From: B.Hamilton@irl.cri.nz (Bruce Hamilton)
Subject: Re: HCFCs (Was benzotrichloride)
Date: Sat, 02 May 1998 20:48:45 GMT
CHEMone <firstname.lastname@example.org> wrote:
> HCFCs intensely hepatotoxic? Which HCFCs are these?
HCFC-123 ( as part of a mixture with HCFC-124 ) was implicated in
an epidemic of liver disease in drivers of an overhead crane with
an airconditioned cabin according to one report from Belgium.
[Lancet, v350 p556 (1997)]
However, no exposure level was identified as all the leaks were
repaired prior to the discovery of the link, but testing on rats
by DuPont in 1990 showed that reversible liver damage could occur
if exposed to 1000ppm for six hours/day for seven days a week,
compared to the current workplace exposure limit of 50ppm.
US National Institute of Health workers had predicted in 1991 that
HCFC-123 ( CHCl2CF3 ), could cause liver damage because it is
metabolised in rats in the same way as the inhalation anesthetic
halothane ( CHBrCLCF3 ), which can cause a rare, serious form of
hepatitis [ Proc. Nat. Acad. Sci. USA, v.88 p.1407 (1991)].
Both halothane and HCFC-123 are oxidised to trifluoroacetyl chloride,
which reacts with liver proteins, and the researchers into the
Belgium incident believe that "it looks possible that HCFC-123 is
more hepatotoxic to humans than halothane ".
In the USA, ASHRAE requires monitors in HCFC-123 chillers that
trigger alarms if concentrations occur above 10ppm, and HCFC-123
is only produced in relattively small quantities (several thousand
tonnes). According to the British Institute of Refrigeration, both
HCFC-123 and HCFC-124 were already being phased out anyway,
( probably because blends are a pain to maintain and service ).
A general discussion of the incident, and the responses to it,
can be found in Chemical & Engineering News 25 August 1997 p.8
and Chemistry and Industry, 1 September 1997 p.670.
It's worth noting that many people believe that CFCs were
essentially non-toxic, hence their replacements are inevitably
more toxic, however the literature has several reports of lethal
exposure that indicates the CFCS are not simply asphyxiants.
It's believed they sensitize the mycocardium to circulating
catecholamines with resulting ventricular dysrhythmias that are
potentially life-threatening [ C&EN, 23 April 1990 p.3 ]
>Are you saying these compounds are even worse than say 1,1,2,2-
>Tetarchloroethane? They would have to be so to describe them
>as 'intensely hepatotoxic'.
I'm not, but I'm looking forward to the expected entertaining kneejerk
from everybody's favorite anti-government, anti-environmentalist