Assessing the Feasibility of Meeting Tolerance Limits for GM Adventitious Presence in Corn Supply Chain Using Probabilistic Modeling

Abstract

Highlights Most simulated scenarios showed low probabilities of meeting with 0.9% and 1.5% tolerance limits. 3.0% and 5.0% tolerance limits were achievable at some supply chain stages under specific conditions. Feasible tolerance limits at individual supply chain stages ranged from 2.25% to 6.25%. Seed purity and cross-pollination were key factors affecting the probability of meeting AP tolerance limits. Abstract. Tolerance limits for the adventitious presence (AP) of GM material in non-GM grain, food, and feed vary worldwide from 0.9% to 5.0%. This research analyzed the likelihood of meeting four common trade tolerance limits for AP (0.9%, 1.5%, 3.0%, and 5.0%) in the U.S. commodity corn supply chain. A model was developed to evaluate existing practices and patterns for bulk corn production, handling, and processing in an open-market supply chain that concurrently handles GM and non-GM products. Monte Carlo simulation was used to test 50,000 iterations of supply chain scenarios to determine the likelihood of successfully meeting specified tolerance limits. The model revealed that the supply chain, as it exists today, does not effectively facilitate the concurrent handling of GM and non-GM streams at 0.9% and 1.5% tolerance limits in most cases. At individual supply chain stages, some tolerance limits were reasonably achievable, such as 3.0% and 5.0% at the farm stage. The probabilities of complying with 0.9% and 1.5% tolerance limits at the farm stage were just over 10% and 67%, respectively, while the probabilities of complying with 3.0% and 5.0% tolerance limits were more than 90%. The grain elevator and grain processor could achieve 3.0% and 5.0% tolerance limits with reasonable likelihood. At the feed mill, a 5.0% tolerance limit was achievable but only when bypassing some supply chain stages. The 99% feasible tolerance limits at individual supply chain stages ranged from 2.25% to 6.25%. Significant factors influencing the ability to meet AP tolerances were identified using sensitivity analysis. These factors included seed impurity, cross-pollination, and transportation vehicles. Keywords: Adventitious presence, Corn, Feed, Genetically modified grain, Monte Carlo simulation, Segregation, Supply chain.