[permaculture] Fwd: [SANET-MG] Bt Toxicity Confirmed (to non-target beneficial insects)
Lawrence F. London, Jr.
lflj at bellsouth.net
Wed Jul 11 10:54:49 EDT 2012
------- Original Message --------
Subject: [SANET-MG] Bt Toxicity Confirmed
Date: Wed, 11 Jul 2012 08:39:55 -0400
From: jcummins <jcummins at UWO.CA>
To: SANET-MG at LISTS.IFAS.UFL.EDU
Bt Toxicity Confirmed: Flawed Studies Exposed
Dr Eva Sirinathsinghji
ISIS Report, 11 July 2012
*Researchers confirm Bt toxicity to non-target beneficial insects and
show how experiments claiming to refute their results were designed not
to find the effect.
A new study confirms that the Cry1Ab Bacillus thuringiensis (Bt) toxin
present in genetically modified (GM) crops kills the larvae of the
two-spotted ladybird (Adalia bipunctata L.), a species that GM
supporters claim to be unaffected by the toxin .
The study raises questions regarding the integrity of previous work
published by GM proponents, whose experimental protocols were re-tested
and shown to lack the scientific rigour required to pick up signs of
toxicity even in target insects that the pesticide is designed to kill.
Bt toxins are present in many GM crops including cotton and maize.
Monsanto’s Mon 810 Bt maize is currently approved for cultivation in
Europe, although it has been banned by individual nations including
Hungary, France, Austria, Germany, Greece and Luxembourg due to health
and environmental concerns. Many previous studies have found effects on
health and the environment (see  Bt Crops Failures and Hazards, SiS
53,  More Illnesses Linked to Bt Crops, SiS 30).
Previous Bt toxicity studies slandered by GM proponents
GM proponents claim that certain Bt toxins are effective against limited
orders of insects, with Cry1Ab killing only Lepidoptera (butterflies and
moths) such as the common maize pest the European cornborer. However, a
peer-reviewed study published by Angela Hilbeck and colleagues at the
Swiss Federal Institute of Technology in 2009 showed increased mortality
in ladybirds exposed to the ‘activated’ toxin that had been coated on
their food – meal moth eggs ; the team had found similar effects in
green lacewings previously [5-7]. The activated version refers to the
cleavage of the pro-toxin to produce the actual toxin.
In response to their original publication, a coordinated effort aimed at
discrediting their findings appeared in the journal Transgenic Research,
which included two highly charged critiques [8, 9] and a study led by
Jörg Romeis from Agroscope, Switzerland, which failed to detect any
toxicity . They concluded that the results of Hilbeck’s team were
‘false-positives’ and artefacts of a poor study design. One critique
went as far as suggesting the work was ‘pseudo-science’. Agroscope, a
Swiss federal governmental research organisation, is linked to the
agrotech giant Syngenta, which along with Monsanto, produces Cry1Ab GM
crops. These hostile attacks were triggered by the ban of Mon 810 maize
in Germany based on results obtained by Hilbeck’s team among 30 other
scientific publications showing harmful effects from the pesticide.
Addressing discrepancies between previous studies
The new work from Hilbeck’s team aimed to address the discrepancies
between their own findings and those of their critics. First they
conducted a ‘proof-of-concept’ experiment where they tested both their
original protocol and Agroscope’s protocol on the target species, the
In the Hilbeck team’s original study, the ladybird larvae were exposed
continuously for 10 days to a microbially-produced purified version of
Cry1Ab or a microbially produced ‘empty’ version lacking the toxin. They
were exposed through coating their food - meal moth eggs - with the
toxin. The Agroscope protocol on the other hand, exposed the larvae for
only 24 hours at a time through a sugar/water droplet with or without
the toxin. As the larvae are carnivorous and cannot survive on a sugar
diet alone, they were transferred to petri dishes with untreated moth
eggs, thus giving them a period to recover from the exposure. This
exposure/recovery was apparently repeated 4 times in total.
So, the aim of the new study was to understand if the differences in
these protocols may have accounted for the opposing results obtained by
Hilbeck’s team and by Agroscope. By testing target species that the
toxin is designed to kill, any weakness in the protocol would become
Hilbeck’s team repeated the basic protocols by exposing 4 day old larvae
to Bt maize as well as near isogenic non-GM maize sprayed with Bt toxins
either continuously for 7 days, or for 24 hours followed by untreated
non-transgenic maize for 6 days. They found high levels of mortality
following continuous exposure as expected (just below 100 % with both
types of exposure). The mortality rates dropped by half when animals
were exposed to Bt sprayed plants for 24 hours only. Exposure to Bt
maize for only 24 hours did not even cause mortality rates to rise above
unexposed control groups.
