Risk assessment aims at identifying and characterizing the risks associated with GM plant cultivation; while risk management determines the necessary measures to be taken in order to mitigate the risks that have been identified through the assessment process that are unacceptable. Risk communication informs the public on the decisions that have been taken, and also allows for collecting public suggestions relevant to the decision making process. Pursuant to the Cartagena Protocol on Biosafety, risk assessment will be carried out in a scientifically sound manner (Article 15), considering all the adverse effects that the cultivation of a GM crop may have on the receiving environment.
Risk assessment involves the identification of the potential adverse effects and an estimation of the probability of such effects occurring (OECD, 2006). It is a process that “uses scientific evidence to estimate the level of risk based on a combination of both the likelihood (= exposure) and consequences of potential harm (= hazard)” (OGTR, 2007). Harm is determined in relation to a country’s protection goals. Risk assessment is not the consideration of all effects, but only those effects that are considered harmful by the jurisdiction in question
Risk assessment is conducted, taking into consideration the data that are collected that are relevant to regulators. In assessing environmental risk, regulators should 1) decide on what needs protection from harm, 2) evaluate how the utilization of GM material might cause harm and what needs to be protected, 3) collect data from available literature or if necessary from new studies, to evaluate the likelihood of and the magnitude of harm resulting from the utilization of that GE material (Raybould and Cooper, 2006)
Note that uncertainty is a key aspect in any risk assessment and “absolute certainty or zero risk in safety assessment is not achievable” (OECD, 2006). Regulators have to make decisions on what nature and level of uncertainty is acceptable for the approval of a GM crop, taking in account social, economic and political aspects.
Relevant comparators must be used to clearly describe levels of hazard, probability of that hazard, and the subsequent risk.
Conducting environmental risk assessment
Despite the critical importance of risk assessment in transgenic products regulation, there is as yet no global, consensus model for conducting risk assessment, even though guidelines have been suggested by several international bodies such as OECD, UNEP-GEF, Biosafety Protocol and EU.
The guidelines suggested by the Biosafety protocol (Annex III) include, among others:
- characterization of the GM traits that could have potential adverse effects on the environment,
- an evaluation of the likelihood of the adverse effects, taking into account the exposure of the receiving environment of the GM material,
- an evaluation of the consequences of the adverse effects,
- characterization of the overall risk, taking into account the likelihood and the consequences of the adverse effects.
The European Union directive and guidelines have proposed the following steps in environmental risk assessment (Commission of the European Communities, 2002; European Economic and Social Committee, 2004)
- identification of the potential adverse effects;
- evaluation of the magnitude of the consequences derived from the adverse effects;
- evaluation of the likelihood of the adverse effects;
- estimation of the risks that may be posed, by combining the likelihood and the magnitude of the potential adverse effects;
- identification of the strategies appropriate to manage the estimated risks;
- identification of the risks, after taking in account the management strategies;
Critically, the receiving environment first must be well characterized so that a “baseline” context can be defined to allow properly identify the potential hazards, and measure the related impacts. Information needed for such characterization include location, geographical, climatic and ecological characteristics , information on the biological diversity features and the status of centres of origin.
Lessons learnt in the past decade of experience in risk assessment have led regulators and researchers to emphasize the necessity of having a streamlined approach. To facilitate decision making, the “problem formulation” approach has been suggested as a critical first step in the risk assessment process (Raybould and Cooper, 2005; Raybould, 2006, 2007; Nickson, 2008). It is based on principles that have been successfully applied to assess risks for chemical products and GM crops (Raybould, 2007).
This approach includes the three following steps (Nickson, 2008):
- definition of the assessment endpoints
- development of a conceptual model
- development of an analysis plan
The assessment endpoints have been defined as the measurable entities that need to be protected. They derived from the protection goals set by governments or international bodies. The assessment endpoints should be “clearly and operationally defined, comprising an entity (example a population of a particular species in a particular area) and a measurable property of this entity (example the population size of that entity)”.
The conceptual model utilizes available information to describe the relationships between the valued entities (e.g. population of honeybees) the stressor (e.g. Bt toxins), the pathways of exposure (e.g. presence of Bt toxins in pollen) and the potential effects in the environment (e.g. decreased levels of pollination). The conceptual model describes the risk scenarios and formulates the risk hypotheses, using information on the characteristics of the conventional crop varieties, the nature and the characteristics of the GM traits introduced in the crop, the characteristics of the likely receiving environment and the likely interactions between these elements.
The analysis plan presents the data needed in risk assessment and describes how to collect it (Nickson, 2008). Thus, an environmental risk assessment will typically require:
- information on the characteristics of the product (transgene) obtained through molecular and expression analysis;
- agronomic and phenotypic characteristics of the plant;
- compositional characteristics of the plant products collected from fields.
Tiered approaches have been found to make the best use of available information in the decision-making process (Romeis et al., 2008, Hancock, 2009). In tiered approaches, decisions are made at several stages using available information whenever possible. The process starts at the lowest tier with laboratory studies and then progresses, if necessary, towards higher tiers through contained experiments and open field tests (Raybould and Cooper, 2006).
