Laboratory rat feeds contaminated with pesticides and GMOs
Date Added to website 20th June 2015
Published: 17 June 2015http://www.gmwatch.org/news/latest-news/16242
from GM-Free Cymru: this is a carefully considered article published in
GM Watch, referring to the implications of the new research.]
New study throws doubt on findings of safety in pesticide and GMO studies. Claire Robinson reports
rodent feeds are highly contaminated with pesticides, toxic metals,
PCBs, and GMOs, according to a new study soon to be published in the
journal PLOS ONE.
The study casts doubt on claims of safety
drawn from hundreds of thousands of animal feeding trials performed for
regulatory approvals of pesticides and GMOs.
study, the team of Prof Gilles-Eric SÚralini at the University of Caen
in France analyzed the dried feed of laboratory animals sourced from 5
continents. These diets are commonly fed to rats used to test the
safety of pesticides and GMOs. The study investigated 13 samples of rat
feeds for traces of 262 pesticides, 4 heavy metals, 17 dioxins and
furans, 18 PCBs and 22 GMOs.
The researchers found that all
the feeds contained significant concentrations of several of these
products at levels likely to cause diseases by disrupting the endocrine
and nervous system of the animals. Considering all the contaminants
measured, these diets, when consumed over a long-term experimental
period, would be considered by standard measurements to pose a very
high hazard to health.
For example, residues of
glyphosate, used on 80% of GMO crops and widely used to “dry down”
non-GMO crops before harvest, were detected in 9 of the 13 diets.
Eleven of the 13 diets contained GMOs that are grown with large amounts
This is a problem for public health because
regulators use tests on animals fed on these diets to assess the safety
of any one pesticide or GMO by looking at the difference between the
exposed animal and the controls. If the treatment (exposed) and control
groups are both eating an uncontrolled assortment of pesticides or
GMOs, any actual toxic effect arising from the pesticide or GMO under
test, unless the effect is massive in size, will be lost amid the
“noise” caused by the jumble of potentially and known toxic substances.
upshot can be that regulators conclude that the pesticide or GMO under
test is safe on the grounds that no significant difference is found
between exposed and control groups, when in fact both groups are
exposed to such a wide variety of toxins that their effects have
drowned out any toxic effect from the pesticide or GMO being
Treatment and control groups both fed uncontrolled GMOs
the new study, eleven out of 13 of the diets were found to contain
GMOs. This is of concern because these standard feeds are commonly used
to test the safety of GMOs in the 90-day rodent feeding trials demanded
by the EU regulatory system.
One of these diets, from the
Purina company, was used in a 90-day rat feeding study by DuPont
authors, which could be used to obtain regulatory approval of a GMO
Roundup-tolerant canola variety. The study concluded that the GM canola
was as safe as the non-GM canola, based on the lack of differences
between the group fed the GM canola and the control group fed non-GM
canola. Yet the new study found that the Purina feed contained around
12.8% GM soy and 35.6% GM maize – and was not even labelled as GM.
new study also found that the feed contained residues of glyphosate and
AMPA (the main metabolite or breakdown product of glyphosate). So
although the control rats were not eating the GM canola under test,
they were eating other GMOs with the same glyphosate-tolerant trait, as
well as residues of the pesticide that the GMOs are grown with. In
other words, the study did not compare rats fed a GM diet with rats fed
a non-GM diet, but rats fed one type of GMO plus pesticides with rats
fed similar GMOs plus pesticides.
Claims of safety based on such badly controlled studies are not worth the paper they are written on.
New findings challenge abuse of historical control data
new findings also challenge the common practice by regulators to
approve pesticides and other chemicals based on comparisons of the test
animals not only with the control group within the experiment, as good
scientific practice demands, but also with so-called “historical
Historical control data are collected from
a wide variety of experiments, some decades-old, done in different
conditions, in which animals are fed diets that will vary widely in
levels and types of contaminants. Unsurprisingly, given these massive
uncontrolled variables, the range of incidence of any one disease or
toxic effect found in the historical control data will be huge.
example, according to these data, 13–71% of control animals in an
experiment would spontaneously or naturally present breast tumours and
26–93% would present pituitary tumours. Thus if the treated (exposed)
animals present an increased incidence of tumours, if the increase
falls somewhere within these very wide ranges, it could still be
dismissed as “spontaneous” and not related to the substance being
This wide range of “spontaneous” tumours also
means that researchers have to use a large number of animals in an
attempt to obtain statistical significance in the results of
carcinogenicity tests, for example.
