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SCIENTIFIC FOUNDATION FOR RISK ASSESSMENTS TO PROTECT NON-TARGET PLANTS FROM HERBICIDES
OLSZYK, D. M., T. G. PFLEEGER, AND E. LEE. SCIENTIFIC FOUNDATION FOR RISK ASSESSMENTS TO PROTECT NON-TARGET PLANTS FROM HERBICIDES. Presented at EPA BOSC Review, RTP, NC, February 01 - 02, 2007.
EPA's Office of Pesticides Programs (OPP) requires scientifically credible information and methods to assess health and ecological risks from chemical pesticides. However the suite of standard bioassays and approaches available to OPP to determine these risks to non-target plants remains incomplete (e.g., lacking standardized methods for assessing plant reproduction effects and effects on native plants) and outdated (e.g., needing a current computer platform for geographically based assessments and probabilistic analysis). Major science questions that need to be addressed to develop new/novel methods to determine risks to non-target plants include: (1) What types of databases, models, and software platforms can be used for regional spatial analysis to identify species for development of testing protocols and to integrate data for risk characterization purposes for pesticides? (2) What are the effects of herbicides on plant reproduction, which is important for crop yield and wildlife habitat? (3) What are the effects of herbicides on regionally important native plants and plant communities, especially threatened or endangered species? (4) Are there molecular indicators (gene expression, proteomics) of potential effects of herbicides on non-target crop and native plant species? Are these indicators specific for herbicides in question and can they be used to predict possible sensitivity of species to these herbicides?
There are four areas of integrated research to broaden the scope of information available for ecological risk assessments. (1) In spatial analysis studies, information is compiled in a GIS platform using ARCINFO (or other GIS software) to identify geographic areas and types of plants with the greatest risk for non-target herbicide effects. (2) For experimental studies, crop and non-crop test species are based on the spatial analysis, prior use in phytotoxicity testing, ecological significance, and cultural characteristics. These species are evaluated for reproductive/ developmental responses to improve proposed life-cycle (reproductive/ developmental) tests and growth responses to improve seedling (e.g., vegetative vigor) tests. (3) For ecological studies, individual non-crop species response information initially will be obtained under controlled greenhouse conditions. These species will be used in large field-plot studies to refine and further develop methodology for determining herbicide effects at the plant community. Both constructed communities with planted species and in situ native plant communities would be studied. (4) To develop molecular indicators, we are evaluating whether gene arrays can be used to indicate whether a plant has been affected by specific herbicides, and what the possible effects of the herbicides may be based on the gene activity, and whether this molecular information can in the future be used for quick tests. We will determine if molecular indicators can predict the potential susceptibility of different plant species to an herbicide (especially native plants and threatened and endangered plant species).
IMPACTS AND OUTCOMES:
These studies will provide EPA¿s Office of Pesticides Programs (OPP) with information on types of data necessary to determine potential non-target effects of chemical pesticides as part of their risk-benefit analysis for registration and labeling. These studies will indicate information needed not only to determine direct toxicity of herbicides to non-target vegetation, but also on indirect effects to plant communities and subsequent ecosystem structure and function within a spatially explicit, geographically based framework. These studies will provide methodologies needed post-registration by OPP, EPA regions and states to monitor pesticide drift and assess impacts to nontarget crops and native plant species. To date the project has provided a framework and a case study (Fresno County, CA) for spatial analysis of the risk from chemical herbicides to nontarget crops and native species, conducted experiments which will improve phytotoxicity tests to determine effects of herbicides on crop and native plant species for terrestrial plant risk assessments, initiated experiments to provide tools to evaluate plant community responses to off-target drift of herbicides, and initiated studies which will provide genomics- and proteomics-based molecular approaches to assess the magnitude of the risk from chemical herbicides to nontarget crops and native species.