In general, the lower tier tests are conducted under worst case scenarios, such as an unavoidable contact between a given organism and high doses of an active ingredient. Studies and tests in tier 1 are not intended to be realistic, but rather to aid in early decision making and thereby minimize unnecessary costs of testing of products that present very low hazard (Raybould, 2006). Lower-tier activities require less complex experimentation than those at higher tiers.
Four tiers are commonly used in insecticidal studies. In Tier # 1, the toxicity of microbially derived protein mixed with diet is analyzed in the laboratory at elevated levels. If potential adverse effects are noted, Tier # 2 is conducted where the toxicity of more natural routes of exposure are analyzed, such as transgenic leaf material and exposed prey. In Tiers # 3 and # 4, long-term, semi-field (greenhouse or cages) and open field studies are utilized to determine population level effects with more realistic environmental exposure levels. The types of monitoring done in Tier # 4 include aerial/flying invertebrates, surface dwelling organisms and below ground invertebrates and microorganisms.
The list of potentially affected organisms in natural and agroecosystems is very wide and for this reason, risk analysis of non-target effects has to be focused on organisms closely related to the target group and representatives of other classes of organisms such as pollinators (exp. honey bees), natural enemies (predators and parasitoids), endangered or insects of cultural and aesthetic value (exp monarch butterfly) and soil dwelling organisms (exps. earthworms, Collembola and microorganisms and microarthropods, protozoans).
To do tiered analysis of potential weediness/gene flow issues, Hancock (2003) suggested that only three main categories of information need to be assessed: 1) the geographical range of compatible relatives; 2) the invasiveness/weediness of the crop and its relatives and 3) the phenotype of the transgene. The most critical factor in assessing risk is the phenotypic trait conferred by the transgene, whether it is selectively neutral, detrimental, or beneficial to fitness in the native environment. Fitness represents the reproductive success of a plant.
The various crop/transgene combinations can be grouped into four tiers. In tier # 1 are combinations involving neutral selectable marker genes transgenes in all crops, deleterious genes in crops with no compatible relatives and herbicide resistance in crops with no native relatives or their relatives are not invasive. In tier # 1, none of the combinations would require any further experimentation. In tier # 2 is the combination of pest resistance into a crop with a compatible native relative. In tier # 2, the necessary experiment would be to show that a similar phenotype exists in wild populations; if it does not, then it must be determined whether the target pest does not significantly impact on natural populations. In tier # 3 is the combination of an advantageous trait into any species with a compatible relative. In tier # 3, the necessary experiment would be to show whether a similar phenotype exists in wild populations. If it does not, the fitness of the transgenic crop will need to be measured in representative native environments. In tier # 4 is the combination of a advantageous trait into any species with a compatible, highly invasive relative. Tier # 4 products should not be released unless containment systems are developed preventing gene flow.
Using tiered approaches in risk assessment allows regulators to structure their data requirements and to prioritize the relevant information needed. Most of the data and information obtained through the tiered approach, especially at the lowest tiers (laboratory studies, toxicity to particular groups of organisms, food toxicology, crop species distribution, etc.) should be accepted and shared among regulatory bodies, so that unnecessary costs can be avoided. The tiered approach is critical for improving the efficiency of regulatory decisions as it allows available resources to be focused on higher risk GE materials.
Click here Risk estimate by USDA-APHIS for an explanation of the new USDA APHIS proposed assessment procedure
Carthagena Protocol on Biosafety to the Convention on Biological Diversity. 2000. Secretariat of the Convention on Biodiversity.
Hancock J. F. 2009. Factors influencing the genetic diversity of crop species and the impact of transgene escape. In press. Michigan State University, USA.
Hancock J. F., Quemada H. 2009. Factor affecting the release of genetically engineered crops. In press. Michigan State University, USA.
Nickson, T. E. 2008. Planning Environmental Risk Assessment for Genetically Modified Crops: Problem Formulation for Stress-Tolerant Crops. Plant Physiol. Vol. 147.
OECD, 2006. Safety Assessment of Trangenic Organisms. OECD Consensus Documents. Volume 1
Office of the Gene Technology Regulator, 2007. Risk Analysis Framework.
Raybould A., Cooper I. 2005. Tiered tests to assess the environmental risks of fitness changes in hybrids between transgenic crops and wild relatives: the example of virus resistant Brassica napus. Envron. Biosafety Res. 4. 127-140.
Romeis, J., Bartsch, D., Bigler, F., Candolfi, M.P., Gielkens, M.M.C., Hartley, S.E., Hellmich, R.L., Huesing, J.E., Jepson, P.C., Layton, R., Quemada, H., Raybould, A., Rose, R.I., Schiemann, J., Sears, M.K., Shelton, A.M., Sweet, J., Vaituzis, Z., Wolt, J.D. 2008. Assessment of risk of insect-resistant transgenic crops to nontarget arthropods. Nat Biotechnol. 26, 203-208.
Traynor, P. L., Frederick, R., J., Koch, M., 2002. Biosafety and Risk Assessment in Agricultural Biotechnology. A workbook for technical training. Michigan State University, USA.
USDA-APHIS. 2008 Importation, Interstate Movement, and Release into the Environment of Certain Genetically Engineered Organisms. Proposed rules.