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.