Because insecticidal proteins from GM crop fields may enter aquatic systems, the potential effect that GM crops may have on those ecosystems is considered in the ERA. Over the past few decades, significant advances have been made in the field of biotechnology, and the cultivation of GM crops is steadily increasing worldwide (James 2009). Consequently, aquatic ecosystems need to be considered in the environmental risk assessment (ERA) of plant protection products, such as pesticides and genetically modified (GM) crops that have insecticidal traits. Because disturbance can lead to profound effects on biotic community structure and function, protection and conservation of aquatic ecosystem services is paramount. Aquatic ecosystems are influenced in many ways by inputs from the surrounding landscape, and agricultural watersheds in particular may be dramatically altered by anthropogenic disturbances over time (Cronan et al. Not only do they assimilate and cycle nutrients and carbon, they also maintain biodiversity, support primary and secondary biomass production, as well as provide habitat and food resources for aquatic and terrestrial food webs (Cummins et al. The processes used to develop the Bt maize case study are intended to serve as a model for performing risk assessments on future traits and crops.Īquatic environments support a wide range of ecological functions and ecosystem services (Jackson et al. Determining if early tier toxicity studies are necessary to inform the risk assessment for a specific GM crop should be done on a case by case basis, and should be guided by thorough problem formulation and exposure assessment. However, even using worst-case assumptions, the exposure of shredders to Bt maize was low and studies supporting the current risk assessments were deemed adequate. Based on exposure estimates, shredders were identified as the functional group most likely to be exposed to insecticidal proteins. Following a tiered approach for exposure assessment, worst-case exposures were estimated using standardized models, and factors mitigating exposure were described.
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Within problem formulation, the insecticidal trait, the crop, the receiving environment, and protection goals were characterized, and a conceptual model was developed to identify routes through which aquatic organisms may be exposed to insecticidal proteins in maize tissue. The purpose of this document is to demonstrate how comprehensive problem formulation can be used to develop a conceptual model and to identify potential exposure pathways, using Bacillus thuringiensis (Bt) maize as a case study.
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The ERA for terrestrial agroecosystems is well-developed, whereas guidance for ERA of GM crops in aquatic ecosystems is not as well-defined. Environmental risk assessments (ERA) support regulatory decisions for the commercial cultivation of genetically modified (GM) crops.