Day 039 - 20 Oct 94 - Page 16
1 this discussion, whereby we do find from time to time that
2 when compounds are tested at a variety of doses in a given
3 population of animals, you do not get a simple increase in
4 the effect as the dose rises. This is frequently
5 disregarded as unreliable evidence indicating that
6 something untoward has occurred.
7
8 I tend to share Verrett's view, not just Verrett's view,
9 there are other toxicologists in the literature who think
10 we ought to take seriously dose effect relationships which
11 do not simply go up either linearly or in a smooth slope.
12 It is realistic biochemically to expect that. In some
13 cases you might get a lower effect at a high dose and a
14 higher effect at some lower doses, even if you get no
15 effect at low dose.
16
17 I think it is again worth drawing attention to what I said
18 in the lower paragraph. This relates to something we were
19 discussing yesterday as to whether or not the acceptable
20 daily intake should be or always is set by reference to
21 what appears to be the most sensitive species. Here we
22 have an example where evidence from chick embryo injecting
23 Amaranth in this case into chicks as they were developing
24 within the shells of the eggs.
25
26 The evidence has been dismissed because the chick embryo
27 test has supposedly not been validated. As I was arguing
28 yesterday, that may be true but exactly the same can be
29 said for all the rest of the animal toxicology work.
30 Simply to pick on this one species or this one test in this
31 particular species and claim that somehow this is
32 demonstrably less valid than the others is, I think,
33 scientifically unsupportable. It has been argued that we
34 should disregard chicks because they are exceptionally
35 sensitive, whereas very recently two Japanese scientists
36 reported in 1991 that, in fact, in some respects chicks
37 might be less susceptible to Amaranth toxicity.
38
39 MR. MORRIS: Than rats?
40 A. Yes, than rats. The details of their paper indicate
41 that they believe that the presence of dietary fibre
42 contributes to or, as it were, provides a protective effect
43 in laboratory animals, and that implies that if we are
44 going to make judgments now about the interpretation of the
45 rodent studies, it would be useful to know what was the
46 dietary fibre content of -- what was the fibre content of
47 the diet which the rodents received, because that might
48 account for some of the variation, the marked variation
49 that has been found in different rodent studies.
50
51 Q. Do you want to make a comment on the so-called botched
52 study in the USA which led to it being banned in the
53 States?
54 A. I can make a few brief observations.
55
56 Q. Not necessarily about that study, but about any other
57 studies that may back that up?
58 A. Forgive me, Mr. Morris. I am not entirely clear
59 I understand your question.
60
