Day 039 - 20 Oct 94 - Page 73
1 A. Yes.
2
3 Q. Quantities vastly in excess of anything that a human being
4 can conceivably get by way of food additives?
5 A. Yes, but you will appreciate, Mr. Rampton, that rodents
6 are small animals with a short lifetime, of a homogeneous
7 kind, eating a strictly controlled diet. The human
8 population whose health we are seeking to protect is
9 massively larger, massively more diverse and massively more
10 complicated, and I do not think that one can simply say:
11 "Oh, because there are no full blown tumours at less than
12 two per cent in those number of rats to a level of
13 statistical significance whereby they are assumed not to
14 have occurred more -- the likelihood of occurring by
15 accident was less than one chance in 20". I do not find
16 that compelling reassurance.
17
18 Q. I do not think you will find, when we come to look at the
19 conclusion, that is what JECFA thought either,
20 Dr. Millstone, nor do I think you will find they confined
21 themselves to rats. I want to ask you this: All those
22 many groups who produced studies using rats did not use the
23 same groups of rats, did they?
24 A. There is some overlap, but there is also some variation
25 amongst the different kinds of rats that are used.
26
27 Q. Not kinds of rats, the same actual rats?
28 A. Certainly not the same rats.
29
30 MR. JUSTICE BELL: Can I ask a question: If you have group of
31 rats they are homogenous rats?
32 A. They are supposed to be ----.
33
34 Q. As near as you can?
35 A. As near as they can.
36
37 Q. That, no doubt, has something to do with the selection of
38 the size of the group. If you have heterogeneous animals
39 or people, as one obviously does, I can see the value of a
40 survey of a very large number of people because the genetic
41 differences ----?
42 A. May be significant.
43
44 Q. -- may very well be significant, but am I just guessing in
45 the dark if I say that the fact that animals of your group
46 are homogeneous, or as near as you can get, will be
47 something at least of the reason for being content, if
48 Professor Ito is content, with a group of 50?
49 A. No. I do not think that is correct. I think you are
50 coupling together two quite separate considerations.
51 Experiments are conducted with laboratory animals in groups
52 of varying sizes, some as low as five, some as high as 50
53 and so on. Whatever the group size, there is an attempt
54 typically to use a homogeneous group of rats.
55
56 The reason for doing that is simply in order to factor out
57 genetic considerations and enable the experimenters to
58 focus just on the effects of the compound and not the
59 variations amongst different animals. There is not a
60 direct coupling between the homogeneity of the group of
