Risk assessment for Bt plants: two concepts

25-11-2006 | |

Before a Bt plant is released, and especially before it is authorised for commercial cultivation, tests have to be carried out to check that this will not be associated with any harmful impacts on non-target organisms.

The authorisation decision is not always easy for the
authorities responsible. On the one hand, they have to reach a result within a
reasonable amount of time, while on the other they have to take into account
complex ecological relationships.

The first  genetically modified Bt maize variety was authorised in the USA over ten years ago. Now Bt
maize and Bt cotton are grown on more than twenty million hectares worldwide,
and the area under cultivation is expanding. With other plant species too,
scientists are looking at ways of using the Bt concept to control harmful
grazing insects.

But again and again there are discussions about whether
the Bt toxin produced in the plant has an effect on other organisms as well as
the pest it is designed to control.

In different cultivation regions,
different non-target organisms come into contact with the Bt plants and the Bt
toxin they produce. Do we need separate research for each crop and the
non-target organisms that might be affected by it? Or is it possible to develop
suitable standard tests that can be applied effectively and that still deliver
comprehensive, reliable results?

In the field
of biological safety research, this discussion has already begun.GMO Safety spoke to
Angelika Hilbeck and Jörg Romeis. These two scientists work in Switzerland.
They represent international working groups dealing with the development of
suitable models for the ecological risk assessment of Bt maize on non-target

Standard tests with representative
Jörg Romeis’s international working group is proposing a
step-by-step process. It is based on a sequence of laboratory, semi-field and
field experiments. The approach follows the globally established methods for
environmental testing of toxic substances and pesticides.

The focus of
the research is on standardised tests in the laboratory with various
‘representative organisms’ selected according to a range of criteria. In the
laboratory, toxic effects can be identified in a targeted manner and with a high
level of statistical confirmation. If the lab tests provide indications of
harmful effects, more investigations are carried out and, if necessary, field
trials as well. With this approach it is possible to reduce the need for
expensive field trials. In some cases they can be avoided altogether.

Studying the most important organisms
Hilbeck’s international working group is advocating a much broader approach. It
believes the existing ecotoxicological test methods are inadequate, especially
for regions with high biodiversity.

In her opinion, the standardised
approach with selected ‘representatives’ in the laboratory does not provide
enough information to be able to make assertions about effects on biodiversity
in the ecosystem. Before a test is conducted in the laboratory, the most
important non-target organisms with key ecological functions for the ecosystem in question need to
be identified. Laboratory tests are then carried out on these organisms and supplemented by
field trials.

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