PARENT SESSION
PM16 - Probabilistic Ecological Risk Assessment
Monday, 18 November 2002
8:00 AM to 6:30 PM
Exhibit Hall
(P373) Assessing the risk to non-target crops through irrigation water .
Dobbs, Michael*,1, Ramanarayanan, Tharacad1,2, Warren-Hicks, William2, Qian, Song2, Giddings, Jeffery3, Kelly, Iain1, Allen, Richard1, Fischer, Reinhard1, 1 Bayer CropScience, RTP, NC, USA2 The Cadmus Group, Durham, NC, USA3 The Cadmus Group, Marion, MA, USA
ABSTRACT- The risk that corn herbicide BALANCE poses to irrigated non-target crops was assessed using probabilistic risk assessment techniques. A series of laboratory (vegetative vigor, seedling emergence and seed germination study designs) and field studies have been conducted to evaluate the toxicity of isoxaflutole and its metabolites to non-target plants. A Bayesian hierarchical modeling framework was used to evaluate the laboratory toxicity data and generate species sensitive distributions (SSD). This approach allowed incorporation of data from multiple studies and includes variability from all sources in the analysis. The field data and commercial use experience provided important checks on the laboratory estimates. Surface water monitoring data was coupled with irrigation schedule simulations for representative crops in order to generate exposure distributions. Soybean, sugarbeet and lettuce were chosen as representative non-target crops. Soybean was chosen as a surrogate crop for field crops, sugarbeet for root crops and lettuce for vegetable crops. The exposure distributions and SSDs or species specific dose response curves were combined into Joint Probability Curves to express the risk as a probability of affecting a percent of species or extent of inhibition for a specific species. The risk to irrigated crops in all scenarios evaluated was extremely low. The relative timing of peak surface water levels versus irrigation events was the most important factor in the risk assessment.
Key words: Isoxaflutole, Probabilistic Risk Assessment, Non-Target Plants, Irrigation Water