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?

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