An experimental protocol that cannot detect toxicity of a pesticide on a
target species is clearly not fit for testing potential harm to
In addition to insufficient exposure time, other flaws in the Agroscope
experiments were noted by Hilbeck. Sugar/water droplets to which Bt
toxin was added were found to dry up overnight, leaving the levels of
exposure undetermined. Only one dose was tested, as opposed to three
tested in the original study by Hilbeck’s team . There was no clear
description of the number of animals used or the number of times the
experiments were replicated, whereas performing 3 replicates is standard
in laboratory studies.
Re-testing effects of Bt toxin on ladybird larvae with a new combined
To counter the criticisms aimed at their previous study, Hilbeck’s team
adopted a combined protocol consisting of 7 days continuous exposure to
a sugar/water solution with or without the Bt toxin placed on cotton
balls to prevent them drying up. After 24 hours, instead of allowing a
recovery period, the cotton balls were replaced with fresh cotton balls
with or without Bt toxin solutions. Additional meal moth eggs coated in
the toxin were given to provide an adequate diet and ensure continuous
exposure to the toxin.
After only 6 days of exposure, mean mortality rate was 40 % compared to
around 25 % in unexposed larvae. The greatest difference in mortality
between treated and untreated animals peaked at 4 days where there was
around a 20 % increase in mortality over untreated animals, after which
it began to level off.
The new work not only corroborates the team’s previous findings , but
also Agroscope’s failure to detect toxicity on non-target insects .
It is important to distinguish the difference between the natural
bacterial toxin and the modified version inserted into GM plants.
Neither of the original studies by Hilbeck or Agroscope used the
versions expressed in GM crops, which are significantly modified.
Modifications are made to increase the ‘performance’ of the toxin,
including changing the promoter and enhancer elements to increase
production of the protein; changes in sequence to increase solubility of
the toxin, as well as altering the final portions of the gene to ensure
the termination of gene expression.
In reality, it is difficult for researchers to obtain the transgenes
made by industry, as there is strict patent laws and resistance to
giving permission to conduct independent research on their products.
Previous studies have shown that the modified toxin is more toxic than
their naturally produced counterparts, with green lacewings suffering
from delayed development and reduced survival (see  GM Food & Feed
Not Fit for "Man or Beast", ISIS Report). T
he new study from Hilbeck’s team was carried out with Cry1Ab toxin from
another independent lab, which is not the same as that produced in Bt
maize or those in earlier work that highlights these differences in
toxicity. The story remains unclear as to which versions are more toxic,
or if there is any non-toxic version. (The variable expression of
transgenes found in different Bt crops under different environmental
conditions also complicate matters (see  Scientists Confirm Failures
of Bt-Crops, SiS 28)).
Currently, no regulatory body requires testing of the modified
transgene, which means that their effects have not been properly
assessed in any version.
Attacks on researchers with ‘inconvenient’ results
The attack on scientists who publish data that happen to go against the
safety of biotech products are under immense pressure from GM
proponents, industry and even regulatory bodies. The work is highly
scrutinised in a manner rarely seen in other non-profit-driven subject
areas. As Hilbeck said in a comment piece, deliberate counter-studies
and confrontational attacks have also been witnessed with other
commercial products such as bisphenol A, asbestos and tobacco . The
team were never given the opportunity to respond to their critiques.
In the case of Bt toxicity, this is not the first time that the
researchers have faced such scrutiny; the publications on lacewing
lethality [5-7] drew a similar response from some of the same authors
that targeted the ladybird study.
Studies into the toxic effects of the Bt toxins are beginning to shed
light on the wider effects of Bt toxins to non-target insects. This
knowledge is critical to agricultural success with insects like the
ladybirds playing an important biological function due to their
predation on crop pests such as aphids and white flies. As it stands,
the full off-target effects of the Bt toxins are not understood, with a
reported 91 % of Bt toxins tested on 10 or less species, most of which
are presumed target species . Independent studies have however, also
linked Bt exposure to abnormal growth in snails  and caddisflies
(see  Bt Crops Threaten Aquatic Ecosystems, SiS 36) and reduced
fitness of water fleas .
Off-target effects need to be investigated thoroughly prior to the
release of such products. With Bt crops already widely commercialised,
we are left with the option of withdrawing them from the market until
irrefutable evidence of their safety becomes available.
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