Explanatory statement for the applicability of the Guidance of the EFSA Scientific Committee on conducting repeated-dose 90-day oral toxicity study in rodents on whole food/feed for GMO risk assessment


European Food Safety Authority
EFSA Journal
EFSA Journal 2014;12(10):3871 [25 pp.].

EFSA wishes to thank the EFSA Staff: Anna Lanzoni, Claudia Paoletti, Laura Martino, Antonio Fernandez Dumont, Yi Liu, Elisabeth Waigmann, Andrea Germini, Wolfgang Gelbmann for the preparation of this scientific output and the external reviewers Diane Benford and David Makowski. EFSA also thanks the EFSA GMO Panel, the EFSA NUTRI Panel and the EFSA Scientific Committee Panel for their comments.

Statement of EFSA
On request from
Question Number
7 October 2014
9 October 2014
European Food Safety Authority (EFSA), Parma, Italy
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The European Food Safety Authority mandated its GMO Unit to prepare a statement supporting the application of the EFSA Scientific Committee ‘Guidance on conducting repeated-dose 90-day oral toxicity study in rodents on whole food/feed’ in the frame of Implementing Regulation (EU) 503/2013, which requires a 90-day study in rodents for the risk assessment of genetically modified (GM) plants. This statement illustrates two possible scenarios for 90-day studies, based on the identification (scenario 1) or not (scenario 2) of hazards in previous analyses, and provides information on the study design, conduct and interpretation accordingly. Considerations on the type and source of the test materials and on preparation of test diets are also provided, with illustrative examples. Detailed analytical characterisation of the test and control materials and diets are recommended, including the detection of the genetic event and, if appropriate, quantification of the newly expressed protein(s). The selection of dose levels is discussed, with a maximum incorporation rate (high dose level) proposed for various crops. The selection of one dose level only (the high dose) is proposed as an option and discussed for scenario 2. The preferred test species is the rat; it should be socially housed, single housing needing justification. Limitations for the identification of appropriate sample sizes are discussed for both scenarios. Technical details for endpoints selection and data collection are provided. Strategies for integrated study interpretation are presented and areas for further scientific development are discussed.


Following the adoption of the Implementing Regulation (EU) 503/2013 , a 90-day study in rodents on whole genetically modified (GM) food/feed is required for all GM plants containing single transformation events or stacked transformation events not obtained by conventional crossing. This new legal requirement changes the study from a hypothesis-driven case-by-case exercise, as indicated by the EFSA GMO Panel ‘Guidance for risk assessment of food and feed from genetically modified plants’ (EFSA, 2011a) and technically detailed in the Scientific Committee ‘Guidance on conducting repeated-dose 90-day oral toxicity study in rodents on whole food/feed’ (EFSA, 2011b), into a mandatory requirement.

EFSA mandated its GMO Unit to develop a statement to clarify the objectives of 90-day feeding studies on whole GM food/feed in this new frame and to provide instructions on how to apply the general principles described in the EFSA Scientific Committee Guidance (EFSA, 2011b) for the study design and analysis.

This statement describes two possible scenarios: scenario 1 – when a specific hypothesis is available, i.e. the preceding analyses have identified a potential risk(s); scenario 2 – when no specific hypothesis is available, i.e. no potential risk has been identified. Under either scenario, the objective of a 90-day study is the detection of toxicologically relevant differences between animals fed diets containing the whole GM food/feed in comparison to those fed a diet containing an appropriate control (EFSA, 2011a), IR (EU) 503/2013).

The test material for the 90-day study (scenario 1 and 2) should be sourced from the field trials performed for the comparative assessment (EFSA, 2011a), whenever possible, and should be representative of the whole GM food/feed. Examples of test material are provided for some common crops, such as soybean, maize, oilseed rape, and sugarbeet. The test material and diets should be characterised, and stability and storage conditions should be documented.

Two dose levels should be tested: a high dose representing the maximum incorporation rate not causing nutritional imbalances; and a low dose above the expected intake level of consumers, representing a proportion of the selected high dose. The statement also discusses the possibility of testing one dose level only (the high dose) as an option in the case of scenario 2.

The rat is the preferred test species for the study; social housing should be chosen; appropriate justification for single housing should be provided.

Statistical considerations to derive appropriate sample sizes are discussed. Under scenario 1 the number of experimental units/sex/group should be established on the basis of a power analysis, taking into account the specific hypothesis to be tested. In the absence of a test hypothesis (scenario 2) EFSA is not in a position to provide specific recommendations on power analysis and sample size.

The parameters to be considered should be in line with those detailed in OECD Test Guideline 408 (OECD TG 408, 1998). Additional parameters should be considered on a case-by-case basis, according to the available body of evidence and the type of whole GM food/feed under investigation. Study interpretation should be integrated and define test material-related effects and their toxicological significance. Additional considerations on further scientific development are presented.

90-day study, whole food/feed, GM plants, experimental design, study conduction, study interpretation
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