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Assessing the safety of genetically modified plants
for non-target organisms
Technical Advisory Group (TAG) of EuropaBio’s Plant Biotechnology Unit (PBU)
A step-wise or ‘tiered’ approach has been used as a rational procedure to conduct environmental risk assessments in many disciplines. The Technical Advisory Group (TAG) of
EuropaBio’s Plant Biotechnology Unit (PBU) proposes that the tiered approach also be recognized as the recommended approach to evaluate the environmental safety of GM
crops, in particular for potential risks to non-target organisms (NTO). The tiered process allows the ‘case-by-case’ assessment of potential risks of a GM crop to NTO and
provides for a logical progression of NTO studies of increasing complexity and refinement where necessary. The tiered approach also allows the practical organization of data
generation and enables rational, science-based decision-making by both registrants and regulators.
GM plants may or may not pose risks to non-target organisms (NTO) in the environment. Risks vary
considerably depending on the crop, the GM trait and/or the scope of use, therefore a ‘case-by-case’
approach to risk assessment is needed. Assessment of potential risks to NTO is a challenging scientific task
and a rapidly developing area of regulation. Applying general principles of environmental risk assessment, the
current European legislation (Directive 2001/18/EC, Annex II) provides some guidance, but the specifics are
subject to interpretation by notifiers and regulators. The challenge is to develop a scientifically sound
approach to assessing risks to NTO, compatible with legislative requirements. To that effect, the TAG of
EuropaBio’s PBU proposes the use of a step-wise risk assessment scheme of increasing complexity and
refinement, known as the ‘tiered approach’.
Decision tree for tiered safety testing of GM plants
to nonnon-target organisms
Tier 0
Identification of hazard potential to non-target organisms, considering weight of evidence
from e.g.:
-type of introduced trait (pesticidal or not)
-activity screening data
-mode/site of action
-existing hazard data (mammalian
-history of safety
-protein homology data
-other data or public literature
(*) Is there a conceivable hazard or
does significant uncertainty remain
(expert judgment)?
The purpose of this poster is to provide a basis for discussion among regulators, notifiers and experts in the
field of environmental risk assessment.
The Tiered approach to risk assessment for NTO
Identification of exposure potential to nontarget organisms, considering weight of
evidence from e.g.:
-extent of intended release (import or
planting, GAP)
-characteristics of GM plant type/species
-protein expression in the GM plant
-physico-chemistry or protein stability data
-other data or public literature
No further studies required
Tiered approach to hazard and exposure assessment
According to the classical risk assessment paradigm:
(*) Is there a conceivable exposure
to the hazard previously identified?
Risk= f (Hazard, Exposure)
One of the most important steps in every evaluation of potential risk is the clear definition of the scope of the
risk assessment. The risk assessment often is an iterative process where the conclusion from a given tier
allows to conclude the assessment or indicates that further data are necessary and, if so, which options for
refinement may be considered. A schematic presentation of the tiered approach for NTO is given in Figure 1.
– STOP –
Tiered testing strategies
Tier 0 is a problem formulation step which focuses the risk assessment and ensures conclusions relevant to
risk-based decision making. If no risks are conceivable, then the risk assessment can stop there. However, if
risks have been identified or cannot be ruled out with reasonable certainty (expert judgment), then the
evaluation is pursued and the risk assessment is refined stepwise at higher tiers.
If tests on NTO are considered necessary, a suitable testing strategy must be formulated. Relevant
representative testing species can then be tested under worst-case conditions (meaning conditions that allow
the consideration of high levels of exposure that would not normally occur in the field or high level doses that
allow compensation for potential uncertainty in the risk assessment). If the risks under worst-case conditions
are considered low or acceptable, then the risk assessment can stop there. The purpose of higher tier tests,
where necessary, is to further reduce uncertainty in the risk characterization and/or, by generating additional
data, to replace conservative lower-tier assumptions with confirmatory or more realistic estimates.
Tier 1
Maximum hazard dose testing under worstworst-case exposure conditions (maximum or
enhanced exposure) for indicator organisms or functions that are representative of
potentially exposed non-target organisms.
(*) Was a significant risk identified?
Tier 2
- STOP No further
studies required
Refined hazard
characterisation in laboratory
for representative non-target
organisms or functions in the
relevant ecological
compartments of the receiving
The risk to NTO is evaluated at every decision point marked with an asterisk (*) in Figure 1 by consideration
of the hazard and exposure data (quantitative or qualitative) available at the respective tier. In the view of
the TAG this means that, depending on the case, a satisfactory risk conclusion can be reached on the basis of
already available data, or through additional data generated according to the tiered testing programme, or
using a combination of both.
Further risk assessment
only if there is a particular
environmental compartment
and NTO of concern
– STOP –
No further studies required
Practical considerations on the methodology to test NTO
(*) Was a specific risk
Which species to test?
Which test substance to use?
There is a range of test substances that can be used in regulatory laboratory tests for GM plants: plant
material (e.g. leaves, pollen or roots), purified protein, protein expressed in a microbial system, etc. The
choice of test substance should be based on the testing strategy that the assessor has decided upon and
the aims of a particular test. However, it can also be influenced by the feasibility of obtaining sufficient test
material to administer the desired test protein concentrations in the various NTO studies.
Refined exposure assessment,
considering e.g. the expected
likelihood or extent of
exposure, plant life cycle data,
ecology and ethology of the
NTO, climatic and
geographical factors, potential
risk management, etc.
(*) Was a significant risk identified?
Tier 3
In most cases, it will be necessary to select a limited number of species for testing. These should be
relevant to the GM plant under assessment and either represent a functional group of NTO with a similar
route of exposure (Figure 2) and/or be representative of the taxon to which they belong. In order to obtain
meaningful results, the species should be amenable to testing in the laboratory. Ideally, validated tests
should already be available or tests that can be readily adapted and validated should be established. The
tests should be conducted in manner that exposes the organism to the test substance by the same route
that it would be in the field (oral, contact,…).
go to Tiered
testing scheme
No further
studies required
Evaluating risk, concluding the testing
NTO that are potentially at risk from the use of GM crops will vary depending on the crop and the inserted
GM trait. Hence, appropriate test species should be selected on a case-by-case basis. Environmental risk
assessment guidelines for GM plants already exist in other countries such as USA and Canada. In
accordance with these, the TAG recommends a list of NTO groups, from which selected test species can be
- Mammals
- A bird
- A fish
- Freshwater invertebrates
- Arthropods: predators, parasitoids, pollinators
- Soil organisms
Tier 4
- STOP No further
Consider other
practices or
• Bees
• Adults of beneficial
• Phytophagous insects
• Wild mammals
• Wild birds
• Other arthropod pest species
• Beneficial arthropods
• Wild mammals
• Wild birds
Leaf/ Plant
• Predators
• Parasitoids
Roots and Exudates
Decomposing plant material
• Mesofauna