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Professor Derek Burke CBE DL
Cambridge
Dear Dr Butt,
I wish to comment briefly on three sections of Dr.
Pusztai's letter of July 31st:
- His implied accusation of my own incompetence.
- His defense of his own work.
- His criticism of some data supporting the conclusion of
the lack of any adverse effect on animals which had been
fed GM foods.
One of Dr Pusztai's remarks which warrants particular rejection
is: "In this context one can also ask that since when
the opinion of a former scientist (Dr Burke) carries such
weight that on his word and without experimental evidence
the results of a peer reviewed paper on GM potatoes are rejected
because a Chinese scientist had done some work on GM tomatoes
and sweet peppers even though this has never been published?"
1. The phrase "a former scientist (Dr Burke)".
I do not need to defend my scientific credentials; they can
be found in any recent edition of 'Who's Who' or 'People of
Today'. But briefly, I was appointed in 1969 as Professor
of Biological Sciences at the University of Warwick and founding
Chairman of the new Department of Biological Sciences, a Department
has since scored at the highest grade in every Research Assessment
Exercise. While I was there I cloned the interferon genes
and isolated the first monoclonal antibody to interferon (Celltech's
first product), and published a number of papers in prestigious
journals, including PNAS, Cell, and Nature. I have over 130
publications, mostly in peer reviewed journals. Later, while
working in Canada, I was appointed a Professor at McMaster
University, and subsequently also at the University of East
Anglia; colleagues will know that all such appointments involve
peer review. I am now an Emeritus Professor and have two honorary
Doctor of Science degrees. Moreover, I have worked on peer
review and science policy for the Medical Research Council,
the Cancer Research Campaign, and the BBSRC. I was a member
of the Technology Foresight Steering Group, and Editor and
Editor in Chief of the Journal of General Virology. In that
latter position, I personally read, edited, and checked referees'
comments on every paper we published - about 200 papers per
year over four years. I consider that I have the credentials
to make a judgment on other people's work, and do not need
to answer to Dr Pusztai or anybody else.
2. A full account of the claims Dr Pusztai makes for his
own work and the subsequent events can be found in Appendix
1 of "Genetically Modified Crops: the ethical and social
issues" pages 140 - 142 (www.nuffieldfoundation.org).
Dr Pusztai first made his claims that feeding GM potatoes
to rats produced damage to the immune system on television
on August 10th, 1998 and then in a series of press releases,
but it was not made clear then or later that this work was
part of a tripartite collaboration, the genetic constructs
having been made at the University of Newcastle, and the GM
potatoes grown at the Scottish Crop Research Institute. Only
the feeding experiments were done in Dr Pusztai's laboratory.
Because of the controversy his claims aroused, an independent
audit committee reviewed his results and the outcome was published
on the Rowett web site on the 28th of October, 1998. The report
made four substantial criticisms of the work, and in addition,
pointed out three ways in which the claims made on television
conflicted with his data. Dr Pusztai rejected some of the
conclusions of the audit committee, but the committee was
not persuaded by his response to alter their conclusion.
Then on 12th of February 1999, scientists from fourteen countries
(at least one of whom rapidly withdrew) announced their support
for Dr Pusztai in a Press Conference at the House of Commons.
In an accompanying Greenpeace press release, the possibility
was raised that the damage claimed to by Dr Pusztai might
be due to the virus that was used as the source of the promoter
in the transgene constructs. On February 19th a full review
by the Royal Society was announced and this was published
in June, 1999 with the title "Review of data on possible
toxicity of GM potatoes" (www.royalsoc.ac.uk). It concluded
that the reported work from the "Rowett [Institute] is
flawed in many aspects of design, execution and analysis and
that no conclusions should be drawn from it." Further:
"We found no convincing evidence of adverse effects from
GM potatoes. Where the data seemed to show slight differences
between rats fed predominantly on GM and on non-GM potatoes,
the differences were uninterpretable because of the technical
limitations of the experiments and the incorrect use of statistical
tests. The work concerned one particular species of animal,
when fed with one particular product modified by the insertion
of one particular gene by one particular method. However skillfully
the experiments were done, it would be unjustifiable to draw
from them general conclusions about whether the genetically
modified foods are harmful to human beings or not. Each GM
food must be assessed individually." Dr Pusztai's data
was not published until later in 1999 (Ewans S W B & Pusztai
A, (1999) The Lancet 354, 1353-1354). It's claims were criticised
by both the Royal Society and the BBSRC.
3. Dr Pusztai writes very critically of some of the results
reported in the review which Professor Michael Gasson (currently
acting Director of the Institute of Food Research, Norwich)
and I wrote after an invitation from Nature, which after peer
review, was published in Nature Reviews Genetics, 202, March
2001 pp.217- 222, with the title "Scientific perspectives
on regulating the safety of genetically modified foods".
This was a detailed review of the scientific issues that have
arisen over the years to in the process of regulation. In
passing, in one sentence, we referred to work carried out
by Professor Z-L. Chen and nine colleagues in China, in an
attempt to repeat Dr Pusztai's claims. Professor Chen's paper,
which was unpublished at the time of writing but was sent
to me by him, and which has now been published in Plant Journal,
is very detailed, running to eleven pages of text, six very
detailed tables and six figures. The summary includes the
statement "The results showed that no significant difference
was found in growth, accumulative body weight gain, food consumption,
haematology, blood biochemical indexes, organ coefficient
and pathological evaluation between rats and mice of either
sex fed with GM diets and those with non-GM diets. It was
also found that GM products had no mutagenic activity either
in vitro or in vivo by micronucleus test, sperm aberration
and Ames test. These results suggest that the GM sweet pepper
and tomato are comparable to the non-GM counterparts in terms
of safety as food."
The Chinese work is, of course, not the only feeding study
that has been done; a very large number of feeding studies
have been carried out with the paste from GM tomatoes and
with GM soya and no adverse effects have been found. No reputable
scientist I know believes that Dr Pusztai's conclusions are
general for the products of GM crops. The explanation for
the effects he reported remains obscure, but they have neither
been able to be repeated, nor are they supported by his own
former institute, nor by an independent audit committee nor
by a specially convened Royal Society Working Group. I believe
they should firmly be set aside.
Derek Burke
October 13th, 2003
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