4 Alternative explanations for the atypical
results
17. At first, the shellfish industry accepted that
the atypical positive DSP results might represent the presence
of something that was, or could be, a threat to public health.[26]
However, as the period of closures continued, the industry began
to doubt the presence of a toxin, as normal episodes of DSP are
generally short-lived.[27]
Furthermore, they argued that outbreaks of DSP are usually associated
with an algal bloom, but that this was not the case in the atypical
results.[28]
18. The industry noted that the atypical results
began to be found when CEFAS took over monitoring for England
and Wales, although DARD began to find some atypical results at
around the same time. Moreover, the atypical results appear to
have stopped since a common method was introduced at all three
laboratories in November. The industry put forward the hypothesis
that the results were an artefact of the method used at CEFAS
and DARD rather than the presence of a novel toxin.[29]
19. When testing was transferred to CEFAS, the laboratory
adopted a different scientific protocol for the MBA to that used
at FRS (DARD used a third version of the method). The industry's
suggestion is that CEFAS's method resulted in solvents used in
the preparation of the shellfish extract remaining in the material
that was injected into mice, and that it was these solvents that
caused the symptoms and death observed in the atypical results.
For example, the CEFAS method involved a more vigorous extraction
method, which the industry suggests may increase the likelihood
of emulsion formation, which in turn could result in greater volumes
of solvent remaining in the final extract.[30]
20. Because none of the laboratories concerned found
atypical results in other shellfish as often as in cockles, despite
using the same procedure, the industry accepts that some factor
associated with cockles was involved too, perhaps the presence
of stress-induced compounds, but maintains that there was no evidence
of any risk to human health.[31]
The industry also criticises other aspects of the way in which
the mouse bioassay was carried out, which it believes may have
allowed certain cockle compounds to remain the final material
and thus contaminate the results.[32]
21. The FSA has investigated the possibility that
solvent carry-over from the production of the extract to the material
that is injected into the mice is responsible for the atypical
symptoms. However no relationship was found between the amount
of solvent present in the injected material and atypical results:
some samples which contained a lot of solvent did not produce
the atypical result and some with little solvent did. FSA says
that it is not possible to ensure that solvent is completely removed
and therefore have not been able to show that samples that are
completely free of solvent may still produce the atypical response.
The FSA has also found no link between the type of solvent used
and the atypical response. It has concluded that there is no evidence
that solvent carry-over explains the atypical response.[33]
22. The atypical results prompted closer scrutiny
of the methods used at the three laboratories and an audit was
carried out by Professor Hugh Makin. This highlighted the fact
that originally the three labs were using three separate versions
of the MBA and identified some poor scientific practice, principally
a lack of quality assurance. Of particular concern was the fact
that there were different approaches to determining whether a
particular test result was positive or negative.[34]
The FSA and the laboratories concerned have taken steps to address
those issues, adopting a common method since November 2003. It
is both astonishing and unacceptable that the three laboratories
conducting statutory toxin monitoring used different methods,
and more importantly, did not appear to have a common standard
for determining whether a result was positive or negative.
23. The FSA was slow to recognise that the atypical
results merited further investigation, slow to take account of
the industry's suggested explanations and was slow to investigate
the possibility that the methodology could be at fault. The flaws
highlighted in the methods applied by the laboratories, even if
they do not explain the atypical results, suggest that the FSA
should, at the very least, have paid closer attention to quality
control in its investigations. These delays have meant that this
crisis has been unduly prolonged.
24. The FSA does not appear to recognise that
the extent to which the industry believes that the atypical results
can be explained by the solvent and methodology hypothesis. As
a result it has not done enough to communicate what it has done
to investigate this hypothesis and on what evidence it has rejected
it, if indeed it has. In such a delicate situation as this, where
the risk of a threat to public health must be balanced against
the risk of severe and lasting damage to individuals' livelihoods
and to businesses, it is imperative that the Agency take all possible
steps to ensure that reasonable hypotheses are rigorously researched
and that the outcomes of such research are made clear to the other
parties involved.
25. The industry's hypothesis is supported by the
fact that the period during which atypical results were found
coincided with the period during which a new version of the test
was in use. The problem of atypical results lasted from the summer
of 2001 to late autumn 2003, and if further atypical results are
discovered, it seems unlikely to be resolved unless the cause
of the results can be discovered. There is an urgent need for
further investigation of the cause of the results and what, if
any, are the implications for human health. We understand that
the FSA has commissioned research with this aim. We recommend
that the FSA pursue its research into the causes of the atypical
response with urgency and it should inform us of the outcome of
such research. The FSA should inform us of its strategy for responding
to any future atypical results should further research prove inconclusive.
26 Ev 12 Back
27
Ev 67 Back
28
Ev 12 Back
29
Ev 1, Ev 12, Ev 67, Ev 86 Back
30
Q3 Back
31
Qq27-28 Back
32
Qq23, 25-26 Back
33
Investigations To Assess Whether Diethyl Ether Or Acetone Carry
- Over During The DSP Standard Operating Procedure Is Responsible
For The Atypical Response In Mice, FSA Report, 01 October 2003 Back
34
An audit of methods and procedures for lipophilic toxin analysis
used by laboratories at CEFAS, FRS and DARD, which undertake the
statutory monitoring of shellfish toxins in the UK. Hugh L. J.
Makin, 1 October 2003, Section 9, para 5. Back
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