Day 011 - 12 Jul 94 - Page 15
1
Q. You spoke of chlorine as an agent which can damage ozone
2 in the stratosphere; is that right?
A. Yes.
3
Q. Is it the only agent that does that, so far as we know?
4 A. It is not the only agent which can damage the ozone in
the stratosphere, but it is the only one which has been
5 increasing, or is known to have been increasing rapidly as
a result of the industrial revolution, and also it is the
6 only one which has been identified in chemical studies
carried out in the stratosphere as being intimately
7 involved with the current large ozone destruction which
occurs in the Antarctic region.
8
Q. Speaking of chlorine, let me ask this question in this
9 way: What is the group of substances which are, for
short, known as CFCs?
10 A. They are known ----
11 MR. JUSTICE BELL: Just pause a minute.
A. CFC is a short version for chlorofluorocarbon, i.e. a
12 substance which contains carbon, chlorine and fluorine.
The two best known chlorofluorocarbons are CFC-11 and
13 CFC-12. CFC-11 is more correctly known as trichlorofluoro
methane; CFC-12 is dichloro-difluoromethane.
14
Q. Can we stick with 11 and 12 for the moment? It is going
15 to be easier! I am going to ask you in a moment about the
mechanism by which those substances, CFC-11 and 12, are
16 perceived to cause damage to the ozone layer. First,
I want you, if you will, to answer this question: Is a
17 CFC, as you described it, different from an HCFC and, if
so, how?
18 A. A CFC is different from an HCFC because an HCFC
contains at least one hydrogen atom which interrupts the
19 perfect halogenation, which is the replacement of hydrogen
by either chlorine in this case, or fluorine, which belong
20 to the family known as halogens.
21 The result is that in the lower atmosphere, the
troposphere, the chemical is rendered liable to attack by
22 what are called free radicals, which are species which are
formed in the troposphere from the break down of other
23 compounds, and the species in particular which can attack
the hydro-chloro fluorocarbons are hydroxyl, which is like
24 water from which a hydrogen atom has been removed, and the
peroxy radical, which is HOO, which is what you get from
25 hydrogen peroxide if you remove a hydrogen atom.
26 Q. Is hydroxyl OH?
A. The hydroxyl is OH.
27
Q. Do or have CFCs, without the extra hydrogen on them, do
28 they behave in the same way in the troposphere or
differently?
29 A. They behave differently. They are, essentially,
chemically inert in the troposphere.
30
Q. Please explain how the CFCs perform their mischief in the