This is a matter of
great public interest. In animal feeding experiments carried out for
regulatory approvals of any one pesticide, industry and regulators
routinely use historical control data to dismiss findings of an
increase in a disease in the group of animals exposed to the pesticide
over and above the incidence of the disease in the controls within the
They do this by pointing to the extremely wide
range of disease incidence found in the historical control data and
saying that as the increase in this disease found in exposed rats falls
within that range, it can be considered “spontaneous” and can be
dismissed. Thus the pesticide is wrongly judged safe – and public
health is placed at risk.
Historical control data used to dismiss birth defects from glyphosate
years ago I came face to face with an example of the abuse of
historical control data to “disappear” toxic effects from glyphosate. I
co-authored a paper on the German regulatory authorities’ analysis of
industry tests on glyphosate. We found that time and time again, the
German authorities dismissed findings of birth defects in laboratory
animals fed glyphosate on the basis of comparisons with unspecified and
unpublished historical control data.
Since the number of
birth defects in the animals fed glyphosate fell within the wide range
of incidence found in the historical control data, the German
authorities concluded that the birth defects were not related to the
glyphosate treatment but were “spontaneous” – in other words, they
could have arisen without exposure to glyphosate.
study shows this conclusion to be invalid. It suggests that there may
be nothing “spontaneous” about tumours found in control animals. Far
from being unexposed, they are in fact exposed to a large number of
known and suspected carcinogens and tumour-promoters.
readers will recall that the SÚralini team’s study that found a trend
of increased tumours in rats fed GM NK603 maize and Roundup was
dismissed by GMO proponents on the grounds that the number of tumours
in exposed rats fell within the range of “spontaneous” tumours found in
the historical control data on the supposedly tumour-prone
The new study’s findings suggest that
such a judgment was ill-considered. In reality the NK603 maize was a
rare example of an experiment where the researchers controlled for
pesticide and GMO content in the diet. In light of the new findings,
the NK603 study appears to have been carefully carried out, while the
studies routinely accepted as proof of GMO safety seem haphazard.
GMO proponents may wrongly exploit these results
all the above, we must not allow GMO proponents and the European Food
Safety Authority to exploit the new findings to argue for abandoning
Europe’s currently mandatory requirement for animal feeding studies
with GMOs on the grounds that it is too difficult to control the feed
This is an outcome that GMO
proponents have long pushed for. It would also please the US
representatives in the TTIP trade deal negotiations, which aim to
dismantle the EU approvals process for GMOs.
Instead the new
results should push animal feed companies to clean up their act. The
fact that no GMO contamination was found in the Italian animal feed
samples shows it’s possible to make laboratory rodent diets without
GMOs. Regarding pesticides, researchers (or the feed company) need to
have to have the crops grown especially, with all chemical inputs
carefully controlled at the farm level.
Animal welfare problem
Feeding lab animals uncontrolled toxins isn’t just a scientific problem: it’s an animal welfare issue.
animals in long-term experiments die before the planned sacrifice time
(two years in the case of cancer studies). Typically the cause is
kidney disease and tumours – diseases that are associated with the
particular contaminants found in the animal feeds tested in the new
Researchers have to compensate for the premature
deaths and ensure that enough animals are left alive at the end of the
experiment to obtain statistical significance in the results. They do
this by designing experiments using large numbers of animals. Purer
diets would enable scientists to use fewer animals because there would
be less statistical “noise” created by toxic contaminants.
tolerates animal experiments if there is a perceived benefit in terms
of protecting public health and the environment from the release of
potentially toxic GMOs, pesticides and other chemicals. But in the case
of experiments conducted with contaminated feeds, there is no payoff
for the animals’ suffering in terms of generating findings that can
help protect public health because the lack of control regarding the
types and amounts of toxins mean no meaningful information can be got
from the experiment.
The potential problems caused by
contaminated diets stretch way beyond the laboratory. That’s because
the same companies that make the laboratory rodent feed diets analyzed
in the new experiment also make pet food. So it’s not only lab rats
that are at risk from contaminated diets, but people’s dogs and
The take-home message from this study is that
feed companies have to improve the quality of their products. This will
enhance the reliability of scientific experiments, improve the
protection of public health, and create a better quality of life for
lab animals and pets alike.