Day 039 - 20 Oct 94 - Page 72
1 really saying is that the reason Professor Ito and
2 colleagues are not using groups ----?
3 A. Large groups.
4
5 Q. -- containing or including more than 50 rats is for
6 financial reasons, although they really must appreciate
7 that they should be using more. Is that not it?
8 A. In my understanding, in my discussions in participation
9 in conferences with toxicologists is that they clearly
10 convey to me the impression they recognise that were the
11 animal sample size to be significantly greater, the
12 sensitivity of the test would be substantially improved and
13 they would be able to do far better science.
14
15 The reason why 50 animals per gender per dose group is used
16 as a standard is because that it is a sort of -- it is a
17 convention reflecting an assessment of the cost. I mean,
18 these things -- may I just explain? Just to do 50 animals
19 per gender per dose group, say, with controls and three
20 doses, for the lifetime of the rodents (which might be two
21 and a half years) and to conduct a comprehensive autopsies
22 on each of the rats, put the tissue on slides, scrutinize
23 it under a microscope and do a proper statistical analysis,
24 at current prices a test of that nature can cost between 10
25 and 15 million pounds. So these tests are already very
26 expensive using these sizes of groups.
27
28 MR. RAMPTON: There have been a very large number of studies on
29 rats alone, have there not?
30 A. Sorry, you turned away; I lost your voice.
31
32 MR. JUSTICE BELL: I sometimes, I have to say, suffer from it
33 myself. I gather your hearing is not of the very best.
34 I have to say nor is mine sometimes.
35
36 MR. RAMPTON: There have been a comparatively large number of
37 studies in rodents using BHA, have there not?
38 A. There have, indeed, yes.
39
40 Q. They all reach more or less the same conclusion, do they
41 not?
42 A. No. I think that is a mistake, Mr. Rampton. I think
43 my reading of these reports is that the results are
44 equivocal. There are studies in which evidence of lesions
45 emerges and other studies in which evidence of lesions does
46 not emerge. I do not see a single simple consistent
47 pattern emerging from these studies.
48
49 Q. There is no study in which carcinomas were observed at less
50 than two per cent of the diet, is there?
51 A. I am not aware of a study in which tumours were
52 observed below two per cent, but I am aware of a study in
53 which premalignant lesions of the kind indicated that the
54 risk of tumours developing did emerge at lower doses in the
55 forestomach.
56
57 Q. Say .5 per cent?
58 A. Yes.
59
60 Q. Or even .25 per cent of the diet?
