A study has been published which blows
all assumptions about the safety of 'Bt' insecticidal GM proteins out
of the water.
Biotech industry genetic engineers have
been getting great mileage out of proteins modelled on those produced
by the soil bacterium Bacillus thuringiensis ('Bt'). These
transgenic look-alikes come in an infinite variety and can be
designed to target specific pests.
Bt proteins' assumed safety is based on
their long history of safe use as cultured spore suspensions in
foliar sprays. It's taken for granted that their protein chemistry
means they will be denatured during digestion, and that their need
for activation by specific gut conditions and cell-surface receptors
found only in insects will make other animals (including humans)
immune to their toxic effects.
All the above assumptions are
over-generalisations: transgenic Bt is different in structure and
origin from the familiar, natural forms, plus, as the authors of the
study note, “little is known about (Bt proteins') toxicological
potential”. Our traditional exposure has been to live bacteria on
our skin and in our lungs, not to large quantities of a single,
concentrated protein sequestered and possibly stabilised inside food
material. Assumptions of digestibility and insect specificity are
theories which were not checked by science prior to the
commercialisation of Bt-generating GM crops.
Experiments have already shown that Bt
proteins (natural or artificial) kill by bursting cells. If
conditions are carefully adjusted, Bt can burst red blood cells from
rats, mice, sheep, horse and humans. Because blood cells are
generated constantly and their production can rapidly be stepped up
in response to adverse events such as a toxin entering the body,
changes in quality, quantity and maturity are quickly apparent.
In the study, mice were fed a single 'meal' of four transgenic Bt toxins in the form of GM bacterial spores. The various Bt proteins were fed both individually and in combination. Blood cell analyses were carried out after one, three and seven days.
The changes observed indicated toxic
effects on the bone marrow tissue which generates blood cells. Red
cells were particularly targetted, and three of the Bt-toxins induced
a highly inflammatory response in the white blood cells. What was
observed wasn't a simple reaction to all Bt proteins, because the
dose- and time-responses were different for each one.
Toxic signs were evident even at the
lowest dose of one of the Bt analogues ('cry1Ab') which is widely
incorporated into commercial GM crops: it has also been found
circulating in pregnant and non-pregnant women and foetuses in Canada
[3]
The authors concluded that the four Bt
toxins tested “can cause some hematological risks to vertebrates,
increasing their toxic effects with long-term exposure. Taking into
account the increased risk of human and animal exposures to
significant levels of these toxins, especially through diet, our
results suggest that further studies are required to clarify the
mechanism involved ... before concluding that these microbiological
control agents are safe for mammals.” 'Mammals' includes, of
course, humans.
OUR COMMENT
The ‘mechanism’ needing 'clarified'
includes:
- how a protein assumed to be digested is, nevertheless, ending up in the body of the consumer
- how a toxin assumed to be activated only in conditions found in an insect gut is, nevertheless, inducing changes in mouse blood and inside mouse bones.
- how a toxin assumed to require an insect molecular receptor on an insect gut cell and insect gut conditions is, nevertheless, harmful to mouse blood cells.
- how the Bt proteins tested are not only unexpectedly toxic, but clearly act and interact in different ways.
Transgenic Bt made by plants isn't, of
course, the same thing as transgenic Bt made by bacteria: the plant
version could be much more damaging.
This paper sounds a very tangible
warning about possible harmful effects from many GM crops available
now or in the pipeline. Given the GM-lobby habit of
shooting-the-messenger, for example Arpad Pusztai after giving his
warning about GM potatoes which weren't even on the market [1], and
Gilles-Eric Séralini since he gave his warning about Roundup
herbicide and at least one Roundup Ready maize which accumulates it
[2], how come this latest damning science has slipped through the
net? Perhaps it's just a matter of time.
Background:
[1] Trials conducted for the UK
Government in Scotland in 1998 found that rats fed insecticide-
generating GM potatoes developed immune
reactions in their gut wall. The scientist, Dr. Arpad Pusztai, was
suspended, gagged and eventually dismissed. The Lancet
recommended that Pusztai's study be repeated: this has not been done.
[2] GM MAIZE IS NOT SAFE TO EAT -
News, October 2012
[3] GM PESTICIDES INSIDE YOU - News,
April 2011
SOURCES:
- Bélin Poleto Mezzomo et al.(2013) Hematoxicity of Bacillus thruringiensis as Spore-crystal Strains Cry1Aa, Cry1Ab, Cry1Ac or Cry2 Aa in Swiss Albino Mice, Journal of Hematology & Thromboembolic Diseases 1:1
- Bt toxins are toxic to the blood of mice, GM Watch 2.05.13
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