Day 038 - 19 Oct 94 - Page 29


     
     1        less trivial than, say, eczema.  I mean, eczema itself can
     2        be very unpleasant, but it is most commonly relatively
     3        mild, itching and skin rashes; whereas hyperactivity is a
     4        major blight on the lives of the children, their families
     5        and their communities.
     6
     7   MR. MORRIS:  Just to deal with some parts of the jigsaw we may
     8        have overlooked before we move on to the specific
     9        compounds.  I might have to jump about here a little bit.
    10        Are the results of tests on animals always consistent?
    11        A.  Let me see if I have understood the question.  Do you
    12        mean if you test one compound on several different kinds of
    13        animals, do you always get the same answer?  Is that what
    14        you are asking?
    15
    16   Q.   Not particularly, but that could include it.  Just in terms
    17        of interpretation of results of animal testing -----
    18
    19   MR. JUSTICE BELL:  Tell the witness what the point is you are
    20        getting at.
    21
    22   MR. MORRIS:  I think I am referring to, you can test a group of
    23        animals and get one result and test the same group and get
    24        a different result in exactly the same circumstances.  Is
    25        that ----
    26        A.  It is not uncommon that a given compound tested in a
    27        given strain of laboratory animals in different
    28        laboratories yields different results.  There are
    29        variations between laboratories, but it does also, from
    30        time to time, happen that a compound may be tested in the
    31        same strain of animal in the same laboratory on different
    32        occasions generating different results.
    33
    34        Moreover, there is very considerable variability between
    35        species, and even between varieties of a particular
    36        species; there are quite a few different kinds of rats and
    37        different kinds of mice used in toxicological tests.  You
    38        do not get consistency even within varieties, within the
    39        species, within laboratories or between laboratories, which
    40        makes the interpretation subsequently of the results of
    41        those studies a very, very difficult matter.  The science
    42        is anything but cut and dried.
    43
    44   Q.   Are particular animal species identified as most relevant
    45        for a particular compound, or ----
    46        A.  I think that is one of the most important questions in
    47        toxicology policy to which no adequate answer has yet been
    48        provided.  Until the mid-80s I was unable to locate within
    49        the toxicological literature any systematic attempt to
    50        estimate the extrapolative validity of laboratory 
    51        animals for human beings.  There were then a few attempts, 
    52        I think, starting in about 1983, 1984, which attempted to 
    53        estimate the extrapolative validity of rat feeding studies
    54        of known human carcinogens to the effects on humans; where
    55        we know compounds cause cancer in humans.  At the time we
    56        were aware of, I think it was about 18 compounds or groups
    57        of compounds where, for this purpose, tobacco smoke counts
    58        as one group or work in the leather tanning industry counts
    59        as one pattern of exposure.
    60

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