozone depleting potential are developed. The
toxicology of these compounds that represent chlorofluorohydrocarbons
(HCFCs) or fluorohydrocarbons (HFCs) has been intensively studied. All
compounds investigated (1,1-dichloro-1-fluoroethane [HCFC-141b],
1,1,1,2-tetrafluoroethane [HFC-134a], pentafluoroethane [HFC-125],
1-chloro-1,2,2,2-tetrafluoroethane [HCFC-124], and
1,1-dichloro-2,2,2-trifluoroethane [HCFC-123]) show only a low
potential for skin and eye irritation. Chronic adverse effects on the
liver (HCFC-123) and the testes (HCFC-141b and HCFC-134a), including
tumor formation, were observed in long-term inhalation studies in
rodents using very high concentrations of these CFC replacements. All
CFC replacements are, to varying extents, biotransformed in the
organism, mainly by cytochrome P450-catalyzed oxidation of C-H bonds.
The formed acyl halides are hydrolyzed to give excretable carboxylic
acids; halogenated aldehydes that are formed may be further oxidized
to halogenated carboxylic acids or reduced to halogenated alcohols,
which are excretory metabolites in urine from rodents exposed
experimentally to CFC replacements. The chronic toxicity of the CFC
replacements studied is unlikely to be of relevance for humans exposed
during production and application of CFC replacements. -- Environ
Health Perspect 104(Suppl 1):75-83 (1996)
Key words: chlorofluorocarbon toxicity, ozone depletion, halogenated
hydrocarbons, biotransformation
_________________________________________________________________
Manuscript received 18 July 1995; manuscript accepted 2 October 1995.
Address correspondence to Dr. W. Dekant, Department of Toxicology,
University of Wurzburg, Versbacher Str. 9, 97078 Wurzburg, FRG.
Telephone: +49 (0931) 201 3449. Fax: +49 (0931) 201 3446. E-mail:
dekant at toxi.uni-wuerzbur.de
_________________________________________________________________
[Table of Contents]
Last update: February 29, 1996
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Regards,
Ian Maclaine-cross (ian at ilm.mech.unsw.edu.au)
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