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

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