Your Daily Poison - Pesticide Action Network UK

conference that a Europe-wide biomonitoring
programme and long-term health outcome
surveillance programme should be started.
The RCEP identifies that the weakness in most
epidemiological studies on pesticides is the
‘considerable difficulty of quantifying exposure
and identifying the particular pesticide or coformulant
mixture concerned 41 .’ Formerly one of
the most senior government toxicologists in the
UK, Dr Tim Marrs considers that ‘Epidemiology
is usually of little value in pesticide evaluation’,
and that ‘the impact on pesticide regulation [for
single pesticides] of epidemiological studies
has been small, with the possible exception of
2,4,5-T in the 1970s 42 . Dr Marrs subsequently
commented that if a serious effect was
occurring post-marketing, something might be
expected to be observed in a large number of
epidemiology studies. The Advisory Committee
on Pesticides describes the system for the
review of epidemiological studies carried out by
its Medical and Toxicology Panel as one of the
key measures in place to check for possible
adverse effects once a pesticide has been
approved 43 .
At the root of failing risk assessment:
inadequate toxicity testing
Questions are now being asked in the most
respected scientific journals about the
effectiveness and relevance of toxicological
tests on laboratory animals which form the
basis of current regulatory safety assessment
of chemicals including pesticides. For example,
the science journal Nature, reporting a new
initiative by the European Commission to
develop alternatives to animal testing
acknowledges the poor quality of most animal
tests, that they are ‘wasteful and poorly
predictive’, and are ‘stuck in a time warp.’ 44
According to the report, Thomas Hartung,
head of the European Centre for the Validation
of Alternative Methods (ECVAM) in Italy said,
‘toxicity tests that have been used for decades
are simply bad science.’ Nature’s senior
European correspondent Alison Abbott
remarks that the experiments have ‘never
undergone the rigours of validation that in vitro
alternatives now face. Most animal tests overor
under-estimate toxicity, or simply don’t
mirror toxicity in humans very well.’
The current system has not always detected
the evidence scientists have discovered in
ecological phenomena of the harmful effects of
chemicals. The recent Prague Declaration on
Endocrine Disruption 45 (Appendix 8), which
over 200 scientists have signed, states that ‘the
existing safety assessment framework for
chemicals is ill-equipped to deal with endocrine
disrupters. Testing does not account for the
effects of simultaneous exposure to many
chemicals and may lead to serious
underestimations of risk … A fundamental
element of chemical safety assessment is the
assumption of a threshold dose below which
there are no effects. This may not be tenable
when dealing with endocrine disrupters,
because certain hormonally active chemicals
act in concert with natural hormones already
present in exposed organisms. Thus even
small amounts of chemicals may add to the
overall effects, irrespective of thresholds that
might exist for these chemicals in the absence
of natural hormones. Additionally, due to
limited sensitivity of established test methods,
it is likely that effects are overlooked.’
The RCEP concurs with the signatories of The
Prague Declaration in advocating the
development of new assays and screening
methods which should ‘take advantage of
modern technologies such as genomics,
proteomics, bioinformatics and metabonomics’:
‘the element of uncertainty inherent in using
animal models might be reduced by the
development of the new integrated and
molecular based technologies, such as the use
of toxicogenomic methods or human cell
culture models and the development of animal
models of multisymptom/multisystem disease.
… Toxicogenomics is a tool in development,
but it has the potential to inform and improve
risk assessment in the future … Under strictly
controlled experimental conditions, human cell
culture models can be used to re-create
human cellular function in an in vitro
environment … This could reduce the need for
animal models and animals for experimentation
and deserves further exploration for those
involved in pesticide regulation 46 .There is,
however, considerable scientific disagreement
on the how accurately different forms of testing
can predict outcomes 47 .
The relevance of animal data to human
disease is questionable when considering the
wide inter- and intra-species variability of just
one toxicological endpoint, the lethal dose
(Appendix 9). Data from the same species but
the second UK pesticide exposure report 15